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posted on 24 August 2015

24 August 2015 Weather and Climate Report - NOAA Issues New Seasonal Outlook - Half an El Nino Approaches

Written by Sig Silber

NOAA has issued their new Seasonal Outlook on Thursday which appears to be essentially similar to the prior outlook.  An El Nino is forecast to arrive which is an unusual use of the English Language as this El Nino has not moved closer to CONUS and if anything has moved slightly further off the coast of South America. But Fall is arriving and Fall is when the impacts of an El Nino are first felt strongly in CONUS, so it is the calendar that has advanced. The El Nino itself is now best viewed as two weather phenomena: a western half that is clearly in decline and an eastern half that is still evolving. This is a bit unusual so we will have to see if the projected impacts which are based on normal El Nino events will apply to this unusual but potentially very powerful El Nino.

This is the Regular Edition of my weekly Weather and Climate Update Report. Additional information can be found here on Page II of the Global Economic Intersection Weather and Climate Report.

NOAA Issues New Seasonal Outlook.

Let's take a look at some of the maps starting with the September - October - November (SON) Outlooks.

Prior SON Temperature Outlook

`SON 2015 Temperature Outlook Issued July 16, 2015

New SON Temperature Outlook

August 20, 2015 SON Temperature Forecast.

As you can see there is not much change.

Prior SON Precipitation Outlook

SON 2015 Precipitation Outlook Issued July 16, 2015

New SON Precipitation Outlook

August 20, 2015 SON Precipitation Outlook

The Southeast is not as wet as in last month's map possibly because of the early arrival of the El Nino. It takes some time for the patterns to work their way east. The precipitation probabilities for Arizona have been increased and there is a drier than climatology area now shown for an area north of a line drawn from Duluth Minnesota to New York City.

Sometimes it is useful to combine the four maps into one graphic and this is done below

September 2015 plus SON 2015 Issued on August 20, 2015

The above shows the slight changes from September through the three month period September - October - November (SON). Personally I would prefer it if this graphic from NOAA showed September and then October/November separately but this is the way they do it.  The SON map includes September so it provides less information than an October/November Map would provide for comparison with September.

I could provide the maps that go out for 15 Months but they are available on Page II of this Report and can also be viewed here for temperature and here for precipitation and here for individual maps in larger size.

For many people, the following summary that I prepared from the maps and the discussion may be sufficient.

Summary of August 20 NOAA Seasonal Forecast Maps
  Precipitation Temperature
Timing Peak Impact Jan/Feb 2016 declining through March (April for CO, NM, TX) Peak Impact January  2016 declining through April (May TX).
Geographical Distribution

North Dry

South Wet

North and West Coast Warm

South Cold

Beyond May 2016 EC because it is too soon to predict a La Nina will follow this El Nino Rising Temperature Trend is used which is geographical in Nature and may be Ocean Cycle or Global Warming: It is not specified.

 

I am not going to comment in this issue on the accuracy of this Seasonal Outlook Update but it is certainly correct that there is a lag between the development of an ENSO Event and the translation to impacts on weather. I will say however that the maps have not changed in the past two updates. I have not checked the shading in detail so in some case, probabilities may have been increased but overall the forecast has not changed over the past two months and I have not bothered to go back further in time so I think the above table is more than adequate to describe the situation. Next week I will compare these maps with the JAMSTEC maps which are already available on Page II of this Report Worldwide Weather: Current and Three-Month Outlooks: 15 Month Outlooks  The JAMSTEC temperature maps are fairly different than the NOAA maps but the JAMSTEC precipitation maps ARE fairly similar until MAM 2016 in that JAMSTEC has extended the impact of this El Nino further into the Spring than has NOAA. But that is a long time from now so model accuracy is questionable that far out.

And now for Excerpts from the NOAA Discussion Released on August 20. 2015

CURRENT ATMOSPHERIC AND OCEANIC CONDITIONS

SSTS NEAR AND ALONG THE EQUATORIAL PACIFIC RANGE BETWEEN 1-4 DEGREES C ABOVE THE LONG-TERM AVERAGE FROM ABOUT THE INTERNATIONAL DATE LINE EASTWARD TO THE SOUTH AMERICAN COAST. WEST OF THE DATE LINE IN THE EQUATORIAL PACIFIC, SSTS ARE NEAR-, OR SLIGHTLY BELOW-, AVERAGE. SUBSURFACE WATER TEMPERATURES FROM NEAR THE DATE LINE EASTWARD TO THE SOUTH AMERICAN COAST, AND DOWN TO ABOUT 200 METERS, ARE ANYWHERE FROM 1-6 DEGREES C ABOVE AVERAGE. THIS SUBSURFACE VOLUME OF ANOMALOUSLY WARM WATER PROVIDES A RESERVOIR OF POTENTIAL HEAT ENERGY TO HELP SUSTAIN THE CURRENT EL NINO. WEST OF THE DATE LINE IN THE NEAR-EQUATORIAL PACIFIC, EXTENDING DOWN TO 200 METERS, WATER TEMPERATURES RANGE FROM 0.5-2.5 DEGREES C BELOW AVERAGE.  [Editor's Note: This possibly signifies the demise of this El Nino but it is a slow process to have cool water at depth in the Eastern Pacific and cool water from the west replace the reservoir of warm water at depth just off the Coast of South America.]

ATMOSPHERIC CONDITIONS ACROSS THE TROPICAL PACIFIC CONTINUE TO BE CONSISTENT WITH A SIGNIFICANT AND STRENGTHENING EL NINO. UPPER-LEVEL (200-HPA) WIND ANOMALIES ARE PRIMARILY WESTERLY OVER THE EASTERN PACIFIC, CENTRAL AMERICA, AND THE CARIBBEAN SEA, WHICH HAS HELPED TO SUPPRESS THE DEVELOPMENT OF TROPICAL CYCLONES IN THE ATLANTIC BASIN THIS SEASON. LOWER-LEVEL (850-HPA) WIND ANOMALIES ARE ALSO WESTERLY, ACROSS A LARGE PORTION OF THE TROPICAL PACIFIC, FROM ABOUT 150E TO 140W. OUTGOING LONGWAVE RADIATION (OLR) ANOMALIES FOR THE PAST MONTH INFER A RAINFALL DISTRIBUTION THAT IS VERY CONSISTENT WITH A MATURE EL NINO. ENHANCED CONVECTION WAS NOTED FROM ABOUT 160E ALONG AND JUST NORTH OF THE EQUATOR TO COSTA RICA AND PANAMA, WHILE SUPPRESSED CONVECTION WAS NOTED ACROSS THE FAR WESTERN PACIFIC AND INDONESIA.

