October 8, 2018 Weather and Climate Report – Fall is Headed East

Written by Sig Silber

Updated at 6 PM EDT October 9, 2018 to update the graphics which were not available on Columbus Day

But there may be a warm up for the relatively dry West following the cool down. El Nino Conditions are coming and NOAA may confirm that on Thursday or decide to wait and see more confirmation. But El Nino Conditions are in place. We still have Tropical Storm activity and we are providing updates on this in a separate article.

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This is a legacy NOAA application meaning the software is not updated but the data should be reliable. My source for that graphic is Tropical Tidbits.com Not sure if Levi Cowan plots the CDAS data or just happens to display the graphic provided by CDAS but that is where I have found it. It is clearly showing a change to El Nino.

We now provide our usual 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.

Sometimes it is useful to see the evolution of the forecasts from the 1 – 5 Day, 6 – 10 Day (which NOAA considers to be Week-1 of their intermediate forecast) , 8 – 14 Day (which NOAA considers to be Week-2) and Week 3 and 4 (which after being issued overlap with Week-2). I do not have comparable maps for the Day 1 – 5 forecast in the same format as the three maps we generally work with. What I am showing for temperature is the Day 3 Maximum Temperature and for precipitation the five-day precipitation: the latter being fairly similar in format to the subsequent set of the maps I present each week but showing absolute QPF (inches of precipitation) not QPF deviation from Normal.

First Temperature

This shows magnitude rather than probability of being higher or lower than Normal and shows the middle day of the five day period.	The pattern is very zonal (west to east versus meridional north to south to north) and deamplifying in Week – 2		The transition from the 8 -14 day forecast shown above to the week 3/4 forecast seems feasible.

And then Precipitation

The five day QPF is shown above. The units are different than the other maps i.e. in units of precipitation (inches) not probabilities of exceeding or being less than climatology.	Zonal but appears to be more stable than the forecast for temperature.		The transition from the 8 -14 day forecast shown above to the week 3/4 forecast seems to be feasible.

A. Now we will begin with our regular approach and focus on Alaska and CONUS (all U.S.. except Hawaii).

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 the recent Western Trough.

Tonight, Monday October 8, 2018, as I am looking at the above graphic, of most interest is the leading edge of that Western Trough.

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

Additional useful forecasts from the Storm Prediction Center and be found here. Storm events are covered by Met Watch which can be accessed here. Explanation of symbols can be found here.

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.

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, we can not really find the Hawaiian High. The Aleutian Low is strong with surface central pressure of 980 hPa and it is located over the eastern Aleutians but extends to the Northwest coast of CONUS. To the north there is an Arctic High with surface central pressure of 1024 hPa. Further east, over Greenland there is a High with surface central pressure of 1012 hPa. North of Hudson Bay there is a Low with surface central pressure of 1000 hPa. There is a large High over the center of CONUS with surface central pressure of 1032 hPa. That High (Day 7) pretty much prevents tropical events from penetrating very far north other than crossing over Florida.

I provided this 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 7. 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.
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
.You can see that trough from the Pacific	The trough shifts east and also does not reach as 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. 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. It is quite complicated.

Day 3 Above, 6 Below	Day 4 Above,7 Below	Day 5 Above.

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 October 8, 2018 was 5 out of 5

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

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

Looking further out.

Here is the 6 – 14 Day NOAA discussion released today October 8, 2018

6-10 DAY OUTLOOK FOR OCT 14 – 18 2018

TODAY’S ENSEMBLE MEAN SOLUTIONS ARE IN GOOD AGREEMENT IN DEPICTING A HIGHLY AMPLIFIED 500-HPA PATTERN ACROSS THE FORECAST DOMAIN. A TROUGH IS FORECAST OVER THE ALEUTIANS WHILE A RIDGE IS EXPECTED TO DOMINATE MUCH OF EASTERN MAINLAND ALASKA AND THE PANHANDLE AS WELL AS THE NORTHWESTERN CONUS. FARTHER TO THE SOUTH, A TROUGH IS EXPECTED OVER THE NORTHEASTERN CONUS. TODAY’S MANUAL 500-HPA HEIGHT BLEND IS BASED PRIMARILY ON THE ENSEMBLE MEANS FROM THE EUROPEAN, GEFS, AND CANADIAN MODEL SUITES. THE RESULTANT MANUAL BLEND INDICATES POSITIVE 500-HPA HEIGHT ANOMALIES OVER MOST OF THE WESTERN AND SOUTHERN CONUS AS WELL AS EASTERN ALASKA, WHILE NEGATIVE ANOMALIES ARE FORECAST OVER OVER MUCH OF THE REMAINDER OF THE FORECAST DOMAIN.

