March 12, 2018 Weather and Climate Report – Storms to the Right and Left

Written by Sig Silber

There is a most likely unwelcome Nor’easter poised to hit New England and a Pacific Coast storm which should bring in some amount of beneficial moisture. Whether that results in an overall wet couple of weeks remains to be seen. These Trans-Nino periods are difficult to forecast. We also discuss sea level rise and a possible slowing of the Gulf Stream. What is the timing on this?

Please share this article – Go to very top of page, right hand side for social media buttons.

Last week I had in my News Section a link to a very interesting article by Bob Henson of the Weather Underground

A Weaker Gulf Stream Means Trouble for Coastal New England Bob Henson: March 5, 2018

It was posted on the same day as I published so I included it in the News Section and indicated that I would study it and comment on it this week. So here is my analysis. The article covers the Nor’easters impacting New England then opines (including in the title) that the Gulf Stream is weakening and this is bad news for New England. So let’s discuss that.

Is the Gulf Stream Fading and if so what is the impact?

Henson provides a current assessment of the impact of the Gulf Stream.

And then his contention

What’s concerning is that any major slowdown in the Gulf Stream would also tend to lessen the contrast in sea level from one side to the other—and this would act to push up sea levels along the Northeast U.S. coast, on top of the global rise produced by warmer seas and melting ice. The most likely mechanism for slowing the Gulf Stream and the broader Atlantic meridional overturning circulation (AMOC) would be an intrusion of fresh water into the North Atlantic from melting of the Greenland Ice Sheet and/or Arctic sea ice.

Here I take exception to the interpretation by Henson: If the Gulf Stream fades I do not see the logic for the near-shore water being warmer and hence less dense and thus higher. Also would not Greenland Ice cap melting keep the waters offshore of New England cool. So I pretty much agree with everything else in this fabulous article by Bob Henson but not this pivotal claim. Most likely the rise in water levels will continue at near the current rate into the foreseeable future.

The straight line fitting shows a rise of 0.3 meters or about a foot per century. This could be due to Global Warming or other factors such as continent subsidence and has been going on at some rate for a very long time. One can fit a different curve, other than a straight line, to the existing data for Boston Harbor sea level rise and possibly see some slight acceleration. One could perhaps convince themselves that a non-linear fit is better and perhaps then convince themselves that a two-foot rise per century is in our immediate future. I do not think that would be an unreasonable thing to do for planning purposes.

I think we need to understand the Gulf stream better.

And here is the Gulf Stream part of the ocean circulation we find in articles written by Stefan Rahmstorm. Stefan Rahmstorf is a German oceanographer and climatologist. Since 2000, he has been a Professor of Physics of the Oceans at Potsdam University. He received his Ph.D. in oceanography from Victoria University of Wellington.

And here is a graphic of the larger circulation pattern. This graphics conveys that it is truly an overturning with deep much cooler water rising in places and being heated on the surface and then being made to sink. There are many different renditions of this current as ocean currents are very complicated. It takes more than a 1,000 years to complete the circuit. Notice the important role of the Antarctic currents.  Rahmstorm provides a lot of detail in this article which is a more recent and comprehensive than the earlier link which was summary which he called a fact sheet.

Henson provide this link to help in understanding the thermohaline circulation. From that article and there are many similar explanations available”

The many ocean currents and wind systems that move heat from the equator northwards towards the poles then transport the cold water back towards the equator make up the thermohaline circulation. (Thermo refers to temperature while haline denotes salt content; both factors determine the density of ocean waters.) It is also called the Great Ocean Conveyor, a term coined in 1987 by Wallace Broecker, Newberry Professor of Geology in the Department of Earth and Environmental Sciences at Columbia University and a scientist at Lamont-Doherty Earth Observatory. Broecker theorized that changes in the thermohaline circulation triggered dramatic changes in the North Atlantic during the last ice age.

In the high latitudes, the cold water on the surface of the ocean gets saltier as some water evaporates and/or salt is ejected in the forming of sea ice. Because saltier colder water is denser and thus heavier, it drops deep into the ocean and moves along the depths until it can rise to the surface near the equator, usually in the Pacific and Indian Oceans. Heat from the sun then warms the cold water at the surface, and evaporation leaves the water saltier. The warm salty water is then carried northwards; it joins the Gulf Stream, a large powerful ocean current that is also driven by winds. The warm salty water travels up the U.S. east coast, then crosses into the North Atlantic region where it releases heat and warms Western Europe. [Editor’s note: But there are many different estimates of the percentage contribution of the Gulf Stream to the warming of Europe. Other factors include relatively warm westerlies.] Once the water releases its heat and reaches the North Atlantic, it becomes very cold and dense again, and sinks to the deep ocean. The cycle continues. The thermohaline circulation plays a key role in determining the climate of different regions of the earth.

The Atlantic Meridional Overturning Circulation, part of the thermohaline circulation which includes the Gulf Stream, is the ocean circulation system that carries heat north from the tropics and Southern Hemisphere until it loses it in the northern North Atlantic, Nordic and Labrador Seas, which leads to the deep sinking of the colder waters.

Because the thermohaline circulation is mainly driven by differences in the water’s density, it depends upon the cold dense waters that sink into the deep oceans. Global warming can affect this by warming surface waters and melting ice that adds fresh water to the circulation, making the waters less saline; this freshening of the water can prevent the cold waters from sinking and thus alter ocean currents.

As the planet warms, more and more fresh water is entering the system. In 2016, the extent of Greenland’s melting sea ice set a new record low. That May, the Arctic lost about 23,600 square miles of ice daily, compared to the long-term average loss of 18,000 square miles per day. A study by Marco Tedesco, a research professor at Lamont-Doherty specializing in Greenland, and colleagues suggested that a reduction in the temperature difference between the polar and temperate regions (the Arctic is warming twice as fast as the rest of the planet) pulled the jet stream air currents northwards. The warm moist air it carried hovered over Greenland, causing the record melting.

Henson included this link to provide some perspective on the issue of the Gulf Stream slowing down and possibly collapsing completely. There are plenty of similar articles including articles that are quite alarmist.

My conclusions on the factors related to the Gulf Stream:

The issue relates to

• Salty water is more dense than fresh water
• Warmer water is less dense than colder water. 
• As water moves north it gets colder and it at some point would sink reinforcing the overturning. (but if diluted with enough freshwater from melting glaciers, it might not sink)
• Warmer temperatures result in more evaporation leading to higher salt content of surface water so this counteracts to some extent the diluting impacts of ice-melt.

You can see why this is so difficult to model.

Attempting to sum it all up:

I am not at all convinced that the situation is different from that described in the IPCC Fifth Assessment.

It remains very unlikely that the AMOC will undergo an abrupt transition or collapse in the 21st century. No model exhibits an abrupt shutdown of the AMOC after 2100 under any RCP simulation. Only one of the CMIP5 models revealed an eventual slowdown of the AMOC to an off state. But this did not occur abruptly.

But they do see a weakening. This seems like a multi-century problem if at all. I say if at all as there is a race between Warming and Glacier Melt and reduction of emission of Greenhouse Gases. I think we will win that race. But there are no guarantees  New England has enough of a problem this century without exaggerating it with this Gulf Stream scare. There will be more and more coastal flooding. I grew up on the East Coast and returned there and have experienced the rise of sea level and the relentless north to south transport of sand. So even at current rates there is a problem for all of the East Coast. Future planning should be based on a sea-level increase of perhaps up to two feet this century. That is not multiple meters but it is enough to require the changing of zoning and building requirements along the coast. Most houses are built with the expectation that they will be useful for a very long time.

One implication of the slowing of the Gulf Stream could be a lengthening of the cycle of the Atlantic Multidecadal Oscillation (AMO). The PDO is widely believed to be correlated with the AMO (with a lag) so that could change the cyclical nature of climate. We could end up with longer positive and longer negative phases of the AMO and PDO. This might lead to longer periods that are wetter or alternatively drier than climatology and or warmer or cooler than climatology. 

How do we value Climate?

