NOAA has released their Seasonal Update which comes out every third Thursday i.e. September 15. The downgrade of the well-publicized La Nina is now showing up in the forecast maps. This impacts mainly the forecast for the winter months. It is not a big change overall, but it is significant for certain areas.
Updated Seasonal Outlook
NOAA issued their updated Seasonal Outlook on the third Thursday of the month i.e. September 15, 2016 as is their normal schedule. Let's take a look.
We have nothing to compare these maps with as NOAA does not in their Update provide a forecast for two months out*. Thus I do not have October maps from the August 18 NOAA Report to compare against. And September is not over so we can not really compare against last month. It is probably best to just try to understand what NOAA is trying to convey about October which can be summarized as warmer than climatology pretty much everywhere and mostly EC when it comes to precipitation.
One could say that this forecast is for Climatology modified by the observed decadal trend in increasing temperatures or one could say that this forecast is for Climatology modified by Global Warming. There is little if any ENSO consideration in the October maps.
* Each month I attempt to get an idea of months two and three by subtracting the current month's map from the three-month map. I could attempt to compare my text analysis of October/November that I made last month with the new October maps but I am not sure that would add a lot of value but anyone interested could go back to my analysis of the Outlook that was issued on August 18. I may do it for my own curiosity to see if that method has any value.
Now we consider the three-month Outlook. (Notice that the three-month periods are abbreviated e.g. October/November/December is shown as OND.)
Prior Temperature Outlook for OND 2016
New Temperature Outlook for OND 2016
The EC area is now forecast to be in the Southeast rather than in Montana/North Dakota.
Prior Precipitation Outlook for OND 2016
New Precipitation Outlook for OND 2016
The dry Southern Tier anomaly has shrunk in size and the small Northwest wet anomaly no longer extends all the way to the Pacific Coast.
Now let us focus on the long-term situation and compare the new set of maps with the maps issued on August 18, 2016.
Prior 14 Month Temperature Outlook: OND 2016 - SON 2017
New 14 Month Temperature Outlook: NDJ 2016/2017 - OND 2017
To compare maps from one release to another one needs to remember that the new release drops one three-month period and adds a later one. So to make the comparisons one has to shift the new maps to the right one position and that makes the map on the right drop down to become the left-most map in the next level. I do not have a computer software tool for doing that for you so you have to do it mentally. When I do the comparison, I print the two sets of maps and put them side by side and number the same three-month maps 1, 2, 3,.....,11 in both sets of maps to make it easier for me to easily compare the same three-month period in the new with the previous forecast. One uses the same procedure to compare the precipitation maps. Based on this procedure, I conclude that:
The major changes are that starting in FMA 2017, the Northwest cool anomaly no longer extends to the Pacific and is gone in MAM. In the prior NOAA Outlook, it continued through AMJ. Presumably this change is due to the downgrading of the potential La Nina.
Prior 14 Month Precipitation Outlook: OND 2016 - SON 2017
New 14 Month Precipitation Outlook: NDJ 2016/2017 - OND 2017
The precipitation changes are minor. Starting in DJF, The dry anomaly along the Southern Tier is reduced in size and probabilities of occurring. This reduction is primarily a shift a bit to the south and a bit to the east. Also the wet anomaly in the Northwest is shifted inland a bit and is gone by MAM.
If you want larger versions of each map (temperature and precipitation) you can find them here. And each of those maps can be clicked on to further enlarge them.
Below are excerpts (significantly reorganized and with some of the redundancy removed) from the Discussion released by NOAA on September 15, 2016. Headings that are "Initial Cap" only rather than all caps were added by the Author of this Update Report for clarity. Also we have organized the sequence of the sections of NOAA Discussion to first present the Atmospheric Conditions and then the Current Month, the Three or Four-month period, and finally the remainder of the 15 Month Forecast. We think that sequence with the three- to four-month period broken out separately, makes the discussion more useful for more readers.
