October 15, 2018 Weather and Climate Report – El Nino is Here (Unofficially)

Written by Sig Silber

I have often wondered where the term “Rex Block” came from given that “Rex” means king. But it turns out that “Rex Block” is named after Daniel F. Rex who documented this pattern and who was in the leadership of the National Center for Atmospheric Research NCAR. A Rex Block in the Northern Hemisphere is a clockwise rotating High Pressure area further north than a counterclockwise rotating Low where they maintain that relationship for a while. Not only does it slow down progression from west to east but it can move colder air further south. Such a pattern is influencing our weather right now. 

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NOAA opted not to declare El Nino Conditions last Thursday presumably because the atmosphere and Equatorial Pacific generally met the El Nino Conditions re Sea Surface Temperature but the coordination of the Equatorial Pacific with the pattern of rising and falling *Walker Cycle” had not developed sufficiently to change the official ENSO status. I was planning to discuss that IMO unwise decision this evening but decided that it fits better in our Monthly article which presents and compares the long-range forecast of NOAA and JAMSTEC which will be published this coming Saturday. The question of the Status of the ENSO process will be in the NOAA discussion and that then is a good time to address the question of “are we there yet”. I do cover that question every Monday  i.e. in this report but on Saturday I will review the NOAA decision to wait a month which is not a horrible decision but IMO silly. 

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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 slightly 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.	Also very slightly zonal and also deamplifying.		The transition from the 8 -14 day forecast shown above to the week 3/4 forecast seems to be feasible. But not so sure about the Northwest dry anomaly.

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 that there is a Low Pressure area off the West Coast. You can see how it goes up and over that ridge of  high pressure.

Tonight, Monday October 15, 2018, as I am looking at the above graphic, you do not see very much happening. That is the characteristic of a Rex Block. The current block may be falling apart to reform later in the week.

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.

Tropical Weather Outlook NWS National Hurricane Center Miami FL 200 PM EDT Mon Oct 15 2018 For the North Atlantic…Caribbean Sea and the Gulf of Mexico:

Showers and thunderstorms associated with a broad area of low pressure located just offshore of northeastern Honduras continue to show some signs of organization. The system is expected to move near or just offshore of north coast of Honduras, and it is possible that it could become a tropical depression before the low moves inland over Belize late Tuesday. Regardless of development, locally heavy rainfall, which could cause flash flooding, is possible across portions of Central America for much of the week.  An Air Force Reserve Hurricane Hunter aircraft is scheduled to investigate this  system on Tuesday afternoon.

* Formation chance through 48 hours…medium…40 percent.

* Formation chance through 5 days…medium…40 percent.

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.

The below makes it easier to focus on a particular day.  The best way to read them is from left to right on the first row and then from left to right in the row below it.

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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.

When I look at this Day 7 forecast, the Aleutian Low is strong with surface central pressure of 984 hPa and it is located south of the eastern Aleutians close to the ideal location for an El Nino. 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 1024 hPa. Northeast of Hudson Bay there is a Low with surface central pressure of 992 hPa. There is a large High over the center of CONUS with surface central pressure of 1028 hPa. That High (Day 7) extends a  bit out to sea and can be considered connected to the Hawaiian High but it looks like the Hawaiian High will show up on this graphic soon as the current area of high pressure moves east. The pattern pretty much prevents tropical events from penetrating very far north and has been funneling cold air south.

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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 the trough here and the Rex Block	The pattern shifts to the east a bit as the Rex Block falls apart.

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. Read from left to right first  row and then left to right on the  second row. 

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We are showing both the situation on the surface and at mid-atmosphere 500 mb and the view is different so sometimes it is useful to simply be able to compare them.

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 15, 2018 was 4 out of 5

8 – 14 Day Temperature Outlook issued today (Note the NOAA Level of Confidence in the Forecast Released on October 15, 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 15, 2018 was 4 out of 5)

8 – 14 Day Precipitation Outlook Issued Today (Note the NOAA Level of Confidence in the Forecast Released on October 15, 2018 was 4 out of 5)

Looking further out.