Do we have a basis for saying that the current climate is optimum? I doubt that but we (all species) are adapted to our current climate. For humans, we have major investments in infrastructure that is optimized to the current climate. So the current climate may or may not be optimum but we are optimized to that climate. This is why we tend to view all changes to climate as being a negative. And that is generally true in the short term where we have adapted to the climate. But in the long term and in areas with sparse human occupation today, a change in climate may well increase the value of that area. We see that in Canada farmlands.  I am writing a book on the Economic Impacts of Global Warming and expect to find both negative and positive impacts not just negative impacts. But in general the short term impacts of a changing climate are often negative because it is not the climate to which we have adapted.

Let’s changes subjects.

Because it is Winter we make it easy to get a snow forecast. This is the six-hour snow forecast.

Looking further out.

NOAA Snow Forecast looking ahead to Days 4,5 (top Row) 6 and 7 (bottom row). When you view these graphics you can click on them to enlarge them.

A. Now we return to our regular approach and focus on Alaska and CONUS (all U.S.. except Hawaii) 

I am starting with a summary first for temperature and then for precipitation of small images of the three short-term maps. You can click on these maps to see larger versions. The easiest way to return to this report is by using the “Back Arrow” usually found top left corner of your screen to the left of the URL Box. Larger maps are available later in the article with the discussion and analysis.

For most people, the summary with the small images will be sufficient. Later in the article for those with sufficient interest there is a full description of the factors determining the maps shown here with a detailed analysis of the ENSO situation which so dramatically impacts the forecasts below.

First Temperature

		Transitioning from the 6 to 10 day outlook on the left (also called Week One) to the 8 to 14 day outlook (Week Two) on the right          →
		The pattern is slightly progressive: west to east perhaps more so in the northern tier.
To the right is the week 3 and 4 Forecast.     → There is a cool anomaly for most of Alaska, the Alaskan Panhandle and the northern tier of CONUS east to Illinois. There is a warm anomaly covering the southern tier of CONUS .			↑ ←  The transition from the 8 -14 day forecast shown above to the week 3/4 shown to the left seems a bit unlikely re the southern tier.

And then Precipitation

		Transitioning from the 6 to 10 day outlook on the left to the 8 to 14 day outlook on the right.                 →
		The pattern is fairly stagnant west to east: maybe even retrograding a bit. .
To the right is the week 3 and 4 Experimental Forecast.    →                Alaska is mostly dry, a large area of the Southwest is dry. The East Coast is dry. There is a wet anomaly extending southeast from Montana almost to the Gulf Coast.			↑ ←  The transition from the 8 -14 day forecast shown above to the week 3/4 shown to the left seems feasible.

Let us focus on the Current (Right Now to 5 Days Out) Weather Situation.

Water Vapor.

This view of the past 24 hours provides a lot of insight as to what is happening.

You can see from this animation that there has been moisture entering British Columbia and California.

Tonight, Monday evening March 12, 2018, as I am looking at the above graphic, you see a continuation of that same pattern but with the Pacific moisture getting closer to the Northwest and a break in the moisture streaming into Southern California.

This graphic is about Atmospheric Rivers i.e. thick concentrated movements of water moisture. More explanation on Atmospheric Rivers can be found by clicking here or if you want more theoretical information by clicking here. The idea is that we have now concluded that moisture often moves via narrow but deep channels in the atmosphere (especially when the source of the moisture is over water) rather than being very spread out. This raises the potential for extreme precipitation events. You can convert this graphic into a flexible forecasting tool by clicking here. One can obtain views of different geographical areas by clicking here.

And Now the Day One and Two CONUS Forecasts

60 Hour Forecast Animation

Here is a national animation of weather fronts and precipitation forecasts with four 6-hour projections of the conditions that will apply covering the next 24 hours and a second day of two 12-hour projections the second of which is the forecast for 48 hours out and to the extent it applies for 12 hours, this animation is intended to provide coverage out to 60 hours. Beyond 60 hours, additional maps are available at links provided below. The explanation for the coding used in these maps, i.e. the full legend, can be found here although it includes some symbols that are no longer shown in the graphic because they are implemented by color coding.

You can enlarge the below daily (days 3 – 7) weather maps for CONUS by clicking on Day 3 or Day 4 or Day 5 or Day 6 or Day 7. These maps auto-update so whenever you click on them they will be forecast maps for the number of days in the future shown. You can see the next East Coast Nor’easter.

What is Behind the Forecasts? Let us try to understand what NOAA is looking at when they issue these forecasts.

Below is a graphic which highlights the forecasted surface Highs and the Lows re air pressure on Day 7. The Day 3 forecast can be found here. the Day 6 Forecast can be found here. Actually all the small graphics below can be clicked on to enlarge them.

When I look at this Day 7 forecast, there is a weak Low over Kamchatka with surface central pressure of 1004 hPa. To the east there is a weak low half in the Alaskan Gulf and half over Southern Alaska with surface central pressure of 1008 hPa. This low on Day 7 is in a position to impact The Alaskan Panhandle. There is now a large High in the Siberian Arctic with surface central pressure of 1032hPa and it really extends over to Greenland and down into the Canadian Northwest Territories where the local High is 1024 hPa. This explains the Negative AO. This week, the Pacific Subtropical High with surface central pressure of 1032 may play a role in controlling the track of storms originating in the Gulf of Alaska and tracking down off California or via the Great Basin. There is a Low with surface central pressure of 1012 hPa which either is or is forecast to be cut off from the main circulation and it on Day 7 has been able to move out to sea rather than hug the coast or be partially inland. Thus this Low has the potential to be fairly wet but there are now also more degrees of freedom re the track beyond Day 7. Inland there is a Great Plains weak Low with surface central pressure of 1000 hPa.

I provided this K – 12 write up that provides a simple explanation on the importance of semipermanent Highs and Lows and another link that discussed possible changes in the patterns of these highs and lows which could be related to a Climate Shift (cycle) in the Pacific or Global Warming. Remember this is a forecast for Day 6. It is not the current situation.

The table below showing the Day 3, Day 4, Day 5, Day 6 and Day 7 of this graphic can be useful in thinking about how the pattern of Highs and Lows is expect to move during the week.

From left to right and then down, Days 3 and 4 top row, Days 5 and 6 second row and Day 7 to the right. These are small images but you can if you want click on them and get larger images but even with the small images you can trace the evolution of the pattern. The graphics update but my commentary below does not so it is just a guide for how to read these graphics.
You can see the Pacific Trough evolving. These graphics update when NOAA updates their graphics so it will be interesting to watch the development of this potential major storm. It looks good right now and perhaps too good. Things to look for in general are the position and strength of the Aleutian Low, the Hawaiian High and any troughs especially if they extend far to the south and are over water.

Looking at the current activity of the Jet Stream.  The below graphics and the above graphics are very related.

Not all weather is controlled by the Jet Stream (which is a high altitude phenomenon) but it does play a major role in steering storm systems especially in the winter The sub-Jet Stream level intensity winds shown by the vectors in this graphic are also very important in understanding the impacts north and south of the Jet Stream which is the higher-speed part of the wind circulation and is shown in gray on this map. In some cases however a Low-Pressure System becomes separated or “cut off” from the Jet Stream. In that case it’s movements may be more difficult to predict until that disturbance is again recaptured by the Jet Stream. This usually is more significant for the lower half of CONUS with the cutoff lows being further south than the Jet Stream. Some basic information on how to interpret the impact of jet streams on weather can be found here and here.  I have not provided the ability to click to get larger images as I believe the smaller  images shown are easy to read.

Current	Day 5
We still seem to have a split Polar Jet Stream with Northern and Southern Branches. It is fairly far south.

Putting the Jet Stream into Motion and Looking Forward a Few Days Also

To see how the pattern is projected to evolve, please click here. In addition to the shaded areas which show an interpretation of the Jet Stream, one can also see the wind vectors (arrows) at the 300 Mb level.

This longer animation shows how the jet stream is crossing the Pacific and when it reaches the U.S. West Coast is going every which way.

