|
About Us
Contact Us
Official 90-day Outlooks are issued once each month near mid-month
at 8:30am Eastern Time. Please consult the of 30 & 90-day outlooks
for exact release dates.
Text Discussions
More Outlooks
Tools Used (see Discussion for explanation)
|
|
|
HOME> Outlook Maps>Seasonal Forecast Discussion |
|
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. $$
|
|
|