THE EXTRA-TROPICAL PACIFIC OCEAN REMAINS CONSISTENT WITH THE POSITIVE PHASE OF THE PACIFIC DECADAL OSCILLATION (PDO), WITH THE MONTHLY INDEX AT +1.84 IN JULY, AS DOCUMENTED BY THE UNIVERSITY OF WASHINGTON. THIS MAY HAVE SOME IMPACT ON CONDITIONS NEAR THE WEST COAST OF NORTH AMERICA, ESPECIALLY THROUGH EARLY AUTUMN.

SEPTEMBER OUTLOOK

THESE CLIMATE MODEL FORECASTS HAVE REMAINED QUITE CONSISTENT OVER THE LAST FEW MONTHS AND AGREE REASONABLY WELL, IN GENERAL, WITH THE TEMPERATURE AND PRECIPITATION ANOMALIES ASSOCIATED WITH PAST EL NINO EVENTS. AT THE CURRENT TIME, THE MJO IS INACTIVE AND PLAYED NO ROLE IN THE SEPTEMBER OUTLOOK.
 
THE SEPTEMBER TEMPERATURE OUTLOOK DEPICTS ENHANCED ODDS FOR ABOVE NORMAL TEMPERATURES FROM CALIFORNIA NORTHWARD TO INCLUDE THE PACIFIC NORTHWEST, PARTS OF THE NORTHERN ROCKIES AND ALASKA. THIS HIGHLIGHTED REGION IS BASED ON SEVERAL FACTORS, WHEN APPROPRIATE, WHICH INCLUDES DYNAMICAL MODEL GUIDANCE, ABOVE-AVERAGE SSTS IN THE NORTH PACIFIC OCEAN, EL NINO CONDITIONS AND ANOMALOUSLY DRY SOIL MOISTURE IN SOME AREAS. ABOVE NORMAL TEMPERATURES ARE ALSO FAVORED FOR PARTS OF THE GULF COAST AND SOUTHEAST BASED ON DYNAMICAL MODEL GUIDANCE AND TO A LESSER EXTENT DRY SOIL MOISTURE CONDITIONS. BELOW NORMAL TEMPERATURES ARE MORE LIKELY FOR A REGION FROM THE SOUTHWEST NORTHEASTWARD INTO THE INTERIOR PORTION OF THE CONUS. THIS AREA IS HIGHLIGHTED BASED ON CORRELATION WITH EL NINO CONDITIONS, NEAR-TO-BELOW AVERAGE TEMPERATURE FORECASTS FROM THE NMME AND ANOMALOUSLY WET SOIL MOISTURE CONDITIONS IN SOME AREAS.
 
EL NINO CONDITIONS, AND STRONG AND CONSISTENT SIGNALS FROM DYNAMICAL MODEL GUIDANCE SUPPORT AN AREA OF FAVORED ABOVE-MEDIAN PRECIPITATION FROM SOUTHERN CALIFORNIA NORTHWARD AND EASTWARD TO INCLUDE SOME OF THE GREAT BASIN, MUCH OF THE ROCKIES, SOUTHWEST AND CENTRAL AND SOUTHERN PLAINS. ABOVE MEDIAN PRECIPITATION IS ALSO HIGHLIGHTED FOR THE SOUTH CENTRAL COAST OF ALASKA
CONSISTENT WITH EL NINO CONDITIONS. BELOW MEDIAN PRECIPITATION IS INDICATED ALONG THE GULF COAST, FOR PARTS OF THE SOUTHEAST AND LOWER MID-ATLANTIC BASED ON DYNAMICAL MODEL GUIDANCE AND CORRELATIONS WITH EL NINO CONDITIONS THIS TIME OF THE YEAR.

September – October – November.

THE SEPTEMBER-OCTOBER-NOVEMBER (SON) 2015 TEMPERATURE OUTLOOK INDICATES ENHANCED PROBABILITIES OF ABOVE-NORMAL TEMPERATURES FOR THE WESTERN CONTIGUOUS U.S., WITH PROBABILITIES REACHING OR EXCEEDING 60 PERCENT IN THE PACIFIC NORTHWEST. ABOVE-NORMAL TEMPERATURES ARE ALSO FAVORED ALONG THE EASTERN SEABOARD, EAST GULF COAST REGION, AND ALASKA, WITH PROBABILITIES REACHING OR EXCEEDING 70 PERCENT FOR THE NORTH SLOPE OF ALASKA. BELOW-NORMAL TEMPERATURES ARE FAVORED ACROSS SOUTH-CENTRAL PORTIONS OF BOTH THE GREAT PLAINS AND MISSISSIPPI VALLEY.

THE SON 2015 PRECIPITATION OUTLOOK INDICATES ENHANCED PROBABILITIES OF ABOVE-MEDIAN PRECIPITATION AMOUNTS FOR THE SOUTHEASTERN HALF OF CALIFORNIA, THE SOUTHWEST, THE CENTRAL AND SOUTHERN ROCKIES, MOST OF THE GREAT PLAINS, FROM THE LOWER MISSISSIPPI VALLEY EASTWARD ACROSS THE INTERIOR SOUTHEAST AND THE TENNESSEE VALLEY, AND ACROSS SOUTHERN ALASKA. ODDS FAVOR BELOW-MEDIAN PRECIPITATION AMOUNTS FOR THE PACIFIC NORTHWEST, AND FROM THE NORTHERN GREAT LAKES EASTWARD ACROSS NEW YORK AND NEW ENGLAND.

IN THE SUBSEQUENT SEASONS, THE OUTLOOK SLOWLY CHANGES TO REFLECT MORE CANONICAL ENSO IMPACTS AS WE HEAD TOWARD METEOROLOGICAL WINTER.

