Written by Sig Silber
As usual on the last day of each month, NOAA updates the “early outlook” for the following month in this case August. We report on that which includes a forecast for partial drought relief and we provide our usual analysis for the next twenty-five days. We also will begin to focus on the potential for the forecasted El Nino to fail.
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Now let us first address the NOAA Update of the August, 2018 Forecast.
First, I present a summary showing the prior and the new August forecast and the previously issued three-month forecast. Larger graphics follow but these smaller graphics can be enlarged.
Temperature | Precipitation | |
Prior Issued on July 19, 2018 | ||
Updated on July 31, 2018 | ||
Three Month Forecast Issued on July 19, 2018 |
Prior August Temperature Forecast Issued on July 19, 2018
New August Temperature Forecast Issued on July 31, 2018
Turning to Precipitation
Prior August Precipitation Forecast issued on July 19, 2018
New August Precipitation Forecast Issued on July 31, 2018
Here is the NOAA Discussion released on July 31, 2018 with the August Update.
30-DAY OUTLOOK DISCUSSION FOR AUGUST 2018
THE UPDATED MONTHLY TEMPERATURE AND PRECIPITATION OUTLOOKS FOR AUGUST 2018 ARE BASED ON THE LATEST MODEL GUIDANCE AND RECENT SHORT AND EXTENDED RANGE OUTLOOKS FROM NCEP CENTERS.
THE UPDATED TEMPERATURE OUTLOOK FOR AUGUST IS SIMILAR OVERALL TO THE AUGUST TEMPERATURE OUTLOOK RELEASED ON JULY 19, WITH SOME CHANGES. ABOVE NORMAL AVERAGE TEMPERATURES FOR AUGUST ARE INCREASINGLY LIKELY FOR THE WESTERN CONUS, WITH DYNAMICAL MODEL FORECASTS FOR MOST AREAS OF THE WEST AT THE BEGINNING OF THE MONTH INDICATING POSITIVE ANOMALIES, AS WELL AS GUIDANCE FROM THE NCEP CFS FOR THE FULL MONTH. BELOW NORMAL TEMPERATURES ARE MOST LIKELY FOR PARTS OF THE PACIFIC NORTHWEST EARLY IN THE MONTH. HOWEVER, BY THE END OF THE MONTH, ABOVE NORMAL TEMPERATURES ARE MORE LIKELY FOR THE ENTIRE WEST. DYNAMICAL MODEL FORECASTS, INCLUDING THE CFS, INDICATE AN INCREASED POTENTIAL FOR BELOW NORMAL TEMPERATURES OVER THE NORTHERN CENTRAL AND SOUTHEASTERN CONUS DURING THE FIRST HALF OF WEEK 1. GUIDANCE FOR THE AVERAGE TEMPERATURES FOR THE WEEK 3 AND 4 PERIOD, INCLUDING THE CFS, ECMWF, AND SUBSEASONAL EXPERIMENT (SUBX) ENSEMBLES, INDICATE BELOW NORMAL TEMPERATURES MAY RETURN LATE IN THE MONTH. HOWEVER GUIDANCE FOR THE WEEK 2 PERIOD, DECADAL TRENDS, AND SEASONAL CLIMATE SIGNALS INDICATE LOW PROBABILITIES THAT AVERAGE AUGUST TEMPERATURES WILL BE BELOW NORMAL. EQUAL CHANCES OF ABOVE, NEAR AND BELOW NORMAL TEMPERATURES IS INDICATED FOR A LARGE AREA OF THE NORTHERN AND CENTRAL PLAINS, THE UPPER AND CENTRAL MISSISSIPPI VALLEY, THE OHIO VALLEY, AND PARTS OF THE SOUTHEAST TO THE ATLANTIC COAST. ABOVE NORMAL TEMPERATURES CONTINUE TO BE LIKELY FOR THE NORTHEAST, AS INDICATED BY FORECAST GUIDANCE FOR WEEKS 1 THROUGH 4. ABOVE NORMAL TEMPERATURES ARE LIKELY FOR MUCH OF THE SOUTHERN PLAINS, FOLLOWING FORECAST GUIDANCE FOR WEEK 2 FROM THE GEFS AND ECMWF ENSEMBLES, AND FOR WEEKS 2 THROUGH 4 FROM VARIOUS MEMBER MODELS OF SUBX. INCREASED CHANCES OF ABOVE NORMAL TEMPERATURES ARE INDICATED FOR ALL REGIONS OF ALASKA, WHERE MODEL FORECASTS INDICATE BELOW NORMAL TEMPERATURES DURING WEEK 2 AND ABOVE NORMAL TEMPERATURES AT THE BEGINNING AND END OF THE MONTH.
THE UPDATED PRECIPITATION OUTLOOK FOR AUGUST IS SIMILAR OVERALL TO THE AUGUST PRECIPITATION OUTLOOK RELEASED ON JULY 19, BUT INDICATES SIGNIFICANT CHANGES IN THE OUTLOOK FOR THE EASTERN CONUS, AS WELL AS SMALLER CHANGES IN OTHER REGIONS. FORECAST GUIDANCE FOR WEEKS 1 THROUGH 4 INDICATE AN INCREASED PROBABILITY OF ABOVE NORMAL PRECIPITATION OVER MUCH OF THE EASTERN CONUS, FROM THE EASTERN GREAT LAKES REGION, SOUTHWARD INTO THE OHIO VALLEY AND MID-ATLANTIC REGION, TO THE SOUTHEAST AND EASTERN GULF COAST STATES. WPC FORECASTS INDICATE A GREATER PROBABILITY OF PRECIPITATION THAN PREVIOUSLY ACROSS PARTS OF THE CENTRAL PLAINS DURING THE END OF WEEK 1. HOWEVER, MODEL GUIDANCE, INCLUDING THE CFS AND SUBX ENSEMBLE MODELS, FOR THE FIRST HALF OF THE MONTH INDICATES BELOW NORMAL PRECIPITATION IS LIKELY FOR MUCH OF THE CENTRAL AND SOUTHERN PLAINS. DYNAMICAL MODEL FORECASTS AND THE CPC EXPERIMENTAL PRECIPITATION OUTLOOK FOR WEEKS 3 AND 4 INDICATE ABOVE NORMAL PRECIPITATION IS MORE LIKELY THAN BELOW NORMAL FOR PARTS OF THE CENTRAL PLAINS, INCLUDING SOUTHERN NEBRASKA, KANSAS, AND NORTHERN OKLAHOMA, LATE IN THE MONTH. THE UPDATED MONTHLY OUTLOOK INDICATES BELOW NORMAL PRECIPITATION FOR AUGUST REMAINS LIKELY FOR A SMALLER AREA OF THE SOUTHERN PLAINS, EXTENDING NORTHWARD INTO CENTRAL OKLAHOMA. ABOVE NORMAL PRECIPITATION CONTINUES TO BE LIKELY FOR MUCH OF THE SOUTHWEST, FROM SOUTHERN CALIFORNIA INTO PARTS OF THE FOUR CORNERS STATES, SUPPORTED BY THE LATEST MODEL GUIDANCE FROM THE CFS, AS WELL AS OTHER ENSEMBLE PREDICTION SYSTEMS. ABOVE NORMAL PRECIPITATION CONTINUES TO BE LIKELY FOR WESTERN ALASKA, SUPPORTED BY DYNAMICAL MODEL FORECASTS, INCLUDING THE CFS.
