Written by Sig Silber
Sea Surface Temperatures (SST) are in an El Nino Pattern but the atmosphere has not yet responded. So for now we are essentially in ENSO Neutral for the next few weeks. I try to explain this in this report. I do not discuss the split Jet Stream but that is just one more part of a pattern that is fairly stagnant waiting for the transition to El Nino and true Fall.
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I thought it useful to repeat certain parts of the report we issued on Saturday Night.
But first this look at recent history
And now the 30-Day Outlook from NOAA
30-DAY OUTLOOK DISCUSSION FOR NOVEMBER 2018
FORECASTS OF AUTUMN CLIMATE ARE ESPECIALLY DIFFICULT, AND THE NOVEMBER 2018 OUTLOOK IS NO EXCEPTION. LOW-FREQUENCY CLIMATE FORCING FROM ENSO IS EXPECTED TO GRADUALLY INCREASE DURING THE NEXT SEVERAL WEEKS, THOUGH THIS HAS LIMITED APPLICATIONS TO THE CURRENT OUTLOOK, ESPECIALLY WITH RESPECT TO TEMPERATURE. THE MJO HAS BEEN ACTIVE OVER THE PAST SEVERAL WEEKS, BUT IS NOT EXPECTED TO PLAY A MAJOR ROLE DURING NOVEMBER – THIS IS DUE TO BOTH UNCERTAIN MJO FORCING ITSELF AS WELL AS ONLY MODEST EXTRATROPICAL TELECONNECTIONS AT THIS POINT IN THE SEASONAL CYCLE. THE FORECAST IS THEREFORE INFORMED FIRSTLY BY A BLEND OF CALIBRATED DYNAMICAL GUIDANCE FROM THE NMME AND STATISTICAL GUIDANCE THAT LARGELY UTILIZES LONG-TERM TRENDS. THIS IS AUGMENTED BY ADDITIONAL DYNAMICAL GUIDANCE FROM THE ECMWF, THE WEEKS 3-4 GUIDANCE, AND THE CURRENT EVOLUTION OF DYNAMICAL MODEL FORECASTS THROUGH THE EXTENDED RANGE (~DAYS 10-16) PERIOD.
This is in line with the current situation re the atmosphere. The Southern Oscillation Index may not be the best way to assess the response of the atmosphere but it has been the way used historically and remains the most used measure. And of course Queensland Australia is the official keeper of the SOI measurements.
And the comparison of the long-term forecasts from NOAA and JAMSTEC
So we know two things
A. El Nino is not a major factor in the November forecast and
B. Beyond November there is a lot a variation among forecasters and of course we have only shown two…NOAA and JAMSTEC so that is not the universe of forecasts but provides a good idea of the range of viewpoints.
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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
And then Precipitation
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 continual eastward flow of moist air from the Eastern Pacific across Mexico into Texas.
Tonight, Monday October 22, 2018, as I am looking at the above graphic, you see the same pattern but with the wave off the West Coast moving closer to land.
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
Day One CONUS Forecast | Day Two CONUS Forecast |
These graphics update and can be clicked on to enlarge but my brief comments are only applicable to what I see on Monday night prior to publishing. | |
Lots of activity showing on this map in the Southern Tier |
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 weak with surface central pressure of 996 hPa and it is located in the Gulf of Alaska but also extends to the west. Further east, there is a Low with surface central pressure of 1008 hPa. which may impact weather in the Northeast on Day 6. There is a large High over the center of CONUS with surface central pressure of 1024 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 not connected to the inland High as the current area of high pressure moves east if it does.
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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 current western ridge and East Coast trough here | The pattern shifts further to the east a bit |
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.
Surface 850MB | Mid Atmosphere 500 MB |
Here is the seven-day cumulative precipitation forecast. More information is available here.
But there may be residual moisture from Willa
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 22, 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 22, 2018 was 3 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 22, 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 22, 2018 was 3 out of 5)
Looking further out.