Here is the 6 – 14 Day NOAA discussion released today October 15, 2018 followed by the Week 3 – 4 Discussion

6-10 DAY OUTLOOK FOR OCT 21 – 25 2018

THE ENSEMBLE MEANS AND THEIR DETERMINISTIC MODEL RUNS INDICATE THAT THE AMPLIFIED UPPER-LEVEL PATTERN IS LIKELY TO PERSIST THROUGH THE LATTER HALF OF OCTOBER. ALTHOUGH THERE ARE SLIGHT TIMING DIFFERENCES AMONG THE MODEL SOLUTIONS, AN EASTWARD PROGRESSION OF THE LONGWAVE TROUGH OVER THE NORTHEAST PACIFIC IS LIKELY DURING THIS PERIOD. THE AMPLIFIED UPPER-LEVEL RIDGE IS FORECAST TO SHIFT EAST TO THE NORTH-CENTRAL U.S. BY DAY 10. A SHORTWAVE TROUGH IN THE SOUTHERN STREAM IS FORECAST ACROSS THE SOUTHWESTERN CONUS. SINCE THE DETERMINISTIC 6Z GFS AND 0Z ECMWF MODEL RUNS ARE IN EXCELLENT AGREEMENT WITH THEIR ENSEMBLE MEANS, THESE DETERMINISTIC MODEL RUNS ARE INCLUDED WITH THEIR RESPECTIVE ENSEMBLE MEANS IN CREATING THE 500-HPA MANUAL BLEND. 

THE AMPLIFIED UPPER-LEVEL TROUGH AND ASSOCIATED BELOW NORMAL 500-HPA HEIGHTS INCREASE CHANCES FOR BELOW NORMAL TEMPERATURES ACROSS MUCH OF THE EASTERN CONUS. THE LIKELIHOOD FOR CLOUDINESS AND WIDESPREAD PRECIPITATION FAVORS BELOW  NORMAL TEMPERATURES FROM THE SOUTHERN ROCKIES AND SOUTHERN GREAT PLAINS EAST TO THE GULF COAST. ALTHOUGH TEMPERATURES ARE FORECAST TO MODERATE LATER IN THIS PERIOD ACROSS THE MIDDLE AND UPPER MISSISSIPPI VALLEY, LARGE NEGATIVE  TEMPERATURE ANOMALIES ON DAYS 6 AND 7 INCREASE CHANCES FOR TEMPERATURES TO AVERAGE BELOW NORMAL DURING THE 5-DAY PERIOD.  

A SHORTWAVE TROUGH IN THE SOUTHERN STREAM OVER THE SOUTHWESTERN U.S. ALONG WITH A NEARLY STATIONARY FRONT ENHANCE ODDS FOR ABOVE NORMAL PRECIPITATION ACROSS THE SOUTHERN TIER OF THE CONUS. AT THE HIGHER LATITUDES OF THE CENTRAL AND EASTERN U.S., SURFACE HIGH PRESSURE AND ANOMALOUS NORTHERLY FLOW WITH CONTINENTAL AIR FAVOR A VERY DRY PATTERN. HOWEVER, COLD AIR ADVECTION IS EXPECTED TO PROMOTE LAKE-EFFECT PRECIPITATION (PERHAPS THE FIRST SIGNIFICANT  LAKE-EFFECT SNOW EVENT) DOWNWIND OF LAKES ERIE AND ONTARIO WHERE NEAR NORMAL  PRECIPITATION IS FAVORED. AN INCREASINGLY WET TREND IS LIKELY ACROSS THE PACIFIC NORTHWEST AND NORTHERN CALIFORNIA AS THE UPPER-LEVEL TROUGH OVER THE NORTHEAST PACIFIC SHIFTS EAST. 

THE AMPLIFIED TROUGH ANCHORED OVER THE ALEUTIANS AND NORTHEAST PACIFIC IS LIKELY TO RESULT IN ANOMALOUS SOUTHERLY FLOW, ENHANCING ODDS FOR ABOVE NORMAL TEMPERATURES AND PRECIPITATION THROUGHOUT MOST OF ALASKA. THE HIGHEST ODDS FOR ABOVE NORMAL PRECIPITATION ARE FORECAST ACROSS COASTAL SOUTHERN AREAS OF MAINLAND ALASKA, KODIAK ISLAND, AND THE KENIA PENINSULA WHERE THE 6Z GFS AND 0Z ECMWF ENSEMBLE MEANS INDICATE 3 TO 6 INCHES OF PRECIPITATION DURING THIS 5-DAY PERIOD. 

