THE WEATHER PREDICTION CENTER

COLLEGE PARK, MD


MODEL DIAGNOSTIC DISCUSSION


[Abbreviations and acronyms used in this product]
Geographic boundaries:    Map 1- [Color] [B/W Print Version]      Map 2 - [Color] [B/W Print Version]



MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
317 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 MODEL EVALUATION WITH FINAL 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/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
AREAS OF VORTICITY BECOMES 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 CONTINUES TO HAVE THE
SUPPORT OF THE LATEST ECMWF WHILE THE 00Z UKMET STUCK TO ITS IDEA
OF KEEPING THE BULK OF THE SHORTWAVE ENERGY OVER THE GULF AND
EVENTUALLY SHARING PART OF THE SHORTWAVE OFF AND BRINGING A WELL
DEFINED VORT CENTER OVER THE FL PANHANDLE BY 02/12Z WHILE THE
CANADIAN TAKES A WEAK SHORTWAVE WESTWARD ACROSS THE CENTRAL GULF
BY THE END OF DAY 3. 

A GENERAL NCEP/ECMWF DETERMINISTIC MODEL COMPROMISE IS
PREFERRED...ALTHOUGH CONFIDENCE IS BELOW AVERAGE.


ADDITIONAL SHORTWAVE ENERGY OVER BRITISH COLUMBIA ADVANCING INTO
THE GREAT LAKES DEEPENING THE LARGE SCALE TROF THU INTO SAT.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~
PREFERENCE: 00Z 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 00Z ECMWF SEEM TO
HAVE THE BEST HANDLE ON TIMING AND STRENGTH...WHILE THE NAM AND
THE UKMET REMAINED 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. 
STILL 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






Last Updated: 317 AM EDT THU JUL 30 2015