Here is the 6 – 14 Day NOAA discussion released today October 22, 2018 followed by the Week 3 – 4 Discussion issued on October 19, 2018
6-10 DAY OUTLOOK FOR OCT 28 – NOV 01, 2018
MODEL SOLUTIONS REMAIN IN GOOD AGREEMENT REGARDING OVERALL 500-HPA GEOPOTENTIAL HEIGHT PATTERN DURING THE 6-10 DAY PERIOD. AT THE ONSET OF THE PERIOD, THE NORTH ATLANTIC OSCILLATION (NAO) IS FORECAST TO BE IN A NEGATIVE PHASE, WITH ANOMALOUS RIDGING FORECAST OFF THE COAST OF GREENLAND, AND AN ANOMALOUS TROUGH FORECAST OVER THE EASTERN CONUS. AS THE NAO TRANSITIONS TO A MORE NEUTRAL STATE BY DAY 10, THE TROUGH IN THE EAST IS FORECAST TO DEAMPLIFY. A RIDGE IS FORECAST OVER THE WESTERN CONUS EXTENDING UP THROUGH EASTERN ALASKA EARLY IN THE PERIOD. AS THIS RIDGE WEAKENS, WEAK TROUGHING IS FORECAST TO DEVELOP OVER MAINLAND ALASKA. A RIDGE AND ASSOCIATED SURFACE HIGH PRESSURE IS FORECAST OVER THE BERING SEA AND THE ALEUTIANS.
BELOW NORMAL TEMPERATURES ARE FAVORED FOR THE EASTERN CONUS UNDER THE INFLUENCE OF THE TROUGH WITH SOME MODERATION FORECAST TOWARD THE END OF THE PERIOD. ABOVE NORMAL TEMPERATURES ARE FAVORED FOR THE WESTERN CONUS, WHICH IS FORECAST TO BE INFLUENCED BY RIDGING. ABOVE NORMAL TEMPERATURES ARE FAVORED FOR ALASKA WHICH IS PROJECTED TO HAVE PREDOMINATELY POSITIVE HEIGHT ANOMALIES, DESPITE ANY WEAK TROUGHING THAT DEVELOPS.
ON DAY-6, A COASTAL LOW IS FORECAST TO BE IMPACTING PARTS OF THE NORTHEAST ENHANCING ABOVE NORMAL PRECIPITATION PROBABILITIES. EVEN AFTER THIS SYSTEM DEPARTS, TROUGHING IN THE EAST WILL CONTINUE TO FAVOR ABOVE NORMAL PRECIPITATION PROBABILITIES, WITH SOME MODERATION POSSIBLE TOWARD THE END OF THE PERIOD AS THE TROUGH WEAKENS. SURFACE HIGH PRESSURE OFF THE CALIFORNIA COAST WILL FAVOR BELOW NORMAL PRECIPITATION FOR PARTS OF THE WESTERN CONUS. ELEVATED PRECIPITATION PROBABILITIES ARE FAVORED FOR PARTS OF COASTAL WASHINGTON AND OREGON AS SHORTWAVE ENERGY MOVES OVER THE TOP OF THE RIDGE AND INTO THE PACIFIC NORTHWEST. ABOVE NORMAL PRECIPITATION IS FAVORED OVER EASTERN ALASKA AS TROUGHING DEVELOPS OVER THAT REGION, WITH SURFACE HIGH PRESSURE OVER THE BERING SEA FAVORING BELOW NORMAL PRECIPITATION OVER PARTS OF WESTERN ALASKA AND THE ALEUTIANS.
FORECAST CONFIDENCE FOR THE 6-10 DAY PERIOD: ABOVE AVERAGE, 4 OUT OF 5, DUE TO GOOD MODEL AGREEMENT AND AN AMPLIFIED PATTERN
8-14 DAY OUTLOOK FOR OCT 30 – NOV 05, 2018
MODEL CONSENSUS FOR THE WEEK-2 PERIOD IS THAT THE PATTERN MAY ONCE AGAIN AMPLIFY, WITH THE MEAN TROUGH AXIS RETROGRADING INTO THE WESTERN CONUS AND POSITIVE HEIGHT ANOMALIES DEVELOPING IN THE EASTERN CONUS. THE RIDGE OVER THE BERING SEA IS FORECAST TO SHIFT OVER MAINLAND ALASKA AND FLATTEN, BECOMING REPLACED BY ZONAL FLOW OR WEAK TROUGHING. DUE TO THE TRANSITIONAL NATURE OF THE PATTERN, THERE IS LESS CONFIDENCE IN BOTH TEMPERATURE AND PRECIPITATION PROBABILITIES.
