HPC Discussion - ...MAJOR WINTER STORM ANTICIPATED
Posted by JAC on 2/3/2010, 7:07 am
EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
236 PM EST MON FEB 01 2010

VALID 12Z THU FEB 04 2010 - 12Z MON FEB 08 2010


...MAJOR WINTER STORM ANTICIPATED FROM THE CAROLINAS TO
SOUTHEASTERN NEW ENGLAND...


PRELIMINARY UPDATE...

THE 00Z/01 GLOBAL NUMERICAL GUIDANCE SHOWS A CONTINUATION OF THE
CURRENT FLOW REGIME ACROSS THE UNITED STATES THROUGH THE MEDIUM
RANGE PERIOD...WITH A STRONG PACIFIC JET COMING INTO THE WEST
COAST...AND A SPLIT...CONFLUENT FLOW OVER THE EASTERN STATES.
THIS PATTERN PRODUCED SNOW AND ICE OVER PORTIONS OF THE CAROLINAS
AND MID ATLANTIC STATES THIS PAST WEEKEND...AND IT APPEARS ANOTHER
WINTER STORM IS IN THE OFFING FOR THE SAME AREAS THIS UPCOMING
WEEKEND...WITH AN EXPANSION OF THE SNOW INTO THE NORTHEAST ON THE
OCEAN SIDE OF I-95.  A COMPLEX WAVE ORGANIZING OVER THE GULF OF
MEXICO EARLY IN THE PERIOD WILL SPREAD MAINLY RAIN INTO THE
SOUTHERN STATES.  THE WAVE IS EXPECTED TO CONSOLIDATE ALONG THE
CAROLINA COAST EARLY DAY 5...WITH A RAPID DEEPENING NEAR CAPE
HATTERAS.  CLIMATOLOGY SUGGESTS THE STORM WILL LIFT ALONG THE
WESTERN EDGE OF THE GULF STREAM...THOUGH THE DOMINANT NORTHERN
STREAM THIS WINTER IS LIKELY TO HERD THE BEST MOISTURE EAST OF
I-95...AS WITH THE EVENT BEFORE CHRISTMAS.  STILL...THE IMPACT FOR
THE MAJOR METROPOLITAN AREAS WOULD BE HIGH.  A MEAN RIDGE OVER THE
ROCKIES WILL MARK THE CUTOFF FOR THE EASTWARD PROGRESSION OF
PACIFIC MOISTURE...WITH MOST OF THE PRECIPITATION WRUNG OUT ALONG
AND WEST OF THE CASCADES AND SIERRA NEVADA.  THE 00Z/01 GFS...GEFS
MEAN...ECMWF...AND EC MEAN ALL CLUSTER FAIRLY WELL ACROSS THE
NATION THROUGH THE PERIOD...BUT WITH ITS STRONG VERIFICATION THIS
SEASON...STUCK CLOSEST TO THE DETERMINISTIC ECMWF FOR THE DETAILS
OF THE PRELIMINARY UPDATE PACKAGE.


FINAL...

THE 12Z/01 DETERMINISTIC GFS WAS AN OUTLIER TO ITS ENSEMBLE
MEAN...AS WELL AS THE NEW GEM GLOBAL...UKMET...AND ECMWF...WITH
THE SUPPRESSED TRACK OF THE CYCLONE ALONG THE EAST COAST DAY 5.
THE ECMWF...UKMET...AND PARTICULARLY THE GEM GLOBAL CRANK UP A
REAL STEMWINDER BETWEEN HATTERAS AND THE LOWER DELMARVA PENINSULA
SATURDAY...WITH INDICATIONS THAT THE MID LEVEL LOW WILL CLOSE OFF
FOR A TIME...PROLONGING THE HEAVY PRECIPITATION AND HIGH WINDS.
THE NORTHERN EDGE OF THE GUIDANCE BRINGS PRECIPITATION AS FAR
NORTH AS BOSTON...AND EXPECT THAT WITH A GRADUAL TREND OF THE LOW
TRACK CLOSER TO THE WESTERN EDGE OF THE GULF STREAM...THAT THE
STORM WILL END UP AFFECTING THE USUAL SUSPECTS ALONG AND EAST OF
THE I-95 CORRIDOR.  THIS WINTER HAS HAD SO MUCH BLOCKING...THAT
THE DEEP INTERIOR OF THE NORTHEAST HAS BEEN LEFT OUT OF MUCH OF
THE HEAVY SNOW.  AT THIS POINT...DO NOT SEE WHY THAT SHOULD NOT BE
THE CASE WITH THIS EVENT AS WELL.  THE ONLY CHANGES MADE FOR THE
FINAL ISSUANCE AFFECT THE EAST...WITH A SLIGHT ADJUSTMENT OF THE
CYCLONIC CIRCULATION NORTHWARD TOWARD CLIMATOLOGY.  STILL PUT
FAITH IN THE ECMWF FOR THE WESTERN STATES.


CISCO





VALID 12Z WED FEB 03 2010 - 00Z FRI FEB 05 2010

BEFORE POTENTIALLY IMPACTING THE SOUTHEAST AND MID ATLANTIC STATES
LATER THIS WEEK WITH A COMBINATION OF HEAVY RAIN...SNOW AND ICE...
A VIGOROUS UPPER LEVEL SYSTEM WILL FIRST SPREAD WIDESPREAD
PRECIPITATION ACROSS THE SOUTHERN TIER STATES FROM THE DESERT
SOUTHWEST TO THE CENTRAL GULF COAST OVER THE NEXT COUPLE OF DAYS.
MODERATE TO HEAVY RAINS ARE LIKELY TODAY ACROSS PORTIONS OF SOUTH
TEXAS...PARTICULARLY ALONG THE LOWER RIO GRANDE VALLEY AND LOWER
TEXAS COAST AS STRENGTHENING SOUTHEASTERLY WINDS BEGIN TO DRAW A
DEEP POOL OF MOISTURE OUT OF THE WESTERN GULF INTO THE REGION.
GENERALLY LIGHTER PRECIPITATION IS EXPECTED ACROSS THE REMAINDER
OF THE STATE...AS WELL AS ACROSS OKLAHOMA INTO THE SOUTHWEST AS
THIS MOISTURE IS DRAWN WESTWARD AROUND A STRONG CYCLONE CENTERED
OVER NORTHERN MEXICO.  THIS PRECIPITATION SHOULD INCLUDE SOME
LIGHT TO MODERATE SNOWS ACROSS THE TEXAS AND OKLAHOMA PANHANDLES
AND SOUTHERN ROCKIES TODAY.  MODERATE TO HEAVY RAINS ARE EXPECTED
TO ADVANCE EASTWARD ACROSS THE CENTRAL GULF COAST STATES TOMORROW
AS A SURFACE LOW IN RESPONSE TO THE ADVANCING UPPER SYSTEM BECOMES
BETTER ORGANIZED AND BEGINS ITS TRACK ACROSS THE NORTHWESTERN
GULF.  MEANWHILE...LIGHT PRECIPITATION WILL EXTEND FURTHER TO THE
NORTH THROUGH THE PLAINS STATES AS A MORE NORTHERLY UPPER LEVEL
SYSTEM MOVING ACROSS THE NORTHWESTERN U.S. WORKS TO DRAW THE
DEEPER MOISTURE FURTHER TO THE NORTH THROUGH THE REGION.

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Possible Significant Storm Friday - IN to VA to FL - JAC, 2/2/2010, 3:59 pm
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