CPC Long Range ENSO and US Outlook

[Anonymous]

Source: http://www.cpc.noaa.gov/products/predic ... xus05.html

PROGNOSTIC DISCUSSION FOR LONG-LEAD SEASONAL OUTLOOKS
NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD
300 PM EDT THU APR 17 2003

. . . . . . . .
SUMMARY OF THE OUTLOOK FOR NON-TECHNICAL USERS

THE SEASONAL OUTLOOK REFLECTS MAINLY THE PRESENCE OF LONG TERM TRENDS ON U.S.
TEMPERATURE AND PRECIPITATION...WITH SOME INPUT FROM SOIL MOISTURE ANOMALIES
AND NUMERICAL MODELS DURING THE FIRST SEVERAL SEASONS. EL NINO HAS WEAKENED
AND IS FORECAST TO WEAKEN MORE AND IS THOUGHT TO BE A NEGLIGIBLE FACTOR FROM
NOW UNTIL ANY SIGNIFICANT CHANGE IN THE EL NINO STATE OCCURS...LEAVING MAINLY
THE INFLUENCE OF LONG TERM TRENDS ON THE FORECAST. SOME EL NINO AND OTHER
WINTER WEATHER EFFECTS MAY CARRY OVER INTO THE LATE SPRING AND SUMMER
INDIRECTLY THROUGH SUCH AGENTS AS SOIL MOISTURE.

THE OUTLOOK FOR MAY - JULY 2003 CALLS FOR ABOVE NORMAL TEMPERATURES OVER MUCH
OF THE U.S. AND ALASKA...DUE TO RECENT TRENDS REINFORCED OR AUGMENTED IN SOME
AREAS BY INDICATIONS FROM NUMERICAL MODELS AND DRY SOIL. ABOVE NORMAL
PRECIPITATION IS EXPECTED FOR PORTIONS OF THE PACIFIC NORTHWEST AND
SOUTHEASTERN ALASKA BASED ON TRENDS AND NUMERICAL MODELS.

EQUATORIAL PACIFIC SEA SURFACE TEMPERATURES IN EARLY APRIL WERE BETWEEN ONE
HALF AND ONE DEGREE C OR MORE ABOVE NORMAL OVER THE EQUATORIAL PACIFIC NEAR THE
DATE LINE. THE SST ANOMALIES IN THE EASTERN PACIFIC HAVE DECREASED
SUBSTANTIALLY AND ARE BELOW NORMAL IN SOME PLACES. NEARLY ALL STATISTICAL
AND OCEANIC MODEL PREDICTION TOOLS INDICATE WEAKENING EL NINO CONDITIONS
THROUGH THE SUMMER WITH A LACK OF CONSENSUS AS TO WHAT MIGHT HAPPEN LATER IN
THE YEAR. POSSIBILITIES FOR NINO 3.4 RANGE FROM A RETURN TO WEAK-TO-MOERATE
WARM CONDITIONS TO A STRONG LA NINA...WITH THE OFFICIAL FORECAST FOR NINO 3.4
BEING VERY CLOSE TO NEUTRAL FROM LATE SUMMER THROUGH NEXT SPRING.

NOTE - AREAS OF UNCERTAINTY THAT FORMERLY WERE LABELED CL (CLIMATOLOGICAL
PROBABILITIES) ARE NOW LABELED EC (EQUAL CHANCES).
. . . . . . . .

BASIS AND SUMMARY OF THE CURRENT LONG-LEAD OUTLOOK

THIS OUTLOOK REFLECTS THE EXPECTED UNITED STATES CLIMATE ANOMALIES BASED ON THE
LONG TERM TREND - PRIMARILY FROM OCN - AND STATISTICALLY-BASED RELATIONSHIPS
BETWEEN PRESENT OCEANIC AND ATMOSPHERIC CONDITIONS AND U.S. TEMPERATURE AND
PRECIPITATION. DYNAMICAL FORECASTS FROM GENERAL CIRCULATION MODELS WERE ALSO
CONSIDERED FOR THE FIRST FOUR SEASONS. AT THIS TIME OF YEAR SOIL MOISTURE
CONSIDERATION GETS SPECIAL ATTENTION.