PROGNOSTIC DISCUSSION OF OUTLOOKS - SON 2015 TO SON 2016 [Editor's Note: there is a lot of redundancy in the discussion now related to SON and the discussion in the above three paragraphs but I have not tried to reduce the redundancy as I think it is easier to follow as written than if I had attempted to reduce  the redundancy]

TEMPERATURE

THE SON 2015 TEMPERATURE OUTLOOK RELIES PRIMARILY ON NMME OUTPUT, THE CFS, IMME, SST CONSTRUCTED ANALOGS, AND TO A LESSER DEGREE EL NINO COMPOSITES. ABOVE -NORMAL TEMPERATURES ARE FAVORED FOR THE WESTERN CONTIGUOUS U.S., WITH PROBABILITIES REACHING OR EXCEEDING 60 PERCENT IN THE PACIFIC NORTHWEST. EL NINO AND POSITIVE PDO EVENTS FAVOR ABOVE-NORMAL TEMPERATURES ALONG PRACTICALLY THE ENTIRE WEST COAST OF NORTH AMERICA. ABOVE-NORMAL TEMPERATURES ARE ALSO FAVORED ALONG THE EASTERN SEABOARD AND EAST GULF COAST REGION, BASED MOSTLY ON THE CFS AND NMME. MOST MODELS AGREE ON ELEVATED ODDS FOR ABOVE-NORMAL TEMPERATURES IN ALASKA, WITH PROBABILITIES REACHING OR EXCEEDING 70 PERCENT ACROSS THE NORTH SLOPE AREA. THESE HIGHER PROBABILITIES ARE ALSO SUPPORTED BY MORE RECENT TRENDS (LAST 10-15 YEARS) IN THE REDUCTION AND/OR DELAY OF SEA ICE ONSET. BELOW-NORMAL TEMPERATURES ARE FAVORED ACROSS SOUTH-CENTRAL PORTIONS OF BOTH THE GREAT PLAINS AND MISSISSIPPI VALLEY. THIS IS BASED ON DYNAMICAL MODELS SUCH AS THE CFS, NMME, AND IMME, AS WELL AS STATISTICS FROM THE SST CONSTRUCTED ANALOGS.

AS THE FORECASTS PROGRESS THROUGH THE AUTUMN AND INTO WINTER, THE PATTERN SLOWLY MORPHS TO ONE CONSISTENT WITH STRONG EL NINO CONDITIONS, LARGELY FAVORING BELOW-NORMAL TEMPERATURES ACROSS THE SOUTH-CENTRAL AND SOUTHEAST CONUS, WITH ABOVE-NORMAL TEMPERATURES ACROSS THE NORTHERN TIER. PROBABILITIES OF BELOW-NORMAL TEMPERATURES ACROSS THE SOUTHERN GREAT PLAINS REACH OR EXCEED 50 PERCENT IN DJF, JFM, AND FMA 2016. PROBABILITIES OF ABOVE-NORMAL TEMPERATURES REACH OR EXCEED 60 PERCENT ACROSS THE PACIFIC NORTHWEST AND THE UPPER MISSISSIPPI VALLEY IN DJF. IN DJF AND JFM, THE EXPECTATION OF A STRONG EL NINO FAVORS ELEVATED PROBABILITIES OF ABOVE-NORMAL TEMPERATURES ACROSS THE CENTRAL MISSISSIPPI AND OHIO VALLEYS, WITH A CORRESPONDING SOUTHWARD SHIFT OF FAVORED BELOW-NORMAL TEMPERATURES. IN GENERAL, PROBABILITIES FOR ABOVE-NORMAL TEMPERATURES WERE INCREASED SLIGHTLY FROM THE CORRESPONDING PREVIOUS SET OF OUTLOOKS ACROSS THE NORTHWESTERN AND NORTH-CENTRAL CONUS, IN ACCORDANCE WITH MORE CONFIDENCE IN A STRONG EL NINO BY LATE AUTUMN AND WINTER. BY FMA, PREDICTED ANOMALIES ARE STILL ROBUST, THOUGH THERE IS A NOTICEABLE DECLINE IN BOTH AREAL COVERAGE AND ANOMALY MAGNITUDES FORECAST DURING MAM AND AMJ 2016. BY SUMMER 2016, THE TRENDS TOWARD ABOVE-NORMAL TEMPERATURES BEGIN TO GAIN INFLUENCE AS THE WANING EL NINO LOSES INFLUENCE, SO THE FORECAST REFLECTS THE CPC CONSOLIDATION AND TRENDS.

PRECIPITATION

THE SON 2015 PRECIPITATION OUTLOOK INDICATES ENHANCED PROBABILITIES OF ABOVE-MEDIAN PRECIPITATION AMOUNTS FOR THE SOUTHEASTERN HALF OF CALIFORNIA, THE SOUTHWEST, THE CENTRAL AND SOUTHERN ROCKIES, MOST OF THE GREAT PLAINS EXTENDING EASTWARD ACROSS THE LOWER MISSISSIPPI AND TENNESSEE VALLEYS, THE INTERIOR  SOUTHEAST, AND SOUTHERN ALASKA. THESE ANOMALIES ARE CONSISTENT WITH HISTORICAL WARM ENSO EVENTS. THE NMME, IMME, CFS, AND SST CONSTRUCTED ANALOGS ALSO SUPPORT THIS PATTERN. THE EASTWARD EXTENSION OF FAVORED ABOVE-MEDIAN PRECIPITATION  ACROSS THE INTERIOR SOUTHEAST TENDS TO SHOW UP IN PAST STRONG EL NINOS, ESPECIALLY LATER IN THE SON SEASON. ODDS FAVOR BELOW-MEDIAN PRECIPITATION AMOUNTS OVER THE PACIFIC NORTHWEST, AND FROM THE NORTHERN GREAT LAKES EASTWARD ACROSS NEW YORK AND NEW ENGLAND. THE FORMER REGION (PACIFIC NORTHWEST) ALSO HAS SUBSTANTIAL SUPPORT FROM THE VARIOUS CLIMATE MODELS. THESE PRECIPITATION SIGNALS ARE ALSO WELL SUPPORTED BY ENSO COMPOSITES FOR SON. FOR OND AND NDJ, PAST EL NINOS HAVE FAVORED THE EASTWARD EXTENSION OF THE SUBTROPICAL JET STREAM ACROSS THE SOUTHERN CONUS. ACCORDINGLY, THE AREA OF PREDICTED ABOVE-MEDIAN PRECIPITATION HAS ALSO BEEN EXTENDED EASTWARD TO THE SOUTHERN ATLANTIC COAST, WITH PROBABILITIES AT OR ABOVE 50 PERCENT IN FLORIDA IN NDJ. ABOVE-MEDIAN PRECIPITATION IS FAVORED IN SOUTHERN ALASKA DURING OND. THE TWIN AREAS OF PREDICTED BELOW-MEDIAN PRECIPITATION, ONE IN THE NORTHWEST, AND THE OTHER IN THE NORTHEAST/GREAT LAKES REGION, ARE ALSO CONSISTENT WITH EL NINO COMPOSITES. DURING OND AND NDJ, THERE IS A PREFERRED TENDENCY FOR THE RELATIVE DRYNESS ACROSS THE NORTHWEST TO EXPAND EASTWARD, AND FOR THE RELATIVE DRYNESS ACROSS THE NORTHEAST AND GREAT LAKES AREA TO CONSOLIDATE ACROSS THE LATTER REGION.

