Prognostic Meteorological Discussion
Issued by NWS

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10

000
FXUS10 KWNH 260643
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
242 AM EDT THU MAR 26 2015

VALID MAR 26/0000 UTC THRU MAR 29/1200 UTC

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

...AN EVALUATION OF THE 00Z MODEL GUIDANCE ALONG WITH FINAL
PREFERENCES/FORECAST CONFIDENCE...

THERE DID NOT APPEAR TO BE ANY INITIALIZATION ERRORS WITH THE 00Z
NAM/GFS DEEMED SIGNIFICANT ENOUGH TO IMPACT THEIR FORECASTS.


...FULL-LATITUDE TROF CROSSING THE EASTERN U.S. BY EARLY IN THE
WEEKEND...
...STRONG COLD FRONT/ASSOCIATED SURFACE WAVES...

FINAL PREFERENCE: BLEND OF THE 00Z GFS/ECMWF...WEIGHTED 2/3 TOWARD
THE 00Z ECMWF
FORECAST CONFIDENCE: SLIGHTLY BELOW AVERAGE

THE CURRENT WATER VAPOR IMAGERY SHOWED A PAIR OF STRONG SHORTWAVES
AFFECTING THE OZARKS AND SOUTHERN ONTARIO...RESPECTIVELY. THE
FORMER HAS HELPED IGNITE A LARGE CLUSTER OF SHOWERS AND
THUNDERSTORMS ACROSS OK/AR WHICH HAS BEEN RESPONSIBLE FOR SEVERE
WEATHER REPORTS AND FLASH FLOODING. ALL FEATURES MOVING FORWARD
SHOULD BECOME MORE PROGRESSIVE IN NATURE AS HEIGHT FALLS PROJECT
EASTWARD IN TIME. A COMPLEX ARRAY OF IMPULSES MOVING IN FROM
CENTRAL CANADA WILL HELP DRAG THE UPPER TROF EASTWARD WITH THE
SYSTEM EVENTUALLY REACHING THE WESTERN ATLANTIC BY LATE IN THE
WEEKEND. THE ACCOMPANYING COLD FRONT WILL FEATURE A MULTITUDE OF
SURFACE WAVES WITH THE GUIDANCE GENERALLY DIFFERING WITH REGARD TO
THE POSITION AND INTENSITY OF EACH OF THESE LOWS.

OVERALL...THE 00Z GFS/GEFS MEAN HAVE TENDED TO BE A BIT QUICKER
WITH THE SOUTHERN EXTENT OF THE UPPER TROF ON FRIDAY EVENING
ACROSS THE SOUTHEASTERN U.S. THIS ULTIMATELY LEADS TO THE GFS
SUITE OF SOLUTIONS BEING MORE PROGRESSIVE WITH THE EJECTING
SURFACE LOW OVER THE WESTERN ATLANTIC. LATER IN THE PERIOD...THE
00Z CMC/UKMET STAND OUT AS BEING RATHER SLOW WITH THE BACK EDGE OF
THE UPPER TROF. IN FACT...THE 12Z/00Z CMC CLOSE OFF A 534-DM UPPER
LOW ACROSS THE MID-ATLANTIC BY 29/0000Z. THIS LEADS TO A MORE
WRAPPED UP COASTAL SOLUTION WHICH KEEPS PRECIPITATION ACROSS THE
MID-ATLANTIC INTO DAY 3. ENSEMBLE LOW PLOTS SUGGEST SUCH A
SOLUTION IS A MINORITY AT THIS POINT. AS A WHOLE LIKE THE COMBO OF
THE 00Z GFS/ECMWF BUT WILL WEIGHT THE SOLUTION TWO-THIRDS TOWARD
THE LATTER GIVEN THE THOUGHT THAT THE GFS IS TOO FAST INTO DAY 3.


...PROGRESSIVE SHORTWAVE REACHING THE PACIFIC NORTHWEST BY LATE
FRIDAY...
...WELL-DEVELOPED SURFACE CYCLONE MOVING THROUGH THE NORTHERN TIER
THIS WEEKEND...

FINAL PREFERENCE: BLEND OF THE 00Z GFS/21Z SREF MEAN
FORECAST CONFIDENCE: BELOW AVERAGE

A STOUT UPPER RIDGE ANCHORING THE WESTERN U.S. WILL QUICKLY GIVE
WAY TO A PROGRESSIVE SHORTWAVE CROSSING THE PACIFIC NORTHWEST BY
FRIDAY NIGHT. THE MODELS CONTINUE TO NOT AGREE WITH THE TIMING OF
THIS IMPULSE AS IT MOVES TOWARD THE UPPER INTERMOUNTAIN WEST. THE
00Z UKMET DID TREND IN THE FASTER DIRECTION RELATIVE TO THE
PREVIOUS SOLUTION WHICH CARRIES A BULK OF ITS ENERGY TOWARD
NORTHERN CA. LOOKING TOWARD DAY 3....THE 00Z/12Z ECMWF START TO
BECOME SLOWER THAN THE ENSEMBLE MEANS INCLUDING ITS OWN 12Z ECMWF
ENSEMBLE MEAN. PREFER TO STAY ON THE MORE PROGRESSIVE SIDE AS
SUPPORTED BY THE ENSEMBLE MEANS. LOOKING AT EACH OF THE
DETERMINISTIC MODELS COMPARED TO THEIR PREVIOUS CYCLE...THERE
CONTINUES TO BE A LOT OF WAFFLING AROUND IN THE SOLUTIONS WHICH
SHOWS CONFIDENCE IS BELOW AVERAGE IN THIS SETUP. WILL CONTINUE TO
FAVOR A COMBINATION OF THE 00Z GFS WITH THE 21Z SREF MEAN. THE 00Z
GFS IS ON THE SOUTHERN END OF THE ENSEMBLE SPREAD REGARDING THE
LOW TRACK. SO WILL SPLIT THE DIFFERENCE BETWEEN THE TWO.


...SHORTWAVES CROSSING THE DESERT SOUTHWEST ON SATURDAY...

FINAL PREFERENCE: BLEND OF THE 00Z GEFS/12Z ECMWF ENSEMBLE MEANS
FORECAST CONFIDENCE: BELOW AVERAGE

THIS AREA OF THE COUNTRY IS PLAGUED BY QUITE A BIT OF SPREAD AS
THE REGION WILL BE AFFECTED BY A PAIR OF DISTURBANCES. AS
MENTIONED EARLIER...SOME OF THE VORTICITY MOVING THROUGH THE
PACIFIC NORTHWEST WILL SLIDE SOUTHWARD INTO THE CENTRAL GREAT
BASIN. MEANWHILE...LURKING TO THE WEST ACROSS THE EASTERN PACIFIC
IS ANOTHER SHORTWAVE EXPECTED TO APPROACH THE AREA LATE IN THE
PERIOD. THE 00Z NAM/UKMET ARE MORE EMPHATIC ABOUT CARRYING THIS
ENERGY INTO THE MAP DOMAIN WHILE THE 00Z/12Z ECWMF CONTINUE TO
SHOW A MORE SHEARED OUT SYSTEM. THE 00Z GFS/CMC SEEMS TO FOLLOW
SOMETHING IN BETWEEN THESE SOLUTIONS. GIVEN THE SPREAD IN PLACE
AND LACK OF CONTINUITY IN THE MODELS...WILL BLEND THE ENSEMBLE
MEANS HERE.



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

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

RUBIN-OSTER

$$




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