ABOVE NORMAL 500-HPA HEIGHTS AND RIDING FAVOR ABOVE NORMAL TEMPERATURES OVER THE WESTERN THIRD OF THE CONUS, WHILE BELOW NORMAL TEMPERATURES ARE MOST LIKELY OVER MUCH OF CENTRAL AND EASTERN CONUS EXCEPT FOR FLORIDA WHERE ABOVE NORMAL TEMPERATURES ARE INDICATED, CONSISTENT WITH THE REFORECAST-CALIBRATED GEFS TOOL. ABOVE NORMAL TEMPERATURES ARE FAVORED FOR MOST OF ALASKA AS MUCH OF THE STATE IS PROJECTED TO BE UNDER THE INFLUENCE OF ANOMALOUS SOUTHERLY FLOW.

PREDICTED POSITIVE 500-HPA HEIGHTS AND RIGING ACROSS THE NORTHWESTERN REGION SUPPORT INCREASED CHANCES OF ANOMALOUSLY DRY CONDITIONS FOR THE NORTHWESTERN CONUS EXTENDING EASTWARD TO THE UPPER GREAT LAKES. PROBABILITIES OF ABOVE NORMAL PRECIPITATION ARE ENHANCED FOR PARTS OF THE SOUTHWEST, THE SOUTHERN ROCKIES, THE SOUTHERN PLAINS, THE LOWER MISSISSIPPI VALLEY, AND FLORIDA. CONSISTENT WITH CALIBRATED PRECIPITATION FROM THE GFS AND ECMWF ENSEMBLE FORECAST TOOLS. ABOVE NORMAL PRECIPITATION IS ALSO FAVORED FOR MUCH OF ALASKA AHEAD OF THE TROUGH PREDICTED OVER THE ALEUTIANS.

FORECAST CONFIDENCE FOR THE 6-10 DAY PERIOD: ABOVE AVERAGE, 4 OUT OF 5, DUE TO GOOD AGREEMENT ON AN AMPLIFIED PATTERN EARLY IN THE PERIOD OFFSET BY A POTENTIAL TRANSITION TO LESS AMPLIFICATION ACROSS THE CONUS AS TIME PROGRESSES.

8-14 DAY OUTLOOK FOR OCT 16 – 22 2018

TODAY’S ENSEMBLE MEAN DYNAMICAL MODEL FORECASTS ARE IN GOOD AGREEMENT ON THE PREDICTED 500-HPA CIRCULATION PATTERN OVER NORTH AMERICA FOR THE WEEK-2 PERIOD.

A TROUGH IS FORECAST OVER WESTERN ALASKA WHILE ANOMALOUS RIDGING IS FORECAST OVER EASTERN ALASKA AND THE NORTHWESTERN CONUS. DOWNSTREAM, A TROUGH IS FORECAST TO WEAKEN AND LIFT TOWARD THE NORTHEAST WITH TIME. POSITIVE 500-HPA HEIGHT ANOMALIES ARE FORECAST OVER MOST OF THE CONUS EXCEPT FOR THE NORTHEAST WHERE NEGATIVE 500-HPA HEIGHT ANOMALIES ARE INDICATED.

ABOVE NORMAL TEMPERATURES ARE FAVORED OVER THE WESTERN CONUS, PARTS OF THE CENTRAL AND NORTHERN PLAINS, AND THE UPPER MISSISSIPPI VALLEY AS A RIDGE PROGRESSES EASTWARD TOWARD THE REGION. BELOW NORMAL TEMPERATURES ARE MOST LIKELY OVER THE SOUTHERN PLAINS AND MUCH OF EASTERN CONUS EXCEPT FOR FLORIDA WHERE ABOVE NORMAL TEMPERATURES ARE FORECAST, CONSISTENT WITH THE REFORECAST-CALIBRATED GEFS TOOL.

PREDICTED POSITIVE 500-HPA HEIGHTS AND ANOMALOUS RIDGING ENHANCE PROBABILITIES OF BELOW NORMAL PRECIPITATION OVER MOST OF THE NORTHERN CONUS. ABOVE NORMAL PRECIPITATION IS FAVORED FOR SOUTHEASTERN ARIZONA, SOUTHERN NEW MEXICO, AND PARTS OF TEXAS AND THE SOUTHEAST, CONSISTENT WITH CALIBRATED PRECIPITATION FROM THE GFS AND ECMWF ENSEMBLE FORECAST TOOLS. NEAR TO ABOVE NORMAL PRECIPITATION IS ALSO FAVORED FOR ALASKA AHEAD OF THE TROUGH PREDICTED OVER WESTERN ALASKA.

FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD: ABOUT AVERAGE, 3 OUT OF 5, DUE TO GOOD AGREEMENT AMONG MODEL CIRCULATION FORECASTS, OFFSET BY SOME DISAGREEMENT IN PRECIPITATION AND TEMPERATURE FORECAST TOOLS.

THE NEXT SET OF LONG-LEAD MONTHLY AND SEASONAL OUTLOOKS WILL BE RELEASED ON OCTOBER 18.

Some Indices of Possible Interest: We should always remember that the forecast is driven by many factors some of which are conflicting in terms of their impacts. Please pay more attention to the graphics than my commentary which does not update on a regular basis once the article is published. The indices will continue to update.

Below is a graphical explanation of the Arctic Oscillation

Left: Effects of the Positive Phase of the Arctic Oscillation. Right:Effects of the Negative Phase of the Arctic Oscillation. -Credit: J. Wallace, University of Washington.

NAO Positive	NAO Negative
Notice the strong Icelandic Low and strong Bermuda High but located east of where it is usually found	Notice the weak Icelandic Low and Bermuda High.
There are many variations on a theme when talking about the NAO.	Some use Lisbon or Gibraltar as the sub-arctic reference point. And there appears to be a low-frequency cycle related to the AMO to some extent. Thus the NAO is a lot more complicated than I am able to show here. I like this explanation better than the graphics I have shown. It better captures the impact of the changing relative strength of the two control factors in the Atlantic namely the Northern and Southern semi-permanent Highs and Lows.

But it gets even more complicated. With a Negative NAO the position of the pattern more east than west or vice versa changes the impacts.

Madden Julian Oscillation (MJO)

The MJO is an area of convective activity along the Equator which circles the globe generally in 30 to 60 days. The location of the convective activity not only impacts the Equator but also the middle latitudes.

There are a lot of models and I try to read the results from all of them. For access to a variety of models, I refer readers here. This weekly report summarizes things. Here is another useful source of information.

First we look at two models that I find very helpful. On the first graphic , the light gray shading shows the tracks which fit with 90% of the forecasts and the dark gray shading shows a smaller area that fits with 50% of the forecasts The large dot is the current location.

First.

And then (but this graphic does not seem to have been updated beyond October 7, 2018)

This tool allows one to translate the location of the forecast MJO to the impacts on CONUS. To make it easier for the reader I am displaying the highest probability interpretation for the time period in question namely September/October/November. This (70% match) of course might miss some other impacts which have less statistical confirmation but may none-the-less be valid.

Remember we are interested in Phase 1 and or Phase 2 as it impacts CONUS weather during October. So that is what I have displayed.

Temperature

Precipitation

I can not display it in the article but this is another link to an application that allows you to figure out the “lagged” impacts on temperature of the MJO. There is a lot of statistical analysis available to predict the impacts of the MJO which is different from predicting the location of the MJO. I am not sure if the lagged impacts are better than what you get with the link I provided earlier.

Analogs to the NOAA 6 – 14 Day Outlook.

Now let us take a detailed look at the “Analogs”.

NOAA normally provides two sets of Analogs.

A. Analogs 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 the recent pattern is used to initialize the models to predict the 6 – 14 day Outlook.

B. There is a second set of analogs associated with the Outlook. It compares the forecast (rather than the prior period) to past weather patterns. I have not been regularly analyzing this second set of information. The first set applies to the 5 and 7 day observed pattern prior to today. The second set, relates to the correlation of the forecasted outlook 6 – 10 days out and 8 – 14 days out with similar patterns that have occurred in the past during a longer period that includes the dates covered by the 6 – 10 Day and 8 – 14 Day Outlook. The second set of analogs also has useful information as it indicates that the forecast is feasible in the sense that something like it has happened before. I am not very impressed with that approach. But in some ways both Approach A and B are somewhat similar. I conclude that if the Ocean Condition now are different then the analogs and if the state of ENSO now is different than the analogs that is a reason to have increased lack of confidence in the forecasts and vice versa.

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. But NOAA prefers the first set (A) as it helps them (or at least they think it does) assess the quality of the forecast.