CURRENT ATMOSPHERIC AND OCEANIC CONDITIONS
SEA SURFACE TEMPERATURES (SSTS) ALONG THE EQUATOR WERE GENERALLY BELOW AVERAGE FROM 170W TO 110W, WHILE SSTS WERE ABOVE AVERAGE TO THE WEST OF THE DATE LINE. CORRESPONDINGLY, THE MOST RECENT THREE-MONTH AVERAGE NINO3.4 SST ANOMALY IS -0.29 DEGREES C FOR JJA. A RESERVOIR OF ANOMALOUSLY COOL SUBSURFACE WATERS EXTENDS TO MORE THAN 150 METERS BELOW THE SURFACE, WITH THE LARGEST NEGATIVE ANOMALIES 2-4 DEGREES C BELOW AVERAGE AT A DEPTH OF ABOUT 125 METERS, BETWEEN 140W-170W. POSITIVE OLR ANOMALIES (SUPPRESSED CONVECTION) WERE PRESENT OVER THE EQUATORIAL PACIFIC, WHILE NEGATIVE OLR ANOMALIES (ENHANCED CONVECTION) WERE PRESENT OVER INDONESIA AND OVER THE WESTERN NORTH PACIFIC, WELL OFF THE EQUATOR. LOW-LEVEL, EASTERLY TRADE WINDS AT THE 850-HPA LEVEL HAVE BEEN NEAR AVERAGE DURING THE PAST MONTH, WHILE THE UPPER-LEVEL, 200-HPA WINDS ARE ANOMALOUSLY WESTERLY OVER THE EQUATORIAL PACIFIC FROM THE DATE LINE EASTWARD TO 150W. THE EXTRATROPICAL PACIFIC OCEAN REMAINS CONSISTENT WITH THE POSITIVE PHASE OF THE PACIFIC DECADAL OSCILLATION (PDO) WITH ABOVE AVERAGE SSTS IN THE NORTH PACIFIC AND ALONG THE COAST OF ALASKA. POSITIVE SST ANOMALIES PERSIST IN THE WESTERN ATLANTIC NEAR THE U.S. EAST COAST, AND THE GULF OF MEXICO.
A REVIEW OF TROPICAL SEASONAL AND INTRASEASONAL CLIMATE CONDITIONS DURING EARLY TO MID SEPTEMBER INDICATE CONTINUED ENSO-NEUTRAL CONDITIONS AND INCOHERENT MJO ACTIVITY. ALTHOUGH EQUATORIAL CENTRAL AND EASTERN PACIFIC SEA SURFACE TEMPERATURES (SST) ARE BELOW NORMAL ON AVERAGE, THEY REMAIN GENERALLY WEAKLY SO ACROSS SUBSTANTIAL PORTIONS OF THE BASIN. NEGATIVE ANOMALIES OF EQUATORIAL OCEAN HEAT CONTENT (OCEAN TEMPERATURE DEPARTURES TO A DEPTH OF 300 METERS) HAVE SLOWLY DECREASED SINCE MAY. ALTHOUGH SUPPRESSED CONVECTION IS INDICATED ACROSS PORTIONS OF THE CENTRAL PACIFIC, SUBSTANTIAL LOWER- AND UPPER-LEVEL WIND ANOMALIES, CONSISTENT WITH LA NINA, ARE LACKING. IN ADDITION TO THESE LATEST OBSERVATIONS, DYNAMICAL MODEL GUIDANCE OF FORECASTS OF NINO3.4 SST HAVE TRENDED TOWARD ENSO-NEUTRAL CONDITIONS FOR THE AUTUMN AND WINTER MONTHS AND THE ODDS FOR LA NINA HAVE DECREASED. THE LA NINA WATCH IS NO LONGER IN PLACE AND ENSO-NEUTRAL CONDITIONS ARE FAVORED THROUGH OCTOBER. THE CHANGE TO FAVORING ENSO-NEUTRAL CONDITIONS RESULTS IN SOME ADJUSTMENTS TO THE OUTLOOKS
PROGNOSTIC DISCUSSION OF SST FORECASTS
THE CPC SST CONSOLIDATION PREDICTS A WEAK LA NINA DURING OND 2016 AND CONTINUING THROUGH FEBRUARY OF 2017. THE MAGNITUDE OF THE ANOMALIES ARE SMALLER THAN LAST MONTH, PEAKING AT -0.6 C DURING DJF 2016-17. THE PROBABILITIES OF NINO3.4 BEING -0.5 C OR GREATER BELOW AVERAGE ARE ALSO LESS THAN LAST MONTH. MOREOVER, MOST DYNAMICAL MODELS HAVE SLIGHTLY WARMER SOLUTIONS FOR THE NINO3.4 REGION, AND THE OFFICIAL CPC/IRI OUTLOOK REFLECTS THE WARMER SOLUTIONS BY INDICATING AN PREFERENCE (55-60 PERCENT CHANCES) FOR ENSO-NEUTRAL CONDITIONS THROUGH THE WINTER MONTHS. [Editors's Note: IRI/CPC has been gyrating a bit with their forecast and the NOAA discussion may not fully reflect the information IRI/CPC released on September 15 after the NOAA Update Release.]