Visual Consistency Testing.
Sometimes it is useful to see how the Monthly forecast fits with the 1 – 5 Day, 6 – 10 Day , 8 – 14 Day and Week 3 and 4 forecasts. 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
Sometimes it is useful to compare the forecast for the current month with the prior three-month forecast to see if the updated forecast for August might impact the prior forecast for August/September/October issued less than ten days ago.
August 2018 Plus August – October 2018 Outlook
One can mentally subtract the First-Month Outlook from the Three-month Outlook and create the Outlook for the last two months in the three-month period.
*The concept is that the probabilities of a deviation from climatology in the First Month and the combined Month Two and Three forecast that one derives must average out to the probabilities shown in the three-month maps.
For comparison purposes, here are the NOAA August – September – October forecast maps on the first set of rows and the September – October – November JAMSTEC forecast maps for North America in the second set of rows. * JAMSTEC did not publish an ASO forecast but a SON forecast.
NOAA July-August-September 2018 Temperature | NOAA July-August-September 2018 Precipitation |
JAMSTEC September October November 2018 Temperature | JAMSTEC September October November Precipitation |
A. Now we will begin with our regular approach and focus on Alaska and CONUS (all U.S.. except Hawaii).
We are skipping the summary because it was provided in the initial section of this report.
Let’s now return our focus back 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 more activity in Mexico than CONUS.
Tonight, Tuesday evening July 31, 2018, as I am looking at the above graphic, the recent pattern continues.
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. |
60 Hour Forecast Animation
Here is a national animation of weather fronts and precipitation forecasts with four 6-hour projections of the conditions that will apply covering the next 24 hours and a second day of two 12-hour projections the second of which is the forecast for 48 hours out and to the extent it applies for 12 hours, this animation is intended to provide coverage out to 60 hours. Beyond 60 hours, additional maps are available at links provided below. The explanation for the coding used in these maps, i.e. the full legend, can be found here although it includes some symbols that are no longer shown in the graphic because they are implemented by color coding.
You can enlarge the below daily (days 3 – 7) weather maps for CONUS by clicking on Day 3 or Day 4 or Day 5 or Day 6 or Day 7. These maps auto-update so whenever you click on them they will be forecast maps for the number of days in the future shown.
What is Behind the Forecasts? Let us try to understand what NOAA is looking at when they issue these forecasts.
Below is a graphic which highlights the forecasted surface Highs and the Lows re air pressure on Day 7. The Day 3 forecast can be found here. the Day 6 Forecast can be found here. Actually all the small graphics below can be clicked on to enlarge them.
When I look at this Day 7 forecast, we see the Hawaiian High with surface central pressure of 1032 hPa. There is also an Alaskan Trough that is moving down the Coast inside of the Hawaiian High and it has surface central pressure of 1000 hPa. We can locate the Bermuda High but the center is off the map but the surface central pressure is at least 1020 hPa. And there is a large Arctic High with surface central pressure of 1020 hPa. The Four Corners High is where it is expected for this time of the year with surface central pressure of 1020 hPa. The exact location and shape of the Four Corners High will be critical. Notice the centroid of the highest pressure of this elongated ridge is in Mexico. The forecast calls for this High to drift east and south which will benefit Arizona and Western New Mexico.
I provided this write up that provides a simple explanation on the importance of semipermanent Highs and Lows and another link that discussed possible changes in the patterns of these highs and lows which could be related to a Climate Shift (cycle) in the Pacific or Global Warming. Remember this is a forecast for Day 7. It is not the current situation.
The table below showing the Day 3, Day 4, Day 5, Day 6 and Day 7 of this graphic can be useful in thinking about how the pattern of Highs and Lows is expect to move during the week.
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.
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 hard to tell but it looks like that West Coast Trough does not make it very far south. The forecasting models are not in agreement on that.
Day 3 Above, 6 Below | Day 4 Above,7 Below | Day 5 Above. |
Here is the seven-day cumulative precipitation forecast. More information is available here.
Four – Week Outlook: Looking Beyond Days 1 to 5, What is the Forecast for the Following Three + Weeks?
I use “EC” in my discussions although NOAA sometimes uses “EC” (Equal Chances) and sometimes uses “N” (Normal) to pretty much indicate the same thing although “N” may be more definitive.
First – Temperature
6 – 10 Day Temperature Outlook issued today (Note the NOAA Level of Confidence in the Forecast Released on July 31, 2018 was 5 out of 5
8 – 14 Day Temperature Outlook issued today (Note the NOAA Level of Confidence in the Forecast Released on July 31, 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 July 31, 2018 was 5 out of 5)
8 – 14 Day Precipitation Outlook Issued Today (Note the NOAA Level of Confidence in the Forecast Released on July 31, 2018 was 4 out of 5)
Looking further out.
Here is the 6 – 14 Day NOAA discussion released today July 31, 2018. I am not showing the weak 3/4 discussion released Friday July 27, 2018 because it really has been superceded.
