Climate Prediction Center issues winter, 12 month outlooks

The Climate Prediction Center’s new outlooks for the months and seasons ahead continue to indicate a warmer and drier than normal winter for Central Texas. See the maps and forecaster discussion below. Click here to see our First Warning Weather Team’s special report on the topic: Winter Predictor.

 

 

PROGNOSTIC DISCUSSION FOR LONG-LEAD SEASONAL OUTLOOKS
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
830 AM EST THU NOV 16 2017

SUMMARY OF THE OUTLOOK FOR NON-TECHNICAL USERS

THE DECEMBER-JANUARY-FEBRUARY (DJF) 2017-18 OUTLOOK AND SUBSEQUENT OUTLOOKS ARE
HEAVILY INFLUENCED BY ONGOING LA NINA CONDITIONS THAT ARE FORECAST TO CONTINUE
THROUGH LATE WINTER. THE DJF OUTLOOK FAVORS ABOVE-NORMAL TEMPERATURES FOR THE
MAJORITY OF THE FORECAST DOMAIN, INCLUDING MUCH OF ALASKA. THE HIGHEST
PROBABILITIES OF WARMER-THAN-NORMAL TEMPERATURES ARE LOCATED ACROSS PORTIONS OF
THE SOUTHWEST AND TEXAS. DURING THE WINTER MONTHS THROUGH THE MARCH-APRIL-MAY
(MAM) 2018 SEASON, ENHANCED ODDS FOR BELOW-NORMAL TEMPERATURES ARE HIGHLIGHTED
IN VARYING AREAS OF THE NORTHERN CONUS, SOUTHEAST ALASKA AND THE ALASKA
PANHANDLE, WHILE ABOVE-NORMAL TEMPERATURES REMAIN FAVORED FOR MUCH OF THE
WESTERN AND SOUTHERN CONUS, AND NORTHERN ALASKA.

THE DJF 2017-18 PRECIPITATION OUTLOOK INDICATES INCREASED CHANCES OF
ABOVE-NORMAL PRECIPITATION FOR WESTERN AND NORTHERN ALASKA, AS WELL AS MUCH OF
THE NORTHERN CONUS, CONSISTENT WITH LA NINA. THIS FOOTPRINT SLOWLY DECREASES
ENTERING THE CORE SPRING MONTHS BEFORE LONG-TERM TRENDS BECOME DOMINANT DURING
THE WARM SEASON.

EQUAL CHANCES (EC) ARE FORECAST OVER AREAS WHERE PROBABILITIES OF ABOVE-,
BELOW-, OR NEAR-NORMAL SEASONAL MEAN TEMPERATURES AND SEASONAL ACCUMULATED
PRECIPITATION AMOUNTS ARE FAVORED TO BE SIMILAR TO CLIMATOLOGICAL PROBABILITIES.

BASIS AND SUMMARY OF THE CURRENT LONG-LEAD OUTLOOKS
NOTE: FOR GRAPHICAL DISPLAYS OF THE FORECAST TOOLS DISCUSSED BELOW SEE:
http://WWW.CPC.NCEP.NOAA.GOV/PRODUCTS/PREDICTIONS/90DAY/TOOLS/BRIEFING

CURRENT ATMOSPHERIC AND OCEANIC CONDITIONS

THE LATEST ENSO DIAGNOSTIC DISCUSSION UPDATED THE LA NINA WATCH TO A LA NINA
ADVISORY, AS ATMOSPHERIC AND OCEANIC CONDITIONS, TAKEN IN TOTALITY, INDICATE
ONGOING LA NINA CONDITIONS. THE LATEST WEEKLY NINO 3.4 VALUE IS -1.1 C, WHILE
THE OCTOBER CONTRIBUTION TO THE ONI WAS -0.53 C. OCEANIC HEAT CONTENT (OCEAN
TEMPERATURES ACROSS THE PACIFIC BASIN FROM THE SURFACE TO 300 METERS DEPTH)
SHOW A CONSIDERABLE RESERVOIR OF COLDER THAN NORMAL WATER, OFTEN A PRECURSOR
FOR THE DEVELOPMENT OF MORE ESTABLISHED LA NINA CONDITIONS.