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. It also helps the reader see the impact of the phases of the PDO and AMO which are shown. The first set (A) which is what I am using today applies to the 5 and 7 day observed pattern prior to today.

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

* Index reads positive for that month but that was a period of time that was generally PDO Negative.

The spread among the analogs from September 17 to October 2 is 15 days which is a very tight spread. 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 September 25. These analogs are centered on 3 days and 4 days ago (October 4 or October 5). So the analogs could be considered to be out of sync with respect to weather that we would normally be getting right now i.e. at last a week late.

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 duplicates, there are five El Nino Analogs, five Neutral analogs and zero La Nina Analogs. The pre-forecast analogs this week are most non-supportive of McCabe C which tends to result in Drought for the Northern Tier and the Middle Atlantic states. I am not sure what to make of the non-support of McCabe C and the analogs being associated with weather more than a week earlier in this season.

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 September 29, 2018	And the 30 Days ending October 6, 2018
The Western Drought is more intense and the Warm anomaly is breaking down.	The dryness is much reduced, the cool anomaly is more pronounced and the warm anomaly is in two distinct areas.
Remember, these maps are a 30 average so the most distant seven days are removed and the most recent seven days are added.

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 moving into Mid-October and we should be returning from the set of positions shown below for July back slowly to the Winter Pattern. For CONUS, the seasonal repositioning of the Bermuda High and the Pacific High are very significant.

World Forecasts

A. Today (University of Maine)

B Short-term set for day six but can be adjusted (BOM – Australia)

C. 8 – 14 Day (NOAA/Canada/Mexico Experimental NAEFS))

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

And now precipitation

Additional Maps showing different weather variables can be found here.

B. 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

Please remember this graphic updates every six hours so the diurnal pattern can confuse the reader.

Now Precipitation

C. And now we have experimental 8 – 14 Day World forecasts from the NAEFS Model.

First Temperature

Then Precipitation

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

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
The Mediterranean. Black Sea, Caspian Sea and Red Sea are slightly warm It is warm off Somalia	Very warm around Kamchatka	Very warm Chukchi Sea, Bering Strait and Bering Sea Warm offshore of Alaska Panhandle Warm off Baja	Hudson Bay cool Warm offshore of Nova Scotia down to Cape Hatteras Warm Western Gulf of Mexico	Warm north of Siberia Warm west of North Africa
Equator	Looks like El Nino
Africa	West of Australia	North, South and East of Australia	West of South America	East of South America
Warm along the Equator between Africa and South America. Cool Gulf of Guinea Mixed south of South Africa	Very Cool	Cool to the south	Slightly cool	Warm off 20S to 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 is mostly cool. Black Sea is cooling. Southern Caspian Sea is warming. Warming in the Arabian Sea	Warming north of and southeast of Japan but cooling south of Japan.	Warming in Bering Sea Warming around and south of Alaska.	Cooling off Nova Scotia and out to sea Warming south of Greenland Warming eastern Gulf of Mexico and around Florida	Significant cooling around British Isles and further to the northeast
Equator	Eastern Pacific showing an El Nino Pattern
Africa	West of Australia	North, South and East of Australia	West of South America	East of South America
Warming west of North Africa. Cooling south and southeast of Africa	Neutral	Cooling to the northeast and southeast. Warming to the southeast	Cooling 20S to 50S	Warming 20S to 40S Cooling 40S to 50S

Switching gears, below is an analysis of projected tropical hazards and benefits over an approximately two-week period. Our full Tropical Report which will be regularly updated can be found here.

* 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.

ENSO Update.

C. Progress of ENSO

This section is organized into four parts.

1. Current and Recent Sea Surface Temperatures (SST)

2. Current and Recent Equatorial Pacific Subsurface Temperatures

3. History of the Nino 3.4 Readings and forecasts from other Meteorological Agencies.

4. The Surface Air Pressure Pattern that confirms the state of ENSO.

1. Current and Recent Sea Surface Temperatures (SST)

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.

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 three-month average compared to today and that is below. These graphics can be clicked on to enlarge.

Three Month Average Anomaly	Current Anomaly
By this point La Nina is gone neutral conditions prevail	We see shades of red all across the Equatorial Pacific now.

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.

2. Current and Recent Equatorial Pacific Subsurface Temperatures Let us look in more detail at the Equatorial Water Temperatures.

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. These currents are very complicated and made even more so by the uneven nature of the ocean floor. So the exact pattern of where this warm water will erupt is beyond my level of understanding. But it will erupt to the surface in multiple different places.