30-DAY OUTLOOK DISCUSSION FOR OCTOBER 2016
MJO INDICES (CPC VELOCITY POTENTIAL AND RMM) INDICATE NO APPRECIABLE COHERENT MJO ACTIVITY DURING THE PAST MONTH AND FORECASTS DO NOT DEPICT CLEAR, LONG TERM STRENGTHENING AT THE CURRENT TIME AND THE MJO DID NOT PLAY A ROLE IN THE HALF-MONTH-LEAD OCTOBER OUTLOOK.
THE OCTOBER 2016 TEMPERATURE AND PRECIPITATION OUTLOOKS ARE PRIMARILY BASED ON AVAILABLE DYNAMICAL MODEL GUIDANCE, ALTHOUGH STATISTICAL BASED TOOLS WERE UTILIZED AS WELL INCLUDING THOSE TARGETING AUTUMN SEASON LONGER TERM TRENDS. COASTAL SST DEPARTURES FROM NORMAL ALSO PLAYED A ROLE IN THE OUTLOOK PRIMARILY FOR AREAS NEAR ALASKA AND NEW ENGLAND.
THE OCTOBER TEMPERATURE OUTLOOK FAVORS ABOVE NORMAL TEMPERATURES FOR MOST OF THE FORECAST DOMAIN. THERE IS NEARLY UNANIMOUS SUPPORT FOR ANOMALOUS WARMTH AS DEPICTED ON THE OUTLOOK MAP FROM THE NMME AND IMME MODEL SUITE WHICH INCLUDES THE CFS AND ECMWF MODELING SYSTEMS, AMONG SEVERAL OTHER PARTICIPANT MODELS. THE PROBABILITIES FOR ABOVE NORMAL TEMPERATURES ARE THE LARGEST FOR AREAS IN ALASKA, THE SOUTHWEST AND NEW ENGLAND. STRONGLY ABOVE NORMAL SSTS SURROUNDING WESTERN AND SOUTHERN ALASKA AND LONG TERM TRENDS ACROSS THE NORTH SLOPE INCREASE ODDS FOR ABOVE NORMAL TEMPERATURES IN THESE AREAS. STRONGLY POSITIVE LONG TERM TEMPERATURE TRENDS AND STATISTICAL GUIDANCE INCREASE PROBABILITIES FOR AREAS IN THE SOUTHWEST AND NEW ENGLAND.
AVAILABLE WEEK 3-4 SPECIFIC MODEL GUIDANCE DOES SHOW AREAS OF FAVORED NEAR TO BELOW NORMAL TEMPERATURES AND GREATER UNCERTAINTY IN GENERAL ACROSS THE INTERIOR OF THE CONUS IN EARLY OCTOBER SO PROBABILITIES FOR ABOVE NORMAL TEMPERATURES ARE LESS FOR PARTS OF THE CENTRAL AND NORTHERN PLAINS AND SOUTHEAST. MOREOVER, THIS UNCERTAINTY AND CONSIDERABLY WEAKER SIGNALS FOR ANOMALOUS WARMTH FROM THE NMME AND IMME DYNAMICAL MODEL SUITE SUPPORT EQUAL CHANCES (EC) FOR ABOVE, NEAR OR BELOW NORMAL TEMPERATURES ACROSS THE SOUTH CENTRAL PART OF THE CONUS.
THERE IS HIGH UNCERTAINTY FOR THE PRECIPITATION OUTLOOK, AS IS TYPICAL FOR THIS TIME OF THE YEAR. THERE ARE SOME SIGNALS THAT CAN BE HIGHLIGHTED, HOWEVER, BASED ON THE CURRENTLY FAVORED FORECAST PATTERN. ANOMALOUS SOUTHERLY FLOW ACROSS THE GULF OF ALASKA FAVORS ABOVE MEDIAN PRECIPITATION FOR THE SOUTHERN AREAS OF ALASKA INCLUDING THE PANHANDLE REGION. DYNAMICAL MODEL GUIDANCE ACROSS TIME SCALES FAVORS BELOW-MEDIAN PRECIPITATION FOR PARTS OF THE PACIFIC NORTHWEST AND INTERIOR SOUTHEAST DURING THE MONTH OF OCTOBER. ABOVE-MEDIAN PRECIPITATION FAVORED BY THE MONTHLY CFS FORECAST AND POTENTIAL TROUGHING ACROSS AREAS OF THE CENTRAL CONUS IS THE REASON FOR ENHANCED ODDS FOR ABOVE MEDIAN PRECIPITATION DEPICTED IN THE CENTRAL PLAINS. EQUAL CHANCES FOR ABOVE, NEAR OR BELOW-MEDIAN PRECIPITATION ARE INDICATED IN REMAINING AREAS.
