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HOME> Outlook Maps>Seasonal Forecast Discussion
 
PROGNOSTIC DISCUSSION FOR LONG-LEAD SEASONAL OUTLOOKS 
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
830 AM EST THU FEB 16 2017

SUMMARY OF THE OUTLOOK FOR NON-TECHNICAL USERS

RECENT OCEANIC AND ATMOSPHERIC OBSERVATIONS SHOW THAT ENSO-NEUTRAL CONDITIONS
HAVE RETURNED TO THE EQUATORIAL PACIFIC OCEAN. THE OFFICIAL CPC ENSO FORECAST
FAVORS ENSO-NEUTRAL CONDITIONS TO PERSIST AT LEAST THROUGHOUT BOREAL SPRING,
WITH SIGNIFICANT UNCERTAINTY IN THE PHASE OF ENSO BEYOND THAT TIME.

THE MARCH-APRIL-MAY (MAM) 2017 TEMPERATURE OUTLOOK FAVORS ABOVE-NORMAL
TEMPERATURES EAST OF A LINE THAT RUNS APPROXIMATELY FROM SOUTHERN CALIFORNIA
THROUGH EASTERN WYOMING TO NORTHERN MINNESOTA, AND OVER WESTERN ALASKA.
PROBABILITIES OF ABOVE-NORMAL TEMPERATURES EXCEED 50-PERCENT OVER PORTIONS OF
THE SOUTHWESTERN AND SOUTH-CENTRAL CONUS, AND OVER MUCH OF THE NORTHEAST.

THE MAM 2017 PRECIPITATION OUTLOOK INDICATES ENHANCED PROBABILITIES OF
ABOVE-MEDIAN PRECIPITATION FROM MICHIGAN WESTWARD ACROSS THE NORTHERN TIER OF
STATES TO THE PACIFIC NORTHWEST. BELOW-MEDIAN PRECIPITATION AMOUNTS ARE FAVORED
OVER SOUTHWESTERN PORTIONS OF THE COUNTRY, AND ALONG MOST OF THE SOUTHERN COAST
OF ALASKA.

EQUAL CHANCES (EC) ARE FORECAST OVER AREAS WHERE ODDS OF ABOVE-, BELOW-, OR
NEAR-NORMAL SEASONAL MEAN TEMPERATURES AND SEASONAL ACCUMULATED PRECIPITATION
AMOUNTS ARE EXPECTED 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

OCEANIC AND ATMOSPHERIC OBSERVATIONS INDICATE THAT THE RECENT LA NINA THAT WAS
IN PLACE ACROSS THE EQUATORIAL PACIFIC HAS GIVEN WAY TO ENSO-NEUTRAL
CONDITIONS. THOUGH A RESIDUAL AREA OF RELATIVELY COOL WATER PERSISTS BETWEEN
THE DATE LINE AND ABOUT 160W, SEA SURFACE TEMPERATURES (SSTS) FOR MOST AREAS
EAST OF ABOUT 150W ARE NOW ABOVE-AVERAGE. ACCORDING TO THE LATEST ENSO
DIAGNOSTIC DISCUSSION ISSUED BY CPC ON 9 FEBRUARY 2017, THE LATEST WEEKLY NINO
INDEX VALUES WERE -0.3 DEG C IN THE WESTERNMOST NINO-4 AND NINO-3.4 REGIONS,
AND +1.5 DEG C IN THE EASTERNMOST NINO 1+2 REGION. THE UPPER-OCEAN (TOP 300
METERS) HEAT CONTENT ANOMALY INCREASED DURING JANUARY, AND FOR THE FIRST TIME
IN NEARLY 11 MONTHS, BECAME SLIGHTLY POSITIVE. THIS REFLECTS THE INCREASE OF
ABOVE-AVERAGE TEMPERATURES AT DEPTH.