6-10 DAY OUTLOOK FOR AUG 06 – 10 2018
TODAY’S ENSEMBLES ARE IN GOOD AGREEMENT ON THE OVERALL 500-HPA FLOW PATTERN OVER THE FORECAST DOMAIN. MODELS DEPICT ANOMALOUSLY DEEP TROUGHS OVER MAINLAND ALASKA AND OFF THE PACIFIC NORTHWEST COAST, AND A RELATIVELY WEAK TROUGH OVER THE NORTHEAST. AN ANOMALOUSLY STRONG RIDGE IS EXPECTED OVER THE ALEUTIANS, AND A RIDGE FORECAST OVER THE CENTRAL CONUS IS EXPECTED TO BE NEAR-AVERAGE IN STRENGTH. THE MANUAL 500-HPA HEIGHT BLEND FOR THE 6-10 DAY PERIOD, FAVORING THE LATEST ECMWF ENSEMBLE MEAN, DEPICTS ABOVE NORMAL HEIGHTS OVER THE ALEUTIANS, BELOW NORMAL HEIGHTS OVER THE REST OF ALASKA AND THE WESTERN THIRD OF THE CONUS, AND NEAR TO ABOVE NORMAL HEIGHTS OVER THE REST OF THE CONUS. THE LAST SEVERAL DETERMINISTIC GFS RUNS SHOW POOR RUN-TO-RUN CONTINUITY, SO THEY WEREN’T CONSIDERED IN TODAY’S BLEND. [Editor’s Note: Given that the GFS, NAEFS and ECMFS disagree on the track of the Pacific Northwest Trough, it seems that assigning a level of confidence of 5 out of 5 might be a bit too optimistic]
PERSISTENT TROUGHING EXPECTED DURING THE PERIOD FAVORS BELOW NORMAL TEMPERATURES FOR ALASKA. UNLIKE YESTERDAY, BELOW NORMAL TEMPERATURES ARE FAVORED THROUGHOUT ALASKA BECAUSE TODAY’S MODELS FAVOR DEEPER TROUGHING OVER ALASKA AND A SLIGHTLY WEAKER RIDGE OVER THE ALEUTIANS. A DEEP TROUGH PREDICTED TO MOVE INTO THE WESTERN CONUS DURING THE 6-10 DAY PERIOD ENHANCES CHANCES OF BELOW NORMAL TEMPERATURES THERE. MODELS CONTINUE TO PREDICT LARGE POSITIVE TEMPERATURE ANOMALIES OVER MUCH OF THE EASTERN TWO-THIRDS OF THE U.S., FAVORING ABOVE NORMAL TEMPERATURES FOR THOSE AREAS (ESPECIALLY FROM THE NORTHERN PLAINS TO THE NORTHEAST WHERE ANOMALIES ARE HIGHEST AND TOOLS ARE IN THE BEST AGREEMENT).
A FEW STORM SYSTEMS MOVING SOUTH FROM ALASKA INTO THE PACIFIC NORTHWEST INCREASE CHANCES OF ABOVE NORMAL PRECIPITATION FOR MOST OF ALASKA AND ESPECIALLY THE PACIFIC NORTHWEST (WHICH IS TYPICALLY FAIRLY DRY THIS TIME OF YEAR). A RELATIVELY QUIET PATTERN FOR PARTS OF WESTERN AND NORTHERN MAINLAND ALASKA FAVORS BELOW NORMAL PRECIPITATION THERE. THE RIDGE OVER THE CENTRAL CONUS IS EXPECTED TO BE IN A POSITION FAVORABLE FOR MONSOON PRECIPITATION, INCREASING THE LIKELIHOOD OF ABOVE NORMAL PRECIPITATION FOR PARTS OF ARIZONA, AND BELOW NORMAL PRECIPITATION FOR MUCH OF THE CENTRAL CONUS. PERSISTENT SOUTHERLY LOW-LEVEL WINDS FORECAST FOR MUCH OF THE EASTERN U.S. ENHANCES ODDS OF ABOVE NORMAL PRECIPITATION FOR PARTS OF THE GULF COAST AND THROUGH THE GREAT LAKES REGION AND PARTS OF THE EASTERN U.S.
FORECAST CONFIDENCE FOR THE 6-10 DAY PERIOD: WELL ABOVE AVERAGE, 5 OUT OF 5, DUE TO GOOD AGREEMENT AMONG THE MODELS AND TOOLS.
8-14 DAY OUTLOOK FOR AUG 08 – 14 2018
BY THE WEEK-2 PERIOD, MODELS SUGGEST THAT THE 500-HPA PATTERN WILL RETROGRADE A BIT AND BECOME SOMEWHAT LESS AMPLIFIED. AS THE ANOMALOUS TROUGHING IS EXPECTED TO WEAKEN SOMEWHAT OVER THE PACIFIC NORTHWEST BY WEEK-2, TEMPERATURES ARE FORECAST TO MODERATE, REDUCING THE CHANCES OF BELOW NORMAL TEMPERATURES THERE.
AN INCREASE IN UNCERTAINTY DURING THE WEEK-2 PERIOD LEADS TO GENERALLY LOWER PROBABILITIES ON THE MAP. THE EASTERN TROUGH IS PREDICTED TO DEEPEN A BIT BY THE WEEK-2 PERIOD, SLIGHTLY FAVORING ABOVE NORMAL PRECIPITATION THROUGHOUT THE EASTERN U.S. THE MID-LEVEL RIDGE OVER THE CENTRAL CONUS IS EXPECTED TO SHIFT SLIGHTLY EASTWARD, SHIFTING THE AREA OF FAVORED ABOVE NORMAL PRECIPITATION OVER THE SOUTHWEST INTO PARTS OF NEW MEXICO FOR THE WEEK-2 PERIOD.
FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD: ABOVE AVERAGE, 4 OUT OF 5, DUE TO FAIRLY GOOD AGREEMENT AMONG THE MODELS AND TOOLS.
THE NEXT SET OF LONG-LEAD MONTHLY AND SEASONAL OUTLOOKS WILL BE RELEASED ON AUGUST 16.
Some Indices of Possible Interest:
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.
Now we look at two models that I find very helpful. On the graphic on the left, 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.
NCEP-NEFS Dynamic Model | Statistical Models |
Analogs to the 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 |
Aug 8, 1952 (2) | El Nino | – | + | |
Jul 22, 1981 | Neutral | + | – | |
Jul 23, 1981 | Neutral | + | – | |
Jul 20, 1990 | Neutral | + | – | |
Jul 21, 1990 | Neutral | + | – | |
Aug 7, 1997 (2) | El Nino | + | + | MegaNino |
Jul 12, 1999 | La Nina | – | + | Following the MegaNino |
Jul 13, 1999 | La Nina | – | + | Following the MegaNino |
(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 July 12 to Aug 8 is 27 days. 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 July 26. These analogs are centered on 3 days and 4 days ago (July 26 or July 27). So the analogs could be considered to be in sync with respect to weather that we would normally be getting right now.