FOR DJF 2015/16 AND JFM 2016, THE FORECAST ANOMALIES REACH THEIR PEAK STRENGTH, WITH PROBABILITIES FOR ABOVE-MEDIAN PRECIPITATION AMOUNTS REACHING OR EXCEEDING 60 PERCENT IN FLORIDA AND FAR SOUTHERN SECTIONS OF BOTH CALIFORNIA AND ARIZONA IN JFM. THE AREAS OF ANTICIPATED BELOW-MEDIAN PRECIPITATION ACROSS THE NORTHWEST AND FROM THE GREAT LAKES SOUTHWARD INTO THE TENNESSEE VALLEY REACH MATURITY DURING THESE TWO SEASONS. ODDS FOR BELOW-MEDIAN PRECIPITATION ARE ALSO ELEVATED ACROSS SOUTHWESTERN ALASKA IN DJF AND JFM, DUE MAINLY TO THE NMME, CFS, SST CONSTRUCTED ANALOGS, IMME, AND IRI PROJECTIONS.

PREDICTED ANOMALIES ARE STILL PRONOUNCED DURING FMA, THOUGH IN MAM THERE IS A NOTABLE DECLINE IN BOTH AREAL COVERAGE AND ANOMALY MAGNITUDES, WHICH CORRESPONDS TO THE EXPECTED WINDING DOWN OF THE CURRENT WARM EVENT. FROM AMJ ONWARD (COINCIDENT WITH THE SPRING BARRIER), THERE IS SIGNIFICANT UNCERTAINTY AS TO WHETHER OR NOT A LA NINA DEVELOPS, AND IF SO, ITS EXPECTED INTENSITY. THEREFORE, EC IS FORECAST FOR THE REMAINING PRECIPITATION OUTLOOKS.

Switching to the Current (Right Now to 5 Days Out) Weather Situation:  

A more complete version of this report with daily forecasts is available in Part II. This is a summary of that fuller report. This link Worldwide Weather: Current and Three-Month Outlooks: 15 Month Outlooks will take you directly to that set of information but in some Internet Browsers it may just take you to the top of Page II where there is a TABLE OF CONTENTS and you may have to wait for a few seconds for your Browser to redirect to the selected section with that Page or if that process is very slow you can simply click a second time within the TABLE OF CONTENTS to get to that specific part of the webpage.

First, here is a national 12 hour to 60 hour forecast of weather fronts shown as an animation. Beyond 60 hours, the maps are available at the link provided above.

current highs and lows

The explanation for the coding used in these maps, i.e. the full legend, can be found here.

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. You can see the location of the Four Corners area where Utah, Colorado, Arizona, and New Mexico meet. At this time of the year there is typically a high pressure system near that area and it is called the Four Corners High. When the Four Corners High is centered directly over the Four Corners area, it creates pretty much a block for the Sonoran Monsoon which only visits its northern neighbor when the highs and lows are located in a way that draws the moist air north.

Small changes in the location of that feature make a big difference in the weather of probably about ten or more states.

This High moves around a lot so by the time you view this report, it most likely it will be located somewhere else which results in a different circulation pattern. The current positon is not favorable for drawing up moisture from Mexico except possibly for Arizona and perhaps California. If you know where the High is, you can always imagine the clockwise circulation and how that might impact the movement of moisture in from the Gulf of Mexico and up from Mexico and in from the Gulf of California. So this graphic can be very very useful. And it auto-updates, I think every six hours. Even without a weather map, you generally can figure it out. Wind to your back, High to your right, Low to your left.

7 Day 500 MB Geopotential Forecast

Because "Thickness Lines" are shown by those green lines on this graphic it is a good place to define "Thickness" and its uses. You can find a full uk.sci.weather style explanation (thorough) at that link or just remember that Thickness measures the virtual temperature (temperature plus moisture content) of the lower attmosphere and is very useful especially in the winter at identifying areas prone to snow and in the summer areas which are going to be hot and humid. Here is a U.S. style explanation of "Thickness" by Jeff Haby who is a valuable source of Haby Hints for anyone who wants an explanation of a meteorological term.

There certainly is a lot of storm activity in the Western Pacific.  The possibility of the trailing Typhoon Atsani curving back towards the U.S. and having its moisture enter the circulation of moisture from the Pacific into CONUS has been discussed. You can see it curving in this animation which gets updated daily or more frequently so you can track it.

Western Pacific Tropical Activity

In the Eastern Pacific Tropical Weather Outlook graphic below, notice that there is no Pacific Tropical Storm projected to be close enough to the coast to significantly impact CONUS right now. The Sonoran Monsoon which we commandeered (as well as a large part of what used to be Mexico and is now the U.S. West) and renamed (probably more recently) the North American Monsoon or the Southwest Monsoon is a series of bursts and pauses in activity as it impacts the ten or so states in CONUS with the major impacts being with respect to New Mexico and Arizona.

At this time of the year warm water off of the coast of Mexico, such as from an El Nino, reduces the ocean/land temperature differential and can weaken the Monsoon overall but the cyclones generated by that warm ocean water can enhance the Monsoon for short periods if those cyclones stay close enough to the Mexican coastline.

So that is what is being watched now and I do not see it happening. In this graphic which is showing the current water vapor with the location of storms forecast out two days so you see what I see. And what I see is a pattern that is keeping Mexico fairly dry.

.Eastern Pacific Tropical Storms

The below graphic is harder to look at but provides more detail on the water vapor being generated by these storms and the normal summer action of the Southwest Monsoon. It covers a much larger area within CONUS so you can see where the moisture currently is and is going. This graphic is very good at pointing out the divisions between cloudy and not cloudy areas. As I am looking at this graphic Monday evening I see a lot of clear sky over the eastern half of CONUS

Water Vapor Imagery

Looking at an even larger area, below is a view which highlights the surface highs and the lows re air pressure on Day 6 (Day 3 can be seen in Part II of this Report). The Eastern Pacific Subtropical High is no longer serving as a total block to all storms attempting to move from the Pacific into CONUS and is now located further offshore. This Subtropical High plays a role in directing most of our weather north into Canada or along the Northern Tier of CONUS and it impacts the positioning of the Four Corners High and thus the strength and location of the Monsoon. The surface High over Colorado has been hanging around there for some time and I suspect it is having a big impact on the weather in much of the West.

Day 6 Weather Forecast

Outlook Days 6 - 14 (but only showing the 8 - 14 Day Maps)

Here is the "Early" Temperature Outlook for September issued on August 20. It will be updated by NOAA on the last day of August. . .