LOW-LEVEL (850-HPA) EASTERLY WINDS WERE SLIGHTLY ENHANCED OVER THE WESTERN
TROPICAL PACIFIC, AND UPPER-LEVEL (200-HPA) WINDS WERE NEAR-AVERAGE. THE
DOMINANT OUTGOING LONGWAVE RADIATION (OLR) ANOMALY PATTERN FOR THE PAST FEW
MONTHS FEATURED ENHANCED CONVECTION ACROSS THE MARITIME CONTINENT REGION, AND
SUPPRESSED CONVECTION OVER APPROXIMATELY THE CENTRAL THIRD OF THE TROPICAL
PACIFIC. THIS DICHOTOMY IN ANOMALOUS CONVECTION BEARS THE SIGNATURE OF THE LA
NINA THAT WAS RECENTLY IN PLACE. THIS PATTERN OF ANOMALOUS CONVECTION IS ALSO
CONSISTENT WITH, AND REFLECTIVE OF, A POSITIVELY PHASED INDIAN OCEAN DIPOLE
(IOD), WHICH HAS ALSO BEEN IN PLACE FOR SOME TIME. THESE SLOWLY VARYING, LOWER
FREQUENCY SIGNALS (THE ENSO AND IOD) HAVE BEEN MODULATING INTRA-SEASONAL
SIGNALS AS THEY PASS THROUGH THESE REGIONS. CONSTRUCTIVE INTERFERENCE WOULD
RESULT WHEN THE ENHANCED CONVECTIVE PHASES OF THESE INTRA-SEASONAL SIGNALS
MOVED ACROSS THE MARITIME CONTINENT REGION, AND DESTRUCTIVE INTERFERENCE WOULD
RESULT WHEN THE ENHANCED CONVECTIVE PHASES OF THESE INTRA-SEASONAL SIGNALS
MOVED ACROSS THE CENTRAL PACIFIC.

PROGNOSTIC DISCUSSION OF SST FORECASTS

THE CPC SST CONSOLIDATION FORECAST, WHICH INCLUDES THREE STATISTICAL FORECASTS
ALONG WITH THE CFS, PREDICTS ENSO-NEUTRAL CONDITIONS WILL PERSIST FROM NOW
UNTIL THE UPCOMING WINTER SEASON, AFTER WHICH A WEAK LA NINA WOULD BE BRIEFLY
FAVORED. IN CONTRAST, THE CFS PREDICTS THE ONSET OF A WEAK EL NINO IN MAM 2017,
WHICH STRENGTHENS TO MODERATE INTENSITY BY THE UPCOMING SUMMER. THE
AMPLITUDE-CORRECTED NMME (NATIONAL MULTI-MODEL ENSEMBLE) PLUME OF NINO 3.4 SST
FORECASTS IS GENERALLY IN-BETWEEN THE CFS AND THE CPC CONSOLIDATION FORECAST.
THE CPC-IRI-CONSENSUS FORECAST DEPICTS DECREASING ODDS OF ENSO-NEUTRAL DURING
THE NEXT FEW MONTHS, AND INCREASING ODDS OF A WARM EVENT. BY JJA AND JAS, THE
PROBABILITY OF EITHER SCENARIO BECOMES AROUND 45 PERCENT EACH, WITH ONLY 10
PERCENT REMAINING FOR A COLD EVENT. THOUGH THERE IS A REASONABLE CHANCE OF AN
EL NINO OCCURRING DURING THE NEXT COLD SEASON, IT IS TOO EARLY, AND TOO
UNCERTAIN AT THIS TIME, TO CONSIDER USING THIS INFORMATION IN THE SEASONAL
TEMPERATURE AND PRECIPITATION OUTLOOKS.

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

THE OUTLOOKS FOR MAM 2017 THROUGH JAS 2017 ARE BASED ON DYNAMICAL MODEL OUTPUTS
FROM THE NMME AND ITS CONSTITUENT INPUTS, BALANCED WITH INPUT FROM THE CPC
CONSOLIDATION AND CONSTRUCTED ANALOG BASED ON SSTS (CA-SST).  BEYOND JAS 2017,
THE OUTLOOKS ARE BASED ON HISTORICAL TRENDS, THE CPC CONSOLIDATION, AND CA-SST.

