PROGNOSTIC DISCUSSION FOR MONTHLY OUTLOOK 
NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD 
300 PM EST SAT JAN 31 2009 
 
30-DAY OUTLOOK DISCUSSION FOR FEBRUARY 2009 
 
THE OVERALL THINKING FOR THE MONTHLY FORECAST HAS NOT CHANGED SUBSTANTIALLY IN 
THE UPDATE. FOR TEMPERATURE, THE EASTERN HALF OF THE CONUS IS EXPECTED TO SEE 
ABOVE-AVERAGE TEMPERATURES DURING THE FIRST PART OF THE MONTH AS INDICATED BY 
DYNAMICAL MODEL ENSEMBLE FORECASTS. BACKGROUND CLIMATE FACTORS - THE ONGOING LA 
NINA, ACTIVE MJO AND STATISTICAL TOOLS - SUPPORT WARMTH ACROSS MUCH OF THE 
SOUTH-CENTRAL AND SOUTHEAST US. PROBABILITIES OF ABOVE-AVERAGE TEMPERATURES ARE 
INCREASED IN THIS REGION FROM THE EARLIER FORECAST. THERE IS ALSO A SLIGHT 
EXPANSION IN ABOVE-AVERAGE TEMPERATURE PROBABILITIES ALONG THE NORTHERN EDGE OF 
THIS HIGHLIGHTED AREA FROM THE ORIGINAL FORECAST. 
 
ALTHOUGH THERE IS CONSIDERABLE SUPPORT FOR ABOVE-AVERAGE TEMPERATURES ACROSS 
THE NORTH-CENTRAL AND NORTHEAST US DURING THE FIRST HALF OF FEBRUARY, THIS 
REGION REMAINS HIGHLIGHTED EC. THE ANTICIPATED PHASES OF THE MJO DURING THE 
SECOND HALF OF THE MONTH WOULD FAVOR BELOW-AVERAGE TEMPERATURES ACROSS MUCH OF 
THE NORTHERN HALF OF THE CENTRAL AND EASTERN US. IN ADDITION, THE POTENTIAL FOR 
AN EXTENDED PERIOD OF NEGATIVE AO CONDITIONS LATER IN THE MONTH IN PART 
ASSOCIATED WITH THE RECENT SUDDEN STRATOSPHERIC WARMING FURTHER INCREASES THE 
UNCERTAINTY FOR THE MONTHLY MEAN TEMPERATURE FOR FEBRUARY IN THESE REGIONS. 
 
 
BELOW-AVERAGE TEMPERATURES REMAIN ACROSS THE PACIFIC NORTHWEST. SNOW COVER 
CONSIDERATIONS ARE NOW EXPECTED TO HAVE LITTLE IMPACT ACROSS PARTS OF THE 
ROCKIES SO THE LOBE OF BELOW-AVERAGE TEMPERATURES IN THIS AREA HAS BEEN 
REMOVED. TEMPERATURES ARE NOW EXPECTED TO BE CONSIDERABLY BELOW-AVERAGE ACROSS 
MUCH OF ALASKA DURING THE FIRST PART OF THE MONTH. 
 
FOR PRECIPITATION, THE AREA OF ABOVE-MEDIAN PRECIPITATION HAS BEEN EXPANDED TO 
COVER MUCH OF THE NORTH-CENTRAL US AND PARTS OF THE NORTHEAST US. DYNAMICAL 
MODEL ENSEMBLE PREDICTIONS INDICATE AN ACTIVE STORM TRACK DURING THE FIRST HALF 
OF THE MONTH ACROSS PARTS OF THE CENTRAL US ASSOCIATED WITH THE MEAN LONGWAVE 
TROUGH ANTICIPATED ACROSS THE WESTERN US. THIS IN COMBINATION WITH THE 
BACKGROUND CLIMATE CONDITIONS OF LA NINA INCREASE THE PROBABILITIES OF 
ABOVE-MEDIAN PRECIPITATION FROM THE OHIO VALLEY INTO THE GREAT LAKES. OTHER 
AREAS REMAINED GENERALLY UNCHANGED FROM THE EARLIER FORECAST. 
 
** PREV DISCUSSION ** 
 
SEA SURFACE TEMPERATURE (SST) ANOMALIES IN THE EQUATORIAL PACIFIC HAVE 
CONTINUED TO DECREASE DURING THE LAST FEW WEEKS AND LA NINA CONDITIONS ARE 
PRESENT. THE SST DEPARTURES IN THE NINO 3.4 REGION (170W TO 120W AND 5N TO 5S) 
ARE NOW -1.1 DEGREES CELSIUS. SST FORECASTS FOR THE NINO 3.4 INDICATE THAT LA 
NINA CONDITIONS ARE EXPECTED TO CONTINUE THROUGH FEBRUARY 2009. ATMOSPHERIC 
CONDITIONS IN THE TROPICAL PACIFIC OCEAN ARE ALSO CONSISTENT WITH LA NINA. 
SUPPRESSED CONVECTION CONTINUES NEAR THE DATE LINE AND LOW-LEVEL EASTERLY AND 
UPPER-LEVEL WESTERLY WIND ANOMALIES ARE EVIDENT IN 30 DAY AVERAGES OVER THE 
PACIFIC. THE MJO HAS STRENGTHENED IN RECENT DAYS WITH THE ENHANCED CONVECTIVE 
PHASE LOCATED IN THE WESTERN HEMISPHERE AND IT IS ALSO CONSIDERED IN THE 
FEBRUARY FORECAST. 
 
