PROGNOSTIC DISCUSSION FOR MONTHLY OUTLOOK
NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD
300PM EST FRIDAY DEC 31 2010

30-DAY OUTLOOK DISCUSSION FOR JANUARY 2011

LA NINA CONDITIONS CONTINUE ACROSS THE TROPICAL PACIFIC OCEAN WITH A SIMILAR 
INTENSITY TO THAT OBSERVED WHEN THE 0.5-MONTH LEAD MONTHLY OUTLOOK WAS ISSUED 
TWO WEEKS AGO. THE LATEST SEA SURFACE TEMPERATURES (SSTS) NEAR THE EQUATOR IN 
THE EASTERN AND CENTRAL PACIFIC OCEAN ARE BETWEEN 1 AND 3 DEG C BELOW NORMAL 
FROM THE SOUTH AMERICAN COAST TO ABOUT 160 E LONGITUDE. BELOW NORMAL SSTS 
EXTEND FROM THE EQUATOR TO 20N AND 20S LATITUDE THROUGHOUT THE EASTERN PACIFIC 
EAST OF AROUND 125W. THE FOUR NINO SST INDICES CONTINUE TO EXHIBIT MINOR 
CHANGES, WITH THE LATEST WEEKLY DEPARTURES RANGING BETWEEN -1.4 C AND -1.8 C. 
SUBSURFACE OCEAN TEMPERATURES ARE BELOW NORMAL TO A DEPTH OF ABOUT 200 METERS 
ALONG THE EQUATOR EAST OF AROUND 160W. THIS IS CONSISTENT WITH A 
SHALLOWER-THAN-AVERAGE THERMOCLINE ACROSS THE CENTRAL AND EASTERN EQUATORIAL 
PACIFIC. THE LARGE SCALE ATMOSPHERIC CIRCULATION OVER THE TROPICAL PACIFIC 
OCEAN CONTINUES TO CLEARLY REFLECT MATURE LA NINA CONDITIONS. CONVECTION IS 
ENHANCED OVER INDONESIA, AND SUBSTANTIALLY REDUCED OVER THE WESTERN AND CENTRAL 
EQUATORIAL PACIFIC OCEAN. LOW LEVEL EASTERLY TRADE WINDS ARE ENHANCED, AS ARE 
WESTERLY WIND ANOMALIES AT UPPER LEVELS OVER THE WESTERN AND CENTRAL PACIFIC.

ALL NUMERICAL AND STATISTICAL ENSO FORECAST MODELS MAINTAIN SUBSTANTIALLY 
NEGATIVE SST ANOMALIES AT LEAST INTO BOREAL SPRING, WITH CONSIDERABLE 
UNCERTAINTY REGARDING HOW FAR INTO THE SPRING THIS COLD EPISODE IS LIKELY TO 
PERSIST. THE MAJORITY OF DYNAMICAL MODEL MJO FORECASTS INDICATE CONTINUED 
LITTLE MJO ACTIVITY DURING THE UPCOMING WEEK, WITH BACKGROUND LA NINA 
CONDITIONS AND OTHER SUBSEASONAL COHERENT TROPICAL VARIABILITY EXPECTED TO 
DOMINATE THE PATTERN OF TROPICAL CONVECTION. THE SST ANOMALIES IN THE NINO 3.4 
REGION ARE FORECAST TO AVERAGE SOMEWHERE BETWEEN -1 C AND -2 C THIS WINTER 
SEASON, SUGGESTING MODERATE TO STRONG LA NINA CONDITIONS FOR JANUARY 2011. BY 
SPRING (MAR-MAY) 2011, THE AVERAGE OF THE STATISTICAL TOOLS, AND THE AVERAGE OF 
THE DYNAMICAL TOOLS, SUPPORT NINO 3.4 INDICES AROUND -1.0 C OR SLIGHTLY COLDER, 
AS DOES THE CPC SST CONSOLIDATION FORECAST. FINALLY, THERE IS THE ARCTIC 
OSCILLATION (AO) TO CONSIDER, WHICH UNFORTUNATELY CANNOT BE RELIABLY PREDICTED 
MORE THAN ABOUT 2 WEEKS IN ADVANCE. THE LATEST EXTENDED-RANGE GUIDANCE SUGGESTS 
THAT A FAIRLY STRONG, NEGATIVELY PHASED AO WILL CONTINUE AT LEAST THROUGH 
MID-JANUARY, AND LITTLE OVERALL CHANGE IN THE ATMOSPHERIC CIRCULATION.