FORECAST CONFIDENCE FOR THE 6-10 DAY PERIOD: ABOVE AVERAGE, 4 OUT OF 5, DUE TO GOOD AGREEMENT BETWEEN THE GFS AND ECMWF ENSEMBLE MEANS AND THEIR DETERMINISTIC  MODEL RUNS IN AN AMPLIFIED LONGWAVE PATTERN.   

8-14 DAY OUTLOOK FOR OCT 23 – 29 2018 

THE ENSEMBLE MEANS ARE IN GOOD AGREEMENT DURING WEEK-2 AND FEATURE A NEGATIVELY-TILTED TROUGH NEAR THE EAST COAST, A RIDGE OVER THE NORTH-CENTRAL U.S., AND AN AMPLIFIED UPPER-LEVEL TROUGH OFFSHORE OF THE WEST COAST. A LARGE NEGATIVE 500-HPA HEIGHT ANOMALY CENTER IS FORECAST OVER THE NORTHEAST PACIFIC WITH THE 6Z GFS ENSEMBLE MEAN DEPICTING ITS MAGNITUDE CLOSE TO -200 METERS. TROPICAL STORM TARA RECENTLY DEVELOPED IN THE EAST PACIFIC AND A SECOND TROPICAL CYCLONE IS LIKELY TO FORM DURING THE NEXT FIVE DAYS. ALTHOUGH A LARGE  SPREAD EXISTS AMONG MODEL SOLUTIONS ON THE FUTURE TRACK OF THIS SECOND TC, ANOMALOUS MOISTURE COULD SPREAD NORTH INTO THE SOUTHWESTERN AND/OR  SOUTH-CENTRAL U.S. DURING WEEK-2. 

THE PREDICTED LONGWAVE PATTERN YIELDS A CONTINUATION OF ENHANCED ODDS FOR BELOW NORMAL TEMPERATURES ACROSS MUCH OF THE EASTERN U.S. EXTENDING SOUTHWEST TO THE SOUTHERN GREAT PLAINS. AN INCREASE IN PACIFIC FLOW, ASSOCIATED WITH THE AMPLIFIED TROUGH OFFSHORE OF THE WEST COAST, FAVORS ABOVE NORMAL TEMPERATURES ACROSS THE WESTERN AND NORTH-CENTRAL CONUS. ANOMALOUS SNOW COVER ACROSS THE CENTRAL ROCKIES IS A FACTOR IN LOWER PROBABILITIES FOR ABOVE NORMAL TEMPERATURES ACROSS THIS REGION. ABOVE NORMAL TEMPERATURES ARE LIKELY TO PERSIST ACROSS ALASKA THROUGH WEEK-2, BASED ON A CONTINUATION OF ANOMALOUS SOUTHERLY FLOW AT THE SURFACE. A LACK OF SNOW COVER FOR THIS TIME OF YEAR IS EXPECTED TO CONTRIBUTE TO ABOVE NORMAL TEMPERATURES ACROSS SOUTHEAST MAINLAND ALASKA.

THE AMPLIFIED TROUGH UPSTREAM OVER THE EAST PACIFIC, POTENTIAL EFFECTS FROM EAST PACIFIC TROPICAL CYCLONES, AND A BLOCKING RIDGE DOWNSTREAM OVER THE NORTH ATLANTIC INCREASE CHANCES FOR A POTENTIAL STORMY END TO OCTOBER FOR MUCH OF THE CONUS. THE HIGHEST ODDS FOR ABOVE NORMAL PRECIPITATION ARE FORECAST ACROSS THE RIO GRANDE VALLEY AND ALONG THE GULF COAST, INCLUDING THE FLORIDA PANHANDLE. 

THE NORTHERN GREAT PLAINS AND UPPER MISSISSIPPI VALLEY ARE FAVORED TO REMAIN RELATIVELY DRY, DUE TO RIDGING ALOFT. STRENGTHENING ONSHORE FLOW ENHANCES ODDS FOR ABOVE NORMAL PRECIPITATION FROM THE PACIFIC NORTHWEST SOUTH TO NORTHERN CALIFORNIA. THE EARLY PART OF WEEK-2 IS LIKELY TO BE ANOMALOUSLY WET ACROSS SOUTHERN COASTAL ALASKA AND THE ALASKA PANHANDLE BUT A DRYING TREND MAY OCCUR LATER IN THE PERIOD AS THE STORM TRACK OVER THE NORTH PACIFIC SHIFTS SOUTH. 