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.

We now have warm water extending east to 100W. Most of this is at depth. One can see why the models predict an El Nino.

The 28C Isotherm is now near the Dateline, the 27C Isotherm is east of 150W, the 25C Isotherm is now at 120W. The 20C Isotherm no longer reaches the surface but the 23C Isotherm does so at 110W.

Tracking the change over a period of a year

The next graphic basically averages out the anomalies by longitude. It averages the anomalies from the surface down to 300 meters.

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 and continues to increase.

Side by side comparison can be useful

Comparison Week Probably Third Week of December 2017	Current Week

3. History of the Nino 3.4 Readings and forecasts from other Meteorological Agencies.

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.

………………………….170W.|…A….|….B…|…C….|…D….|…E…|120W………………………

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 Tuesday October 2, 2018 , in the afternoon working from the October 1 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 +0.9 which is an El Nino value. NOAA has reported the weekly Nino 3.4 to be +0.7 which is also an el Nino value. Nino 4 is reported to be a bit warmer than last week at +0.8. Nino 3 is reported to be a bit warner at +0.7. Nino 1 + 2 which extends from the Equator south rather than being centered on the Equator is reported a lot warmer at +0.7. It was 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.

Here is the history

Here is another way of looking at the TAO/TRITON Graphic. It is a fast way to assess the strength of an ENSO Event and provides a way to track it.

The below table only looks at the Equator 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. The rows below the next break point were used during the La Nina and could be removed now as the have no data but I show them to illustrate the process. For a strong El Nino two more rows would be added at the top of this table.

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. We expect new information on October 11.

Forecasts from Other Meteorological Agencies.

Here is the newly issued JAMSTEC Model Forecast. It suggests a less strong El Nino than their forecast last month. 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.

Forecasts from Other Meteorological Agencies.

Here is the newly issued JAMSTEC Model Forecast. It suggests a less strong El Nino than their forecast last month. 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.

There should be a new JAMSTEC discussion soon.

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

And the ENSO Outlook Discussion Issued on October 9, 2018

El Nino ALERT; positive Indian Ocean Dipole likely underway

The Bureau’s ENSO Outlook has been raised to El Nino ALERT. This means there is approximately a 70% chance of El Nino occurring in 2018-around triple the normal likelihood. Similarly, in the Indian Ocean, a positive Indian Ocean Dipole (IOD) may have started.

When combined, these two events in spring increase the possibility of a dry and warm end to the year. It also raises the risk of heatwaves and bushfire weather in the south, but reduces the risk of tropical cyclone activity in the north.

The tropical Pacific Ocean has warmed in recent weeks due to weakening of the trade winds, while the Southern Oscillation Index has fallen to typical El Nino levels. Models suggest further warming of the Pacific is likely. Four of eight models predict El Nino thresholds will likely be exceeded in the coming months, with another two falling just short.

El Nino onset during December would be later than usual, although not unprecedented.

And of course Queensland Australia is the official keeper of the SOI measurements.

Indian Ocean IOD (It updates every two weeks)

Indian Ocean Dipole outlooks (October 9, 2018)

The Indian Ocean Dipole (IOD) has been displaying signs of a positive IOD event for a number of weeks. The weekly index value to 7 October was +0.58 degC. The IOD index has now remained above the positive IOD threshold value (+0.4 C) for four weeks. Along with warm SST anomalies across most of the northern Indian Ocean and cool anomalies near the Indonesian island of Sumatra, this strongly suggests that a positive IOD event is currently underway; nevertheless, these values need to persist until at least November for this to be considered an event.

Four of the six international climate models surveyed by the Bureau suggest that index values will remain above positive IOD thresholds for the remainder of October. All models expect a return to neutral by December. The IOD typically has little influence on Australian climate from December to April.

A positive IOD event typically reduces spring rainfall in central and southern Australia, and can exacerbate any potential El Nino driven rainfall deficiencies.

It is useful to understand where the IOD is measured. This is shown in the below graphic.

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

D. Putting it all Together.

At this time, La Nina Conditions along the Equator have come to an end and we are solidly into ENSO Neutral and entering into El Nino Conditions. But the drivers of a transition to El Nino are not solidly in place.

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 so it may need to become a bit more negative for the “McCabe A” pattern to become established. Our assessment is that the standard time for Climate Shifts in the Pacific is 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.

E. Relevant Recent Articles and Reports

Weather in the News

Nothing to Report

Weather Research in the News

Nothing to Report

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