THE MONTHLY FORECAST PLACES CONSIDERABLE WEIGHT ON LA NINA COMPOSITES DUE TO 
THE RECENT MARKED DECREASE IN PACIFIC SSTS AND CIRCULATION PATTERNS AND 
TEMPERATURE AND PRECIPITATION ANOMALIES ACROSS THE US AVERAGED OVER THE LAST 30 
DAYS THAT ARE CONSISTENT WITH LA NINA. THERE IS LARGE UNCERTAINTY IN THE 
PREDICTION OF THE MJO AT A LEAD TIME OF TWO WEEKS, HOWEVER, IF THE MJO 
CONTINUES TO STRENGTHEN AND PROPAGATE ITS ENHANCED CONVECTIVE PHASE IS EXPECTED 
TO BE LOCATED ACROSS THE EASTERN INDIAN OCEAN, INDONESIA AND FAR WESTERN 
PACIFIC DURING A SUBSTANTIAL PORTION OF FEBRUARY – POTENTIALLY REINFORCING THE 
BASE LA NINA CIRCULATION. 
 
THERE IS GOOD AGREEMENT AMONGST THE FORECAST TOOLS FOR TEMPERATURE – BOTH 
STATISTICAL AND DYNAMICAL. THE CCA, OCN, SMLR, AND CFS ALL POINT TO 
ABOVE-AVERAGE TEMPERATURES FOR MUCH OF THE LOWER HALF OF THE CONTINENTAL US 
FROM PARTS OF THE SOUTHWEST TO THE MID-ATLANTIC. LA NINA AND MJO COMPOSITES 
ALSO SUPPORT ABOVE-AVERAGE TEMPERATURES IN THIS REGION. THE CCA FORECAST 
INDICATES ADDITIONAL WARMTH ACROSS THE FAR NORTHERN PLAINS BUT THIS WAS 
DISCOUNTED DUE TO CONFLICTING COLD SIGNALS FROM LA NINA COMPOSITES AND THE CFS 
AS WELL AS EXTENSIVE SNOW COVER. COLDER THAN AVERAGE TEMPERATURES ARE FORECAST 
FOR PORTIONS OF THE NORTHWEST US CONSISTENT WITH LA NINA COMPOSITES, THE CCA 
TOOL, CFS, AND BELOW AVERAGE SSTS ALONG THE WEST COAST. AN EXTENSION OF COLD IS 
DEPICTED ACROSS PARTS OF THE INTERIOR ROCKIES IN PART DUE TO CONSIDERABLE SNOW 
COVER. THE TEMPERATURE TOOLS CONFLICTED FOR ALASKA SO EC IS INDICATED. 
 
THE PRECIPITATION FORECAST ALSO RELIED SIGNIFICANTLY ON LA NINA COMPOSITES BUT 
INFORMATION FROM THE CCA AND CFS WERE ALSO CONSULTED. BELOW-MEDIAN 
PRECIPITATION IS FORECAST ACROSS MUCH OF THE SOUTHEAST US FROM THE GULF COAST 
TO THE SOUTHERN MID-ATLANTIC DUE TO LA NINA COMPOSITES, THE CCA TOOL, THE CFS 
AND STRONG RECENT TRENDS. ABOVE-MEDIAN PRECIPITATION IS FORECAST FOR THE 
PACIFIC NORTHWEST AND OHIO VALLEY REGIONS BASED ON THE RELATIONSHIP WITH LA 
NINA CONDITIONS FOR THESE TWO REGIONS. THE PRECIPITATION TOOLS FOR ALASKA ALSO 
CONFLICTED SO EC IS INDICATED. 
 
 
FORECASTER: JON GOTTSCHALCK 
 
NOTES: AREAS OF UNCERTAINTY THAT FORMERLY WERE LABELED CL (CLIMATOLOGICAL 
PROBABILITIES) ARE NOW LABELED AS EC (EQUAL CHANCES). 
 
THE NEXT MONTHLY OUTLOOK...FOR MARCH 2009...WILL BE ISSUED ON THU FEB 19 2009 
 
THESE OUTLOOKS ARE BASED ON DEPARTURES FROM THE 1971-2000 BASE PERIOD. 
 
$$