BELOW NORMAL TEMPERATURE PROBABILITIES WILL CONTINUE TO BE FAVORED FOR THE EASTERN CONUS AT THE START OF THE PERIOD. HOWEVER, AS THE TROUGH IN THE EAST FLATTENS AND BEGINS TO RETROGRADE TO THE WEST, NEAR NORMAL TO ABOVE NORMAL TEMPERATURES ARE FORECAST TO DEVELOP OVER THE EASTERN CONUS TOWARD THE END OF THE PERIOD, FAVORING NEAR NORMAL TEMPERATURES OVERALL WHEN THE ENTIRE PERIOD IS CONSIDERED. RIDGING OFF THE WEST COAST WILL CONTINUE TO FAVOR ABOVE NORMAL TEMPERATURE PROBABILITIES FOR THE WESTERN CONUS. BELOW NORMAL TEMPERATURES WILL BECOME FAVORED FURTHER INLAND ACROSS THE ROCKIES AND PLAINS AS TROUGHING BECOMES THE DOMINANT INFLUENCE. THE POSITIVE 500-HPA GEOPOTENTIAL HEIGHT ANOMALY OFF THE WEST COAST ALSO TELECONNECTS WELL WITH BELOW NORMAL TEMPERATURES ACROSS THE NORTHERN ROCKIES.
RIDGING OFF THE WEST COAST WILL FAVOR BELOW NORMAL PRECIPITATION PROBABILITIES FOR PARTS OF CALIFORNIA AND OREGON FOR THE WEEK-2 PERIOD. WITH THE TROUGH DEAMPLIFYING OVER THE EAST AND THEN POSSIBLY AMPLIFYING AGAIN OVER THE WESTERN CONUS LATE IN WEEK-2, ENHANCED PRECIPITATION PROBABILITIES ARE FAVORED ACROSS MOST OF THE CONUS ASIDE FROM THE AFOREMENTIONED WEST COAST REGIONS. ANALOG GUIDANCE FAVORS THE HIGHEST PROBABILITIES FOR ABOVE NORMAL PRECIPITATION IN THE EASTERN CONUS AND THE NORTHERN ROCKIES, WHILE THE REFORECAST TOOLS FORM THE ECMWF ENSEMBLES AND GEFS FAVOR PARTS OF SOUTHERN CONUS FOR THE HIGHEST PROBABILITIES FOR ABOVE NORMAL PRECIPITATION. THE OVERALL STORM TRACK WOULD BE FAVORED TO SHIFT TO THE WEST AS THE TROUGH RETROGRADES, FAVORING DISTURBANCES TO TRACK THROUGH THE PLAINS AND MISSISSIPPI VALLEY, AND BRING ASSOCIATED FRONTAL PRECIPITATION TO AREAS FURTHER EAST. AS ALASKA BECOMES UNDER THE INFLUENCE OF TROUGHING, ABOVE NORMAL PRECIPITATION IS FAVORED ACROSS THE ENTIRE STATE.
FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD: NEAR AVERAGE, 3 OUT OF 5, DUE TO A TRANSITIONAL PATTERN LEADING TO A FAIR AMOUNT OF UNCERTAINTY
THE NEXT SET OF LONG-LEAD MONTHLY AND SEASONAL OUTLOOKS WILL BE RELEASED ON NOVEMBER 15.
Week 3-4 Forecast Discussion Valid Sat Nov 03 2018-Fri Nov 16 2018
An interesting circulation setup appears in play for the upcoming Weeks 3-4 outlook. Model guidance has converged on the Arctic Oscillation (AO)/North Atlantic Oscillation (NAO) becoming sharply negative, following a prolonged period in its positive phase. Associated with this evolution is a prominent anomalous ridge over the North Atlantic that is anticipated to persist into the outlook period somewhere south of Greenland or Iceland. Elsewhere, the transition towards El Nino in the Pacific continues to appear likely, while the active phase of the MJO is approaching the Maritime Continent. Whether an active MJO can cross the Maritime Continent is a frequent question in these scenarios, further compounded by adjustments to the equatorial trades and warm pool from the building low frequency state. The resulting forecast looks to primarily leverage the evolving AO, given its e-folding time scale lying within the Weeks 3-4 period and consistent evolution from the Week-2 outlook. The ECMWF model is favored among dynamical model guidance for its AO representation and greatest persistence with the North Atlantic block, given empirical evidence of dynamical models often breaking down these features too rapidly. Also of note is the constructed analogue tool, conditioned upon the observed 200-hPa streamfunction across the Northern Hemisphere, represents a similarly realistic evolution of the extratropical circulation in line with the ECMWF guidance.