PROGNOSTIC DISCUSSION OF OUTLOOKS - MAM 2017 TO MAM 2018

TEMPERATURE

THE OUTLOOK FOR MAM 2017 WAS CHANGED LITTLE FROM LAST MONTH. PROBABILITIES FOR
ABOVE-NORMAL TEMPERATURES WERE EXPANDED WESTWARD ACROSS THE GREAT LAKES REGION
AND UPPER MISSISSIPPI VALLEY, BASED ON THE NMME AND MANY OF ITS COMPONENT
INPUTS (SUCH AS THE CANADIAN CANCM3 AND CANCM4 MODELS, GFDL FLOR, CFS, NCAR,
AND NASA). PROBABILITIES FOR ABOVE-NORMAL TEMPERATURES WERE ALSO INCREASED TO
50-PERCENT IN NEW ENGLAND, BASED ON MANY OF THESE SAME DYNAMICAL MODELS.
PROBABILITIES FOR RELATIVE WARMTH WERE ALSO INCREASED ACROSS MUCH OF THE EAST,
FROM BETWEEN 33-40 PERCENT, TO BETWEEN 40-50 PERCENT. THE FAVORED ABOVE-NORMAL
TEMPERATURES IN WESTERN ALASKA (ESPECIALLY THE ALEUTIANS) FOR THE MAM SEASON
ARE BASED PRIMARILY ON DYNAMICAL MODEL INPUTS. ONE REGION THAT WAS ORIGINALLY
CONSIDERED FOR A FORECAST OF BELOW-NORMAL TEMPERATURES WAS THE NORTH-CENTRAL
CONUS, WHERE A ENSO-TREND BASED FORECAST TOOL THAT USES THE CPC SST
CONSOLIDATION AS A PREDICTOR INDICATED THIS POTENTIAL. HOWEVER, WITH THE RECENT
TRANSITION OF LA NINA TO ENSO-NEUTRAL CONDITIONS, AS WELL AS LITTLE DYNAMICAL
MODEL SUPPORT, IT WAS DECIDED NOT TO INCLUDE THIS AREA OF BELOW-NORMAL
TEMPERATURES ON THE MAP.

FROM AMJ THROUGH JAS 2017, ONLY MINOR ADJUSTMENTS WERE MADE TO THE PREVIOUS
OUTLOOKS, BASED PRIMARILY ON DYNAMICAL AND STATISTICAL MODEL GUIDANCE. ACROSS
THE WESTERN CONUS, PROBABILITIES FAVORING ABOVE-NORMAL (UPPER-TERCILE)
TEMPERATURE ANOMALIES EXPANDED GENERALLY TOWARDS THE NORTHWEST. THE
PROBABILITIES IN EXCESS OF 50-PERCENT ACROSS THE SOUTHWEST ARE CONSISTENT WITH
SPRINGTIME TEMPERATURE TRENDS. BY MJJ, THE PREDICTED AREA OF EC IS CONFINED TO
THE NORTH-CENTRAL CONUS, AND A NOTICEABLE WEAKNESS IN THE PROBABILITIES FOR
ABOVE-NORMAL TEMPERATURES TAKES SHAPE FROM THE MIDWESTERN STATES TOWARDS THE
CAROLINAS. THIS IS A FEATURE THAT IS PREDICTED BY MANY OF THE DYNAMICAL AND
STATISTICAL MODELS, AND THIS SUGGESTS THE POTENTIAL FOR COLDER AIR MASSES TO
MOVE THROUGH THIS CORRIDOR. ABOVE-NORMAL TEMPERATURES ARE FAVORED FOR ALL OF
ALASKA BY MJJ. IN JJA, THE PROBABILITIES FOR ABOVE-NORMAL TEMPERATURES EXCEEDS
50-PERCENT ACROSS NEW ENGLAND, BASED ON SUCH MODELS AS THE CFS, CALIBRATED NMME
AND IRI. BY JAS, THE CORRIDOR OF RELATIVE WEAKNESS NOTED EARLIER (WHICH ALSO
CONTAINED SOME EC) FILLS IN COMPLETELY WITH MODEST PROBABILITIES FOR
UPPER-TERCILE WARMTH. FROM ASO ONWARD, THE CPC CONSOLIDATION TOOL (WHICH
INCORPORATES HISTORICAL TRENDS) AND THE SST-CA TOOL WERE USED. THE GENERAL
SHAPE OF THE PREDICTED PATTERN FAVORING RELATIVE WARMTH CONTINUES ACROSS THE
CONUS AND ALASKA, THOUGH WITH DIMINISHED PROBABILITIES. DURING THE SON AND OND
SEASONS, PROBABILITIES FOR UPPER-TERCILE TEMPERATURE ANOMALIES INCREASE TO OVER
60-PERCENT FOR THE NORTH SLOPE OF ALASKA. THIS IS PRIMARILY ATTRIBUTED TO THE
DELAYED ONSET, AND REDUCED COVERAGE OF, SEA ICE FORMATION IN RECENT YEARS. BY
FMA AND MAM 2018, THE FAVORED ABOVE-NORMAL TEMPERATURES OVER THE EASTERN CONUS
GRADUALLY GIVE WAY TO EC, WHILE THE WARM SIGNAL TREND PERSISTS OVER THE WESTERN
CONUS AND ALASKA.