For more information on Analogs see discussion in the GEI Weather Page Glossary. For sure it is a rough measure as there are so many historical patterns but not enough to be a perfect match with current conditions. I use it mainly to see how our current conditions match against somewhat similar patterns and the ocean phases that prevailed during those prior patterns. If everything lines up I have my own measure of confidence in the NOAA forecast. Similar initial conditions should lead to similar weather. I am a mathematician so that is how I think about models.
Including duplicates, there are four Neutral Analogs, two La Nina analogs and four El Nino Analogs. The pre-forecast analogs this week disfavor McCabe Condition B. The cheat sheet below the McCabe graphics summarizes McCabe B and the fact that the analogs are not consistent with it adds some confidence to the NOAA 6 – 10 and 8 – 14 Day Forecasts.
The seminal work on the impact of the PDO and AMO on U.S. climate can be found here. Water Planners might usefully pay attention to the low-frequency cycles such as the AMO and the PDO as the media tends to focus on the current and short-term forecasts to the exclusion of what we can reasonably anticipate over multi-decadal periods of time. One of the major reasons that I write this weather and climate column is to encourage a more long-term and World view of weather.
In color | Black and White same graphics |
McCabe Condition | Main Characteristics |
A | Very Little Drought. Southern Tier and Northern Tier from Dakotas East Wet. Some drought on East Coast. |
B | More wet than dry but Great Plains and Northeast are dry. |
C | Northern Tier and Mid-Atlantic Drought |
D | Southwest Drought extending to the North and also the Great Lakes. This is the most drought-prone combination of Ocean Phases. |
You may have to squint but the drought probabilities are shown on the map and also indicated by the color coding with shades of red indicating higher than 25% of the years are drought years (25% or less of average precipitation for that area) and shades of blue indicating less than 25% of the years are drought years. Thus drought is defined as the condition that occurs 25% of the time and this ties in nicely with each of the four pairs of two phases of the AMO and PDO.
Historical Anomaly Analysis
When I see the same dates showing up often I find it interesting to consult this list.
A Useful Read
Some might find this analysis which you need to click to read interesting as the organization which prepares it focuses on the Pacific Ocean and looks at things from a very detailed perspective and their analysis provides a lot of information on the history and evolution of ENSO events.
Recent CONUS Weather
This is provided mainly to see the pattern in the weather that has occurred recently.
The U.S. Drought Monitor is a comprehensive way of understand the drought situation for the U.S. If is issued every Thursday and reflects the conditions as of the prior Tuesday. The drought monitor is not just based on precipitation but the condition of the land so it generally reflects more than a month’s precipitation and temperature and wind. The latest version of our report can be found here.
B. Beyond Alaska and CONUS Let’s Look at the World which of course also includes Alaska and CONUS
It is Useful to Understand the Semipermanent Pattern that Control our Weather and Consider how These Change from Winter to Summer. These two graphics (click on each one to enlarge) are from a much larger set available from the Weather Channel. They highlight the position of the Bermuda High which they are calling the Azores High in the January graphic and is often called NASH and it has a very big impact on CONUS Southeast weather and also the Southwest. You also see the north/south migration of the Pacific High which also has many names and which is extremely important for CONUS weather and it also shows the change of location of the ITCZ which I think is key to understanding the Indian Monsoon. A lot of things become much clearer when you understand these semi-permanent features some of which have cycles within the year, longer period cycles and may be impacted by Global Warming. We are now into early August and we should be starting to return 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.
Forecast for Today (you can click on the maps to enlarge them)
Additional Maps showing different weather variables can be found here.
Forecast for Day 6 (Currently Set for Day 6 but the reader can change that)
World Weather Forecast produced by the Australian Bureau of Meteorology. Unfortunately I do not know how to extract the control panel and embed it into my report so that you could use the tool within my report. But if you visit it Click Here and you will be able to use the tool to view temperature or many other things for THE WORLD. It can forecast out for a week. Pretty cool. Return to this report by using the “Back Arrow” usually found top left corner of your screen to the left of the URL Box. It may require hitting it a few times depending on how deep you are into the BOM tool. Below are the current worldwide precipitation and temperature forecasts for six days out. They will auto-update and be current for Day 6 whenever you view them. If you want the forecast for a different day Click Here
Temperature | Precipitation |
Please remember this graphic updates every six hours so the diurnal pattern can confuse the reader. | Other than the Equator, it looks quite dry. |
And now we have experimental forecasts from the U.S. NAEFS Model. They are difficult to read without first enlarging them.
Temperature | Precipitation |
You can really see that North America is warm. | You have click on this to read it. There are a lot of extremes dry and wet shown. But CONUS looks dry. |
Looking Out a Few Months
Here is the precipitation forecast from Queensland Australia:
It is kind of amazing that you can make a worldwide forecast based on just one parameter the SOI and changes in the SOI. This graphic has been updated and now is in line with the actual SOI. Of interest is wet western CONUS and the two belts of wet in the mid Asian Continent and dry for Equatorial Africa and the Middle East.
Sea Surface Temperature (SST) Departures from Normal for this Time of the Year i.e. Anomalies
My focus here is sea surface temperature anomalies as they are one of the two largest factors determining weather around the World. If we want to have a good feel for future weather we need to look at the oceans as our weather mostly comes from oceans and we need to look at
- Surface temperature anomalies (weather develops from the ocean surface and
- The changes in the temperature anomalies since that may provide clues as to how the surface anomalies will change based on the current trend of changes. This is not that easy to do since the oceans are deep, there are many currents, winds have an impact etc. Two ways that are available to use are to look at the change in the situation today compared to the average over a period of time and NOAA also produces a graphic of monthly changes. I use both. The first set of graphics is simply looking at the average compared to today and that is below.
Three Month Average Anomaly | Current Anomaly |
By this point La Nina is gone | Traces of El Nino but the Indo-Pacific Warm Pool is cool. I am not convinced an El Nino will materialize. |
And when we look in more detail at the current Sea Surface anomalies below, we see a lot of them not just along the Equator related to ENSO. Currently this graphic is not updating so the discussion remains as per last week. If NOAA updates this graphic in the next day or so I might update the discussion.
