PROGNOSTIC DISCUSSION FOR MONTHLY OUTLOOK 
NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD 
300 PM EST WED DEC 31 2008 
 
30-DAY OUTLOOK DISCUSSION FOR JANUARY 2009 
 
ADDED PMD AT THE END OF DECEMBER: 
 
AS FAR AS TROPICAL SST IS CONCERNED WE APPEAR TO BE WITNESSING A VERY LATE AND 
VERY RAPID TRANSITION TO MORE DEFINITIVE LA NINA CONDITIONS. THIS HAPPENED JUST 
IN THE LAST 2 WEEKS AND EVEN THE MONTHLY MEAN FOR DECEMBER DOES NOT DO MUCH 
JUSTICE TO THE PRESENT CONDITION. WE THUS FEEL MORE COMFORTABLE ADJUSTING THE 
JAN FORECAST IN THE DIRECTION OF A LA NINA COMPOSITE. 
THE CFS HAD BEEN THE OUTLIER AMONG ALL TOOLS TO PREDICT LA NINA CONDITIONS, SO 
SOME CREDIT IS DUE. THE JANUARY PATTERN PREDICTED BY A 40 MEMBER MEAN CFS 
ENSEMBLE IS USED TO ADJUST THE JANUARY OUTLOOK. WE ALSO USE THE SHORT TERM 
HIGHRES GFS AND HPC'S 5-DAY PRECIP TOTALS. MJO IS NOT A FACTOR AT THIS TIME. 
 
WE EXTENDED THE AREA OF ABOVE NORMAL TEMPERATURE, ALBEIT AT WEAK PROBABILITIES 
FOR MUCH OF THE INTERIOR WEST. THIS IS BASED ON CFS AND GFS CONCURS FOR WEEK 1 
AND 2. WE SUBSTANTIALLY REDUCED THE PROBABILITIES FOR ABOVE NORMAL TEMEPRATURE 
FROM WISCONSIN TO WEST VIRGINIA BECAUSE THE GFS SIGNALS VARIABLE BUT COLD 
CONDITIONS IN THE FIRST 2 WEEKS OF JANUARY. WE EXTENDED THE ABOVE NORMAL TILT 
INTO THE ENTIRE SOUTHEAST BASED ON CFS AND LA NINA CONDITIONS - THE GFS BEING 
LESS IN AGREEMENT HERE. THE NET RESULT IS A MAP OF WEAK PROBABILITIES FOR ABOVE 
NORMAL TEMPERATURE CONDITIONS ACROSS MOST OF THE SOUTHERN TWO-THIRDS OF THE 
NATION. NO COLD IS PREDICTED ANYWHERE FOR THE JANUARY MEAN WITH ELEVATED 
PROBABILITY. 
 
FOR PRECIPITATION THE ADJUSTMENT OF THE ZERO LEAD MONTHLY FORECAST FOR HIGH 
AMOUNTS IN THE FIRST 5 DAYS AS INDICATED BY NWP CAN ONLY BE MADE FOR THE 
NORTHWEST WHERE A SERIES OF STORMS, PERSISTENCE OF AN EXISTING PATTERN, WILL 
BRING PRECIPITATION FROM WASHINGTON AND NORTHERN OREGON TO IDAHO. THIS WOULD 
ALSO BE CONSISTENT WITH LA NINA AND CFS. FARTHER EAST THE GFS DOES NOT SHOW 
HEAVY PRECIPITATION. WE NEVERTHELESS EXTENDED THE AREA FOR ABOVE MEDIAN 
PRECIPITATION IN THE OHIO VALLEY SOUTHWESTWARD INTO ARKANSAN AND NORTHWARD INTO 
SEVERAL GREAT LAKES STATES. THIS IS CONSISTENT WITH CFS AND WITH STORMTRACKS 
DURING A LA NINA. THE SOUTHEAST IS UNCHANGED AND INDICATES DRY CONDITIONS. WE 
MOVED THE TILT FOR DRY OUT OF LOUISIANA BECAUSE THE NEXT 1 OR 2 STORMS COULD 
BRING ENOUGH RAIN TO INVALIDATE BELOW MEDIAN MONTHLY TOTALS. 
 