August 20 Early Outlook September Temperature Outlook

Here is the current 8 - 14 Day Temperature Outlook which will auto-update and thus be current when you view it. It covers the week following the current week. Today's 6 - 14 Day Outlook is just nine days of the month and the map shown below of the 8 to 14 day Outlook only shows seven days. The 6 - 10 Day Map is available on Page II of this report. As I view this map on August 24 (it updates each day) it appears that the first week of September is now forecast to be totally different from the September Outlook issued just four days ago.

8-14 Day Temperature Outlook

Here is the "Early" Precipitation Outlook for outlook for September issued on August 20, 2015. It will be updated by NOAA on the last day of August which is next Monday August 31.

August 20, 2015 Early Precipitation Outlook for September

Below is the current 8 - 14 Day Precipitation Outlook which will auto-update daily and thus be current when you view it. And again remember that this map shows only seven days and the  6 - 14 Day map is available on Page II of this report. As I view this map on August 24 (it updates each day), the pattern bears no similarity to the monthly Precipitation Outlook Issued just four days ago and overall the outlook is much drier.

Current 8 - 14 Day Precipitation Outlook

Here are excerpts from the NOAA discussion released today August 24, 2015.

6-10 DAY OUTLOOK FOR AUG 30 - SEP 03, 2015

TODAY'S ENSEMBLE MEAN AND DETERMINISTIC SOLUTIONS ARE IN GOOD AGREEMENT ON THE 500-HPA MEAN CIRCULATION PATTERN FORECAST OVER MOST OF THE NORTH AMERICA DOMAIN FOR THE 6-10 DAY PERIOD. TROUGHS ARE PREDICTED JUST WEST OF THE BERING  SEA AND ALONG THE WEST COAST OF THE CONTINENT, WHILE ANOMALOUS RIDGING IS EXPECTED OVER THE SOUTHERN AND CENTRAL CONUS. TODAY'S MANUAL BLEND CHART  INDICATES BELOW-NORMAL HEIGHTS FOR THE WESTERN CONUS AND PARTS OF THE SOUTHEAST, WITH NEAR TO ABOVE-NORMAL HEIGHTS OVER THE REMAINDER OF THE CONUS.  TODAY'S MANUAL 500-HPA HEIGHT BLEND IS COMPOSED PRIMARILY OF THE ENSEMBLE MEAN SOLUTIONS AND BASED LARGELY ON CONSIDERATIONS OF RECENT SKILL AND ON ANALOG CORRELATIONS, WHICH MEASURE HOW CLOSELY THE MODEL SOLUTIONS RESEMBLE CASES THAT HAVE OCCURRED IN THE PAST. THE ENSEMBLE SPAGHETTI DIAGRAMS INDICATE LOW TO MODERATE SPREAD ACROSS THE MAJORITY OF THE FORECAST DOMAIN.

BELOW-NORMAL 500-HPA HEIGHTS INCREASE THE CHANCES FOR NEAR TO BELOW-NORMAL TEMPERATURES FOR THE WESTERN CONUS AND MUCH OF ALASKA. NEAR TO ABOVE-NORMAL  MEAN TEMPERATURES ARE FORECAST OVER THE CENTRAL AND EASTERN CONUS, AS WELL AS  THE ALEUTIANS, CONSISTENT WITH GEFS REFORECAST GUIDANCE. 

TROUGHING AND SOUTHWESTERLY ANOMALOUS FLOW ENHANCE CHANCES OF ABOVE-MEDIAN PRECIPITATION AMOUNTS FOR THE PACIFIC NORTHWEST, THE UPPER MISSISSIPPI VALLEY AND THE UPPER GREAT LAKES. RIDGING OVER THE CENTRAL AND SOUTHERN CONUS FAVORS NEAR TO BELOW MEDIAN PRECIPITATION FOR MOST PARTS OF THE SOUTHERN CONUS. THERE ARE ENHANCED CHANCES OF BELOW MEDIAN PRECIPITATION FOR SOUTHERN ALASKA AND ABOVE MEDIAN PRECIPITATION FOR NORTHERN ALASKA IN CONSISTENT WITH PRECIPITATION ESTIMATES FROM THE GEFS AND ECMWF ENSEMBLE MEMBERS. 

FORECAST CONFIDENCE FOR THE 6-10 DAY PERIOD: ABOVE AVERAGE, 4 OUT OF 5, DUE TO GOOD AGREEMENT AMONG THE MODELS AND VARIOUS TOOLS. 

8-14 DAY OUTLOOK FOR SEP 01 - 07 2015 

TODAY'S ENSEMBLE MEAN AND DETERMINISTIC SOLUTIONS ARE IN GOOD AGREEMENT ON THE 500-HPA MEAN CIRCULATION PATTERN FORECAST OVER MOST OF NORTH AMERICA FOR THE WEEK-2 PERIOD. THE PREDICTED CIRCULATION PATTERN IS SIMILAR TO THAT EXPECTED FOR THE 6-10 DAY PERIOD. TROUGHS ARE PREDICTED JUST WEST OF THE BERING SEA AND ALONG THE WEST COAST OF THE CONTINENT, WITH RIDGING OVER THE SOUTHERN CONUS.

THE EXPECTED TEMPERATURE ANOMALY PATTERNS FOR WEEK-2 ARE SIMILAR TO THOSE PREDICTED FOR DAYS 6-10. BELOW-NORMAL 500-HPA HEIGHTS INCREASE THE CHANCES FOR NEAR TO BELOW-NORMAL TEMPERATURES FOR PARTS OF THE WESTERN CONUS AND MUCH OF ALASKA. NEAR TO ABOVE-NORMAL MEAN TEMPERATURES ARE EXPECTED OVER THE CENTRAL AND EASTERN CONUS, AS WELL AS THE ALEUTIANS, CONSISTENT WITH GEFS REFORECAST GUIDANCE. 

SOUTHWESTERLY ANOMALOUS FLOW AND TROUGHING FAVOR ABOVE-MEDIAN PRECIPITATION AMOUNTS FROM THE PACIFIC NORTHWEST TO THE NORTHERN ROCKIES. SHORT WAVE DISTURBANCES ARE EXPECTED NEAR THE NORTHERN EXTENT OF THE DOWNSTREAM RIDGE, ENHANCING CHANGES FOR ABOVE-MEDIAN PRECIPITATION FOR THE NORTHERN PLAINS, THE UPPER MISSISSIPPI VALLEY, THE GREAT LAKES, THE OHIO VALLEY AND TENNESSEE VALLEY. RIDGING OVER THE CENTRAL AND SOUTHERN CONUS ENHANCES CHANCES OF NEAR TO BELOW MEDIAN PRECIPITATION FOR MOST PARTS OF THE SOUTHERN CONUS. THERE ARE ENHANCED CHANCES OF BELOW MEDIAN PRECIPITATION FOR SOUTHERN ALASKA AND ABOVE MEDIAN PRECIPITATION FOR NORTHERN ALASKA IN CONSISTENT WITH PRECIPITATION ESTIMATES FROM THE GEFS AND ECMWF ENSEMBLE MEMBERS. 

FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD IS: ABOVE AVERAGE, 4 OUT OF 5, DUE TO GOOD AGREEMENT AMONG THE MODELS AND VARIOUS TOOLS. 

Analogs to Current Conditions

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

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

Analog

Centered

Day

ENSO

Phase

PDO AMO Other Comments
1959 August 30 Neutral - +  
1959 August 31 Neutral - +  
1969 August 4 El Nino Neutral - Followed earlier Modoki Type II*
1984 August 29 La Nina + -  
1992 September 7 El Nino + - Tail end of Modoki
1996 August 5 Neutral Neutral Neutral  
1996 August 6 Neutral Neutral Neutral  
2005 August 29 - - +  

 

* The 1968/69 situation is a bit like our current situation.

Again the analogs do not suggest that this El Nino will impact our weather over the next two weeks. The current situation does look like both oceans have about equal control right now. There is a slight bias towards McCabe Conditions A and D. They are pretty much the opposites of each other confirming the confusion of the current situation re making forecasts. The seminal work on the impact of the PDO and AMO on U.S. climate can be found here.

 McCabe Maps modified to include the subtitles

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.

With respect to relating analog dates to ENSO Events, the following table might be useful. In most cases this table will allow the reader to draw appropriate conclusions from NOAA supplied analogs. If the analogs are not associated with an El Nino or La Nina they probably are not significant. Remember, an analog is indicating a similarity to a weather pattern in the past. So if the analogs are not associated with a prior El Nino or prior La Nina the computer models are not likely to generate a forecast that is consistent with an El Nino or a La Nina.

  El Ninos La Ninas
  Start Finish Max ONI PDO AMO Start Finish Max ONI PDO AMO
            DJF 1950 J FM 1951 -1.4 - N
T   JJA 1951  DJF 1952 0.9 - +          
   DJF 1953  DJF 1954 0.8 - + AMJ 1954  AMJ 1956 -1.6 - +
M MAM 1957   JJA 1958 1.7 + +          
M SON 1958  JFM 1959 0.6 + -          
M   JJA 1963  JFM 1964 1.2 - - AMJ 1964  DJF 1965 -0.8 - -
M  MJJ 1965 MAM 1966 1.8 - - NDJ 1967 MAM 1968 -0.8 - -
M OND 1968   MJJ 1969 1.0 - -          
T  JAS 1969   DJF 1970 0.8 N -  JJA 1970  DJF 1972 -1.3 - -
T AMJ 1972  FMA 1973 2.0 - - MJJ 1973 JJA 1974 -1.9 - -
            SON 1974 FMA 1976 -1.6 - -
T ASO 1976  JFM 1977 0.8 + -          
M ASO 1977  DJF 1978 0.8 N -          
M SON 1979  JFM 1980 0.6 + -          
T MAM 1982  MJJ 1983 2.1 * - SON 1984 MJJ 1985 -1.1 + -
M ASO 1986  JFM 1988 1.6 + - AMJ 1988 AMJ 1989 -1.8 - -
M MJJ 1991    JJA 1992 1.6 + -          
M SON 1994   JMA 1995 1.0 - - JAS 1995 FMA 1996 -1.0 + +
T AMJ 1997   AMJ 1998 2.3 + + JJA 1998 FMA 2001 -1.6 - +
M MJJ 2002   JFM 2003 1.3 + N          
M  JJA 2004 MAM 2005 0.7 + +          
M ASO 2006   DJF 2007 1.0 - - JAS 2007  MJJ 2008 -1.4 - +
M JJA 2009 MAM 2010 1.3 - + JJA 2010 MAM 2011 -1.4 + +
            JAS 2011 FMA 2012 -0.9 - +
T MAM 2015 NA 1.0 + N          

 

Recent Analogs Reported by NOAA

I do not plan to do this every week but I thought it might be useful to take a look at how variable the reported analogs are day by day. Here are four days of reported analogs. Each column has two sets of five representing 3 days in the past and 4 days in the past.separated by a blank row. They are organized by degree of correlation which is different than how I do things earlier in this report. When I look at this array and I have not had the time to study it carefully, the year 1996 shows up for all for sets of analogs and August in that year was ENSO Neutral. The most recent two days are fairly similar but quite different from the prior two days. This raises the question of the ability at this time of the year to make 6 - 14 day forecasts.

August 21 Analogs August 22 Analogs August 23, Analogs August 24, Analogs
1952 August 31 1996 August 5 1996 August 6 1996 August 6
2002 August 13 2002 August 13 2001 Sept 6 2005 August 29
1962 August 26 1952 Sept 1 1959 August 30 1984 August 29
1996 August 4 1962 August 29 1984 August 28 1959 August 31
1964 August 24 1984 August 28 1992 Sept 6 1992 Sept 7
                         
1952 August 30 1996 August 5 1996 August 5 1996 August 5
2002 August 13 1959 August 13 1959 August 29 1959 August 30
1962 August 26 2002  August 29 1984 August 29 1984 August 29
1996 August 4 1984 August 28 1992 Sept 5 2005 August 29
1959 August 29 1992 Sept 4 1980 Sept 1 1969 August 4

 

Progress of the Warm Event

Let us start with the SOI.

Below is the Southern Oscillation Index (SOI) reported by Queensland, Australia. The first column is the tentative daily reading, the second is the 30 day moving/running average and the third is the 90 day moving/rolling average.

Date Current Reading 30-Day Average 90 Day Average
 18 August 2015  -7.7 -19.5 -12.24
 19 August 2015 -16.2 -19.42 -12.34
 20 August 2015 -31.3 -20.46 -12.55
 21 August 2015 -21.8 -20.95 -12.6
 22 August 2015 -10.6 -20.93 -12.68
 23 August 2015  -2.6 -20.53 -12.77
 24 August 2017  -7.1 -20.23 -12.84

 

This past week has continued to be consistent with the presence of the current El Nino but has been somewhat less strong than in recent weeks. The 30-day average, which is the most widely used measure, on August 24 was reported as being -20.23  which is clearly a reading associated with a strong El Nino. The 90-day average also is solidly in El Nino territory at -12.84.  The SOI is clearly indicative of an El Nino Event in progress. However, the SOI values this past week have been less extreme than in recent weeks.

Here are the low-level wind anomalies. It has been fairly calm although there is some activity between 160W and 140W.

