402
FXUS07 KWBC 302005
PMD30D
PROGNOSTIC DISCUSSION FOR MONTHLY OUTLOOK
NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD
300 PM EST FRI NOV 30 2007
30-DAY OUTLOOK DISCUSSION FOR DECEMBER 2007
SST IN THE EASTERN EQUATORIAL PACIFIC ARE WELL BELOW NORMAL SUGGESTING AT LEAST
MODERATE LA NINA CONDITIONS ARE CURRENTLY IN PLACE. SSTS IN THE PACIFIC HAVE
REMAINED STEADY ALONG THE EQUATOR IN THE PAST FEW WEEKS... WITH SST ANOMALIES
NEAR -3 DEGREES C IN PLACES BETWEEN 90 AND 110W AND DEPARTURES MORE THAN 1
DEGREE C BELOW NORMAL FROM AROUND 170E TO THE SOUTH AMERICAN COAST. WATER
TEMPERATURES IN THE UPPER 300 M OF THE EASTERN PACIFIC OCEAN REMAIN WELL BELOW
AVERAGE... SUGGESTING THAT SSTS ANOMALIES WILL PERSIST NEAR THEIR CURRENT
LEVELS THROUGH THE END OF DECEMBER. CONSISTENT WITH THESE CONDITIONS, THE
LOW-LEVEL EASTERLY WINDS WERE STRONGER THAN AVERAGE ACROSS THE CENTRAL
EQUATORIAL PACIFIC, 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 WESTERN PACIFIC THAT IS ASSOCIATED WITH THE
MADDEN-JULIAN OSCILLATION (MJO). THE MJO HAS BEEN GAINING STRENGTH IN RECENT
WEEKS AND MAY HAVE SIGNIFICANT IMPACT ON THE WEATHER IN THE EQUATORIAL REGIONS
OF THE PACIFIC OCEAN AS THE AREA OF ACTIVE CONVECTION MOVES EASTWARD. AN
ACTIVE MJO HAS SOME IMPACT ON THE TEMPERATURE AND PRECIPITATION ANOMALIES IN
THE CONUS... ALTHOUGH ITS INFLUENCE IS FAIRLY WEAK IN MOST CASES.
LA NINA CONDITIONS ARE EXPECTED TO HAVE CONSIDERABLE IMPACT ON U.S.
TEMPERATURE AND PRECIPITATION IN DECEMBER... WITH SOME ADDITIONAL INFLUENCE
FROM THE MJO. THESE CLIMATIC SIGNALS ARE FURTHER INFLUENCED BY WEATHER SYSTEMS
PREDICTABLE IN THE FIRST TWO WEEKS OF THE MONTH. THE GFS AND OTHER WEATHER
PREDICTION MODELS FORECAST A PERSISTENT UPPER LEVEL TROUGH OVER THE EASTERN
U.S. IN THE FIRST TWO WEEKS OF DECEMBER... ELEVATING THE CHANCES OF BELOW
NORMAL TEMPERATURES FROM THE GREAT LAKES TO THE NORTHEASTERN U.S. THIS
FORECAST IS CONSISTENT WITH COMPOSITE TEMPERATURES BASED ON THE PREDICTED MJO
PHASE IN THE EARLY PART OF DECEMBER. THE TEMPERATURES THROUGHOUT MUCH OF THE
EASTERN U.S. HAS SIMILARLY BEEN REVISED TO REFLECT A COOL START TO THE MONTH...
HOWEVER BECAUSE ABOVE NORMAL TEMPERATURES ARE FAVORED FOR MUCH OF THE SOUTHEAST
IN LA NINA WINTERS... THE MONTHLY MEAN TEMPERATURES OVER MUCH OF THE EASTERN
U.S. IS UNCERTIAN EXCEPT FOR THE DEEP SOUTH WHERE ABOVE NORMAL TEMPERATURES ARE
FAVORED. ABOVE NORMAL TEMPERATURES ARE FAVORED FOR THE SOUTHWEST AND TEXAS DUE
BOTH TO A WARM START TO THE MONTH... AND LA NINA INFLUENCE. THE CFS PREDICTS
ABOVE NORMAL TEMPERATURES IN ALASKA, HOWEVER THIS CONFLICTS WITH LA NINA
COMPOSITES, SO ABOVE NORMAL TEMPERATURES ARE FAVORED IN THE SOUTHWEST PART OF
THE STATE WITH ADDITIONAL SUPPORT FROM THE GFS FORECASTS OUT THROUGH 14 DAYS.
THE PRECIPITATION FORECAST FOR THE EARLY PART OF DECEMBER IS IN GENERAL
AGREEMENT WITH LA NINA COMPOSITES EXCEPT NOTABLY FOR THE SOUTHWEST WHERE A
STORM IS EXPECTED TO BRING SIGNIFICANT PRECIPITATION ON THE FIRST DAY OF THE
MONTH. SINGLE DAY TOTALS ARE EXPECTED TO EXCEED MONTHLY NORMALS IN SOME
PLACES... ALTHOUGH SOME PRECIPITATION MAY COUNT TOWARD THE NOVEMBER TOTAL... SO
THE FORECAST FOR ABOVE MEDIAN PRECIPITATION IN THE SOUTHWEST IS LARGELY AN
ARTIFACT OF A SINGLE UNUSUAL EVENT WITH TIMING A FACTOR. DRY CONDITIONS ARE
FAVORED FROM TEXAS TO THE SOUTHEASTERN STATES DUE TO LA NINA. AN ACTIVE STORM
TRACK IS EXPECTED OVER THE GREAT LAKES INTO NEW ENGLAND IN THE FIRST WEEK OF
DECEMBER... AND THIS... COMBINED WITH SOME WEAK BUT CONSISTENT INDICATIONS FROM
LA NINA COMPOSITES RESULTED IN A FORECAST OF ELEVATED CHANCES OF ABOVE NORMAL
PRECIPITATION FROM THE GREAT LAKES TO NEW ENGLAND. SIGNIFICANT PRECIPITATION
FORECAST BY THE GFS IN THE PACIFIC NORTHWEST... THE NORTHERN ROCKIES... AND IS
CONSISTENT WITH LA NINA COMPOSITIES. SHORT TERM FORECASTS ARE ALSO CONSISTENT
WITH THE FORECAST FOR ABOVE MEDIAN PRECIPITATION AMOUNTS IN SOUTHWESTERN ALASKA
ISSUED EARLIER THIS MONTH.
FORECASTER: DAVID UNGER
NOTES: AREAS OF UNCERTAINTY THAT FORMERLY WERE LABELED CL (CLIMATOLOGICAL
PROBABILITIES) ARE NOW LABELED AS EC (EQUAL CHANCES).
THE NEXT MONTHLY OUTLOOK...FOR JANUARY 2008...WILL BE ISSUED ON THU DEC 20 2007
THESE OUTLOOKS ARE BASED ON DEPARTURES FROM THE 1971-2000 BASE PERIOD.
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