Latest HPC Discussions on the Trof
Posted by JAC on 8/19/2009, 7:54 am
EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
313 PM EDT TUE AUG 18 2009

VALID 12Z FRI AUG 21 2009 - 12Z TUE AUG 25 2009


PRELIMINARY UPDATE...

THE PRELIMINARY FRONTS AND PRESSURES FOR DAYS 3 THROUGH 7 WERE
UPDATED PRIMARILY USING THE 00Z/18 ECMWF.  THE LAST FOUR EC
ENSEMBLE MEANS HAVE TRENDED TOWARD MORE AMPLITUDE WITH THE TROUGH
CROSSING THE GREAT LAKES DURING THE FIRST HALF OF THE PERIOD...AND
TOWARD A SLOWER...SHARPER TROUGH APPROACHING BRITISH COLUMBIA BY
THE END OF THE FORECAST.  THE LATEST DETERMINISTIC ECMWF REFLECTS
THESE TRENDS WELL...ADDING MORE RIGOR TO ITS SOLUTION.  THE 00Z/18
GFS IS OUT OF SYNC WITH BOTH THE EUROPEAN CENTRE GUIDANCE AND THE
GEM GLOBAL MODEL DURING THE SECOND HALF OF THE PERIOD...SHOWING A
SPRAWLING POLAR VORTEX FROM HUDSON BAY EASTWARD.  THE GEM GLOBAL
HANGS ONTO THE TROUGH OVER THE EASTERN UNITED STATES LONGER THAN
THE OTHER MODELS...AND WHILE THIS SOLUTION IS NOT OUT OF THE
QUESTION BASED ON THE SPREAD EVEN IN THE EC ENSEMBLE MEMBERS...THE
ODDS ARE AGAINST IT.


FINAL...

THE 12Z/18 GFS IS STILL OFFERING A SIGNIFICANTLY DIFFERENT
CONFIGURATION TO THE FLOW OVER EASTERN CANADA DURING THE SECOND
HALF OF THE FORECAST PERIOD THAN THE EUROPEAN CENTRE
GUIDANCE...DEPICTING A CONSOLIDATED VORTEX.  THE 12Z/18 ECMWF IS
CLOSE TO ITS 00Z/18 SOLUTION...AND WHERE IT DOES DIFFER...IT IS
WITHIN TOLERANCE WITH THE MOST RECENT EC ENSEMBLE MEAN.


CISCO



PRELIMINARY EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
451 AM EDT WED AUG 19 2009

VALID 12Z SUN AUG 23 2009 - 12Z WED AUG 26 2009

OPERATIONAL MODEL AND ENSEMBLE GUIDANCE MAINTAINS REASONABLE
CONTINUITY WITH THE FCST OF LARGE SCALE FLOW CONSISTING OF A
DEEPENING NERN PAC TROF... CNTRL NOAM RIDGE... AND ERN NOAM TROF.
AS FOR DETAILS WITHIN THIS MEAN FLOW... A TROF AND EMBEDDED CLOSED
LOW NEAR THE PAC NW/BC COAST EARLY DAY 3 SAT SHOULD PROGRESS EWD
ACROSS SRN CANADA AND EXTREME NRN CONUS AND THEN BEGIN TO RELOAD
THE ERN TROF.  AHEAD OF THIS FEATURE EXPECT A TROF INITIALLY OVER
THE ERN STATES TO WEAKEN/LIFT OUT... POSSIBLY LEAVING SOME WEAK
ENERGY BEHIND OVER OR NEAR THE SOUTHEAST.  THIS ERN TROF SHOULD
DEFLECT HURCN BILL FROM THE EAST COAST.  CONSULT TPC
DISCUSSIONS/ADVISORIES FOR LATEST INFO REGARDING THE EXPECTED
TRACK OF BILL... WHOSE FCST POSNS ON THE EARLY PRELIM HPC FCST ARE
BASED ON THE 03Z TPC ADVISORY THRU DAY 4 SUN FOLLOWED BY A
COMPROMISE BETWEEN EXTRAPOLATION OF THE TPC TRACK AND YDAYS
TPC/HPC COORDINATED FCST.  THE 00Z GFS STRAYS A LITTLE FASTER THAN
CONSENSUS WITH PARTS OF THE INITIAL ERN CONUS SYSTEM... BECOMES
FLATTER THAN MOST MODEL/ENSEMBLE MEAN GUIDANCE WITH FLOW ACROSS
SRN CANADA AND EXTREME NRN CONUS BY DAYS 4-5 SUN-MON... AND SHOWS
A GREATER SEWD EXTENT OF THE NERN PAC TROF BY DAY 7 WED.  AS 00Z
GEFS/12Z ECMWF ENSEMBLES PROVIDE CONSIDERABLY MORE SUPPORT TO THE
00Z ECMWF SCENARIO... THE 00Z ECMWF SERVES AS THE INITIAL BASIS
FOR THE DAYS 3-7 SAT-WED FCST.  DAYS 5-7 INCORPORATE HALF
WEIGHTING OF THE 12Z ECMWF MEAN... WHICH HAS SOMEWHAT BETTER
DEFINITION OF THE SYSTEM CROSSING SRN CANADA MOST OF THE PERIOD
COMPARED TO THE 00Z GEFS MEAN... TO ALLOW FOR TYPICAL DETAIL
UNCERTAINTIES AT THAT TIME FRAME.

RAUSCH
!
135
In this thread:
Some models---Bill a little too close for comfort to NE?? - jack ruby, 8/19/2009, 7:19 am
< Return to the front page of the: message board | monthly archive this page is in
Post A Reply
This thread has been archived and can no longer receive replies.