Low Level Wlind Anomalies

In this graphic, you can see how the convection pattern (really cloud tops has since May shifted to the East from a Date Line (180) Modoki pattern to a 170W to 120W Traditional/Canonical El Nino Pattern. But recently the signs of an El Nino are getting quite faint and shifting back to the west. You can see the lack of convection over at 120E which is Indonesia but the convection has withdrawn to the West not moved to the East as would be the case with a normal El Nino. That may still happen. In the 1997/1998 El Nino, that did not happen until 1998 which is why the Fall and Winter of 1997 were not wet for CONUS. When I hear that with this El Nino the atmosphere is strongly coupled with the ocean, I really wonder what those meteorological agencies are smoking. It might be true on a worldwide basis but it does not appear to be the case as it impacts CONUS.

OLR Anomalies Along the Equator

Let us now take a look at the progress of the Kevin wave which is the key to the situation. Since February there have been three successive downwelling Kelvin Waves without really an upwelling Kelvin Wave on any consequence to counter their impact. The first wave which started in February was the most effective at getting this El Nino started. The second wave reinforced to some extent but not much and this third (and I believe last) downwelling Kelvin Wave has created an El Nino that will have a major peak coming soon and an extended life but at a diminished strength..

The main impact of this latest Kelvin Wave has already moved east to 170W where it is not ready to exist stage right just yet but it will within two or three months.  You can see where some of the warmer water has moved to the east a bit to 155W. You also see the intense activity between 140W and 120W which is in the area where the ONI is measured. You also see the cooling down of the water east of 90W which may signify the end stage of this El Nino. 

But continued SOI activity could create yet another Kelvin Wave although I think the Pacific Warm Pool at this point has been substantially depleted. The ENSO "battery" is weakening and will need a La Nina to recharge itself.  

Kelvin Waves Auto-updates

We are now going to change the way we look at a three dimensional view of the Equator and move from the surface view to the view from the surface down. When I examine the current situation as compared to the 1997/1998 El Nino which I described graphically last week, the current El Nino has developed more rapidly. This El Nino is a couple of months further along in its evolution than the 1997/1998 El Nino and will end earlier in the winter than the 1997/1998 El Nino. Also the 1997/1998 had a larger amount of slightly warmer subsurface water in the Eastern Pacific and that water takes time to surface, create convection, and thus cool. Something happens to allow the Easterlies to resume their strength and that in turn moves this water back towards the Western Pacific Warm Pool.

Subsurface Heat AnomaliesCurrent Sub-Surface Conditions

Top Graphic (Anomalies)

The above graphic showing the current situation has an upper and lower graphic.  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 150W to 90W Longitude and from the surface down to 450 meters.

The top graphic is the most useful of the two and shows where 2C (anomaly) water is impacting the area in which the ONI is measured i.e. 170W to 120W. The 2C anomaly now extends to 160W which is very impressive. There is also a small blip over at 175W. The subsurface warm water appears to be making its way to the surface in the Eastern Pacific.

The big issue is where will the +6C and +5C anomaly water go as it reaches the beaches of Ecuador? To the extent it surfaces, it can create convection and impact the Walker Circulation which could then provide positive feedback to this El Nino. But that warm water might tend to go north or south or both. That is part of the phase out process for an El Nino and that is where we are in the life of this El Nino. It is peaking and will soon begin its decline. But it is certainly taking its sweet time probably because of the large amount of the subsurface warm water. Water is a very good insulator: I believe it has the second highest specific heat capacity of all known substances. 

So that means that other than by mixing, that warm water under the surface will stay warm until it rises to the surface where it can be cooled by evaporation (while making clouds) or moves to the north where it will impact Mexico and the Southern Coast of the U.S. That is part of the basis for models predicting that the ONI of this El Nino will continue to rise but I am a bit skeptical because I see it as rising to the east of the ONI measurement area and not being counted.

Bottom Graphic (Absolute Values which highlights the Thermocline.

The bottom half of the graphic is not that useful in terms of tracking the progress of this Warm Event as it simply shows the thermocline between warm and cool water which pretty much looks like this as shown here during a Warm Event and you can see that the cooler water is not yet fully making it to the surface to the east along the coast of Ecuador. However, one now can see the increase in the slope of the thermocline (look at the 25C dividing line for example which has now reached the surface). We can now begin to monitor the 20C Isotherm which is often thought of as being the middle or lower edge of the thermocline where the slope is also steepening and looks like it may reach the surface fairly soon.

TAO/TRITON GRAPHIC

"Taking a close look at the bottom half of the TAO/TRITON graphic, notice that the 1.5C+ anomaly in the western part of the Nino 3.4 Measurement Area north of the Equator has vanished. It is almost as if the ENSO process is working in reverse and the weaker Easterlies or actual Westerlies in the Central Pacific are now moving cooler water into the Nino 3.4 area. The 1C anomaly has now moved all the way East to 150W north of the Equator. So it has been replaced by the 0.5C to 1C anomaly which is still an El Nino value but a very weak level. That has not happened yet south of the Equator but it will soon. But at the same time, the subsurface warm water in the Eastern Pacific is coming to the surface and that makes the anomalies in the eastern part of Nino 3.4 larger. You can see a small area of 2.5C to 3C surface water and a much larger area of 2C to 2.5C water which combined might be considered to be an area of 2.5C water which if it extended thorughout the Nino 3.4 measurement area would result in an ONI of 2.5C which would make this the most powerful El Nino ever. But in half of the Nino 3.4 measurement area, you have an ONI of perhaps 1.0 or slightly higher which is pretty much a run of the mill El Nino.

So this raises real questions about how we measure an El Nino and how we do regression analysis on historical El Ninos. Are the likely impacts to be correlated with a 1.0 ONI which has minimal impact or a 2.5 ONI which is off the charts? I guess we will find out. The distribution of SST anomalies has changed dramatically over the last two weeks.

For my own amusement, I calculate the ONI each week using a method that I have devised. To refine my calculation, I have divided the 170W to 120W ONI measuring area into five subregions (that I have designated A through E (from west to east) with a location bar shown under the TAO/TRITON Graphic) and have mentally integrated what I see below and recorded that in the table I have constructed. Then I take the average of the anomalies I estimated for each of the five subregions.

 Current SST and wind anomalies

Location Bar for Nino 3.4 Area Above
-----------------------------------------------  A      B      C      D      E      ----------------

 

So as of Monday August 24 in the afternoon working from the August 23 TAO/TRITON report, this is what I calculated which is basically the same as my calculation last week although the patterns of the anomalies have been changing around quite a bit but the changes have een cancelling each other out.