The forecast 500-hPa circulation field of the ECMWF model depicts the aforementioned block south of Greenland, with widespread positive height anomalies at the polar latitudes. Upstream of the block, anomalous troughing is forecast to extend from the Northern Plains through New England, shifting closer to the east coast by Week-4. Anomalous ridging over the northeastern Pacific is forecast to approach the West Coast by Week-3, and become established through the Great Basin by Week-4. Across the Pacific, a negative North Pacific Oscillation is forecast with ridging over the Bering Strait and troughing south of the Aleutians. Among the other models, the CFS fails to maintain the negative AO or the North Atlantic block, even by Week-3, which is highly suspect. The JMA maintains the negative AO and North Atlantic block, but retrogrades the block towards the Hudson Bay which results in a warmer (cooler) forecast over the eastern (western) CONUS. Subseasonal experiment models without the CFS feature the North Atlantic block and negative height anomalies along the eastern seaboard and ridge across the West, but also feature a substantial trough in the North Pacific that is much closer to North America than the other guidance.
With a ridge-trough pattern favored across the West and East, respectively, above- and below-normal temperatures are broadly forecast across each region. The highest confidence for above-normal temperatures across the West lies near the Pacific Coast, with the anomalous ridge axis in the vicinity for Week-3 and slightly inland for Week-4. The greatest confidence for below-normal temperatures is across the Midwest, in association with the anomalous trough upstream of the North Atlantic block. Enhanced probabilities for below-normal temperatures are forecast to extend from the Southern Plains northeastward through the interior of New England. Above-normal temperatures are also favored across the Florida Peninsula due to concerns about how far south the colder air associated with the anomalous trough will make it. Anomalous ridging forecast across Alaska, coupled with the relatively warm sea surface temperatures suggesting slow development of sea ice around the state, leads to above-normal temperatures being favored here as well. The largest probabilities for above-normal temperatures in Alaska are near the Gulf of Alaska and Bering Sea, given the relatively warm waters and implications for sea ice growth.
An active storm track is favored across the Gulf and East Coasts, tied to the southern and eastern flanks of the anomalous trough. This yields enhanced probabilities for above-median precipitation for these areas. Odds are also increased for above-median precipitation in southern Alaska, with the storm track shifted northward away from the CONUS, and into Alaska instead. This shifted storm track leads to increased probabilities for below-median precipitation across much of the West, tied to the anomalous ridging anticipated here. Below-median precipitation is also forecast across the Great Plains through the western Great Lakes, given limited moisture availability behind the forecasted trough axis.
Relatively warm and wet conditions continue to be favored across the Hawaiian islands given the anomalously warm sea surface temperatures in the vicinity of the archipelago. Enhanced rainfall is also typically associated with the transition towards El Nino, before drier conditions prevail during the bulk of the wet season.
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) Because the MJO is not impacting our weather much right now, I am moving this section into the ENSO discussion as it is more related to that right now than current weather.
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.
Centered Day | ENSO Phase | PDO | AMO | Other Comments |
Nov 4, 1952 | Neutral | – | + | |
Oct 25, 1962 | Neutral | – | + | |
Oct 26, 1965 (2) | El Nino | – | – | |
Oct 17,1972 | El Nino | – | – | |
Oct 18,1974 | La Nina | – | – | |
Oct 19, 1974 | La Nina | – | – | |
Oct 17, 1978 | Neutral | – | – | |
Oct 30, 1980 (2) | Neutral | + | – |
(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 17 to November 4 is 18 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 October 26. These analogs are centered on 3 days and 4 days ago (October 18 or October 19). 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. It explains why it feels cold.