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 |
Eastern Mediterranean, Black Sea and Caspian Sea are cooling. Persian Gulf And Arabian Sea Cooling. | Warming around Japan and south of Kamchatka. | Warming Bering Straits. Cooling Anadyr Cooling from British Columbia out to sea south of the warm swath from Asia. Warming west of Baja and to the north and south
. | Warming Hudson Bay Warming off Nova Scotia Cooling off the U.S. Southeast. Cooling eastern Caribbean | Warming around British Isles. |
Equator | Eastern Pacific showing slight cooling. | |||
Africa | West of Australia | North, South and East of Australia | West of South America | East of South America |
Cool Gulf of Guinea | Cooling Southwest | Warming Maritime Content Warming west of New Zealand | Warming 20S to 30S | Cooling north and south of Equator. |
This may be a good time to show the recent values to the indices most commonly used to describe the overall spacial pattern of temperatures in the (Northern Hemisphere) Pacific and the (Northern Hemisphere) Atlantic and the Dipole Pattern in the Indian Ocean. Notice the change in the PDO in July of 2017 and the stability of the AMO index.
Most Recent Six Months of Index Values | PDO Click for full list | AMO click for full list. | Indian Ocean Dipole (Values read off graph) | |
October | -0.67 | +0.39 | -0.3 | |
November | +0.84 | +0.40 | 0.0 | |
December | +0.56 | +0.34 | -0.1 | |
January | +0.12 | +0.23 | 0.0 | |
February | +0.05 | +0.23 | +0.2 | |
March | +0.14 | +0.17 | +0.0 | |
April | +0.53 | +0.29 | +0.2 | |
May | +0.29 | +0.32 | +0.2 | |
June | +0.21 | +0.31 | 0.0 | |
July | -0.50 | +0.31 | 0.0 | |
August | -0.62 | +0.31 | +0.4 | |
September | -0.25 | +0.35 | +0.2 | |
October | -0.61 | +0.44 | 0.0 | |
November | -0.46 | +0.35 | 0.0 | |
December 2017 | -0.13 | +0.36 | -0.4 | |
January 2018 | +0.29 | +0.17 | -0.1 | |
February | -0.19 | +0.06 | 0.0 | |
March | -0.60 | +0.13 | -0.1 | |
April | -0.85 | +0.06 | 0.0 | |
May | -0.61 | -0.00 | -0.1 | |
June | -0.96 | -0.01 | -0.4 | |
July |
Switching gears, below is an analysis of projected tropical hazards and benefits over an approximately two-week period.
* Moderate Confidence that the indicated anomaly will be in the upper or lower third of the historical range as indicated in the Legend.** High Confidence that the indicated anomaly will be in the upper or lower third of the historical range as indicated in the Legend.
Tropical Activity Possibly Impacting CONUS.
When there is activity and I have not provided the specific links to the storm of “immediate” interest, one can obtain that information at this link. At this point in time, no (new) tropical events are expected to appear in this graphic during the next 48 hours. If that changes, we will provide an update.
Now let us look at the Western Pacific in Motion.
The above graphic which I believe covers the area from the Dateline west to 100E and from the Equator north to 45N normally shows the movement of tropical storms towards Asia in the lower latitudes (Trade Winds) and the return of storms towards CONUS in the mid-latitudes (Prevailing Westerlies). This is recent data not a forecast. But, it ties in with the Week 1 forecast in the graphic just above this graphic. Information on Western Pacific storms can be found clicking U.S. Navy Joint Typhoon Warning Center This (click here to read) is an unofficial private source but one that is easy to read but not working right now. And then there is the Central Pacific Hurricane Warning Center.
In the above graphic, it is difficult to reference the storms to geography. If you are patient and look closely you can see bodies of land under the storms. Mostly I am interested in
- How much of the tropical activity gets caught up in the westerlies and returns to CONUS and
- How much of the Asian storms return along the northern route to Alaska and British Columbia.
C. Progress of ENSO
A major driver of weather is Surface Ocean Temperatures. Evaporation only occurs from the Surface of Water. So we are very interested in the temperatures of water especially when these temperatures deviate from seasonal norms thus creating an anomaly. The geographical distribution of the anomalies is very important. To a substantial extent, the temperature anomalies along the Equator have disproportionate impact on weather so we study them intensely and that is what the ENSO (El Nino – Southern Oscillation) cycle is all about. Subsurface water can be thought of as the future surface temperatures. They may have only indirect impacts on current weather but they have major impacts on future weather by changing the temperature of the water surface. Winds and Convection (evaporation forming clouds) is weather and is a result of the Phases of ENSO and also a feedback loop that perpetuates the current Phase of ENSO or changes it. That is why we monitor winds and convection along or near the Equator especially the Equator in the Eastern Pacific.
Starting with Surface Conditions.
TAO/TRITON GRAPHIC (a good way of viewing data related to the part of the Equator and the waters close to the Equator in the Eastern Pacific where we monitor to determining the current phase of ENSO. It is probably not necessary in order to follow the discussion below, but here is a link to TAO/TRITON terminology.
And here is the current version of the TAO/TRITON Graphic. The top part shows the actual temperatures, the bottom part shows the anomalies i.e. the deviation from normal.
Location Bar for Nino 3.4 Area Above and Below
———————————————— | A | B | C | D | E | —————– |
My Calculation of the Nino 3.4 Index
I calculate the current value of the Nino 3.4 Index each Monday using a method that I have devised. To refine my calculation, I have divided the 170W to 120W Nino 3.4 measuring area into five subregions (which I have designated from west to east as A through E) with a location bar shown under the TAO/TRITON Graphic). I use a rough estimation approach to integrate what I see below and record that in the table I have constructed. Then I take the average of the anomalies I estimated for each of the five subregions.
So as of Tuesday July 31, in the afternoon working from the July 30 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 | +0.3 | +0.3 |
B. 160W to 150W | +0.4 | +0.2 |
C. 150W to 140W | +0.6 | +0.3 |
D. 140W to 130W | +0.8 | +0.5 |
E. 130W to 120W | +0.8 | +0.5 |
Total | +2.9 | +1.8 |
Total divided by five i.e. the Daily Nino 3.4 Index | (+2.9)/5 = +0.6 | (+1.8)/5 = +0.4 |
My estimate of the daily Nino 3.4 SST anomaly tonight is lower at +0.4 which is an ENSO Neutral value. NOAA has reported the weekly Nino 3.4 to be +0.3 which is an ENSO Neutral value. Nino 4 is reported to be the same as last week at +0.3. Nino 3 is reported to be cooler at +0.3. Nino 1 + 2 which extends from the Equator south rather than being centered on the Equator is reported the same at -0.3. It was up there close to -3.0 at one time so this index has been declining as an anomaly (rising) quite a bit and also fluctuating quite a bit which is not surprising as it is the area most impacted by the Upwelling off the coast. So it is an indication of the interaction between surface water and rising cool water. Thus it is subject to larger changes. I am only showing the currently issued version of the NINO SST Index Table as the prior values are shown in the small graphics on the right with this graphic. The same data in graphic form but going back a couple of more years can be found here. The full table of values can be found here.