IN TERMS OF THE ATMOSPHERE, SUPPRESSED CONVECTION REMAINS OBSERVED ACROSS MUCH
OF THE WEST-CENTRAL EQUATORIAL PACIFIC WHILE ENHANCED RAINFALL CONTINUES ACROSS
THE MARITIME CONTINENT REGION. THE TRADE WINDS IN THE PACIFIC REMAIN ONLY
WEAKLY ENHANCED OVER THE PAST 30 DAYS, THOUGH MORE ROBUST UPPER-LEVEL WESTERLY
WIND ANOMALIES ARE CURRENTLY OBSERVED. THE MJO HAS RECENTLY WEAKENED AND IS NOT
EXPECTED TO CONTRIBUTE TO STRONG FLUCTUATIONS IN WINDS AND SSTS OVER THE COMING
WEEKS.

PROGNOSTIC DISCUSSION OF SST FORECASTS

THERE HAS NOT BEEN MUCH CHANGE TO PREDICTIONS OF EQUATORIAL PACIFIC SST
ANOMALIES FROM LAST MONTH WITH MOST STATISTICAL AND DYNAMICAL MODEL SOLUTIONS
INDICATING A WEAK LA NINA EVENT, THOUGH SOME DYNAMICAL MODEL SOLUTIONS FORECAST
NINO 3.4 VALUES TO FALL BELOW -1.0 C. SPECIFICALLY, THE CPC NINO3.4 SST
CONSOLIDATION, WHICH OBJECTIVELY WEIGHTS STATISTICAL GUIDANCE (CCA, CA AND
MARKOV) AND THE CFS, FORECASTS THE NINO3.4 SST ANOMALY TO PEAK BETWEEN -0.6 AND
-0.7 EARLY, BEFORE APPROACHING ZERO BY SPRING. RELATIVE TO LAST MONTH, THESE
VARIOUS STATISTICAL AND DYNAMICAL FORECASTS ARE IN BETTER AGREEMENT WITH
RESPECT TO THE OVERALL EVOLUTION, THOUGH THE SST-CA REMAINS A BIT OF AN OUTLIER
IN COLD NEUTRAL TERRITORY.

THE NMME SUITE OF MODELS FOLLOW THIS GENERAL THEME, ALTHOUGH THE PERIOD OF THE
MOST NEGATIVE NINO3.4 SST ANOMALIES CONTINUES TO VARY FROM MODEL TO MODEL. THE
ENSEMBLE MEAN PREDICTION IS QUITE CONSISTENT WITH THE CPC NINO3.4 SST
CONSOLIDATED FORECAST, ALTHOUGH WITH SOMEWHAT MORE NEGATIVE TEMPERATURE
DEPARTURES REACHING -0.9 DEGREES C DURING DECEMBER 2017 AND JANUARY 2018.

THE STATUS OF ENSO DURING SUMMER 2018 AND BEYOND IS UNCERTAIN. THE OFFICIAL SST
CONSOLIDATION FAVORS NEUTRAL ENSO CONDITIONS DURING SUMMER 2018, WITH A SLIGHT
TILT TOWARD LA NINA IN LATE 2018.

PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOKS

THE OFFICIAL TEMPERATURE AND PRECIPITATION OUTLOOKS FOR THE SEASONS FROM DJF
2017-18 THROUGH FMA 2018 TOOK INTO CONSIDERATION IMPACTS OFTEN OBSERVED DURING
LA NINA EVENTS AS THE LATEST OFFICIAL ENSO OUTLOOK FORECASTS LA NINA CONDITIONS
TO CONTINUE THROUGH THE UPCOMING COLD SEASON. STATISTICAL FORECAST TOOLS, SUCH
AS REGRESSIONS ANCHORED TO THE CPC NINO3.4 SST CONSOLIDATION FORECAST AND THE
CCA, ALONG WITH DYNAMICAL MODEL GUIDANCE FROM THE NMME SUITE OF MODELS, BOTH IN
DETERMINISTIC AND CALIBRATED PROBABILISTIC FORM, CONTRIBUTED HEAVILY TO THE
OUTLOOK. LONG TERM TRENDS IN BOTH TEMPERATURE AND PRECIPITATION WERE ALSO
UTILIZED QUITE STRONGLY IN SOME AREAS IN THE OUTLOOKS, THOUGH THESE TRENDS ARE
NOT INDEPENDENT OF THE AFOREMENTIONED FORECAST TOOLS. INTERNATIONAL MODEL
GUIDANCE FROM THE ECMWF, UKMET, AND JMA, ARE ALL BROADLY CONSISTENT WITH THE
OFFICIAL OUTLOOKS. THE SST-CA IS UTILIZED THIS MONTH SINCE IT IS LESS OF AN
OUTLIER WITH RESPECT TO ONGOING AND FORECAST TROPICAL PACIFIC SSTS.