Click here to gain access to a very flexible computer graphic. You can adjust what is being displayed by clicking on “earth” adjusting the parameters and then clicking again on “earth” to remove the menu. Right now it is set up to show the 500 hPa wind patterns which is the main way of looking at synoptic weather patterns. This amazing graphic covers North and South America. It could be included in the Worldwide weather forecast section of this report but it is useful here re understanding the wind circulation patterns.

500 MB Mid-Atmosphere View

The map below is the mid-atmosphere 7-Day chart rather than the surface highs and lows and weather features. In some cases it provides a clearer less confusing picture as it shows only the major pressure gradients. This graphic auto-updates so when you look at it you will see NOAA’s latest thinking. The speed at which these troughs and ridges travel across the nation will determine the timing of weather impacts. This graphic auto-updates I think every six hours and it changes a lot. Because “Thickness Lines” are shown by those green lines on this graphic, it is a good place to define “Thickness” and its uses. The 540 Level generally signifies equal chances for snow at sea level locations. Thickness of 600 or more suggests very intensely heat and fire danger. Sometimes Meteorologists work with the 500 mb heights which provide somewhat similar readings to the “Thickness” lines but IMO provide slightly less specific information. Thinking about clockwise movements around High Pressure Systems and counter- clockwise movements around Low Pressure Systems provides a lot of information.

Here is the whole suite of similar maps for Days 3, 4, 5, 6 and repeated for Day 7. 

Notice you can see the fairly rapid movement of the pattern crossing CONUS. You can see the next Pacific trough entering the West Coast but perhaps dissipating. The models are not in agreement at this point re the exact track on Day 7 and beyond.

Here is the seven-day cumulative precipitation forecast. More information is available here.

Four – Week Outlook: Looking Beyond Days 1 to 5, What is the Forecast for the Following Three + Weeks?

I use “EC” in my discussions although NOAA sometimes uses “EC” (Equal Chances) and sometimes uses “N” (Normal) to pretty much indicate the same thing although “N” may be more definitive.

First – Temperature

6 – 10 Day Temperature Outlook issued today (Note the NOAA Level of Confidence in the Forecast Released on March 12 was 4 out of 5

8 – 14 Day Temperature Outlook issued today (Note the NOAA Level of Confidence in the Forecast Released on March 12, 2018 was 4 out of 5).

Looking further out.

Now – Precipitation

6 – 10 Day Precipitation Outlook Issued Today (Note the NOAA Level of Confidence in the Forecast Released on March 12, 2018 was 4 out of 5)

8 – 14 Day Precipitation Outlook Issued Today (Note the NOAA Level of Confidence in the Forecast Released on March 12, 2018 was 4 out of 5)

Looking further out.

Here is the 6 – 14 Day NOAA discussion released today March 12, 2018 and the Week 3/4 (assumption rich) discussion released Friday March 9, 2018

6-10 DAY OUTLOOK FOR MAR 18 – 22 2018  

TODAY’S ENSEMBLE MEAN SOLUTIONS ARE IN GOOD AGREEMENT ON THE EXPECTED 500-HPA FLOW PATTERN OVER THE FORECAST DOMAIN. ALL OF TODAY’S SOLUTIONS FORECAST A STRONG RIDGE SOUTHEAST OF THE ALEUTIANS, A TROUGH NEAR THE WEST COAST OF THE CONUS, AND RIDGING OVER EASTERN PORTIONS OF THE SOUTHERN TIER OF THE U.S. TODAY’S MANUAL 500-HPA BLEND DEPICTS POSITIVE HEIGHT ANOMALIES OVER THE ALEUTIANS AND PARTS OF THE SOUTHEASTERN U.S., WITH NEGATIVE HEIGHT ANOMALIES ELSEWHERE.

RIDGING FORECAST OVER THE ALEUTIANS FAVORS ABOVE NORMAL TEMPERATURES FOR THE ALEUTIANS AND PARTS OF WESTERN MAINLAND ALASKA, WITH NEAR TO BELOW NORMAL 

TEMPERATURES FAVORED ELSEWHERE IN THE STATE. PERSISTENT TROUGHING PREDICTED THROUGHOUT THE WESTERN CONUS STRONGLY FAVORS BELOW NORMAL TEMPERATURES FOR THE WESTERN AND NORTH-CENTRAL CONUS. FORECAST TROUGHS ALSO ENHANCE CHANCES OF BELOW NORMAL TEMPERATURES IN THE NORTHEAST. A PREDICTED SOUTHEAST RIDGE INCREASES THE LIKELIHOOD OF ABOVE NORMAL TEMPERATURES FROM TEXAS EASTWARD TO THE SOUTHEAST COAST.

STRONG WESTERLY ONSHORE FLOW PREDICTED FOR ALASKA FAVORS ABOVE NORMAL PRECIPITATION FOR THE ENTIRE STATE. STORM SYSTEMS FORECAST TO COME ONSHORE IN THE WESTERN CONUS INCREASE THE LIKELIHOOD OF ABOVE NORMAL PRECIPITATION FOR MUCH OF THE WESTERN CONUS. SEVERAL STORM SYSTEMS ARE EXPECTED TO TRAVEL ACROSS THE NORTHERN CONUS AND INTENSIFY IN THE EASTERN U.S., WITH PRECIPITATION FOCUSING ALONG A STATIONARY FRONT PREDICTED BETWEEN THE SOUTHEAST RIDGE AND THE TROUGHING TO THE WEST. THIS FAVORS ABOVE NORMAL PRECIPITATION THROUGHOUT THE EASTERN U.S., ESPECIALLY OVER THE TENNESSEE VALLEY. NEAR TO BELOW NORMAL PRECIPITATION IS FAVORED FOR PORTIONS OF THE SOUTH CENTRAL CONUS, CONSISTENT WITH DYNAMICAL MODEL GUIDANCE. THE SOUTHEAST RIDGE IS EXPECTED TO LIMIT PRECIPITATION OVER THE FLORIDA PENINSULA, FAVORING BELOW NORMAL PRECIPITATION THERE.

FORECAST CONFIDENCE FOR THE 6-10 DAY PERIOD: ABOVE AVERAGE, 4 OUT OF 5, DUE TO GOOD MODEL AND TOOL AGREEMENT. 

8-14 DAY OUTLOOK FOR MAR 20 – 26 2018 

BY THE WEEK-2 PERIOD, THE LARGE-SCALE PATTERN OVER THE FORECAST DOMAIN IS EXPECTED TO BE VERY SIMILAR TO THAT FORECAST IN THE 6-10 DAY PERIOD, EXCEPT SLIGHTLY LESS AMPLIFIED. THE WEEK-2 TEMPERATURE PROBABILITY FORECAST IS VERY SIMILAR TO THE 6-10 DAY FORECAST, WITH A COUPLE SMALL EXCEPTIONS. 500-HPA HEIGHTS ARE EXPECTED TO FALL SLIGHTLY BY THE WEEK-2 PERIOD OVER PARTS OF THE GREAT LAKES REGION, INCREASING CHANCES FOR BELOW NORMAL TEMPERATURES FOR ALL OF THE GREAT LAKES REGION. THE SOUTHEAST RIDGE IS FORECAST TO BECOME SLIGHTLY SUPPRESSED, DECREASING PROBABILITIES OF ABOVE NORMAL TEMPERATURES FOR PARTS OF THE SOUTHERN CONUS, AND SHIFTING THEM SLIGHTLY SOUTHWARD. THE WEEK-2 

PRECIPITATION PROBABILITY FORECAST IS ALSO VERY SIMILAR TO THE 6-10 DAY FORECAST.

FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD: ABOVE AVERAGE, 4 OUT OF 5, DUE TO GOOD MODEL AND TOOL AGREEMENT. 

THE NEXT SET OF LONG-LEAD MONTHLY AND SEASONAL OUTLOOKS WILL BE RELEASED ON MARCH 15.  