 
 
WHAT FOLLOWS IS THE PWD AS OF MID-DECEMBER: 
SST ANOMALIES IN THE NINO 3.4 REGION OF THE PACIFIC (170W TO 120W AND 5N TO 5S) 
HAVE BECOME SLIGHTLY MORE NEGATIVE AND NOW ARE ABOUT .7 DEGREES C BELOW NORMAL 
IN THE LATEST WEEKLY AVERAGE. SST FORECASTS FOR THE NINO 3.4 NOW INDICATE VERY 
WEAK LA NINA CONDITIONS FOR JANUARY. ATMOSPHERIC CONDITIONS IN THE TROPICAL 
PACIFIC OCEAN ARE ALSO CONSISTENT WITH BORDERLINE NEUTRAL OR LA NINA 
CONDITIONS, WITH THE ASSOCIATED WIND AND CONVECTIVE PATTERNS. MJO ACTIVITY IS 
PRESENTLY WEAK SO NO SIGNIFICANT PREDICTABLE IMPACTS ARE EXPECTED AT THIS TIME 
FROM THE MJO. 
 
AT THIS POINT - A 2 WEEK LEAD - THE FORECAST FOR JANUARY IS BASED ON 
CCA-OCN-SMLR-CFS WHILE OTHER TOOLS SUCH AS CA-SST AND CAS WERE CONSULTED AS 
WELL. REFERENCE IS ALSO MADE TO LA NINA COMPOSITES. AS A RULE PROBABILITIES ARE 
MODEST FOR A PERIOD AS SHORT AS A MONTH. IT IS TOO EARLY TO RELY ON NWP FOR THE 
EARLY PART OF JANUARY. 
 
ABOVE NORMAL TEMPERATURES ARE INDICATED BY AT LEAST 2 TOOLS IN SOME 60% OF THE 
LOWER 48 STATES. SIGNIFICANTLY NO TOOL INDICATES BELOW NORMAL TEMPERATURES 
ANYWHERE IN THE LOWER 48. THEREFORE - WITH THE EXCEPTION OF THE NORTHEAST, THE 
SOUTHEAST AND THE NORTHWEST - ABOVE NORMAL TEMPERATURES ARE FORECAST. THE 
HIGHEST PROBABILITIES ARE ASSIGNED TO THE INTERIOR SOUTHWEST AND AN AREA 
STRETCHING FROM MINNESOTA TO WEST VIRGINIA WHERE TWO IF NOT THREE TOOLS AGREE. 
FOR THE MOST PART THESE INDICATIONS ARE BASED ON TREND AND ONLY WEAKLY ON 
OCEANIC PREDICTORS RELATED TO PACIFIC SST AND LA NINA. 
 
FOR AK INDICATIONS ARE WEAK BUT WE FOLLOW THE CFS WHICH INDICATES COLDER THAN 
AVERAGE CONDITIONS IN PARTS OF THE SOUTHERN HALF OF THE STATE. THIS IS ALSO 
CONSISTENT WITH LOCAL SST AND LA NINA COMPOSITES AND THE SEASONAL JFM 
PREDICTION. 
 
BELOW MEDIAN PRECIPITATION IS EXPECTED IN FL AND ALONG THE GULF AND ATLANTIC 
COASTS FROM LOUISIANA TO VIRGINIA. MUCH OF THIS IS BASED ON TRENDS BUT 
REINFORCED BY THE STRENGTH OF THE RELATIONSHIP OF RAINFALL IN THE SOUTHEAST TO 
TROPICAL PACIFIC SST. ALONG THE SAME LINES OF REASONING - WEAK LA NINA - AND TO 
BE CONSISTENT WITH THE SEASONAL FORECAST - AN AREA OF ABOVE MEDIAN 
PRECIPITATION WAS INTRODUCED IN THE NORTHERN OHIO VALLEY. 
INDICATIONS FOR AK ARE TOO WEAK TO BE TRUSTED THEREFORE EC. 
 
 
FORECASTER: HUUG VAN DEN DOOL 
 
NOTES: AREAS OF UNCERTAINTY THAT FORMERLY WERE LABELED CL (CLIMATOLOGICAL 
PROBABILITIES) ARE NOW LABELED AS EC (EQUAL CHANCES). 
 
THE NEXT MONTHLY OUTLOOK...FOR FEBRUARY 2009...WILL BE ISSUED ON THU JAN 15 2009 
 
THESE OUTLOOKS ARE BASED ON DEPARTURES FROM THE 1971-2000 BASE PERIOD. 
 
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