PROGNOSTIC DISCUSSION OF OUTLOOKS – DJF 2017 TO DJF 2018

TEMPERATURE

THE UPDATED SET OF TEMPERATURE OUTLOOKS THIS MONTH KEEP NEAR PERFECT CONTINUITY
WITH THOSE ISSUED LAST MONTH, AS ONLY MINOR CHANGES WERE NEEDED. STATISTICAL
AND DYNAMICAL FORECAST TOOLS THAT IN LARGE PART ARE CONSISTENT WITH TYPICAL LA
NINA IMPACTS, ESPECIALLY THOSE OBSERVED IN THE MORE RECENT PORTION OF THE
AVAILABLE RECORD, ARE A STRONG CONTRIBUTION TO THE TEMPERATURE OUTLOOK
EVOLUTION FROM DJF 2017-18 THROUGH FMA 2018. LONG-TERM TRENDS IN MANY AREAS
ALSO PLAYED A CONSIDERABLE ROLE IN THE OUTLOOK EVOLUTION AT NEARLY ALL FORECAST
LEADS. OUTLOOKS FROM SUMMER 2018 WERE PRIMARILY DRIVEN BY LONG TERM TRENDS AND
THE SST-CA STATISTICAL TOOL AFTER ANY CONSIDERATIONS FOR RESIDUAL LA NINA
IMPACTS ARE ANTICIPATED TO END.

THE DJF 2017-18 TEMPERATURE OUTLOOK IS LARGELY UNCHANGED FROM THE OUTLOOK
RELEASED LAST MONTH. THE MAIN CHANGE WAS A DECREASE IN COVERAGE IN FAVORED
ABOVE-NORMAL TEMPERATURES FOR PORTIONS OF THE SOUTH-CENTRAL U.S. AND A SLIGHT
ENHANCEMENT OF PROBABILITIES FAVORING BELOW-NORMAL TEMPERATURES OVER THE
NORTHERN PLAINS AND UPPER MIDWEST. THIS CHANGE IS BASED LARGELY ON STATISTICAL
GUIDANCE THAT SUGGESTS THE CURRENT SST CONDITIONS OVER THE TROPICS AND NORTHERN
HEMISPHERE ARE SLIGHTLY CLOSER TO THOSE PRECEDING WINTERS WITH COLDER OUTCOMES
ACROSS THE NORTHERN CONUS. AS WE EVOLVE FROM THE WINTER SEASON THROUGH MAM
2018, AN ENHANCED LIKELIHOOD OF BELOW-NORMAL TEMPERATURES REMAINS HIGHLIGHTED
FOR PORTIONS OF SOUTHEAST ALASKA INCLUDING THE PANHANDLE, THE PACIFIC
NORTHWEST, AND THE NORTHERN PLAINS. RECENT TEMPERATURE TRENDS IN THE GREAT
LAKES REGION AND MIDWEST, AS CHARACTERIZED BY 15 YEAR OCN METHODOLOGY, ARE VERY
SLIGHTLY NEGATIVE AND CONTRIBUTE TO AN OUTLOOK THAT IS COOLER THAN THE NMME
ANOMALY FORECAST (AND UNCALIBRATED PROBABILITIES) FOR THAT REGION.

THE REMAINING OUTLOOKS FROM AMJ 2018 ONWARD THROUGH DJF 2018-19 ARE PRIMARILY
BASED ON LONGER TERM TEMPERATURE TRENDS THAT CAN BE STRONG AND REASONABLY
PREDICTABLE IN MANY AREAS OF THE CONTIGUOUS U.S. AND ALASKA. ALONG WITH TRENDS,
PREDICTIONS FROM THE SST-CA ALSO CONTRIBUTED TO THE OUTLOOKS.