Week 3-4 Forecast Discussion Valid Sat Mar 24 2018-Fri Apr 06 2018

The Week 3-4 this week is issued against the background of La Nina and an MJO event that continues to propagate eastward with a larger-than-forecast amplitude. Additionally, a high amplitude -AO/NAO event over the past one to two weeks is forecast to be nearer to normal heading into the Week 3-4 period. The recent OLR anomaly maps indicate a large-scale convective structure over the deep tropics that is consistent with La Nina, while the recent evolution of tropical 200-hPa velocity potential anomalies is consistent with the active MJO phase approaching the Maritime Continent, ostensibly resulting in constructive interference with the background ENSO state. Given the observed presence of anomalous tropical forcing mechanisms, statistical guidance that incorporates ENSO and MJO, along with long-term trends, is weighted heavily in both the temperature and precipitation outlooks.

The dynamical model guidance varies quite a bit, with a very cold North America predicted by the ECMWF, and the CFS and JMA favoring a warmer solution across much of the central and eastern CONUS. The various models from the SubX suite tend to favor the ECMWF solution, but with large differences among them as well. Most dynamical models favor the continuation of positive height anomalies near and northwest of the Aleutians, with negative height anomalies stretching west-east over the Pacific near 30N. The ECMWF solution, however, reintensifies a -NAO signal over the northwest Atlantic, and its upper-level height pattern over North America appears well-teleconnected to that downstream center of action. The CFS maintains low-amplitude anomalous ridging over the east-central CONUS, more consistent with teleconnections upon the upstream centers of action and MJO forcing. Over Alaska the dynamical blend favors high probabilities of below-normal temperatures; in the official outlook these are tempered by long-term trends (including those related to sea ice extent adjacent to the western and northern Alaska).

The temperature outlook consists of a subjective blend of the correlation-weighted, calibrated dynamical model blend and the multiple linear regression tool that inputs ENSO, MJO, and long-term trend time series. These forecast inputs are the most skillful over the past couple of years. These forecasts conflict over parts of the West and Northeast, where areas of EC are depicted. Given the manifestation of ENSO and MJO in important tropical variables (OLR and VP), it is not obvious that the dynamical guidance should be preferred. An objective blend of statistical and dynamical inputs is under development, and until that is ready a prudent course of action is to consider both on nearly equal footing given recent skill evaluations.

The aforementioned approach to the temperature outlook is also taken for the precipitation outlook. The various dynamical guidance as well as statistical guidance are in good agreement on above-median rainfall over parts of the Mississippi and Tennessee River Valleys, and to a lesser extent, the northern High Plains. Likewise there is good agreement for increased chances of below-median precipitation over the southwestern CONUS. Over the Northwest and northern California equal chances is depicted due to uncertainty with respect the longitudinal position of the mean trough axis; a slight westward (eastward) shift would favor above-(below-)median precipitation. Below-median precipitation is favored over parts of the Great Lakes, Northeast, and Eastern Seaboard. Dynamical model consensus is the strongest over the Northeast and eastern Great Lakes, while the statistical guidance is more robust over the Southeast coast.

Sea surface temperatures are slightly above normal for most of the Hawaiian Islands, although below-normal SSTs are showing up just to the northeast. Anomalous troughing is favored to the west of the islands, supporting anomalous southerly flow. This troughing to the west also supports relatively high probabilities for above-normal precipitation across the entire island chain.

Some Indices of Possible Interest:

Phases of the PNA pattern (N.C. State)  PNA Negative is on the right. The Pacific Hawaiian High is out to sea allowing the Pacific Troughs that we have been having and also Gulf Coast moisture entering CONUS. .

NCEP-NEFS	CFSv2

Analogs to the Outlook.

Now let us take a detailed look at the “Analogs” which NOAA provides related to the 5 day period centered on 3 days ago and the 7 day period centered on 4 days ago. “Analog” means that the weather pattern then resembles the recent weather pattern and was used in some way to predict the 6 – 14 day Outlook.

Here are today’s analogs in chronological order although this information is also available with the analog dates listed by the level of correlation. I find the chronological order easier for me to work with. There is a second set of analogs associated with the Outlook but I have not been regularly analyzing this second set of information. The first set which is what I am using today applies to the 5 and 7 day observed pattern prior to today. The second set, which I am not using, relates to the correlation of the forecasted outlook 6 – 10 days out with similar patterns that have occurred in the past during the dates covered by the 6 – 10 Day Outlook. The second set of analogs may also be useful information but they put the first set of analogs in the discussion with the second set available by a link so I am assuming that the first set of analogs is the most meaningful and I find it so.

(t) = a month where the Ocean Cycle Index has just changed or does change the following month.

The spread among the analogs from February 21 to March 26 is 33 days which is wider than last week. I have not calculated the centroid of this distribution which would be the better way to look at things but the midpoint, which is a lot easier to calculate, and fairly accurate if the dates are reasonably evenly distributed, is about March 10. These analogs are centered on 3 days and 4 days ago (March 8 or March 9). So the analogs could be considered to be in sync with respect to weather that we would normally be getting right now. For more information on Analogs see discussion in the GEI Weather Page Glossary.  For sure it is a rough measure as there are so many historical patterns but not enough to be a perfect match with current conditions. I use it mainly to see how our current conditions match against somewhat similar patterns and the ocean phases that prevailed during those prior patterns. If everything lines up I have my own measure of confidence in the NOAA forecast. Similar initial conditions should lead to similar weather. I am a mathematician so that is how I think about models.

Including the duplicates, there are two Neutral Analogs, two La Nina analogs and six El Nino Analogs. The phases of the analogs this week correlate best with McCabe C and McCabe D which are opposites but both have some sort of western drought. The are both associated with AMO+. The presence of so many El Nino analogs and the correlation with McCabe C and McCabe D gives me a bit of a pause re the 6 – 14 Day Forecast but I do see that Pacific Storm lurking out there and it will go somewhere.

The seminal work on the impact of the PDO and AMO on U.S. climate can be found here. Water Planners might usefully pay attention to the low-frequency cycles such as the AMO and the PDO as the media tends to focus on the current and short-term forecasts to the exclusion of what we can reasonably anticipate over multi-decadal periods of time. One of the major reasons that I write this weather and climate column is to encourage a more long-term and World view of weather.

In color	Black and White same graphics

You may have to squint but the drought probabilities are shown on the map and also indicated by the color coding with shades of red indicating higher than 25% of the years are drought years (25% or less of average precipitation for that area) and shades of blue indicating less than 25% of the years are drought years. Thus drought is defined as the condition that occurs 25% of the time and this ties in nicely with each of the four pairs of two phases of the AMO and PDO.

Historical Anomaly Analysis

When I see the same dates showing up often I find it interesting to consult this list.

A Useful Read

Some might find this analysis which you need to click to read interesting as the organization which prepares it focuses on the Pacific Ocean and looks at things from a very detailed perspective and their analysis provides a lot of information on the history and evolution of ENSO events.

Recent CONUS Weather

This is provided mainly to see the pattern in the weather that has occurred recently.

And the 30 Days ending  February 24, 2018	And the 30 Days ending March 3, 2018
Some major changes with a bit of drought relief in New Mexico a lot of precipitation from NE Texas to New England. The Temperature Anomalies are also very different with a larger North Central cool anomaly and the elimination of the South Central cool anomaly among other things.	The precipitation picture is not much changed but the anomalies are somewhat less amplified. The temperature pattern is more changed with the cold anomaly in the West much expanded except for Texas which is not an extension of the Eastern warm anomaly.
Remember, these maps are a 30 average so the most distant seven days are removed and the most recent seven days are added.

The U.S. Drought Monitor is a comprehensive way of understand the drought situation for the U.S. If is issued every Thursday and reflects the conditions as of the prior Tuesday. The drought monitor is not just based on precipitation but the condition of the land so it generally reflects more than a month’s precipitation and temperature and wind.

Because of the current drought conditions we now publish a Drought Update on Thursdays. You can access the most recent report here.

This is the summary from last Thursday Report.

Reference Forecasts Full Month and Three Months.