This graphic brings the Nino 3.4 up to date and is easy to read. It may be more reliable than the NOAA readings. And Memorial Day is not a Holiday in Australia.
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.
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 | |||||
1C to 1.5C (strong) | NA | NA | 0 | 0 | 15 |
+0.5C to +1C (marginal) | 135W | LAND | 40 | 15 | |
These Rows Below Show the Extent of ENSO Neutral Impacts on the Equator | |||||
0.0 to 0.5C (warmish neutral) | 175E | 135W | 50 | 35 | 35 |
-0,5C to 0C (coolish neutral) | LAND | LAND | 0 | 0 | |
These Rows Below Show the Extent of La Nina Impacts on the Equator. | |||||
-0.5C or cooler Anomaly | LAND | LAND | 0 | 0 | 0 |
-1.0C or cooler Anomaly | LAND | LAND | 0 | 0 | |
-1.5C or cooler Anomaly | LAND | LAND | 0 | 0 | |
-2.0C or cooler Anomaly | LAND | LAND | 0 | 0 | |
-2.5C or cooler Anomaly | LAND | LAND | 0 | 0 | |
This week there are zero degrees of longitude along the Equator in the Nino 3.4 Measurement Area which registers La Nina values. There are 15 degrees that register El Nino. The other 35 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. |
The next graphic overlaps with the subsequent topic but I will show it here.
The discussion in this slide says it better than I could. One might compare the current reading to Oct/Nov 2017. The anomaly had returned to zero then reversed for a month and then returned to zero and now has gone positive. It now seems to be declining a bit.
Side by side comparison can be useful
Comparison Week Probably Third Week of December 2017 | Current Week |
Sea Surface Temperature and Anomalies
It is the ocean surface that interacts with the atmosphere and causes convection and also the warming and cooling of the atmosphere. So we are interested in the actual ocean surface temperatures and the departure from seasonal normal temperatures which is called “departures” or “anomalies”. Since warm water facilitates evaporation which results in cloud convection, the pattern of SST anomalies suggests how the weather pattern east of the anomalies will be different than normal.
A major advantage of the Hovmoeller method of displaying information is that it shows the history so I do not need to show a sequence of snapshots of the conditions at different points in time. This Hovmoeller provides a good way to visually see the evolution of this ENSO event. I have decided to use the prettied-up version that comes out on Mondays rather that the version that auto-updates daily because the SST Departures on the Equator do not change rapidly and the prettied-up version is so much easier to read. The bottom of the Hovmoeller shows the current readings. Remember the +5, -5 degree strip around the Equator that is being reported in this graphic. So it is the surface but not just the Equator.
This next graphic is more focused on the Equator and looks down to 300 meters rather than just being the surface.
Let us look in more detail at the Equatorial Water Temperatures.
We are now going to look at a three-dimensional view of the Equator and move from the surface view and an average of the subsurface heat content to a more detailed view from the surface down This graphic provides both a summary perspective and a history (small images on the right).
.
Anomalies are strange. You can not really tell for sure if the blue area is colder or warmer than the water above or below. All you know is that it is cooler than usual for this time of the year. A later graphic will provide more information. Aside from buoyancy the currents tend to bring water from that depth up to the surface mostly farther east. 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 with a maximum anomaly of +3C from 140W to 120W with additional warm water, but not quite as warm, extending west to Indonesia. |
The 28C Isotherm is now just west of the Dateline, the 27C Isotherm is just west of 140W, the 25C Isotherm is now at 120W. The 20C Isotherm is no longer close to reaching the surface near the coast due to reduced impact of the cool water being pushed to the surface. But the 23C Isotherm has reached the surface as the Kelvin Wave has pretty much played out. |
Tracking the change.
And now let us look at the atmosphere.
And Now the Air Pressure to Confirm that the Atmosphere is Reacting to the Sea Surface Temperature Pattern. The most Common way to do that is to use an Index called the SOI.
This index provides an easy way to assess the location of and the relative strength of the Convection (Low Pressure) and the Subsidence (High Pressure) near the Equator. Experience shows that the extent to which the Atmospheric Air Pressure at Tahiti exceeds the Atmospheric Pressure at Darwin Australia when normalized is substantially correlated with the Precipitation Pattern of the entire World. At this point there seems to be no need to show the daily preliminary values of the SOI but we can work with the 30 day and 90 day values.
Current SOI Readings
The 30 Day Average on July 31, 2018 was reported as +1.55 which is an ENSO Neutral value. The 90 Day Average was reported at -0.56 which is also an ENSO Neutral value. Looking at both the 30 and 90 day averages is useful with the 90 day lagging the 30 day as one would expect. |
SOI = 10 X [ Pdiff – Pdiffav ]/ SD(Pdiff) where Pdiff = (average Tahiti MSLP for the month) – (average Darwin MSLP for the month), Pdiffav = long term average of Pdiff for the month in question, and SD(Pdiff) = long term standard deviation of Pdiff for the month in question. So really it is comparing the extent to which Tahiti is more cloudy than Darwin, Australia. During El Nino we expect Darwin Australia to have lower air pressure and more convection than Tahiti (Negative SOI especially lower than -7 correlates with El Nino Conditions). During La Nina we expect the Warm Pool to be further east resulting in Positive SOI values greater than +7).
To some extent it is the change in the SOI that is of most importance. The MJO or Madden Julian Oscillation is an important factor in regulating the SOI and Ocean Equatorial Kelvin Waves and other tropical weather characteristics. More information on the MJO can be found here. Here is another good resource.
Forecasting the Evolution of ENSO
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 not 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. | Notice that since February, 2018 the Nino 3.4 Index has been rising. The CDAS data is not in conflict with the primary NOAA model but shows daily values rather then smoothing them out like the CFSv2 Model does. The CDAS data has recently risen to neutral with an El Nino trend. But it has recently returned to just plain neutral. |
The CFS.v2 is not the only forecast tool used by NOAA. The CPC/IRI Analysis which is produced out of The International Research Institute (IRI) for Climate and Society at Columbia University is also very important to NOAA.
Here is the most recent update.
Forecasts from Other Meteorological Agencies.
Here is the newly issued JAMSTEC Model Forecast. It suggests a less strong El Nino than their forecast last month. One can always find the latest JAMSTEC maps by clicking this link. You will find additional maps that I do not general cover in my monthly Update Report. Remember if you leave this page to visit links provided in this article, you can return by hitting your “Back Arrow”, usually top left corner of your screen just to the left of the URL box.