PRECIPITATION

THE MAM 2017 PRECIPITATION OUTLOOK DEPICTS A FEW DIFFERENCES WITH THE PREVIOUS
OUTLOOK. BASED PRIMARILY ON THE DYNAMICAL MODEL SUITE, THE FAVORED AREA OF
ABOVE-MEDIAN PRECIPITATION WAS EXPANDED WESTWARD ACROSS THE NORTHERN ROCKIES
AND THE PACIFIC NORTHWEST. THE AREA OF FAVORED BELOW-MEDIAN PRECIPITATION OVER
THE SOUTHEAST WAS REMOVED DUE TO THE LARGE DIFFERENCES (AND HENCE LARGE
UNCERTAINTIES) BETWEEN THE VARIOUS MODELS. THE AREA OF PREDICTED BELOW-MEDIAN
(OR LOWER-TERCILE) PRECIPITATION ACROSS THE SOUTHWEST WAS INCREASED IN SIZE,
WHILE A SLIVER OF LOWER-TERCILE PRECIPITATION WAS ADDED TO THE SOUTHERN COAST
OF ALASKA. THIS LATTER FEATURE IS OFTEN OBSERVED DURING LA NINA WINTERS, AND IS
SUPPORTED BY THE NMME, THE CANADIAN CANCM3 MODEL, GFDLS FLOR AND CM2.1 MODELS,
AND NCARS CCSM4 AND CESM MODELS. THE CFS AND INTERNATIONAL MULTI-MODEL ENSEMBLE
(IMME), HOWEVER, DID NOT PREDICT THIS FEATURE.

DURING AMJ AND MJJ 2017, THE ONLY SIGNAL CONSIDERED RELIABLE WAS AN AREA OF
ABOVE-MEDIAN PRECIPITATION ACROSS THE NORTHWESTERN PORTION OF THE LOWER 48
STATES. THE NMME AND CFS ALSO PREDICTED EXTENSIONS OF THIS WET AREA INTO THE
SOUTHWEST, BUT THESE WERE DEEMED UNRELIABLE. BY JJA AND JAS, AN AREA OF
BELOW-MEDIAN PRECIPITATION IS FAVORED ACROSS THE NORTHWEST, WHICH IS A FAIRLY
RELIABLE TREND SIGNAL, AS IS THE FAVORED WET SIGNAL OVER THE NORTHEAST. THE
LATTER SIGNAL CONTINUES THROUGH ASO. FOR SON AND OND, THERE ARE NO RELIABLE
PRECIPITATION SIGNALS, HENCE THE NATIONAL FORECAST OF EC. FROM NDJ 2017 THROUGH
MAM 2018, THE PRECIPITATION OUTLOOKS ARE PRIMARILY BASED ON HISTORICAL TRENDS,
BUT ALSO ON THE SST-CA TOOL. LOWER-TERCILE PRECIPITATION IS FAVORED FOR PARTS
OF THE WEST COAST AND GULF COAST IN BOTH NDJ AND DJF. THIS SIGNAL OF RELATIVE
DRYNESS CONTINUES ACROSS THE EASTERN GULF COAST REGION AND EXPANDS ACROSS THE
CAROLINAS OUT TO MAM 2018, WHILE A DRY SIGNAL EMERGES OVER THE DESERT SOUTHWEST
DURING THE FMA AND MAM 2018 SEASONS.

FORECASTER: ANTHONY ARTUSA

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 MAR 16 2017


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

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