CURRENT ATMOSPHERIC AND OCEANIC CONDITIONS

THE EL NINO OF 2002/03 HAS WEAKENED...WITH THE POSITIVE TEMPERATURE ANOMALIES
DECREASING TO LESS THAN ONE DEGREE C OVER THE MOST OF THE CENTRAL PACIFIC.
COOLER THAN NORMAL TEMPERATURES BELOW THE SURFACE NOW UNDERCUT THE WARM
ANOMALIES NEAR THE SURFACE ACROSS MUCH OF THE EQUATORIAL PACIFIC. THIS IS
CONSISTENT WITH A DECLINING EL NINO. OCEANIC AND ATMOSPHERIC INDICATORS ARE
STILL CONSISTENT WITH WEAK EL NINO CONDITIONS...WITH ENHANCED CONVECTION IN
PLACE SOME OF THE TIME NEAR THE DATELINE IN THE EQUATORIAL PACIFIC. EVEN IF
THE ATMOSPHERIC RESPONSE TO EL NINO IN THE TROPICS CONTINUES - ITS IMPACT ON
THE MID-LATITUDE WOULD BE SMALL BECAUSE THE SEASONAL WINDOW FOR SUCH
TELECONNECTIONS IS CLOSING.

. . . . . . . .

PROGNOSTIC DISCUSSION OF SST FORECASTS

MOST DYNAMICAL COUPLED OCEAN-ATMOSPHERE MODEL AND STATISTICAL MODEL FORECASTS
INDICATE EL NINO CONDITIONS WILL WEAKEN THROUGH SPRING 2003. SOME TOOLS
INDICATE POSITIVE ANOMALIES OF BETWEEN .5 AND 1 DEGREE C IN THE NINO 3.4 REGION
WILL PERSIST THROUGH THE REMAINDER OF THE YEAR...WHILE OTHERS SHOW A RETURN TO
NEAR NORMAL OR BELOW NORMAL SSTS IN THE SAME REGION BY EARLY SUMMER. A
CONSOLIDATION FORECAST OF IN HOUSE TOOLS SHOWS TEMPERATURE ANOMALIES IN
THE NINO 3.4 SST REGION NEAR ZERO FOR NEXT WINTER AND SPRING 2004.

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

THE STATISTICAL TOOLS - CCA - OCN - SMLR - WERE CONSULTED AT ALL LEAD TIMES.
DYNAMICAL MODEL FORECASTS FROM NCEP AND OTHER FORECAST CENTERS WERE EXAMINED
FOR THE PERIOD MJJ 2003 - ASO 2003. IN THIS SEASON WE ALSO PAY ATTENTION TO
SOIL MOISTURE TOOLS...BOTH THE CAS AND SMT.

. . . . . . . .
PROGNOSTIC DISCUSSION OF OUTLOOKS - MJJ 2003 TO MJJ 2004

TEMPERATURE:

TEMPERATURES FOR MJJ 2003 REFLECT LONG TERM TRENDS OVER THE EASTERN...WESTERN
AND GULF COAST STATES...WITH THE COVERAGE OF ABOVE NORMAL EXPANDED TO INCLUDE
MUCH OF THE INTERIOR OF THE NATION BASED IN AREAS OF INITIALLY DRY SOIL AND
THE OUTPUT FROM SOME STATISTICALLY POST-PROCESSED NUMERICAL MODELS. RECENT
TRENDS SUPPORT ABOVE NORMAL TEMPERATURES THROUGHOUT MUCH OF ALASKA...ALTHOUGH
SOME NUMERICAL MODELS CALL FOR BELOW NORMAL WHICH CAUSED A REDUCTION IN
COVERAGE OF ABOVE FROM THE PREVIOUS MJJ OUTLOOK.