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 just three El Nino Analogs, five Neutral analogs and two La Nina Analogs. The pre-forecast analogs this week are most supportive of McCabe B and totally unsupportive of McCabe C. In general the analogs are fairly supportive of the NOAA 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.
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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.
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 Gulf of Oman But cooling in the Arabian Sea | Warming north of Japan but cooling southwest of Japan. | Slight warming in Bering Sea Warming in Gulf of Alaska but cooling further west. Cooling off Baja | Cooling off Nova Scotia and out to sea Sleight warming Western Gulf of Mexico | Warming south of Greenland |
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. Warming Gulf of Guinea Warming south of Africa Cooling around Madagascar | Neutral | Warming to northwest, south, southwest and southeast | Neutral | Cooling off Equator, north and south and extends to Africa. 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.
For this week only, I am covering the MJO here. The MJO often become muted during the development of an El Nino but it does play a part in the regulation of the onset. So it is important but most likely will become more interesting in November. So the following discussion explains why it is not very important rght now and how it is impacting World Weather and for those who are so inclined, just jump over it.
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.
And then the CPC version.
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.
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.
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 22, 2018 , in the afternoon working from the October 21 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
Anomaly Segment | Estimated Anomaly | |
Last Week | This Week | |
A. 170W to 160W | +1.2 | +1.1 |
B. 160W to 150W | +1.1 | +1.2 |
C. 150W to 140W | +0.8 | +0.9 |
D. 140W to 130W | +0.7 | +0.0 |
E. 130W to 120W | +1.1 | +1.0 |
Total | +4.9 | +6.1 |
Total divided by five i.e. the Daily Nino 3.4 Index | (+4.9)/5 = +1.0 | (+6.1)/5 = +1.2 |
My estimate of the daily Nino 3.4 SST anomaly tonight is +1.2 (Tau-Triton seems to be running warm) which is an El Nino value. NOAA has reported the weekly Nino 3.4 to be +0.9 which is also an el Nino value. Nino 4 is reported to be the same as last week at +0.9. Nino 3 is reported to be warmer at 1.0. Nino 1 + 2 which extends from the Equator south rather than being centered on the Equator is reported a bit cooler at +0.3. 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.
Subareas of the Anomaly | Westward Extension | Eastward Extension | Degrees of Coverage | Total by ENSO Phase | |
Total | Portion in Nino 3.4 Measurement Area | ||||
These Rows below show the Extent of El Nino Impact on the Equator | |||||
1.5C to 2.0C | NA | NA | 0 | 0 | 0 |
1C to 1.5C (strong) | 140E | LAND | 125 | 50 | 50 |
+0.5C to +1C (marginal) | LAND | LAND | 0 | 0 | |
These Rows Below Show the Extent of ENSO Neutral Impacts on the Equator | |||||
0.0 to 0.5C (warmish neutral) | LAND | LAND | 0 | 0 | 0 |
-0.5C to 0C (coolish neutral) | LAND | LAND | 0 | 0 | |
This week there are 0 degrees of longitude along the Equator in the Nino 3.4 Measurement Area which registers La Nina values. There are 50 degrees that register El Nino. The other 0 degrees register Neutral. That is not the case for the full +5N and +5S width of the Nino 3.4 Measurement Area but in this analysis we are just looking at the Equator. Roughly speaking, the ratio of the El Nino Value to 50 tells us if we are close to being in El Nino. And we are 50/50X100% = 100% compared to 100% last week. |
Forecasting the Evolution of ENSO
Here is the primary NOAA model for forecasting the ENSO Cycle. | The CDAS model is a legacy “frozen” NOAA system meaning the software is maintained but not updated. We find it convenient to obtain this graphic from Tropical Tidbits.com |
This model is forecasting El Nino. I am no longer showing the larger version of this graphic but if you click on it it will enlarge. Also, click here to see a month by month version of the same model but without some of the correction methodologies applied. It gives us a better picture of the further out months as we are looking at monthly estimates versus three-month averages. | The CDAS readings were headed down until very recently when they reversed up. |
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.
The JAMSTEC discussion was presented in our October 20 Article. .