Calculation of ONI from TAO/TRITON Graphic
Anomaly Segment Estimated Anomaly
A. 170W to 160W 1.1
B. 160W to 150W 1.0
C. 150W to 140W 1.6
D. 140W to 130W 2.0
E. 130W to 120W 2.3.
Total 8.0
Total divided by five subregions i.e. the ONI (8.0)/5 = 1.6

 

My estimate of the Nino 3.4 ONI remains at 1.6. NOAA has today reported the weekly ONI as being 2.1 a slight increase from what was reported last week and certainly a psychologically important level and much higher than my rough calculation which makes me wonder why we are getting such very different results. The increase in the NOAA estimated ONI is I believe mostly due to the subsurface water in the Eastern Pacific backing up to the west as it comes to the surface. This warm water certainly impacts the weather in Ecuador and Peru but may not have a direct impact on weather in CONUS other than by spawning tropical cyclones which move north and enter the circulation of the Southwest Monsoon. That activity seems to have decreased recently.

Nino 4.0 is now reported as being 1.1. which is somewhat of a surprise. You can already see (in my calculation table) the gradient from West to East that has formed with the higher values in the East and the Western part of the Zone having a smaller anomaly which I believe has already begun to decline.

The real action is in Nino 1+2 which is now reported as being down to 1.7 which again is a very large decline from recent weeks and shows that this El Nino is dying. The issue remains the extent to which warm water off of Ecuador and Peru impacts CONUS weather. I think it has very little impact and that is what we are seeing right now.

Here is another way of looking at it: Unlike the Upper Ocean Heat Anomaly Hovmoeller which takes an average down to 300 meters this just measures the surface temperature anomaly. It is the surface that interacts with the atmosphere. As you can see the warm water rising off the South American Coast has worked its way all the way over to 170W so it fully contributes to the increasing ONI. But at the same time one can now clearly see that the water immediately off the coast of South American is cooling down. It is a dynamic process and this El Nino is both continuing to grow  while beginning to wane.

.SST Anomalies Hovmoeller

El Nino in the News

2 typhoons over Pacific: 1 could strike Japan, clip Philippines, Taiwan: CNN read more here

2015 US Fall Forecast: Fire Danger to Worsen in West; September May Yield Tropical Impact in South  Accuweather  here  [Editors Note: Accurate but Quite an Interesting Twist]

Asia-Pacific Region: El Niño Snapshot - August 2015  more here.

I found this map from that article which was produced by the UN to be quite interesting. It illustrates how in some cases the impacts are organized by layers that relate to the distance from the Equator. Every El Nino is different and I am not sure if the Phillippines are suffering from drought right now. 

Asia - Pacific Forecast from UNForecast of a 2015 “Godzilla El Niño” Threatens the Global Coffee Community more here.

Recent Impacts of Weather Mostly El Nino but possibly Also PDO and AMO Impacts.

I was not satisfied showing a 90 day and a 30 picture since the 30 day is subsumed into the 90 day so I decided to show three one-month pictures as I think that is a lot easier to follow. I do not plan to update the prior two months each week but monthly.

First the Temperature and Precipitation Departures from two months ago

June 15, 2015 30 Day Temperature and Precipitation Departures.

Then the same graphic one month later

July 13, 2015 30 Day Temperature and Preciptiation Departures

And then what was the current 30-Day picture one week ago. So this gives us a three-month sequence of monthly departures.

August 10 2015 30 Day Temperature and Precipitation Departures

That series of graphics showed a drying trend which is not exactly what you would expect with an El Nino arriving. For many parts of CONUS, it was a cooling trend also which may be associated with an El Nino.

And now the view from one week later

August 17 30Day Temperature and Precipitaiton Departures

And now the most recent 30 days.

August 24, 30 Day Temperature and Precipitation Departures.

It is difficult to see much difference especially considering that these are 30 day averages with only 7 days of new data replacing the earliest 7 days of data but it does appear to be drier overall especially on the West Coast where earlier the Pacific Hurricanes off the Coast of Mexico were providing moisture. But that has pretty much at least temporarily come to an end and the cooling of the water directly off of Ecuador might indicated that the trend of fewer closer in storms might continue. The El Nino ate the Monsoon that is for sure.

Comparison with 1997/1998 El Nino

And I think it is useful to take a look at the 1997 second half of the year impacts of the 1997/1998 Super El Nino. It had the opposite impact on precipitation as currently forecasted by NOAA and JAMSTEC for this Fall.

1997 Precipitation Impacts of 1997/1998 El Nino

Notice the impacts on CONUS precipitation might have been different than one might have expected. This graphic and the OLR graphic are very related. This graphic measures precipitation which fell to the ground. The OLR measures clouds. The two are fairly well correlated but not identical. .

Putting it all Together.

We are in El Nino conditions now. The actually impacts on CONUS are not clear. We started by having wetter conditions than usual in the Southwest but that has tapered off quite a bit. It is probably influencing the IOD to tend towards being positive thus providing a double whammy for parts of Asia and Australia. The length and intensity of this El Nino is still not clear mostly in terms of whether or not it will extend into the early part of 2016.  All the computer models predict that it will last longer than my mental model suggests to me. The disagreement is in terms of a couple of months but a couple of months makes a difference in terms of agriculture and other economic impacts. We may or may not have a Pacific Climate Shift as the PDO+ may be simply related to the Warm Event (and quite frankly at this point appears to be). But for now we do have PDO+. The AMO being an overturning may be more predictable so the Neutral status moving towards AMO- is probably fairly reliable but not necessarily proceeding in a straight line. So none of this is very difficult to figure out actually if you are looking at say a five-year 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.

We are beginning to speculate on the winter of 2016/201 which I believe will tend to be ENSO Neutral but I am not so sure that it will not lean towards being a cool event or at least closer to a La Nina than neutral. One thing is fairly certain for the U.S. it will be less wet and warmer than the winter of 2015/2016 which will be quite wet and cool. JAMSTEC is predicting that the Spring of 2017 will begin a mild La Nina.

TABLE OF CONTENTS FOR PART II OF THIS REPORT  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. 

A. Worldwide Weather: Current and Three-Month Outlooks: 15 Month Outlooks   (Usefully bookmarked as it provides automatically updated current weather conditions and forecasts at all times. It does not replace local forecasts but does provide U.S. national and regional forecasts and, with less detail, international forecasts)

B. Factors Impacting the Outlook

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

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

C. Computer Models and Methodologies

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

TABLE OF CONTENTS FOR PART 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.

D1. Introduction

D2. Climate Impacts of Global Warming

D3. Economic Impacts of Global Warming

D4. Reports from Around the World on Impacts of Global Warming.

Click here for a list of Sig Silber's Weather Posts

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