Below are the Temperature followed by the Precipitation Outlooks for the month and three months shown in the Legend. These maps are issued on the Third Thursday of the Month. The maps for the following month (but not the three-month maps) are updated on the last day of the month. The 6 – 10 day and 8 – 14 Day update daily and the Week 3/4 Map Updates every Friday so usually these are more up to date. Also the three shorter-term maps will generally cover a slightly different time period since they update daily as the month progresses. But these reference maps are sometimes useful if one wants to understand how the current month was originally forecast to play out.

	To the left is the full month Temperature Outlook. To the right is the three-month Temperature outlook
	To the left is the full month Precipitation outlook. To the right is the three-month Precipitation outlook.

B. Beyond Alaska and CONUS Let’s Look at the World which of course also includes Alaska and CONUS

It is Useful to Understand the Semipermanent Pattern that Control our Weather and Consider how These Change from Winter to Summer. These two graphics (click on each one to enlarge) are from a much larger set available from the Weather Channel.  They highlight the position of the Bermuda High which they are calling the Azores High in the January graphic and is often called NASH and it has a very big impact on CONUS Southeast weather and also the Southwest. You also see the north/south migration of the Pacific High which also has many names and which is extremely important for CONUS weather and it also shows the change of location of the ITCZ which I think is key to understanding the Indian Monsoon. A lot of things become much clearer when you understand these semi-permanent features some of which have cycles within the year, longer period cycles and may be impacted by Global Warming. We are now into Mid-March and should be returning to the set of positions shown below for July (and that appears to be happening at least in the Pacific).For CONUS, the seasonal repositioning of the Bermuda High and the Pacific High are very significant. Notice the Winter position of the Pacific High. It is further north than usual right now for this time of the year.

Forecast for Today (you can click on the maps to enlarge them)

Temperature.	Precipitation.
Not a lot of surprises here.	We again see the dry belt stretching from Northern Africa to Eastern Asia now including Southeast Asia. You also see a lot of precipitation off the West Coast of North America.

Additional Maps showing different weather variables can be found here.

Forecast for Day 6 (Currently Set for Day 6 but the reader can change that)

World Weather Forecast produced by the Australian Bureau of Meteorology. Unfortunately I do not know how to extract the control panel and embed it into my report so that you could use the tool within my report. But if you visit it Click Here and you will be able to use the tool to view temperature or many other things for THE WORLD. It can forecast out for a week. Pretty cool. Return to this report by using the “Back Arrow” usually found top left corner of your screen to the left of the URL Box. It may require hitting it a few times depending on how deep you are into the BOM tool. Below are the current worldwide precipitation and temperature forecasts for six days out. They will auto-update and be current for Day 6 whenever you view them. If you want the forecast for a different day Click Here

And now we have experimental forecasts from the U.S. NAEFS Model. They are difficult to read without first enlarging them.

Looking Out a Few Months

Here is the precipitation forecast from Queensland Australia:

It is kind of amazing that you can make a worldwide forecast based on just one parameter the SOI and changes in the SOI. Western CONUS looks fairly wet, Australia is dry. 

JAMSTEC Forecasts

One can always find the latest JAMSTEC maps by clicking this link. You will find additional maps that I do not general cover in my monthly Update Report. Remember if you leave this page to visit links provided in this article, you can return by hitting your “Back Arrow”, usually top left corner of your screen just to the left of the URL box.

Sea Surface Temperature (SST) Departures from Normal for this Time of the Year i.e. Anomalies

My focus here is sea surface temperature anomalies as they are one of the two largest factors determining weather around the World. If we want to have a good feel for future weather we need to look at the oceans as our weather mostly comes from oceans and we need to look at

• Surface temperature anomalies (weather develops from the ocean surface and
• The changes in the temperature anomalies since that may provide clues as to how the surface anomalies will change based on the current trend of changes. This is not that easy to do since the oceans are deep, there are many currents, winds have an impact etc. Two ways that are available to use are to look at the change in the situation today compared to the average over a period of time and NOAA also produces a graphic of monthly changes. I use both. The first set of graphics is simply looking at the average compared to today and that is below.

Three Month Average Anomaly	Current Anomaly
La Nina shows up	The cool anomaly is displaced to the west a bit but not as much as a few days ago.

And when we look in more detail at the current Sea Surface anomalies below, we see a lot of them not just along the Equator related to ENSO.

First the categorization of the current daily SST anomalies.
Mediterranean, Black Sea and Caspian Sea	Western Pacific	West of North America	North and East of North America	North Atlantic
Slightly warm eastern Mediterranean and also Caspian Sea	Fairly warm along coast of Asia	Slight Warm Southeast Gulf of Anadyr	Warm off Nova Scotia Slightly Warm Gulf of Mexico	Fairly Neutral but warm north of Scandinavia also north of British Isles.
Equator	The La Nina cool anomaly is displaced to the west and in places has moved away from the Equator and there are many gaps.
Africa	West of Australia	North, South and East of Australia	West of South America	East of South America
Cool west of Angola Cool East of South Africa extending south of Madagascar Warm south of Africa	cool but way offshore	Warm southeast all the way to and beyond New Zealand	Cool but now mostly offshore Warm anomaly way offshore at 40S.	Warm off 40S

Then we look at the change in the anomalies.  The SST  anomaly is sort of like the first derivative and the change in the anomaly is somewhat like a second derivative. It tells us if the anomaly is becoming more or less intense.

Here it gets a little tricky as for this graphic red does not mean a warm anomaly but a warming of the anomaly which could mean more warm or less cool and blue does not mean cool but more cool or less warm.
Mediterranean, Black Sea and Caspian Sea	Western North Pacific	West of North America	East of North America	North Atlantic
Mediterranean Neutral. Black Sea and Caspian Sea cooling	Slight cooling between China and Japan	Warming in Bering Sea Cooling west of CONUS Warming east of Dateline at Midlatitudes The changes are definitely in the direction of a more negative PDO. .	Mixed warming and cooling off Nova Scotia and Newfoundland Warming Gulf of Mexico	Warming south of Greenland Cooling around British Isles Slight warming west of North Africa.  .
Equator	Eastern Pacific consistent warming to the east.  Warming west of Maritime Continent and slight cooling west of Africa.
Africa	West of Australia	North, South and East of Australia	West of South America	East of South America
Cooling off Gulf of Guinea and further south. Warming Southwest of Africa. Warming Arabian Sea Cooling off Mozambique to and beyond Madagascar	Cooling	Warming Northeast then extending past New Zealand all the way to Chile. Cooling south	Neutral except warming west of Ecuador as previously mentioned Warming off 30S Cooling offshore at 50S	Slight warming in far west Caribbean Warming off 30S Warming off 50S

This may be a good time to show the recent values to the indices most commonly used to describe the overall spacial pattern of temperatures in the (Northern Hemisphere) Pacific and the (Northern Hemisphere) Atlantic and the Dipole Pattern in the Indian Ocean. Notice the change in the PDO in July of 2017 and the stability of the AMO index.

Switching gears, below is an analysis of projected tropical hazards and benefits over an approximately two-week period.

 * Moderate Confidence that the indicated anomaly will be in the upper or lower third of the historical range as indicated in the Legend. ** High Confidence that the indicated anomaly will be in the upper or lower third of the historical range as indicated in the Legend.

C. Progress of ENSO

A major driver of weather is Surface Ocean Temperatures. Evaporation only occurs from the Surface of Water. So we are very interested in the temperatures of water especially when these temperatures deviate from seasonal norms thus creating an anomaly. The geographical distribution of the anomalies is very important. To a substantial extent, the temperature anomalies along the Equator have disproportionate impact on weather so we study them intensely and that is what the ENSO (El Nino – Southern Oscillation) cycle is all about. Subsurface water can be thought of as the future surface temperatures. They may have only indirect impacts on current weather but they have major impacts on future weather by changing the temperature of the water surface. Winds and Convection (evaporation forming clouds) is weather and is a result of the Phases of ENSO and also a feedback loop that perpetuates the current Phase of ENSO or changes it. That is why we monitor winds and convection along or near the Equator especially the Equator in the Eastern Pacific.