We now have the short discussion that goes with the above ENSO Forecast.
Prediction from 1st Jul., 2018
ENSO forecast:
The SINTEX-F predicts that a moderate-to-strong El Niño event may start in summer and reach its peak in winter. This El Niño is more or less of Modoki-type and we need to be careful of its impact that may be different from that of the canonical El Niño.
Indian Ocean forecast:
Occurrence of a positive Indian Ocean Dipole is clearly predicted by the SINTEX-F seasonal prediction system; the ensemble mean prediction suggests its evolution from summer and its peak in fall. In accord to the positive IOD evolution, sea level anomalies are expected to be negative (positive) in the eastern (western) tropical Indian Ocean. We may observe co-occurrence of a positive Indian Ocean Dipole and an El Niño/El Niño Modoki-like state in the latter half of 2018; this is as we observed in 1994 (with El Niño Modoki) or 1997 and 2015 (with El Niño).
Regional forecast:
On a seasonal scale, most part of the globe will experience a warmer-than-normal condition in fall, while some parts of eastern Russia, southern U.S.A., northern Brazil, and East Africa will experience a cooler-than-normal condition. In winter, most part of the globe will be in a warmer-than-normal condition, while U.S.A., Argentine, western Europe, and Tibet will experience a relatively cold condition.
As regards to the seasonally averaged rainfall in boreal fall, a wetter-than-normal condition is predicted for most parts of western/northern Canada, southern U.S.A., northern Brazil, East Africa, southern West Africa, and western/northern Europe. In contrast, northwestern/northeastern U.S.A., southern Brazil, eastern Europe, the Far East, northeastern India, northern Southeast Asia, the Philippines, Indonesia and Australia will experience a drier-than-normal condition. In particular, we notice that Indonesia and Australia may be extremely drier than normal, owing to the expected co-occurrence of a positive Indian Ocean Dipole and an El Niño/El Niño Modoki-like state.
In winter, we expect a drier-than-normal condition in U.S.A, Mexico, northern South American Continent, northern/western Australia, northern Mozambique, eastern Tanzania, a western part of southern Africa, western Europe, the Philippines, and Indonesia. On the other hand, eastern U.S.A, eastern Brazil, southeastern Australia, eastern South Africa, southern Mozambique, and central Africa will be wetter-than-normal.
Most part of Japan will experience warmer-than-normal and drier-than-normal conditions in fall as a seasonal average. However, more detailed monthly prediction suggests a rather wet condition in September. In winter, overall Japan will experience warmer-than-normal and drier-than normal conditions.
Here is the Nino 3.4 report from the Australian BOM (it updates every two weeks)
And the ENSO Outlook Discussion Issued on July 31, 2018
El Niño WATCH continues
The El Niño–Southern Oscillation (ENSO) remains neutral. While the central Pacific Ocean has cooled very slightly in the past fortnight, more than half of international climate models predict warming to recommence in the coming weeks, and El Niño likely to develop in spring. Therefore, the Bureau’s ENSO Outlook remains at El Niño WATCH. El Niño WATCH means there is approximately a 50% chance of El Niño forming in 2018; double the normal chance.
Oceanic ENSO indicators remain neutral. The surface of the tropical Pacific Ocean has cooled slightly in the past fortnight but remains warmer than average. Likewise, the water below the surface of the central and eastern tropical Pacific has also cooled recently, but remains warmer than average. Atmospheric indicators such as the trade winds and the Southern Oscillation Index (SOI), remain neutral.
Most international climate models surveyed by the Bureau indicate warming of the tropical Pacific is likely to recommence in the coming weeks. Five of eight models indicate El Niño levels will be reached in the southern hemisphere spring, while a sixth model reaches El Niño levels in December.
During El Niño, winter-spring rainfall in eastern Australian is typically below average while daytime temperatures are typically warmer than average in the south.
Indian Ocean IOD (It updates every two weeks)
This graphic shows a collection of models used to forecast the NINO 3.4 Index
Indian Ocean Dipole Outlook Discussion Issued July 31, 2018
The Indian Ocean Dipole (IOD) remains neutral. The weekly index value to 29 July was −0.35 °C. Three of six international climate models indicate a positive IOD event may develop, with a fourth model close to meeting thresholds. A positive IOD event typically reduces winter–spring rainfall in central and southern Australia, and can exacerbate any El Niño driven rainfall deficiencies.
It is useful to understand where and how the IOD is measured.
IOD Positive is the West Area being warmer than the East Area (with of course many adjustments/normalizations). IOD Negative is the East Area being warmer than the West Area. Notice that the Latitudinal extent of the western box is greater than that of the eastern box. This type of index is based on observing how these patterns impact weather and represent the best efforts of meteorological agencies to figure these things out. Global Warming may change the formulas probably slightly over time but it is costly and difficult to redo this sort of work because of long weather cycles.
D. Putting it all Together.
At this time, La Nina Conditions along the Equator have come to an end and we are solidly into ENSO Neutral and possibly entering El Nino Conditions. But the drivers of a transition to El Nino are not solidly in place.
Forecasting Beyond Five Years.
So in terms of long-term forecasting, none of this is very difficult to figure out actually if you are looking at say a five-year or longer forecast.
The research on Ocean Cycles is fairly conclusive and widely available to those who seek it out. I have provided a lot of information on this in prior weeks and all of that information is preserved in Part II of my report in the Section on Low Frequency Cycles 3. Low Frequency Cycles such as PDO, AMO, IOBD, EATS. It includes decade by decade predictions through 2050. Predicting a particular year is far harder.
The odds of a climate shift for the Pacific taking place has significantly increased. It may be in progress. The AMO is pretty much neutral at this point so it may need to become a bit more negative for the “McCabe A” pattern to become established. Our assessment is that the standard time for Climate Shifts in the Pacific is likely to prevail and it most likely will be a gradual process with a speed up in less than five years but more than two years. The next El Nino may be the trigger.
E. Relevant Recent Articles and Reports
Weather in the News
Nothing to Report
Weather Research in the News
Nothing to Report
Global Warming in the News
Attribution of the 2018 Heat in Northern Europe
The article is tainted by both the title and the mission of the organization that produced it: “Attribution.” And this sentence from the article further taints it. From the paper.
“This method assumes that global warming is the main factor affecting local temperatures since about 1900, and that virtually all global warming is attributable to anthropogenic factors.”
