FXUS02 KWNH 270900
PREEPD
 
PRELIMINARY EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
359 AM EST FRI NOV 27 2009
 
VALID 12Z TUE DEC 01 2009 - 12Z FRI DEC 04 2009
 
A MID LVL TROF EXTENDING FROM THE GRTLKS INTO THE PLAINS AS OF DAY
3 MON SHOULD CONTINUE NEWD WHILE UPSTREAM ENERGY POISED TO ENTER
WRN NOAM IS FCST TO AMPLIFY INTO THE CNTRL CONUS BY MID-LATE WEEK.
 THIS DEEPENING TROF WILL HELP TO EJECT A SRN STREAM UPR LOW THAT
SHOULD INITIALLY BE OVER EXTREME NRN MEXICO.  ONE OR MORE PIECES
OF ERN PAC ENERGY MAY FLOW AROUND OR THRU A MEAN RIDGE OVER THE
ERN PAC.  
THE 00Z GFS DOES NOT COMPARE WELL TO OTHER MODEL AND ENSEMBLE
GUIDANCE INCLUDING THE 00Z GEFS RUN WITH RESPECT TO A NUMBER OF
FEATURES IN THE MEDIUM RANGE FCST.  TO START WITH THE GFS IS A
FLAT AND PROGRESSIVE OUTLIER WITH THE TROF EXPECTED TO AMPLIFY
INTO THE CNTRL CONUS BY WED... WHICH LEADS TO A FAST TIMING OF THE
LEADING SHRTWV DEPARTING FROM THE NORTHEAST.  THEN THE GFS IS A
STRONG/NRN OUTLIER WITH A COMPACT MID LVL SYSTEM WHICH THE MODEL
BRINGS TO OREGON TUE NIGHT/WED.  THE 00Z ECMWF IS WEAKER/SWD WITH
THIS FEATURE WHILE THE UKMET/CANADIAN DO NOT EVEN SHOW A WELL
DEFINED FEATURE.  ENSEMBLES ARE NOT ENTHUSIASTIC ABOUT SUCH A
FEATURE.  THE LARGE SCALE MEAN RIDGE OVER THE ERN PAC DOES NOT
FAVOR THE GFS SCENARIO AS WELL... THOUGH THE RIDGE IS SUFFICIENTLY
AMPLIFIED THAT SOME UNDERCUTTING FLOW MAY BE PRESENT AS HINTED AT
BY THE 12Z ECMWF ENSEMBLE MEAN.  THEN THE GFS IS EXTREME COMPARED
TO OTHER MODELS/ENSEMBLES WITH ENERGY WHICH THE MODEL BRINGS TO
THE WEST COAST BY LATE NEXT WEEK.  HOWEVER THE CANADIAN... 00Z
GEFS/12Z CANADIAN ENSEMBLES AND TO A LESSER EXTENT 12Z ECMWF
ENSEMBLES ALL SUGGEST THAT SOME UPSTREAM ENERGY MAY REACH WRN NOAM
EARLIER THAN FCST BY THE PAST TWO ECMWF RUNS THAT MAINTAIN A
STRONG RIDGE ALONG THE WEST COAST THRU DAY 7 FRI.  EITHER SCENARIO
IS PLAUSIBLE IN TERMS OF A MULTI-DAY MEAN.  HOWEVER THE ECMWF
COULD BE A LITTLE TOO PERSISTENT WITH THE CONUS TROF BY LATE NEXT
WEEK AS THE 00Z RUN HAS ADJUSTED SLIGHTLY EWD WITH THE WRN PART OF
THE TROF AND A LARGE SCALE MEAN TROF HAS A TENDENCY TO BE
MAINTAINED BY A SERIES OF SYSTEMS RATHER THAN ONE LARGE PERSISTENT
TROF.  FINALLY THERE IS STILL A DECENT SPREAD WITH THE SYSTEM
EJECTING FROM NRN MEXICO.  ECMWF RUNS ARE ON THE SLOWER SIDE OF
THE SPECTRUM BUT THE CANADIAN GLBL/GEFS MEAN ARE NOT TO FAR AWAY
SO WILL AWAIT FUTURE GUIDANCE BEFORE ADJUSTING FROM THE ECMWF HERE
IN LIGHT OF ITS PREFERRED HANDLING OF FLOW ELSEWHERE.
DUE TO THE MULTIPLE EXTREME/OUTLIER ASPECTS OF THE GFS... THE DAYS
3-7 MON-FRI FCST IS BASED PRIMARILY ON A BLEND OF THE 00Z AND
12Z/26 ECMWF RUNS.  LATE PERIOD CONSIDERATIONS AND TYPICALLY
INCREASED UNCERTAINTY ALLOW FOR MODEST INCLUSION OF THE 12Z/26
ECMWF ENSEMBLE MEAN BY DAYS 6-7.
RAUSCH
$$