201
FXUS07 KWBC 312113
PMD30D
PROGNOSTIC DISCUSSION FOR MONTHLY OUTLOOK
NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD
300 PM EST MON DEC 31 2007
30-DAY OUTLOOK DISCUSSION FOR JANUARY 2008
SEVERAL ADJUSTMENTS SUGGEST THEMSELVES ON DEC 31 RELATIVE TO THE LONG LEAD
FORECAST NOW THAT WE HAVE INFORMATION REGARDING WEEK 1 AND WEEK 2 OF JANUARY
2008 DERIVED FROM THE NUMERICAL WEATHER PREDICTION TOOLS. CHANGES ARE LARGER
FOR PRECIPITATION THAN FOR TEMPERATURE.
AS FOR TEMPERATURE WE ADDED COLD TO ALASKA AND SOME OF THE WEST AND WITHDREW
HIGH PROBABILITIES FOR WARMTH FROM NEVADA AND ARIZONA. HIGH PROBABILITY WARMTH
WAS PUSHED OR NUDGED NORTHEASTWARD.
AS FOR PRECIPITATION WE EXENDED THE PROBABILITY FOR ABOVE MEDIAN PRECIPITATION
FROM THE NORTHWEST INTO MUCH OF THE WEST...INCLUDING AREAS THAT SHOULD BE DRY
AS PER LA NINA COMPOSITES SUCH AS SOUTHER CALIFORNIA AND ARIZONA. THIS IS BASED
ON A HIGH PRECIPITATION EVENT THAT IS IMMINENT AS WELL AS THE PHASE AND
STRENGTH OF THE MADDEN AND JULIAN OSCILATION. WE ALSO EXTENDED THE PROBABILITY
FOR ABOVE MEDIAN PRECIPITATION FROM THE OHIO VALLEY INTO MUCH OF THE NORTHEAST.
WE ADDED BELOW MEDIAN PRECIPITATION FOR NEARLY ALL OF ALASKA AND NUDGED THE
BELOW MEDIAN ISOPROBABILITY LINES FROM TEXAS INTO OKLAHOMA.
TEXT AS OF DEC 20 WAS
SST IN THE EASTERN EQUATORIAL PACIFIC ARE WELL BELOW NORMAL SUGGESTING AT LEAST
MODERATE LA NINA CONDITIONS ARE IN PLACE. SSTS IN THE PACIFIC HAVE REMAINED
STEADY ALONG THE EQUATOR IN THE PAST FEW WEEKS... WITH SST ANOMALIES MORE THAN
1 DEGREE C BELOW NORMAL FROM AROUND 170E TO THE SOUTH AMERICAN COAST WITH LOCAL
ANOMALIES OF -2 OR EVEN -3C. WATER TEMPERATURES IN THE UPPER 300 M OF THE
EASTERN PACIFIC OCEAN REMAIN WELL BELOW AVERAGE... SUGGESTING THAT SST
ANOMALIES WILL PERSIST NEAR THEIR CURRENT LEVELS THROUGH THE END OF JANUARY AND
BEYOND. CONSISTENT WITH THESE CONDITIONS, THE LOW-LEVEL EASTERLY WINDS WERE
STRONGER THAN AVERAGE ACROSS THE CENTRAL EQUATORIAL PACIFIC EXCEPT WHEN AN MJO
PASSED THROUGH AND CONVECTION REMAINED SUPPRESSED THROUGHOUT THE CENTRAL AND
EASTERN EQUATORIAL PACIFIC. COLLECTIVELY, THESE OCEANIC AND ATMOSPHERIC
CONDITIONS REFLECT MODERATE LA NINA CONDITIONS. THERE IS AN AREA OF ENHANCED
CONVECTIVE ACTIVITY IN THE INDIAN OCEAN THAT IS ASSOCIATED WITH THE
MADDEN-JULIAN OSCILLATION (MJO). FOR IT TO BE A CONTINUED MJO IT HAS TO START
MOVING EAST SOON. AN ACTIVE MJO HAS SOME IMPACT ON THE TEMPERATURE AND
PRECIPITATION ANOMALIES IN THE CONUS.
LA NINA CONDITIONS ARE EXPECTED TO HAVE CONSIDERABLE IMPACT ON U.S. TEMPERATURE
AND PRECIPITATION IN JANUARY. FOR THE MOST PART THE TEMPERATURE OUTLOOK
REFLECTS OUR USE OF A TREND ADJUSTED DJF LA NINA COMPOSITE...WHICH HAS WARMTH
OVER AT LEAST 2/3RDS OF THE NATION THE EXCEPTION BEING THE FAR WEST. WE
MODERATED THE PROBABILITIES BECAUSE WE APPLY A DJF COMPOSITE TO JUST THE
CENTRAL MONTH. THE TRADITIONAL TOOLS EITHER AGREE, OR DO NOT DISAGREE MUCH WITH
THE LA NINA COMPOSITE...HENCE FAIRLY HIGH CONFIDENCE AND COVERAGE. THE
IMPRESSIVE SNOW COVER FROM MINNESOTA EASTWARD FORCED US TO REDUCE THE CHANCES
FOR WARMTH ALONG THE NORTHERN STATES. COOL SST IS THE REASON TO PREDICT
ELEVATED CHANCES FOR BELOW NORMAL TEMPERATURE ALONG THE CALIFORNIA COAST.
THE PRECIPITATION FORECAST FOR JANUARY IS IN GENERAL AGREEMENT WITH DJF LA NINA
COMPOSITES...WHICH WOULD MEAN DRY ACROSS THE SOUTH AND WET IN THE NORTHWEST AND
THE OHIO AND TENNESSEE VALLEY. WE REDUCED THE CHANCES FOR A DRY OUTCOME IN
OKLAHOMA AND TEXAS BECAUSE TRENDS ARE UPWARDS. AS EXPECTED IN A LA NINA WINTER
THE CHANCES FOR BELOW MEDIAN ARE TRULY IMPRESSIVE IN FLORIDA AND ADJACENT PARTS
OF THE SOUTHEAST.
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 2008...WILL BE ISSUED ON THU JAN 17 2008
THESE OUTLOOKS ARE BASED ON DEPARTURES FROM THE 1971-2000 BASE PERIOD.
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page