Well if you assume that global warming is anthropogenic and you validate that there is warming, exactly what have you proven other than the models have predictive power and I do not think they really did that in the paper? I think they have shown that it continues to warm. When you compare current three-day max average temperatures to the hottest three-day period in 1981-2010 and assess the probability of that happening, you are showing that it continues to warm. You are not really doing attribution. But it is an interesting paper never the less.
F. Table of Contents for Page II of this Report Which Provides a lot of Background Information on Weather and Climate Science
The links below may take you directly to the set of information that you have selected but in some Internet Browsers it may first take you to the top of Page II where there is a TABLE OF CONTENTS and take a few extra seconds to get you to the specific section selected. If you do not feel like waiting, you can click a second time within the TABLE OF CONTENTS to get to the specific part of the webpage that interests you.
1. Very High Frequency (short-term) Cycles PNA, AO,NAO (but the AO and NAO may also have a low frequency component.)
2. Medium Frequency Cycles such as ENSO and IOD
3. Low Frequency Cycles such as PDO, AMO, IOBD, EATS.
4. Computer Models and Methodologies
5. Reserved for a Future Topic (Possibly Predictable Economic Impacts)
G. Table of Contents of Contents for Page III of this Report – Global Warming Which Some Call Climate Change.
The links below may take you directly to the set of information that you have selected but in some Internet Browsers it may first take you to the top of Page III where there is a TABLE OF CONTENTS and take a few extra seconds to get you to the specific section selected. If you do not feel like waiting, you can click a second time within the TABLE OF CONTENTS to get to the specific part of the webpage that interests you.
2. Climate Impacts of Global Warming
3. Economic Impacts of Global Warming
4. Reports from Around the World on Impacts of Global Warming
H. Useful Background Information
The current conditions are measured by determining the deviation of actual sea surface temperatures from seasonal norms (adjusted for Global Warming) in certain parts of the Equatorial Pacific. The below diagram shows those areas where measurements are taken.
NOAA focuses on a combined area which is all of Region Nino 3 and part of Region Nino 4 and it is called Nino 3.4. They focus on that area as they believe it provides the best correlation with future weather for the U.S. primarily the Continental U.S. not including Alaska which is abbreviated as CONUS. The historical approach of measurement of the impact of the sea surface temperature pattern on the atmosphere is called the Southern Oscillation Index (SOI) which is the difference between the atmospheric pressure at Tahiti as compared to Darwin Australia. It was convenient to do this as weather stations already existed at those two locations and it is easier to have weather stations on land than at sea. It has proven to be quite a good measure. The best information on the SOI is produced by Queensland Australia and that information can be found here. SOI is based on Atmospheric pressure as a surrogate for Convection and Subsidence. Another approach made feasible by the use of satellites is to measure precipitation over the areas of interest and this is called the El Nino – Southern Oscillation (ENSO) Precipitation Index (ESPI). We covered that in a weekly Weather and Climate Report which can be found here. Our conclusion was that ESPI did not differentiate well between La Nina and Neutral. And there is now a newer measure not regularly used called the Multivariate ENSO Index (MEI). More information on MEI can be found here. The jury is still out on MEI and it it is not widely used.
The below diagram shows the usual location of the Indo-Pacific Warm Pool. When the warm water shifts to the east we have an El Nino; to the west a La Nina.
Interaction between the MJO and ENSO
This Table is a first attempt at trying to relate the MJO to ENSO
El Nino | La Nina | MJO Active Phase | MJO Inactive Phase | |
---|---|---|---|---|
Eastern Pacific Easterlies |
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Western Pacific Westerlies |
|
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MJO Active Phase |
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MJO Inactive Phase |
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History of ENSO Events as measured by the ONI
The new SON reading of -0.1 is clearly and ENSO Neutral reading. The full history of the ONI readings can be found here. The MEI index readings can be found here.
Four Quadrant Jet Streak Model Read more here This is very useful for guessing at weather as a trough passes through. It would apply to the states that are at the apex of the trough.
If the centripetal accelerations owing to flow curvature are small, then we can use the “straight” jet streak model. The schematic figure directly below shows a straight jet streak at the base of a trough in the height field. The core of maximum winds defining the jet streak is divided into four quadrants composed of the upstream (entrance) and downstream (exit) regions and the left and right quadrants, which are defined facing downwind.
Isotachs are shaded in blue for a westerly jet streak (single large arrow). Thick red lines denote geopotential height contours. Thick black vectors represent cross-stream (transverse) ageostrophic winds with magnitudes given by arrow length. Vertical cross sections transverse to the flow in the entrance and exit regions of the jet (J) are shown in the bottom panels along A-A’ and B-B’, respectively. Convergence and divergence at the jet level are denoted by “CON” and “DIV”. “COLD” and “WARM” refer to the air masses defined by the green isentropes.
[Editor’s Note: There are many undefined words in the above so here are some brief definitions. Isotachs are lines of equal wind speed. Convergence is when there is an inflow of air which tends to force the air higher with cooling and cloud formation. Divergence is when there is an outflow of air which tends to result in air sinking which causes drying and warming, Confluence is when two streams of air come together. Diffluence is when part of a stream of air splits off.]
Here is a time sequence animation. You may have to click on them to get the animation going.
When we discuss the jet stream and for other reasons, we often discuss different layers of the atmosphere. These are expressed in terms of the atmospheric pressure above that layer. It is kind of counter-intuitive to me. The below table may help the reader translate air pressure to the usual altitude and temperature one might expect at that level of air pressure. It is just an approximation but useful.
Re the above, H8 is a frequently used abbreviation for the height of the 850 millibar level (which is intended to represent the atmosphere above the Boundary Layer most impacted by surface conditions), H7 is the 700 mb level, H5 is the 500 mb level, H3 is the 300 mb level. So if you see those abbreviations in a weather forecast you will know what they are talking about.
MJO (Madden Julian Oscillation)
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. Here is a good description of the MJO.
This is the source of the analysis of the impact of the MJO on CONUS. “A composite study of the MJO influence on the surface air temperature and precipitation over the Continental United States Shuntai Zhou • Michelle L’Heureux • Scott Weaver • Arun Kumar”
The below shows the various phases of the MJO. Where the above average convection (green) is found is described by one of 8 phases shown below. The dry part of the pattern is shown in brown and is called the Inactive or dry part of the MJO.
The below is the summary analysis for precipitation in the July to September Season. The full data set for all seasons can be found here for Temperature and here for Precipitation. My analysis of that data was that there is not much difference between the level of significance of the temperature and precipitation in the JAS three-month period.