PRECIPITATION

FOR PRECIPITATION, THE OUTLOOKS ARE AGAIN VERY SIMILAR TO THE SET OF OUTLOOKS
RELEASED LAST MONTH. IN DJF THE MINOR CHANGES INCLUDE SUBTLE INCREASES IN THE
PROBABILITIES FOR ABOVE-(BELOW-)NORMAL PRECIPITATION ACROSS THE NORTHWEST
(CALIFORNIA). PROBABILITIES ARE INCREASED OVER ALASKA AS WELL, WITH
BELOW-NORMAL PRECIPITATION NOW FAVORED OVER THE SOUTH COAST AND PANHANDLE.
INTERESTINGLY, THE CALIBRATED NMME PROBABILITIES INDICATED ENHANCED ODDS OF
ABOVE-NORMAL PRECIPITATION OVER TEXAS DURING DJF, WHICH IS AT ODDS WITH
STATISTICAL GUIDANCE AND THE ECMWF SEASONAL FORECAST. A SMALL REDUCTION IN
PROBABILITIES FAVORING BELOW-NORMAL PRECIPITATION WAS MADE IN THAT AREA AS A
RESULT OF SOMEWHAT INCREASED UNCERTAINTY. PROGRESSING FROM THE DJF 2017-18
PERIOD THROUGH THE SPRING, ELEVATED ODDS FOR ABOVE-NORMAL PRECIPITATION ACROSS
THE NORTHERN CONUS, DIPPING DOWN INTO THE OHIO AND TENNESSEE VALLEYS AT TIMES,
REMAIN INTACT. BELOW-NORMAL PRECIPITATION OVER THE SOUTHERN TIER OF THE U.S. IS
ALSO FAVORED INTO SPRING. OVER WESTERN AND CENTRAL MAINLAND ALASKA,
ABOVE-NORMAL PRECIPITATION IS NOW FAVORED THROUGH MJJ 2018 BASED ON THE LATEST
DYNAMICAL AND STATISTICAL GUIDANCE.

THE PRECIPITATION OUTLOOKS FROM AMJ 2018 ONWARD THROUGH OND 2018 WERE SIMILAR
FROM THE OUTLOOKS PREPARED LAST MONTH. THESE FORECASTS ARE HIGHLIGHTING
GENERALLY SMALL REGIONS WHERE LONG-TERM PRECIPITATION TRENDS ARE EVIDENT AND
WHERE HISTORICAL CROSS VALIDATED PREDICTION SKILL HAS BEEN SHOWN TO BE
POSITIVE. PROBABILITIES FAVORING BELOW-NORMAL PRECIPITATION WERE INTRODUCED
OVER PARTS OF THE INTERIOR NORTHWEST FROM MJJ THROUGH JAS 2018 BASED ON
LONG-TERM TRENDS.

FORECASTER: STEPHEN BAXTER

THE CLIMATIC NORMALS ARE BASED ON CONDITIONS BETWEEN 1981 AND 2010, FOLLOWING
THE WORLD METEROLOGICAL ORGANIZATION CONVENTION OF USING THE MOST RECENT 3
COMPLETE DECADES AS THE CLIMATIC REFERENCE PERIOD. THE PROBABILITY ANOMALIES
FOR TEMPERATURE AND PRECIPITATION BASED ON THESE NEW NORMALS BETTER REPRESENT
SHORTER TERM CLIMATIC ANOMALIES THAN THE FORECASTS BASED ON OLDER NORMALS.

FOR A DESCRIPTION OF OF THE STANDARD FORECAST TOOLS – THEIR SKILL- AND THE
FORECAST FORMAT PLEASE SEE OUR WEB PAGE AT
http://WWW.CPC.NCEP.NOAA.GOV/PRODUCTS/PREDICTIONS/LONG_RANGE/TOOLS.HTML
(USE LOWER CASE LETTERS)
INFORMATION ON THE FORMATION OF SKILL OF THE CAS FORECASTS MAY BE FOUND AT:
http://WWW.CPC.NCEP.NOAA.GOV/PRODUCTS/SOILMST_MONITORING/US/OUTLOOK/OUTLOOK.SHTM
L
(USE LOWERCASE LETTERS)
NOTES – THESE CLIMATE OUTLOOKS ARE INTENDED FOR USE PRIOR TO THE START OF THEIR
VALID PERIOD. WITHIN ANY GIVEN VALID PERIOD OBSERVATIONS AND SHORT AND MEDIUM
RANGE FORECASTS SHOULD BE CONSULTED.

THIS SET OF OUTLOOKS WILL BE SUPERSEDED BY THE ISSUANCE OF THE NEW SET NEXT
MONTH ON DEC 21 2017

1981-2010 BASE PERIOD MEANS WERE IMPLEMENTED EFFECTIVE WITH THE MAY 19, 2011
FORECAST RELEASE.
$$

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