THEREFORE, ONLY LOW PROBABILITIES FOR ABOVE NORMAL PRECIPITATION ARE FORECAST FOR THIS REGION OF ALASKA. THE SOUTHWARD SHIFTING STORM TRACK INCREASES CHANCES FOR BELOW NORMAL PRECIPITATION ACROSS THE ALEUTIANS AND PARTS OF WESTERN MAINLAND ALASKA. 

FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD: ABOVE AVERAGE, 4 OUT OF 5, DUE TO CONTINUED GOOD AGREEMENT AMONG THE GFS AND ECMWF ENSEMBLE MEANS AND GOOD MODEL CONTINUITY.

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

Week 3-4 Forecast Discussion Valid Sat Oct 27 2018-Fri Nov 09 2018

While the most recent weekly Nino 3.4 sea surface temperature anomaly is greater than +0.6 C, ENSO-neutral conditions are present in atmospheric conditions across the equatorial Pacific Ocean. The RMM MJO indices indicate that the MJO remains active across the Western Hemisphere during the past week. Some eastward propagation of the MJO signal is favored over the next couple of weeks, according to statistical forecasts, while dynamical ensembles indicate significant uncertainty in the RMM-based MJO forecast. The Week 3-4 temperature and precipitation outlooks rely primarily on dynamical model forecasts from the NCEP CFS, the ECMWF, and the JMA operational ensemble prediction systems, as well as forecasts from the Subseasonal Experiment (SubX), a multi-model ensemble (MME) of experimental ensemble prediction systems. Consideration is also given to the possible evolution of the predicted circulation pattern for Week-2.

Dynamical model guidance from the various models is broadly consistent, depicting a trough over the Aleutian Islands into the North Pacific in the ECMWF and JMA or over mainland Alaska in the CFS, and a ridge over western North America. Most dynamical model ensembles, including the CFS and ECMWF, predict a relative trough over the eastern CONUS, with near or below normal 500-hPa heights over the Southeast CONUS. The JMA, as well as some member models of the SubX, indicate broader above normal 500-hPa heights across the northern CONUS. Statistical guidance from a multivariate linear regression (MLR) model indicates impacts into the Week 3-4 period of the currently active MJO, more closely aligned with the prediction of a broader ridge centered over the Northeast CONUS. The Week 3-4 temperature and precipitation outlooks are broadly consistent with evolution of the Week 2 circulation forecasts, including de-amplification of predicted troughs and ridges over North America.

Predicted anomalous southerly flow and anomalously low sea ice cover near much of the northern Alaska coast leads to enhanced probabilities of above-normal temperatures over most of Alaska. Likely above-normal temperatures are indicated for most of the western CONUS across the Northern and Central Rocky Mountains into the Northern and Central Plains, according to dynamical model forecasts including the CFS, ECMWF, and JMA ensembles, and the SubX MME consensus. The ECMWF ensemble and the SubX MME probabilities indicate an increased chance of below-normal temperatures over the Northeast CONUS. However, statistical guidance using the current state of MJO and decadal temperature trends indicates greater probabilities of above-normal temperatures for this region. Equal chances is indicated in the Week 3-4 outlook over the Northeast, where there is greater uncertainty in climate signals. Below-normal temperatures are more likely over parts of the Southern Plains, the Lower Mississippi and the Tennessee Valleys, and much of the Southeast region to the Mid-Atlantic and southern New England. Above-normal temperatures are forecast for the Florida Peninsula, consistent with probabilistic guidance from the SubX MME.

While there is greater uncertainty in the precipitation outlook compared to the temperature outlook, the various model guidance indicates some areas of agreement on the Week 3-4 period. Above-normal precipitation is likely for the southern coastal region of mainland Alaska and the Alaska Panhandle, ahead of a predicted trough to the west. Forecast positive 500-hPa heights over the northwestern CONUS support increased probabilities of below-normal precipitation for inland areas of the northwestern CONUS, including the Northern Rocky Mountains and Northern Plains. Above-normal precipitation is likely over parts of the Atlantic coast of the Southeast and the Florida Peninsula, related to troughing over the eastern CONUS in dynamical model guidance. Above-normal precipitation is also likely for parts of the Southwest along the Mexico border, following most operational and experimental dynamical model guidance.