Starting with Surface Conditions.

TAO/TRITON GRAPHIC (a good way of viewing data related to the part of the Equator and the waters close to the Equator in the Eastern Pacific where we monitor to determining the current phase of ENSO. It is probably not necessary in order to follow the discussion below, but here is a link to TAO/TRITON terminology.

And here is the current version of the TAO/TRITON Graphic. The top part shows the actual temperatures, the bottom part shows the anomalies i.e. the deviation from normal.

Location Bar for Nino 3.4 Area Above and Below

The below table only looks at the Equator (and starting this week I am including large anomalies just off the Equator also) and shows the extent of anomalies along the Equator. The ONI Measurement Area is the 50 degrees of Longitude between 170W and 120W and extends 5 degrees of Latitude North and South of the Equator so the above table is just a guide and a way of tracking the changes. The top rows show El Nino anomalies. The two rows just below that break point contribute to ENSO Neutral.

My Calculation of the Nino 3.4 Index

I calculate the current value of the Nino 3.4 Index each Monday using a method that I have devised. To refine my calculation, I have divided the 170W to 120W Nino 3.4 measuring area into five subregions (which I have designated from west to east as A through E) with a location bar shown under the TAO/TRITON Graphic). I use a rough estimation approach to integrate what I see below and record that in the table I have constructed. Then I take the average of the anomalies I estimated for each of the five subregions.

So as of Monday March 12 in the afternoon working from the March 11 TAO/TRITON report [Although the TAO/TRITON Graphic appears to update once a day, in reality it updates more frequently.], this is what I calculated.

Calculation of Nino 3.4 from TAO/TRITON Graphic

My estimate of the daily Nino 3.4 SST anomaly tonight is -0.7 which is a La Nina value. NOAA has reported the weekly Nino 3.4 to be less cool at -0.7 which is still a La Nina value and the same as my estimate. Nino 4 is reported to be -0.1 this week. Nino 3 is more cool at -0.9. Nino 1 + 2 which extends from the Equator south rather than being centered on the Equator is reported much cooler at -0.4. It was up there close to -3.0 at one time so this index has been declining as an anomaly (rising) quite a bit and also fluctuating quite a bit which is not surprising as it is the area most impacted by the Upwelling off the coast. So it is an indication of the interaction between surface water and rising cool water. Thus it is subject to larger changes. I am only showing the currently issued version of the NINO SST Index Table as the prior values are shown in the small graphics on the right with this graphic. The same data in graphic form but going back a couple of more years can be found here.  The full table of values can be found here.

This graphic brings the Nino 3.4 up to date and is easy to read.

This overlaps with the next topic but I will show it here.

The discussion in this slide says it better than I could. One might compare the current reading to Oct/Nov 2017. The anomaly had returned to zero then reversed for a month and then returned to zero and now has gone positive. In retrospect it was the Kelvin Wave Activity the Upwelling Phase and the MJO which caused the brief reversal of the warming trend.

A side by side comparison can be useful

Comparison Week Probably Third Week of December 2017	Current Week

Sea Surface Temperature and Anomalies

It is the ocean surface that interacts with the atmosphere and causes convection and also the warming and cooling of the atmosphere. So we are interested in the actual ocean surface temperatures and the departure from seasonal normal temperatures which is called “departures” or “anomalies”. Since warm water facilitates evaporation which results in cloud convection, the pattern of SST anomalies suggests how the weather pattern east of the anomalies will be different than normal.

A major advantage of the Hovmoeller method of displaying information is that it shows the history so I do not need to show a sequence of snapshots of the conditions at different points in time. This Hovmoeller provides a good way to visually see the evolution of this ENSO event. I have decided to use the prettied-up version that comes out on Mondays rather that the version that auto-updates daily because the SST Departures on the Equator do not change rapidly and the prettied-up version is so much easier to read. The bottom of the Hovmoeller shows the current readings. Remember the +5, -5 degree strip around the Equator that is being reported in this graphic. So it is the surface but not just the Equator.

This next graphic is more focused on the Equator and looks down to 300 meters rather than just being the surface.

We have two phases of a Kelvin Wave in operation. There is an up-welling phase at 120W and a down-welling phase at 175W. The up-welling phase is impacting areas east of the Nino 3.4 Measurement Area. The down-welling phase will impact the Nino 3.4 readings after a lag.

 Let us look in more detail at the Equatorial Water Temperatures.

We are now going to look at a three-dimensional view of the Equator and move from the surface view and an average of the subsurface heat content to a more detailed view from the surface down This graphic provides both a summary perspective and a history (small images on the right).

.

Anomalies are strange. You can not really tell for sure if the blue area is colder or warmer than the water above or below. All you know is that it is cooler than usual for this time of the year. A later graphic will provide more information. Aside from buoyancy the currents tend to bring water from that depth up to the surface mostly farther east.

Now for a more detailed look. Below is the pair of graphics that I regularly provide. The date shown is the midpoint of a five-day period with that date as the center of the five-day period. The bottom graphic shows the absolute values, the upper graphic shows anomalies compared to what one might expect at this time of the year in the various areas both 130E to 90W Longitude and from the surface down to 450 meters. At different times I have discussed the difference between the actual values and the deviation of the actual values from what is defined as current climatology (which adjusts every ten years except along the Equator where it is adjusted every five years) and how both measures are useful for other purposes.

There is cold water from 170W to 130W and it is mostly warmer further east. At the west end of the-1C cool anomaly is now about 75 meters deep (it was once over 200 meters deep). We now have warm water with a maximum anomaly of +4C developing west of the Dateline and crossing the Dateline at depth to 140W, possibly the result of another Downwelling Kelvin Wave. La Nina’s days are numbered and it does not have much longer to go.

The 28C Isotherm is just west of the Dateline, the 27C Isotherm is at the Dateline, the 25C Isotherm is now east of 150W and in places at the surface further east. The 20C Isotherm no longer is reaching the surface. It had been fairly stable for a number of weeks but the Indo-Pacific Warm Pool is gradually moving East.

The flattening of the Isotherm Pattern is an indication of ENSO Neutral just as the steepening of the pattern indicates La Nina or El Nino depending on where the slope shows the warm or cool pool to be. That flattening has occurred and we have gone to a Weak La Nina thermocline.

Tracking the change.

And now let us look at the atmosphere.

This graphic shows the Low-Level Wind Anomalies near the Equator. The 850 hPa level is above the surface but close to the surface.	And now the Outgoing Long-wave Radiation (OLR) Anomalies which tell us where convection has been taking place. The bottom of a Hovmoeller graphic shows the most recent readings.
Reds and browns would be suppressed easterlies or enhanced westerlies and are typical of El Nino. You see the recent change in the pattern.	We see the change in the pattern of suppressed OLR as the MJO moves through and the La Nina declines.

And Now the Air Pressure to Confirm that the Atmosphere is Reacting to the Sea Surface Temperature Pattern. The most Common way to do that is to use an Index called the SOI.

This index provides an easy way to assess the location of and the relative strength of the Convection (Low Pressure) and the Subsidence (High Pressure) near the Equator. Experience shows that the extent to which the Atmospheric Air Pressure at Tahiti exceeds the Atmospheric Pressure at Darwin Australia when normalized is substantially correlated with the Precipitation Pattern of the entire World. At this point there seems to be no need to show the daily preliminary values of the SOI but we can work with the 30 day and 90 day values.

Current SOI Readings

SOI = 10 X [ Pdiff – Pdiffav ]/ SD(Pdiff) where Pdiff = (average Tahiti MSLP for the month) – (average Darwin MSLP for the month), Pdiffav = long term average of Pdiff for the month in question, and SD(Pdiff) = long term standard deviation of Pdiff for the month in question. So really it is comparing the extent to which Tahiti is more cloudy than Darwin, Australia. During El Nino we expect Darwin Australia to have lower air pressure and more convection than Tahiti (Negative SOI especially lower than -7 correlates with El Nino Conditions). During La Nina we expect the Warm Pool to be further east resulting in Positive SOI values greater than +7).