RECENT TRENDS INDICATE ABOVE NORMAL TEMPERATURES FOR THE SUMMER OVER MUCH OF
THE U.S. EXCEPT FOR THE INTERIOR PORTIONS AND FOR NORTHERN NEW ENGLAND.
STATISTICALLY POST-PROCESSED NUMERICAL MODELS ARE QUITE CONSISTENT FOR THE
FIRST FOUR SEASONS IN CALLING FOR ABOVE NORMAL OVER MOST OF THE LOWER 48
STATES. CCA ALSO SUPPORTS ABOVE NORMAL IN SOME REGIONS. EVEN WHERE THE
STATISTICAL TOOLS OCN AND CCA DO NOT SHOW A PRIORI SKILL...THEY CALL FOR
ABOVE NORMAL IN MOST PLACES. THUS WITH NO TOOLS SIGNIFICANTLY OPPOSING ABOVE
NORMAL FOR MOST OF THE LOWER 48 STATES...THE TEMPERATURE OUTLOOKS THROUGH ASO
2003 HAVE ABOVE NORMAL OVER MUCH OF THE LOWER 48 STATES. TRENDS GRADUALLY
DIMINISH AS THE TRANSITIONAL FALL SEASON APPROACHES AND...COUPLED WITH THE
LACK OF AVAILABILITY OF NUMERICAL MODELS AFTER THE FIRST FOUR SEASONS...WHAT
REMAINS IN THE OUTLOOK ARE ONLY THE REGIONS OF STRONGEST WARMING TRENDS BY SON
2003. FROM THERE THE FORECAST RAPIDLY TRANSITIONS TO WINTERTIME TEMPERATURE
TRENDS...AS INDICATED BY THE DJF OUTLOOK...SHOWING ABOVE NORMAL TEMPERATURES
OVER MUCH OF THE COUNTRY EXCEPT FOR THE NORTHWESTERN U.S. INTO THE NORTHERN
PLAINS...EASTERN NEW ENGLAND...AND SOUTHERN ALASKA. WARMING TRENDS WEAKEN
EAST OF THE ROCKIES AS SPRING APPROACHES LEAVING ABOVE NORMAL TEMPERATURES
ONLY IN THE WESTERN U.S. AND PORTIONS OF ALASKA IN OUTLOOKS FOR MAM 2004 AND
BEYOND.

THE CHANGES MADE IN THE TEMPERATURE FORECASTS FOR CORRESPONDING SEASONS FROM
LAST MONTHS OUTLOOK SERIES REFLECT THE CCA. REVISIONS PRIMARILY SHOW INCREASED
COVERAGE OF ABOVE NORMAL...WHICH IS CONSISTENT WITH THE TREND EVEN IN REGIONS
WHERE IT HAS NO A PRIORI SKILL. CHANGES IN THE FORECASTS FROM JFM THROUGH MAM
2004 ALSO REFLECT THE TREND UPDATE PROVIDED BY NEW DATA THROUGH MARCH 2003.

. . . . . . . .
PRECIPITATION:

THE ABOVE MEDIAN PRECIPITATION FORECAST FOR MJJ 2003 FOR PORTIONS OF THE
PACIFIC NORTHWEST IS BASED ON OCN AND STATISTICALLY POST-PROCESSED NUMERICAL
MODELS...WHILE THE ABOVE MEDIAN PRECIPITATION FOR SOUTHEASTERN ALASKA IS BASED
ONLY ON THE LATTER ALTHOUGH IT IS NOT STRONGLY OPPOSED BY THE STATISTICAL
TOOLS. ONLY SLIGHT CHANGES WERE MADE IN THE PRECIPITATION FORECASTS FOR
CORRESPONDING SEASONS FROM LAST MONTHS OUTLOOK SERIES...AND THESE ARE BASED
ALMOST EXCULSIVELY ON OCN.
. . . . . . . .

[Colin]

Thanks for the information, Rob... looks very interesting.

[Kevin_Wx]

I'm still of the consensus that a weak La Nina influence on Atlantic TC activity is likely during the peak of the hurricane season. Given the trends this spring, the wind anomalies becoming easterly over the Eastern Pacfic, and some cooling taking place (especially under the surface), I'd say a weak La Nina is most likely this for the peak of the season. This is beginning to sound very redundant, but it's true.

[cycloneye]

Every time that there is an outlook it confirms what we know already for months.

[Anonymous]

Every time that there is an outlook it confirms what we know already for months.

Agree 100%. The only time they make much of a forecast is when they call for neutral conditions for the next 12 months.

[Kevin_Wx]

From that outlook, it is quite obvious that the CPC ENSO "experts" don't know how to look at a group of model outputs and form an opinion on which models can be trusted, and finally develop an outlook.

All I can say is, well, they must have forgotten about the subsurface SSTA's.

[Anonymous]

All I can say is, well, they must have forgotten about the subsurface SSTA's.

Yeah I know, how can you even SPECULATE on the possibility of El Nino regeneration later in the year with subsurface temps looking like this...

[Anonymous]

Surface SSTAs...