HPC Discussion: GFS trending toward Euro. Watch out for the 12th.
Posted by JAC on 1/3/2011, 9:39 am
PRELIMINARY EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
900 AM EST MON JAN 03 2011

VALID 12Z FRI JAN 07 2011 - 12Z MON JAN 10 2011

THE MAIN ALTERATION TO THE UPDATED PRELIM PROGS WAS TO ADJUST SWWD
A POSSIBLE MAJOR STORM ALONG THE NRN MID ATLANTIC COAST IN THE DAY
4-6 FRI-SUN TIME FRAME. WHILE THE DETERMINISTIC ECMWF IS A RATHER
EXTREME SWRN OUTLIER IN DROPPING A PIECE OF POLAR VORTEX SSE ALL
THE WAY FROM HUDSON BAY TO VA...THE 06Z/03 GFS HAS TRENDED A BIT
TOWARDS THE ECMWF SOLUTION SAT...GIVING A NEWD ADJUSTED ECMWF
SCENARIO SOME CREDIBILITY. THIS MAINTAINS REASONABLE HPC
CONTINUITY WITH THIS POTENTIAL E COAST SYS OVER THE PAST TWO DAYS.
WHILE NOT OVERPLAYING ANALOGS...I STILL WANT TO POINT OUT SOME
SIMILARITY IN THE PRESENT HPC SCENARIO THIS WEEKEND TO THAT OF FEB
6 1978...ESPECIALLY AT 500 MILLIBARS...WHICH WAS A MAJOR BLIZZARD
FOR ERN PA/NY/NEW ENG.

THE 00Z ECENS AND 06Z GEFS MODEL MEANS SUGGEST THAT AN ANOTHER
AREA TO WATCH CONCERNS THE NEW TROF DIGGING INTO THE WERN
STATES... WHERE ECMWF ENSEMBLE MEBERS SUGGEST A DEEPER TROF EARLY
NEXT WEEK.




AN INCREASINGLY BROAD AREA OF THE CONUS WILL SEE BELOW NORMAL HGTS
AS RIDGING OVER THE NRN PAC/ALASKA AND VICINITY ENCOURAGES HGT
FALLS TO SINK SWD OVER THE WRN STATES... AND ANOTHER RIDGE ALBEIT
A WEAKENING ONE OVER NRN CANADA KEEPS HGTS LOW OVER THE EAST
ESPECIALLY LATE WEEK INTO THE WEEKEND.  WITHIN A DEEP ERN CONUS
MEAN TROF THERE ARE SIGNIFICANT DIFFS WITH THE PATH OF CLOSED LOW
ENERGY FCST TO BE OVER ONTARIO AS OF EARLY DAY 3 THU AND/OR
UPSTREAM ENERGY THAT MAY UNDERCUT THE CLOSED LOW.  THE 00Z ECMWF
TAKES AN EXTREMELY SRN TRACK WHICH RESULTS IN A DEEP WRN ATLC SFC
LOW THAT IS FARTHER SWWD THAN NEARLY ALL OTHER GUIDANCE BY EARLY
DAY 5 SAT.  AT THAT TIME THE 00Z ECMWF POSN IS FARTHER SWWD THAN
ALL BUT ONE 12Z ECMWF ENSEMBLE MEMBER AND ALL 00Z GEFS/12Z
CANADIAN ENSEMBLE MEMBERS.  THE 00Z GFS COMPARES BETTER TO
ENSEMBLE GUIDANCE ALOFT BUT ITS SFC EVOLUTION SHOWS SOME DETAILS
THAT ARE NOT INDICATED IN THE MAJORITY OF OTHER MODEL/ENSEMBLE
MEAN SOLNS.  THE CANADIAN GLOBAL USES UPSTREAM ENERGY TO GENERATE
A PROGRESSIVE WAVE THAT TRACKS OFF THE MID ATLC COAST FRI NIGHT.
FARTHER WWD... THE GFS IS SOMEWHAT SLOWER THAN MOST OTHER SOLNS TO
BRING NERN PAC/WRN CANADA HGT FALLS INTO THE WEST.  00Z ECMWF
TIMING IS CLOSER TO THE ENSEMBLE MEANS BUT THE CLOSED LOW WHICH
THE MODEL DEVELOPS JUST NE OF MT IS CONSIDERED A LOW PROBABILITY
SOLN.  ACROSS THE SRN STREAM THERE IS SOMEWHAT IMPROVED MODEL
CLUSTERING WITH RESPECT TO THE EWD EJECTION OF A CLOSED LOW FCST
TO BE SW OF CA DAY 3 THU AND PROGRESSION OF AN ASSOC SFC WAVE.
THE GEFS MEAN IS ON THE SLOWER SIDE OF THE SPREAD WHILE THE 12Z
ECMWF ENSEMBLE MEAN IS RELATIVELY FAST AS IT REFLECTS EARLIER
OPERATIONAL RUNS THAT WERE FASTER THAN THE NEW 00Z RUN AND OTHER
LATEST MODEL SOLNS.  

CONFIDENCE IN A NUMBER OF OPERATIONAL MODEL SPECIFICS IS
SUFFICIENTLY LACKING TO FAVOR A BLEND OF 00Z GEFS/12Z ECMWF
ENSEMBLE MEANS AS THE STARTING POINT FOR THE DAYS 3-7 THU-MON
FCST.  MINOR ADJUSTMENTS TO THE INITIAL BLEND WERE MADE ON ONE OR
MORE DAYS TO INCREASE DEFINITION SLIGHTLY OVER PORTIONS OF THE
NORTHWEST AND ERN CONUS/WRN ATLC.  IN ADDITION SOME DEFINITION WAS
ADDED TO THE EXPECTED SRN STREAM WAVE IN LIGHT OF IMPROVED MODEL
CLUSTERING.  TIMING WAS ADJUSTED TO BE JUST SLIGHTLY FASTER THAN
THE GFS/ECMWF IN LIGHT OF PRIOR CONTINUITY THAT WAS FASTER.

RAUSCH/FLOOD
49
In this thread:
Looks like the next Noreaster is pushed out to around the 12th - JAC, 1/3/2011, 8:28 am
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