To some extent it is the change in the SOI that is of most importance. The MJO or Madden Julian Oscillation is an important factor in regulating the SOI and Ocean Equatorial Kelvin Waves and other tropical weather characteristics. More information on the MJO can be found here. Here is another good resource.

Forecasting the Evolution of ENSO

The CFS.v2 is not the only forecast tool used by NOAA. The CPC/IRI Analysis which is produced out of The International Research Institute (IRI) for Climate and Society at Columbia University is also very important to NOAA.

Here is the most recent update. It is quite dramatic. We should have a new update very soon.

This is the discussion

CPC/IRI ENSO Update, Published: March 08, 2018

El Niño/Southern Oscillation (ENSO) Diagnostic Discussion issued jointly by the Climate Prediction Center/NCEP/NWS and the International Research Institute for Climate and Society

ENSO Alert System Status: La Niña Advisory

Synopsis: A transition from La Niña to ENSO-neutral is most likely (~55% chance) during the March-May season, with neutral conditions likely to continue into the second half of the year.

During February 2018, La Niña weakened, but was still reflected by below-average sea surface temperatures (SSTs) in the east-central equatorial Pacific Ocean (Fig. 1). The latest weekly index values were -0.8°C and -0.6°C in the Niño-3.4 and Niño-3 regions, respectively, and were near zero in the surrounding Niño.4 and Niño1+2 regions. While negative anomalies were maintained near the surface, the sub-surface temperature anomalies (averaged across 180°-100°W) warmed to near zero. This warming was due to the eastward propagation of above-average temperatures along the thermocline in association with a downwelling equatorial oceanic Kelvin wave  The atmospheric anomalies typical of La Niña weakened considerably across the tropical Pacific.  Convection was suppressed near Indonesia and was only weakly enhanced over the far western Pacific. Also, low-level wind anomalies were westerly over the western and central Pacific, while upper-level winds remained anomalously westerly over the eastern Pacific.  Overall, the ocean and atmosphere system suggests La Niña is weakening.

Most models in the IRI/CPC plume predict La Niña will decay and return to ENSO-neutral during the Northern Hemisphere spring 2018 . The forecast consensus similarly favors a transition during the spring, with a continuation of ENSO-neutral conditions through the summer.  In summary, a transition from La Niña to ENSO-neutral is most likely (~55% chance) during the March-May season, with neutral conditions likely to continue into the second half of the year (click CPC/IRI consensus forecast for the chance of each outcome for each 3-month period).

This discussion is a consolidated effort of the National Oceanic and Atmospheric Administration (NOAA), NOAA’s National Weather Service, and their funded institutions. Oceanic and atmospheric conditions are updated weekly on the Climate Prediction Center web site (El Niño/La Niña Current Conditions and Expert Discussions). Forecasts are also updated monthly in the Forecast Forum section of CPC’s Climate Diagnostics Bulletin. Additional perspectives and analysis are also available in an ENSO blog.

The next ENSO Diagnostics Discussion is scheduled for 12 April 2018.

The above is based on looking at a variety of models and other information but we should not forget that NOAA has their own model.

Here is another view of the same model with on the right the forecasts of the sea surface temperatures that result from the forecast. It is the model as of January 14 and is frozen i.e. will not update.

And here is what is called the plume of a varied of forecast models. We expect to have an updated version of this graphic next week.

Forecasts from Other Meteorological Agencies.

Here is the JAMSTEC Model Forecast

And the short discussion. (we will have an updated map and perhaps an updated discussion next Monday.

Feb. 19, 2018  Prediction from 1st Feb., 2018

ENSO forecast:

The La Niña-like condition will disappear by late spring. Then the tropical Pacific will return to a normal state by summer.

Indian Ocean forecast:

A normal state in the tropical Indian Ocean will persist until summer. Then we expect evolution of a moderately positive Indian Ocean Dipole in fall. However, there is a large uncertainty in the prediction at present because of the large spread in the prediction plumes of the dipole mode index.

Atlantic Ocean forecast:

The Atlantic Niño and the Benguela Niño appear to develop in 2018. [Editor’s Note: We had noticed the strange temperature pattern along the Equator in the Atlantic and will research this further]

Regional forecast:

On a seasonal scale, most part of the Eurasian Continent will experience a warmer-than-normal condition except for western Europe. Northern/eastern U.S., southern Canada, central America, northern Brazil, Peru, Ecuador, Indochina, western, central and southern Africa, and northern Australia will experience a colder-than-normal condition in boreal spring.

As regards to the seasonally averaged rainfall, a wetter-than-normal condition is predicted for the Philippines, Indochina, central and southern Africa, Mexico, Ecuador, and northeastern Brazil during boreal spring, whereas most parts of Indonesia, southern China, Korea, East Africa, eastern U.S, and northern Brazil will experience a drier condition during boreal spring.

Most part of Japan will experience somewhat warmer-than-normal and drier-than-normal conditions in spring.

Here is the Nino 3.4 report from the Australian BOM (it updates every two weeks)

And the ENSO Outlook Discussion Issued on March 13, 2018

La Niña ends, El Niño-Southern Oscillation returns to neutral

The 2017–18 La Niña has ended. El Niño–Southern Oscillation (ENSO) indicators have eased back to neutral levels over the past several weeks. This means the ENSO Outlook has shifted from LA NIÑA to INACTIVE.

The end of the La Niña is clear in oceanic and atmospheric indices. Sea surface temperatures have warmed steadily since December, and are now in the neutral range. Waters beneath the surface have also warmed. In the atmosphere, cloudiness near the Date Line has returned to near-average levels, and trade winds are generally near average across the equatorial Pacific. Likewise, the Southern Oscillation Index (SOI) is well within the neutral range.

All eight of the surveyed international climate models indicate equatorial Pacific sea surface temperatures are likely to continue to warm over the coming months. Only one model anticipates NINO3.4 will meet La Niña thresholds for May, and all models predict ENSO will be in a neutral phase during the southern hemisphere winter.

All eight of the surveyed international climate models indicate equatorial Pacific sea surface temperatures are likely to continue to warm over the coming months. Only one model anticipates NINO3.4 will meet La Niña thresholds for May, and all models predict ENSO will be in a neutral phase during the southern hemisphere winter.

However, model accuracy during autumn is lower than at other times of year. A neutral ENSO pattern does not necessarily signify average rainfall and temperature for Australia. Rather, it indicates a reduced chance of prolonged very wet or dry, or very hot or cold conditions, and that other climate drivers may have greater influence over the coming months.

The weak and short–lived La Niña had relatively little effect on Australian rainfall patterns over the 2017–18 summer. However, it may have kept temperatures higher than average in southern parts of the country due to weather patterns being slower moving, and further south than normal.

Indian Ocean IOD (It updates every two weeks)

Indian Ocean Dipole Outlook  Discussion Issued March 13, 2018

The Indian Ocean Dipole (IOD) is neutral. The weekly index value to 11 March was +0.23 °C. All six of the climate models surveyed by the Bureau indicate that the IOD will remain neutral into the southern hemisphere winter of 2018.

The influence of the IOD on Australian climate is weak during December to April. This is because the monsoon trough shifts south over the tropical Indian Ocean changing wind patterns, which prevents the IOD pattern from being able to form.

The IOD Forecast is indirectly related to ENSO but in a complex way. It is important to understand how and where the IOD is measured.

IOD Positive is the West Area being warmer than the East Area (with of course many adjustments/normalizations). IOD Negative is the East Area being warmer than the West Area. Notice that the Latitudinal extent of the western box is greater than that of the eastern box. This type of index is based on observing how these patterns impact weather and represent the best efforts of meteorological agencies to figure these things out. Global Warming may change the formulas probably slightly over time but it is costly and difficult to redo this sort of work because of long weather cycles.

D. Putting it all Together.

At this time it would seem that La Nina Conditions along the Equator are coming to an end. The actual impacts on Worldwide weather lag the change in conditions along the Equator so we will have impacts from this La Nina for two or three more months. But the situation for next Summer is not yet totally clear.