Here is the Nino 3.4 report from the Australian BOM (it updates every two weeks)
And the ENSO Outlook Discussion Issued on October 23, 2018
El Niño ALERT; positive Indian Ocean Dipole may be underway
The Bureau’s ENSO Outlook remains at El Niño ALERT, indicating there is approximately a 70% chance of El Niño occurring in 2018—around triple the normal likelihood. In the Indian Ocean there are signs that a positive Indian Ocean Dipole (IOD) is underway.
An El Niño and a positive IOD increase the likelihood of a dry and warm end to the year across most of Australia. They also raise the risk of heatwaves and bushfire weather in the south, while there are typically fewer tropical cyclones in the Australian region.
The surface of the tropical Pacific has warmed over the past month due to weakening of the trade winds. Sub-surface waters also remain warmer than average, increasing the potential for further warming at the surface. However, atmospheric indicators in the tropical Pacific such as the Southern Oscillation Index (SOI), cloudiness and trade winds, are yet to indicate that the ocean and atmosphere have coupled and hence are reinforcing each other. A positive feedback between the ocean and atmosphere is what defines and sustains an El Niño event.
International climate models suggest further warming of the tropical Pacific Ocean is likely, increasing the chance of coupling occurring in the coming months. Six of eight models predict El Niño thresholds will be met or exceeded in November.
Six of the eight models surveyed indicate El Niño thresholds are likely to be met or exceeded during November 2018, with a seventh reaching threshold values later during the summer. El Niño onset during November or 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 23, 2018)
The IOD index has exceeded the positive threshold (+0.4 °C) for five of the last six weeks. If these values persist for anther fortnight, 2018 will be considered a positive IOD year. The latest weekly index value to 21 October was +0.45 °C. These values need to persist until at least November for 2018 to be considered a positive IOD year.
All of the six international climate models surveyed by the Bureau indicate that the positive IOD event will breakdown during November; this would be in line with the typical seasonal pattern of the IOD. Due to the movement of the monsoon trough in the Indian Ocean, the IOD typically has little influence on Australian climate from December to April. When the monsoon trough shifts southwards into the southern hemisphere, it changes the broadscale wind patterns, meaning that the IOD pattern is unable to form.
The passage of tropical cyclone Luban across the Arabian Sea and north of the Indian Ocean appears to have temporarily cooled sea surface temperatures near the western node of the IOD, but warm SST anomalies generally persist across most of the northern Indian Ocean. Waters near the Indonesian island of Sumatra (close to the eastern node of the IOD) and near northwestern Australia are close to average.
A positive IOD event typically reduces spring rainfall in central and southern Australia, and can exacerbate any potential El Niño 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
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.
The SOI Index is marginally in El Nino territory.
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.
The potential for a near or marginal El Nino this winter may extend the period needed for a shift in the PDO. We are looking for a powerful El Nino to signal the change not a weak to moderate El Nino. But JAMSTEC which was forecasting a moderate to strong El Nino has backed off on the intensity of the forecast El Nino so it may be that we may not yet be moving to McCabe A and the U.S. will not have just yet get used to being wet for the next 20 to 30 years but instead have another two to five years of the current pattern .
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. Useful Reference Information
The current conditions are measured by determining the deviation of actual sea surface temperatures from seasonal norms (adjusted for Global Warming) in certain parts of the Equatorial Pacific. The below diagram shows those areas where measurements are taken.
NOAA focuses on a combined area which is all of Region Nino 3 and part of Region Nino 4 and it is called Nino 3.4. They focus on that area as they believe it provides the best correlation with future weather for the U.S. primarily the Continental U.S. not including Alaska which is abbreviated as CONUS. The historical approach of measurement of the impact of the sea surface temperature pattern on the atmosphere is called the Southern Oscillation Index (SOI) which is the difference between the atmospheric pressure at Tahiti as compared to Darwin Australia. It was convenient to do this as weather stations already existed at those two locations and it is easier to have weather stations on land than at sea. It has proven to be quite a good measure. The best information on the SOI is produced by Queensland Australia and that information can be found here. SOI is based on Atmospheric pressure as a surrogate for Convection and Subsidence. Another approach made feasible by the use of satellites is to measure precipitation over the areas of interest and this is called the El Nino – Southern Oscillation (ENSO) Precipitation Index (ESPI). We covered that in a weekly Weather and Climate Report which can be found here. Our conclusion was that ESPI did not differentiate well between La Nina and Neutral. And there is no