UPDATE FOR 30-DAY OUTLOOK DISCUSSION FOR FEBRUARY 2005

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PROGNOSTIC DISCUSSION FOR MONTHLY OUTLOOK
NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD
330 PM EST MON JAN 31 2005

UPDATE FOR 30-DAY OUTLOOK DISCUSSION FOR FEBRUARY 2005
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SSTS ALONG THE EQUATOR IN THE PACIFIC CONTINUE MORE THAN 1 DEGREE C ABOVE
NORMAL FROM ABOUT 160E TO 160W LONGITUDE AND AVERAGE ABOUT 0.5 DEGREE C ABOVE
NORMAL FROM 150W TO JUST OFF THE SOUTH AMERICAN COAST WHERE THEY ARE JUST ABOUT
NORMAL. SST ANOMALIES IN THE ENSO-SENSITIVE REGIONS OF THE PACIFIC HAVE
REMAINED CLOSE TO THEIR CURRENT VALUES FOR SEVERAL WEEKS AND WEAK EL NINO
CONDITIONS ARE EXPECTED TO CONTINUE THROUGH AND BEYOND FEBURARY 2005. NO
SIGNIFICANT CONVECTIVE ACTIVITY HAS OCCURED EAST OF THE DATELINE... SO THE
INFLUENCE OF THIS WEAK WARM ENSO EVENT ON THE ATMOSPHERE AND PARTICULARLY THE
CIRCULATION OVER THE EASTERN PACIFIC AND NORTH AMERICA HAS BEEN NEGLIGIBLE.
BEGINNING IN THE LATTER PART OF DECEMBER 2004 MJO ACTIVITY BECAME MORE ACTIVE
AND HAS BEEN THE PRIMARY COMPONENT OF TROPICAL FORCING ON THE MID-LATITUDE
CIRCULATION AND THE ACCOMPANYING CLIMATE OVER NORTH AMERICA.

BECAUSE THE TROPICAL FORCING WILL PROBABLY CONTINUE TO VARY WITH TIME... IT IS
DIFFICULT TO KNOW WHAT ITS NET EFFECT WILL BE FOR THE MONTH OF FEBURARY... AND
ADDITIONAL UNCERTAINTIES ARE INTRODUCED BY THE UNCERTAINTIES IN PREDICTIONS OF
THE PHASES OF THE AO AND NAO BEYOND A WEEK OR TWO AHEAD AT BEST. THE NAO HAS
INDEED REVERSED SIGN AS WAS HINTED WHEN THE LONG-LEAD VERSION OF THE FOPRECAST
FOR FEBRUARY WAS ISSUED ON JAN 20... WITH A STRONG BLOCK RETROGRADING ACROSS
THE ATLANTIC JUST NORTH OF 50N. THE AO HAS BEEN IN NEGATIVE TERRITORY... AND
THE ONLY THING THAT PREVENTS A MAJOR COLD PATTERN IS THAT HEIGHTS HAVE BEEN
AND ARE PREDICTED TO CONTINUE TO BE BELOW NORMAL OVER NORTHWESTERN cANADA AND
MOST OF ALASKA. THERE IS STILL PLENTY OF COLD ARCTIC AIR AVAILABLE IN THAT
AREA BUT MOST OF IT IS REMAINING IN THE ARCTIC OR MOVING SLOWLY SOUTHWARD
ACROSS ALASKA. WITH THE CIRCULATION PATTERNS PREDICTED FOR THE NEXT COUPLE OF
WEEKS... MOST OF THE ARCTIC AIR WILL BE AFFECTING ALASKA WITH ONLY THE
SOUTHERN FRINGE OF SOME OF THE ARCTIC AIR AFFECTING THE CONUS BRIEFLY FROM
TIME TO TIME. THE STRONG BLOCKING RETROGRADING ACROSS THE ATLANTIC TOWARDS
EASTERN CANADA MEANS THAT THE AIR FROM COLD SOURCES AFFECTING THE CONUS WILL
BE MILDER THAN USUAL ONCE THE MARITIME REGIME TAKES HOLD.

THE INDICATIONS FROM THE MODELS ARE NOT AS USEFUL AS ONE MIGHT HOPE.
ALTHOUGH THERE IS THE USUAL GOOD AGREEMENT FOR THE FIRST 5 OR 6 DAYS...
THE MODELS BEGIN TO DIVERGE AT THE BEGINNING OF THE 6-10 DAY PERIOD.
MOST OF THE RECENT GFS MODELS FORECAST ABOVE NORMAL HEIGHTS ACROSS MOST OF
THE CONUS AND ALL BUT EXTREME NORTHWESTERN CANADA... WHILE THE ECMWF
SOLUTION INITIALIZED AT 12Z JAN 30 AND ITS ENSEMBLE MEAN BOTH FORECAST A FULL
LATITUDE TROUGH OVER WESTERN NORTH AMERICA FOR THE 6-10 DAY PERIOD... AND THE
CANADIAN ENSEMBLE MEAN AND THE DAVA MODEL ALSO HAVE SIMILAR SOLUTIONS...
PLACING THE GFS MODEL SOLUTIONS IN A DECIDED MINORITY. A COUPLE OF THE
INDIVIDUAL OPERATIONAL GFS FORECASTS FROM A FEW DAYS BACK SHOWED THIS TYPE OF
PATTERN... BUT NONE HAVE SINCE THEN.... WHILE THE ECMWF MODEL SOLUTIONS HAVE
CONSISTENTLY TRENDED MORE TOWARDS THE FULL LATITUDE TROUGH OVER THE WEST.
FOR THE 8-14 DAY PERIOD ONLY THE GFS SOLUTIONS AND DAVA AREA AVAILALBE...
WITH THE GFS SOLUTIONS BEGINNING TO SLIGHTLY WEAKEN THE POSITIVE HEIGHT
ANOMALIES OVER THE U.S. ... BUT MORE IN THE EAST THAN IN THE WEST. THE
DAVA PATTERN FOR WEEK TWO IS VERY SIMILAR TO THE ECMWF AND CANADIAN MEAN
PATTERNS FOR THE 6-10 DAY PERIOD... SO THE LATTER WERE PREFERRED AS AN
ESTIMATE OF THE WEEK TWO PATTERN.

THERE IS LITTLE DOUBT THAT EXCEPT FOR THE PANHANDLE ALASKA WILL HAVE BELOW
NORMAL TEMPERATURES FOR THE FIRST TWO WEEKS OF FEBRUARY IF THE MODELS ARE
ANYWHERE NEAR CORRECT... WHILE THE NORTHEASTERN AND MUCH OF THE CENTRAL U.S.
WILL BE MILDER THAN NORMAL. MOST OF THE AREA WEST OF THE DIVIDE AND THE
SOUTHEAST HAVE WEAK INDICATIONS... SO WERE LEFT SIMILAR TO WHAT WAS FORECAST
IN THE LONG-LEAD MONTHLY FORECAST PREVIOUSLY ISSUED TO TAKE ADVANTAGE OF
WHATEVER LONG-LEAD SIGNALS WERE AVAILABLE.

MOST OF THE TOOLS BASED ON THE MODELS FOR THE FIRST TWO WEEKS OF FEBRUARY
WERE SUGGESTING THAT STORMS COULD BE BRINING ABOVE MEDIAN PRECIPITATION TO
MUCH OF THE MIDDLE OF THE COUNTRY... WHILE MOST OF ALASKA... THE FAR WEST...
AND PARTS OF FLORIDA AND SOUTHERN GEORGIA ARE LIKELY TO HAVE LESS
PRECIPITATION THAN USUAL.