Forecasting Beyond Five Years.

So in terms of long-term forecasting, none of this is very difficult to figure out actually if you are looking at say a five-year or longer forecast.

The research on Ocean Cycles is fairly conclusive and widely available to those who seek it out. I have provided a lot of information on this in prior weeks and all of that information is preserved in Part II of my report in the Section on Low Frequency Cycles 3. Low Frequency Cycles such as PDO, AMO, IOBD, EATS. It includes decade by decade predictions through 2050. Predicting a particular year is far harder.

The odds of a climate shift for the Pacific taking place has significantly increased. It may be in progress. The AMO is pretty much neutral at this point (but more positive i.e. warm than I had expected) so it may need to become a bit more negative for the “McCabe A” pattern to become established. That seems to be slow to happen so I am thinking we need at least a couple more years for that to happen. Our assessment is that the standard time for Climate Shifts in the Pacific are likely to prevail and it most likely will be a gradual process with a speed up in less than five years but more than two years. The next El Nino may be the trigger and it is probably three or more years out.

E. Relevant Recent Articles and Reports

Weather in the News  

Another Nor’easter

Weather Research in the News

Fading La Nina may Cause Extreme Weather for the Southern Plains.

and this related article.

Global Warming in the News

Nothing to report.

F. Table of Contents for Page II of this Report Which Provides a lot of Background Information on Weather and Climate Science

The links below may take you directly to the set of information that you have selected but in some Internet Browsers it may first take you to the top of Page II where there is a TABLE OF CONTENTS and take a few extra seconds to get you to the specific section selected. If you do not feel like waiting, you can click a second time within the TABLE OF CONTENTS to get to the specific part of the webpage that interests you.

1. Very High Frequency (short-term) Cycles PNA, AO,NAO (but the AO and NAO may also have a low frequency component.)

2. Medium Frequency Cycles such as ENSO and IOD

3. Low Frequency Cycles such as PDO, AMO, IOBD, EATS.

4. Computer Models and Methodologies

5. Reserved for a Future Topic (Possibly Predictable Economic Impacts)

G. Table of Contents of Contents for Page III of this Report – Global Warming Which Some Call Climate Change.

The links below may take you directly to the set of information that you have selected but in some Internet Browsers it may first take you to the top of Page III where there is a TABLE OF CONTENTS and take a few extra seconds to get you to the specific section selected. If you do not feel like waiting, you can click a second time within the TABLE OF CONTENTS to get to the specific part of the webpage that interests you.

1. Introduction

2. Climate Impacts of Global Warming

3. Economic Impacts of Global Warming

4. Reports from Around the World on Impacts of Global Warming

H. Useful Background Information

The current conditions are measured by determining the deviation of actual sea surface temperatures from seasonal norms (adjusted for Global Warming) in certain parts of the Equatorial Pacific. The below diagram shows those areas where measurements are taken.

NOAA focuses on a combined area which is all of Region Nino 3 and part of Region Nino 4 and it is called Nino 3.4. They focus on that area as they believe it provides the best correlation with future weather for the U.S. primarily the Continental U.S. not including Alaska which is abbreviated as CONUS. The historical approach of measurement of the impact of the sea surface temperature pattern on the atmosphere is called the Southern Oscillation Index (SOI) which is the difference between the atmospheric pressure at Tahiti as compared to Darwin Australia. It was convenient to do this as weather stations already existed at those two locations and it is easier to have weather stations on land than at sea. It has proven to be quite a good measure. The best information on the SOI is produced by Queensland Australia and that information can be found here. SOI is based on Atmospheric pressure as a surrogate for Convection and Subsidence. Another approach made feasible by the use of satellites is to measure precipitation over the areas of interest and this is called the El Nino – Southern Oscillation (ENSO) Precipitation Index (ESPI). We covered that in a weekly Weather and Climate Report which can be found here. Our conclusion was that ESPI did not differentiate well between La Nina and Neutral. And there is now a newer measure not regularly used called the Multivariate ENSO Index (MEI). More information on MEI can be found here. The jury is still out on MEI and it it is not widely used.

The below diagram shows the usual location of the Indo-Pacific Warm Pool. When the warm water shifts to the east we have an El Nino; to the west a La Nina.

Click for Source

Interaction between the MJO and ENSO

This Table is a first attempt at trying to relate the MJO to ENSO

El Nino La Nina MJO Active Phase MJO Inactive Phase Relationship of MJO and ENSO Eastern Pacific Easterlies Western Pacific Westerlies MJO Active Phase MJO Inactive Phase

Table needs more work. Is intended to show the interactions. What is more difficult is determining cause and effect. This is a Work in Progress.

History of ENSO Events as measured by the ONI

The new SON reading of -0.8 is the fourth La Nina Reading. These would have to extend through JFM 2018 for this to be recorded as a La Nina. The chances of this are about  80:20. These are three-month averages so JFM is pretty much determined since two months are in. The key will be March. Will March be sufficiently Neutral to have the three-month average be Neutral? It would have to be slightly positive to have the average be above -0.5 and that is now unlikely but possible. Not all Meteorological Agencies Worldwide will necessarily accept this La Nina to be legitimately declared. The full history of the ONI readings can be found here. The MEI index readings can be found here.

Four Quadrant Jet Streak Model Read more here This is very useful for guessing at weather as a trough passes through. It would apply to the states that are at the apex of the trough.

If the centripetal accelerations owing to flow curvature are small, then we can use the “straight” jet streak model. The schematic figure directly below shows a straight jet streak at the base of a trough in the height field. The core of maximum winds defining the jet streak is divided into four quadrants composed of the upstream (entrance) and downstream (exit) regions and the left and right quadrants, which are defined facing downwind.

Isotachs are shaded in blue for a westerly jet streak (single large arrow). Thick red lines denote geopotential height contours. Thick black vectors represent cross-stream (transverse) ageostrophic winds with magnitudes given by arrow length. Vertical cross sections transverse to the flow in the entrance and exit regions of the jet (J) are shown in the bottom panels along A-A’ and B-B’, respectively. Convergence and divergence at the jet level are denoted by “CON” and “DIV”. “COLD” and “WARM” refer to the air masses defined by the green isentropes.

[Editor’s Note: There are many undefined words in the above so here are some brief definitions. Isotachs are lines of equal wind speed. Convergence is when there is an inflow of air which tends to force the air higher with cooling and cloud formation. Divergence is when there is an outflow of air which tends to result in air sinking which causes drying and warming, Confluence is when two streams of air come together. Diffluence is when part of a stream of air splits off.]

Here is a time sequence animation. You may have to click on them to get the animation going.

When we discuss the jet stream and for other reasons, we often discuss different layers of the atmosphere. These are expressed in terms of the atmospheric pressure above that layer. It is kind of counter-intuitive to me. The below table may help the reader translate air pressure to the usual altitude and temperature one might expect at that level of air pressure. It is just an approximation but useful.

Re the above, H8 is a frequently used abbreviation for the height of the 850 millibar level (which is intended to represent the atmosphere above the Boundary Layer most impacted by surface conditions), H7 is the 700 mb level, H5 is the 500 mb level, H3 is the 300 mb level. So if you see those abbreviations in a weather forecast you will know what they are talking about.

Tropical Activity Possibly Impacting CONUS.

When there is activity and I have not provided the specific links to the storm of “immediate” interest, one can obtain that information at this link. At this point in time, no (new) tropical events are expected to appear in this graphic during the next 48 hours. If that changes, we will provide an update.

Now let us look at the Western Pacific in Motion.

The above graphic which I believe covers the area from the Dateline west to 100E and from the Equator north to 45N normally shows the movement of tropical storms towards Asia in the lower latitudes (Trade Winds) and the return of storms towards CONUS in the mid-latitudes (Prevailing Westerlies). This is recent data not a forecast. But, it ties in with the Week 1 forecast in the graphic just above this graphic. Information on Western Pacific storms can be found by clicking here. This (click here to read) is an unofficial private source but one that is easy to read.