Prognostic Meteorological Discussion
Issued by NWS

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9
000
FXUS10 KWNH 020645
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
244 AM EDT WED SEP 02 2015

VALID SEP 02/0000 UTC THRU SEP 05/1200 UTC

...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...

00Z NAM/GFS EVALUATION INCLUDING THE UKMET/CANADIAN/ECMWF AND
PREFERENCES

UPPER TROUGH FORMING ACROSS THE PACIFIC NORTHWEST...

PREFERENCE: MODEL CONSENSUS
CONFIDENCE: AVERAGE

THE MAIN DIFFERENCES INVOLVE STRENGTH.  THE GFS IS STRONGER WITH
THE CLOSED LOW CENTER OVER NORTHERN CALIFORNIA BY 12Z SAT...WITH
THE NAM/ECMWF SLIGHTLY WEAKER.  A CONSIDERABLE NUMBER OF
GFS/ENSEMBLE MEMBERS INCLUDING THE PARALLEL GEFS PROVIDE
SUFFICIENT SUPPORT OF THE STRONGER GFS TO BE WORTHY OF INCLUSION
WITH THE WEAKER SCENARIO.  THUS...RECOMMEND A SOLUTION NEAR THE
CONSENSUS AT THIS TIME.

SHORTWAVE TROUGH ACROSS THE UPPER MIDWEST...

PREFERENCE: BEFORE 12Z THU...EQUAL BLEND GFS/ECMWF
             AFTER 12Z THU...GRADUALLY SWITCH TO GFS
CONFIDENCE: BEFORE 12Z THU...AVERAGE
             AFTER 12Z THU...BELOW AVERAGE

MODEL INITIALIZATION AND SHORT TERM TRENDS FAVOR A CONSENSUS
APPROACH TO BEGIN THE PERIOD...WITH THE HI-RES SOLUTIONS LOSING
THEIR SOUTHWARD EMPHASIS BY TONIGHT AND SHIFTING CONVECTION
NORTHWARD ALONG THE STATIONARY BOUNDARY.  WHILE CERTAINLY
POSSIBLE...THESE HIGHER RES SOLUTION MAY BE LACKING A SUFFICIENT
TRIGGER TO OVERCOMING THE CAPPING INVERSION.  MEANWHILE...ALL
GLOBAL GUIDANCE IS MUCH FARTHER SOUTH BY TONIGHT AND
THURSDAY...PERHAPS DUE TO THEIR CONVECTIVE PARAMETERIZATIONS THAT
ALLOW FOR EASIER TRIGGERING.  GIVEN THAT GROWTH OF THE SHORTWAVE
TROUGH IS ALREADY OCCURRING DUE TO CONVECTION AND THAT
TRAINING/BACKBUILDING MAY SUSTAIN DEVELOPMENT FARTHER SOUTH...THE
CURRENT PREFERENCE IS FOR THE MORE SOUTHWARD ORIENTED SOLUTIONS
GLOBAL.  THAT SAID THOUGH...THE ECMWF DOES MOVE TOWARD THE OUTER
EDGES OF THE GUIDANCE BY THU-FRI...BY STALLING AND EVENTUALLY
RETROGRADING THE TROUGH...ALTHOUGH LESS EGREGIOUSLY THAN THE 12Z
RUN...WITH THE GFS CLOSER TO THE CONSENSUS AND THUS MORE PROBABLE
AFTER THU.

SHORTWAVE TROUGH MOVING FROM THE SOUTHWEST TO THE PLAINS THU-FRI...

PREFERENCE:  NAM OR GFS OR ECMWF
CONFIDENCE:  ABOVE AVERAGE

THE NAM AND GFS HAVE TRENDED WESTWARD WITH ITS TRACK AND SHOW GOOD
AGREEMENT WITH EACH OTHER THROUGH 84 HRS...WITH SUPPORT FROM THE
00Z ECMWF.

...MODEL TREND GRAPHICS AT
www.wpc.ncep.noaa.gov/html/model2.shtml...

...500 MB FORECASTS AT
www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml...



$$




USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.