Prognostic Meteorological Discussion
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000
FXUS10 KWNH 300456
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1255 AM EDT THU JUL 30 2015

VALID JUL 30/0000 UTC THRU AUG 02/1200 UTC

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

00Z NCEP MODEL EVALUATION WITH ANALYSIS AND INITIAL PREFERENCES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
ANY NAM/GFS INITIALIZATION ERRORS DO NOT APPEAR TO AFFECT SHORT
TERM FORECAST ERRORS


WELL DEFINED UPPER LOW ACROSS WESTERN ONTARIO SETS UP OVER HUDSON
BAY BY FRIDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z GFS/NAM AND 12Z ECMWF CONSENSUS
CONFIDENCE: ABOVE AVERAGE

OVERALL MODEL AGREEMENT WAS GOOD WITH RESPECT TO THE
STRENGTH/TIMING OF THE UPPER LOW AND SURFACE COLD FRONT MOVING
EAST ACROSS THE REGION.


LOW-LEVEL SHEAR AXIS WITH EMBEDDED WEAK SURFACE LOWS ACROSS THE
GULF OF MEXICO
ASSOCIATED WEAK UPPER LOW/ELONGATED TROF
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL NCEP/ECMWF DETERMINISTIC MODEL CONSENSUS
CONFIDENCE: BELOW AVERAGE

MODELS START OFF IN GOOD AGREEMENT WITH THE TROUGH AXIS AND
GENERAL CORRIDOR OF VORTICITY MAXIMA THURSDAY INTO THE DAY ON
FRIDAY. SPREAD AMONG THE GUIDANCE EMERGES BY LATE FRIDAY AND
BECOMES GREATER SATURDAY INTO EARLY SUNDAY.

AS MENTIONED IN THE PREVIOUS DISCUSSION...MODELS DIVERGE ON WHICH
VORT AREAS BECOME DOMINANT AND HOW MUCH OF THE ENERGY IS PUSHED
NORTHEAST WITH THE LONG WAVE UPPER TROUGH OVER THE EAST
COAST...AND HOW MUCH IS LEFT BEHIND TO PROGRESS WEST INTO THE GULF
OF MEXICO.

IN THE BROADEST SENSE...THE 00Z NCEP MODEL RUNS STAYED WITH THE
IDEA THAT MORE OF THE SHORTWAVE ENERGY WOULD BE OFF THE EAST COAST
OF FL AND PULLING TOWARDS THE EAST WHILE LEAVING LESSER AMOUNTS OF
ENERGY OVER THE GULF OF MEXICO.  THIS IDEA HAD THE SUPPORT OF THE
29/12Z ECMWF WHILE THE 29/12Z RUNS OF THE CANADIAN AND UKMET
FAVORED KEEPING THE BULK OF THE SHORTWAVE ENERGY OVER THE GULF.


ADDITIONAL SHORTWAVE ENERGY OVER BRITISH COLUMBIA ADVANCING INTO
THE GREAT LAKES DEEPENING THE LARGE SCALE TROF THU INTO SAT.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~
PREFERENCE: 12Z GFS/ECMWF
CONFIDENCE: AVERAGE

ON THURSDAY EVENING ONE SHORTWAVE IS EXPECTED TO MOVE ACROSS THE
GREAT LAKES AND PUSH NORTHEAST INTO NEW ENGLAND ON FRIDAY.
ADDITIONAL SHORTWAVE ENERGY WILL DIVE INTO THE GREAT LAKES FRIDAY
INTO SATURDAY ACTING TO DEEPEN THE LARGE SCALE TROUGH OVER THE
EASTERN PORTION OF THE COUNTRY.

WITH THE FIRST SHORTWAVE...THE 00Z GFS AND THE 29/12Z ECMWF SEEM
TO HAVE THE BEST HANDLE ON TIMING AND STRENGTH...WHILE THE 00Z NAM
AND THE 29/12Z UKMET WERE TOO SLOW AND FAST RESPECTIVELY.  THE
MOST RECENT RUN OF THE ENSEMBLES LEND SUPPORT TO THE GFS/ECMWF.

AS THE SHORTWAVE ENERGY MOVES INTO THE GREAT LAKES REGION...THE
00Z NAM AND THE UKMET WERE SHARP OUTLIERS.  IN THE CASE OF THE
UKMET...IT OUTRAN OTHER GUIDANCE AND ENSEMBLE MEANS BY DAY 3.
THINK THE GFS/ECMWF COMBINATION IS THE BEST BET AT THIS POINT.


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

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

BANN


$$





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