Three-Month Outlook: October, November, December (OND)
THE OND 2016 TEMPERATURE OUTLOOK INDICATES INCREASED PROBABILITIES OF ABOVE-NORMAL TEMPERATURES ACROSS MOST OF THE CONTIGUOUS U.S. AND ALASKA, WITH THE EXCEPTION OF THE SOUTHEAST, WHERE THERE IS MORE UNCERTAINTY IN THE OUTLOOK RELATIVE TO THE REST OF THE CONTIGUOUS 48 STATES. DYNAMICAL MODEL SUPPORT AND/OR HISTORICAL TRENDS FAVOR PROBABILITIES IN EXCESS OF 50 PERCENT ACROSS THE SOUTHWESTERN STATES AND THE NORTHERN AND WESTERN PORTIONS OF ALASKA. THE GREATEST PROBABILITIES OF ABOVE-NORMAL MEAN TEMPERATURES ARE IN EXCESS OF 60 PERCENT ACROSS THE NORTH SLOPE OF ALASKA. THIS IS LARGELY DUE TO WARMING TRENDS OVER THE PAST FEW DECADES AND THE ASSOCIATED DELAYED ONSET OF SEA ICE FORMATION (AND REDUCED COVERAGE OF MULTI-YEAR ICE) ACROSS THE NEARBY ARCTIC OCEAN.
THE OND 2016 PRECIPITATION OUTLOOK INDICATES INCREASED PROBABILITIES OF ABOVE-MEDIAN PRECIPITATION FOR THE NORTHERN ROCKIES AND NORTHERN GREAT PLAINS, AS WELL AS MUCH OF ALASKA. THE OND 2016 PRECIPITATION OUTLOOK IS BASED ON AVAILABLE CLIMATE MODEL GUIDANCE AND THE CPC CONSOLIDATION. BELOW-MEDIAN PRECIPITATION IS FAVORED FOR THE SOUTHEAST QUADRANT OF THE COUNTRY, WHERE SIGNALS IN THE DYNAMICAL MODELS WERE STRONGEST, AND WHERE THOSE SIGNALS ALIGNED WITH TRENDS AND ANY POTENTIAL IMPACTS DUE TO TELECONNECTIONS FROM THE TROPICAL PACIFIC OCEAN.
PROGNOSTIC DISCUSSION OF OUTLOOKS - OND 2016 TO OND 2017
THE OUTLOOKS FAVOR ABOVE NORMAL TEMPERATURES ACROSS THE SOUTHERN TIER OF THE CONTIGUOUS 48 STATES, WITH BELOW NORMAL TEMPERATURES FAVORED OVER PORTIONS OF THE NORTHERN GREAT PLAINS AND GREAT LAKES. THE OUTLOOKS REFLECT THE LOWERED PROBABILITIES OF LA NINA IN THAT SIGNALS TRADITIONALLY ASSOCIATED WITH LA NINA WERE REDUCED IN COVERAGE AND INTENSITY. BY NEXT SPRING, ONLY A SMALL REFLECTION OF ANY POTENTIAL IMPACTS OF TROPICAL PACIFIC VARIABILITY ARE INCLUDED IN THE OUTLOOKS.
THE OUTLOOKS FROM AMJ 2017 AND BEYOND REFLECT THE CPC CON AND TREND, WHICH GENERALLY FAVOR ABOVE NORMAL TEMPERATURES FOR MUCH OF THE CONUS AND ALASKA. DURING NEXT SUMMER, THE CPC CON DOES INDICATE LESS CERTAINTY OVER THE NORTHERN GREAT PLAINS AND GREAT BASIN. BY NEXT AUTUMN, THAT LOWERED CERTAINTY EXTENDS TO THE MID-ATLANTIC/SOUTHEAST COAST. BY LEAD 13, MUCH OF THE COUNTRY HAS A WEAK SIGNAL FOR ABOVE NORMAL TEMPERATURES.