THE JANUARY 2011 TEMPERATURE AND PRECIPITATION OUTLOOKS ARE BASED ON THE 
LATEST, EXTENDED-RANGE NWP MODEL GUIDANCE FOR THE FIRST TWO WEEKS OF JANUARY, 
WITH CONSIDERATION OF TRADITIONAL STATISTICAL TOOLS, LA NINA COMPOSITES, RECENT 
TEMPERATURE AND PRECIPITATION OBSERVATIONS, AND THE EXPECTATION THAT A 
SIGNIFICANT, NEGATIVE AO WILL PREVAIL OVER THE EASTERN CONTIGUOUS US THROUGH AT 
LEAST THE MIDDLE OF JANUARY. BEYOND THIS, THERE IS SUBSTANTIAL UNCERTAINTY OF 
THE STATUS OF THE AO AND THE PREDICTED TEMPERATURE AND PRECIPITATION PATTERNS 
ACROSS THE EASTERN CONTIGUOUS UNITED STATES.

THE UPDATED TEMPERATURE OUTLOOK FOR JANUARY 2011 CALLS FOR ENHANCED ODDS OF 
BELOW AVERAGE MEAN TEMPERATURES FROM THE SOUTHERN GREAT LAKES REGION AND OHIO 
VALLEY SOUTHWARD AND EASTWARD TO THE EASTERN GULF COAST (INCLUDING ALL OF 
FLORIDA), AND THE ATLANTIC COAST STATES FROM DELAWARE SOUTHWARD. THERE ARE 
ENHANCED ODDS OF BELOW AVERAGE MEAN TEMPERATURES ALSO OVER SOUTHEAST ALASKA, 
INCLUDING THE ENTIRE PANHANDLE REGION. THESE ANTICIPATED AREAS OF 
COLDER-THAN-AVERAGE MEAN TEMPERATURES ARE SUPPORTED PRIMARILY BY THE LATEST 
SUITE OF EXTENDED-RANGE GUIDANCE, AND (IN THE EASTERN CONUS) ARE CONSISTENT 
WITH ENDURING, NEGATIVE AO CONDITIONS. ELSEWHERE, EQUAL CHANCES (EC) OF BELOW-, 
NEAR-, AND ABOVE-NORMAL MEAN TEMPERATURES ARE PREDICTED.

THE UPDATED PRECIPITATION OUTLOOK FOR JANUARY 2011 CALLS FOR ELEVATED ODDS OF 
ABOVE MEDIAN PRECIPITATION OVER SOUTHERN CALIFORNIA, AND MUCH OF THE SOUTHERN 
INTERMOUNTAIN REGION. THIS PATTERN IS WELL SUPPORTED BY  THE LATEST DYNAMICAL 
MODEL GUIDANCE, AND SEEMS REASONABLE GIVEN THE RECENT BOUT OF HEAVY 
PRECIPITATION ACROSS THIS SAME GENERAL AREA. THERE ARE ELEVATED ODDS OF BELOW 
MEDIAN PRECIPITATION ACROSS THE EAST GULF COAST REGION INCLUDING ALL OF 
FLORIDA, AND THE SOUTHERN ATLANTIC COAST, AS WELL AS FOR A NARROW BAND OVER THE 
SOUTHERN COAST OF ALASKA, FROM KODIAK ISLAND TO NEAR YAKUTAT. THESE DRIER 
SIGNALS ARE BASED ON THE LATEST NWP EXTENDED-RANGE GUIDANCE, AS WELL AS LA NINA 
COMPOSITES. ELSEWHERE, EQUAL CHANCES (EC) OF BELOW-, NEAR-, AND ABOVE-MEDIAN 
PRECIPITATION ARE PREDICTED.


FORECASTER: ANTHONY ARTUSA


NOTES: AREAS OF UNCERTAINTY THAT FORMERLY WERE LABELED CL (CLIMATOLOGICAL 
PROBABILITIES) ARE NOW LABELED AS EC (EQUAL CHANCES).


THE NEXT MONTHLY OUTLOOK...FOR FEB ... WILL BE ISSUED ON THU JAN 20 2011


THESE OUTLOOKS ARE BASED ON DEPARTURES FROM THE 1971-2000 BASE PERIOD.

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