Positive SST anomalies surrounding the Hawaiian Islands, support increased chances of above-normal temperatures and precipitation, as indicated by consensus probability forecasts from the SubX MME.

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. I provide these indices as they are guidelines to the weather. It is in a way looking at the factors that are impacting the weather.

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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 GFS 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. Recent History

Then

And then

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 how the MJO 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.

The spread among the analogs from October 8 to October 29 is 21 days which is a fairly 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 October 20. These analogs are centered on 3 days and 4 days ago (October 11 or October 12). 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 early. So we have gone from a week late to a week early which is why for some of us it is a shock.

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 eight El Nino Analogs, zero Neutral analogs and two La Nina Analogs. The pre-forecast analogs this week are most supportive of McCabe A and C which are opposites. This raises questions  about the high level of confidence in the 6  to 14 Day forecast.

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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 October 7, 2018 (dates  off a bit since NOAA  published on Tuesday that week)	And the 30 Days ending October 13, 2018
The dryness is much reduced, the cool anomaly is more pronounced and the warm anomaly is in two distinct areas.	The pattern is a lot wetter. The temperature pattern has not changed that much but you see subtle differences in the West both Northern Tier and Southern Tier.
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 Late-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, Red Sea and Persian Gulf are slightly warm It is slightly warm off Somalia	Warm around Kamchatka and Anadyr	Very warm Chukchi Sea, Bering Strait and Bering Sea Warm offshore of Alaska Panhandle Just slightly warm off Baja	Hudson Bay cool Warm offshore of Nova Scotia down to Florida Warm Western Gulf of Mexico	Warm north of Siberia Slightly warm west of North Africa
Equator	Looks like El Nino but not extreme and stretched out to the West
Africa	West of Australia	North, South and East of Australia	West of South America	East of South America
Mixed south of South Africa	Slightly Cool	Mostly Neutral	Slightly cool	Cool offshore of 10S 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 cooler. Black Sea is cooling. Warming in the Arabian Sea and Gulf of Oman	Warming north of and southeast of Japan but cooling southwest of Japan.	Slight warming in Bering Sea Warming in Gulf of Alaska.	Cooling off Nova Scotia and out to sea Warming Western Gulf of Mexico	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
Extreme warming west of North Africa. Cooling Gulf of Guinea Cooling south of Africa	Neutral	Cooling to the north Warming to northwest, south, southwest and southeast	Cooling 30S to 50S	Cooling off 20S Warming 30S 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.

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. The temperature threshold for El Nino is currently being met everywhere in the Nino 3.4 Measurement Area and the warm anomaly extends west to 160E and in many places extends down to 250 meters. So this El Nino criteria will be met for some time.

The 29C Isotherm is now at 170W. The 28C Isotherm at 155W. The 27C Isotherm is at 145W and 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 15, 2018 , in the afternoon working from the October 14 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 +1.0 which is an El Nino value. NOAA has reported the weekly Nino 3.4 to be +0.6 which is also an el Nino value but which I believe is miscalculated. Nino 4 is reported to be a bit warmer than last week at +0.9. Nino 3 is reported to be the same at +0.7. Nino 1 + 2 which extends from the Equator south rather than being centered on the Equator is reported a bit cooler at +0.4. 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 will discuss this in detail in our Saturday 15 Month Forecast Update (15 months by NOAA, three seasons by JAMSTEC). As you can see the odds for El Nino are high. 

Forecasts from Other Meteorological Agencies.

Here is the newly issued JAMSTEC Model Forecast.  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 fairly 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.

The Indian Ocean Dipole is different than ENSO but there are interactions between the two cycles.

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

IOD Background Information

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4. The Surface Air Pressure that Confirms the Nino 3.4 Index

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

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).

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

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F. Useful Reference Information

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Interaction Between MJO and ENSO

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Understand How the Jet Stream Impacts Weather

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Standard Pressure Levels

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Part II and Part III of this Report

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