THROUGH WINTER 2016-17, THE FORECAST PATTERN CONTINUES TO FAVOR BELOW MEDIAN PRECIPITATION FOR THE SOUTHERN TIER, WITH THE MOST CERTAINTY OVER THE SOUTHEAST WHERE THE MODELS AND TRENDS ALIGN. MODEL GUIDANCE SUGGESTS AN ACTIVE NORTHERN STREAM, WHICH IS CONSISTENT WITH TELECONNECTIONS FROM THE FORECAST PATTERN IN TROPICAL PACIFIC SST ANOMALIES. BY SPRING OF 2017, THE CPC CON IS THE PRIMARY DRIVER OF THE OUTLOOKS. ABOVE MEDIAN PRECIPITATION FROM THE GREAT LAKES TO THE NORTHEAST AND BELOW MEDIAN PRECIPITATION OVER PORTIONS OF THE NORTHWEST ARE FAVORED DURING NEXT SUMMER. BY NEXT AUTUMN, THE ONLY REMAINING SIGNAL IS FOR ABOVE MEDIAN PRECIPITATION OVER THE NORTHEAST.
It would be helpful if NOAA divided "Decadal Trends" in the impact of the AMO and PDO and the impact of the secular trend of Global Warming. As it is, the reader is left with trying to figure out what NOAA is saying when they discuss Decadal Trends.
Here is the latest NOAA forecast of Nino 3.4 temperature anomalies. This graphic does auto-update daily but changes slowly. The Oceanic Niño Index (ONI) which is the three-month rolling average of the Nino 3.4 values is NOAA's primary indicator for monitoring El Niño and La Niña. The secondary indicator is the Southern Oscillation Index (SOI) which compares the air pressure in Tahiti with the air pressure in Darwin Australia. It is a complicated formula and is intended to assess the response of the atmosphere to the changes in the pattern of warm and cool anomalies measured by the Nino 3.4 Index. It confirms rather than predicts the phases of ENSO.
At this point in time, the forecast is that Nino 3.4 will rise in October and then decline to -0.6 during NDJ and DJF. Those are La Nina values but most likely all the criteria for having a La Nina declared (in particular a sufficient duration of the ONI being -0.5 or lower) will not have been met which is why so far I am describing this event as La Nina-ish. That could change.
And here is the newly released JAMSTEC Nino 3.4 Forecast. It does not auto-update.
Based on the Nino 3.4 projection, JAMSTEC is saying "no" to La Nina...NOAA says "Maybe but if so marginal". We do not yet have the JAMSTEC Precipitation or Temperature forecasts. When I get them I may update this post or post them separately depending on how interesting they are.
Sometimes it is useful to compare the present month outlook to the three-month outlook
One can mentally subtract the October Outlook from the three-month Outlook and create the Outlook for the last two months in the three-month period namely November and December 2016. When I do that, I deduce that:
With respect to temperature, October has an EC area centered on Texas but the EC area for the three-months is centered in the Southeast. This suggests that the Texas may have to do some catching up in November and December and the Southeast may need to be a bit on the cool side in November and December for the three-month averages to work out. The precipitation is more difficult to analyze because the three-month map is very different from October except for a part of the Southeast that includes but is larger than the Tennessee Valley. So the areas in October which are A(wet) or B(dry) except for the dry anomaly in the Southeast which is also shown as B(dry) in the three month average may need to be slightly opposite in November or December for the three-month average to be EC. The A(wet) area in the Northwest in the three-month map may need to have a somewhat higher probability of being wet in November and December and the B (dry area) other than the area indicated as dry in October may need to be even more dry than shown in the three-month map for the three-month average to work out.
The whole idea is that a three-month average set of probabilities for anomalies is the sum of that information for three months. If you have the first month differing in places from the three-month average you can calculate what a map of the second and third month would look like.for the sum of the two maps ( October and November/December) to equal the published three-month map.
If you wish to transfer to the Current Weather and Climate report, Click Here for the list of Weather Posts and if this Update is listed first, go to the one right below it. If this Update is not listed first, the current weekly Weather and Climate Report will be the top link. You can tell from the date and wording which is the most recent Weekly Weather and Climate Report. That link takes you to the archive of all wealther reports written by Sig Silber so you can go back to an earlier report but please keep in mind that the graphics in earlier reports in some case auto-update and the text may no longer apply to the graphics shown.
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