Prognostic Meteorological Discussion
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FXUS10 KWNH 240449
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1248 AM EDT THU APR 24 2014

VALID APR 24/0000 UTC THRU APR 27/1200 UTC

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

...AN EVALUATION OF THE 00Z NAM/GFS ALONG WITH PRELIMINARY
PREFERENCES/FORECAST CONFIDENCE...

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


...STRONG CLOSED LOW EXITING INTO THE CANADIAN MARITIMES MIDDAY
THURSDAY...

PRELIMINARY PREFERENCE: GENERAL MODEL COMPROMISE
FORECAST CONFIDENCE: HIGH

A BROAD NEGATIVELY-TILTED TROF CURRENTLY ANCHORING THE
NORTHEASTERN CONUS WILL SHIFT EASTWARD EARLY THIS MORNING AND
DEVELOP INTO A CLOSED LOW OFFSHORE. IN GENERAL THE MODELS ARE VERY
CLOSE TO ONE ANOTHER SO WILL FAVOR A GENERAL MODEL COMPROMISE FOR
THIS SYSTEM.


...PAIR OF SYSTEMS MOVING IN TANDEM TOWARD THE UPPER GREAT
LAKES/OH VALLEY...RESPECTIVELY...
...ASSOCIATED SURFACE LOWS MARCHING EASTWARD...

PRELIMINARY PREFERENCE: BLEND OF THE 00Z NAM/GFS WITH THE 12Z
ECMWF ENSEMBLE...MORE TOWARD THE 00Z NAM
FORECAST CONFIDENCE: SLIGHTLY BELOW AVERAGE

MODELS DEPICT SPLIT FLOW IN PLACE WITH A PAIR OF OF SYSTEMS
SLIDING EASTWARD WHILE BEING NEARLY IN TANDEM. WITH THE NORTHERN
STREAM UPPER TROF...THE 12Z ECMWF IS A BIT SLOWER THAN THE
CONSENSUS NOTED FURTHER DOWNSTREAM. EVENTUALLY THIS SYSTEM
DEVELOPS A CLOSED LOW ACROSS SOUTHERN ONTARIO BY 26/0000Z WHILE
THE OTHER BATCH OF ENERGY SHEARS AND MOVES THROUGH THE
MID-ATLANTIC FRIDAY EVENING. ENSEMBLE SURFACE LOW PLOTS AGREE THAT
A PAIR OF SURFACE WAVES WITH ACCOMPANY THIS SYSTEM WITH THE
SOUTHERN MOST LOW DOMINATING. CURRENTLY THE 12Z CMC/21Z SREF MEAN
DISAGREE WITH THE STRONGER CLUSTERING IN THE VICINITY OF UPSTATE
NY FRIDAY EVENING. EVENTUALLY MODELS DEVELOP A WAVE OFF THE
DELMARVA COAST WITH THE 00Z GFS A BIT TOO AGGRESSIVE WITH THE
INTENSITY WITH ONLY A FEW 12Z GEFS MEMBERS SUPPORTING SUCH A
SOLUTION. INTERESTINGLY THE 12Z ECMWF DIVERGES SIGNIFICANTLY FROM
ITS OWN MEAN AS THE LOW MOVES OFFSHORE. THROUGHOUT THE FORECAST
PERIOD THE 00Z NAM/GFS APPEAR TO FOLLOW THE 18Z GEFS/12Z ECMWF
ENSEMBLE MEANS MOST CLOSELY. HOWEVER...WILL WEIGHT AWAY FROM THE
00Z GFS GIVEN ITS AFOREMENTIONED STRONGER SURFACE SOLUTION.


...DEEP UPPER TROF CROSSING THE DESERT SOUTHWEST/FOUR CORNERS
REGION THIS WEEKEND...
...POWERFUL SURFACE CYCLONE ACROSS THE MIDDLE OF THE U.S...

PRELIMINARY PREFERENCE: BLEND OF THE 12Z CMC/ECMWF WITH THE 12Z
ECMWF ENSEMBLE MEAN
FORECAST CONFIDENCE: BELOW AVERAGE

THE FLOW REALLY BEGINS TO AMPLIFY ACROSS THE SOUTHWESTERN CONUS BY
EARLY IN THE UPCOMING WEEKEND. THE 00Z NAM/GFS ARE QUICKER
EJECTING THIS SYSTEM TOWARD THE FOUR CORNERS REGION WITH
CORRESPONDING SUPPORT FROM THE 18Z GEFS/21Z SREF MEANS.
MEANWHILE...THE 12Z CMC IS DECIDEDLY SLOWER WITH THE 12Z
ECMWF/UKMET SIT SOMEWHERE IN THE CENTER OF THE SPREAD. THE PAST
COUPLE OF RUNS OF THE GUIDANCE SHOW THE NCEP MODELS HAVE
CONSISTENTLY BEEN ON THE FURTHER EAST SIDE OF THE MODEL ENVELOPE.
THE SEPARATION IS ALSO WELL ESTABLISHED IN THE PAST FOUR SPAGHETTI
PLOTS ALTHOUGH THE DIFFERENCES HAVE DECREASED. PER COORDINATION
WITH WPC MEDIUM RANGE ALONG WITH THE TENDENCY OF MODELS TO BE TOO
QUICK TO EJECT CLOSED LOWS OUT OF THE SOUTHWESTERN U.S...WILL
FAVOR THE SLOWER SOLUTIONS HERE. THE 12Z ECMWF/CMC FIT THAT BILL
AND WILL THROW IN THE 12Z ECMWF ENSEMBLE MEAN TO ACCOUNT FOR THE
GROWING MODEL UNCERTAINTY.


...NEXT PACIFIC SYSTEM REACHING THE PACIFIC NORTHWEST BY EARLY
SUNDAY...

PRELIMINARY PREFERENCE: BLEND OF THE 18Z GEFS/12Z ECMWF ENSEMBLE
MEANS
FORECAST CONFIDENCE: BELOW AVERAGE

AS THE INITIAL UPPER TROF TRACKS TOWARD THE SOUTHERN HIGH PLAINS
BY EARLY SUNDAY...ANOTHER SYSTEM IS EXPECTED TO APPROACH THE
PACIFIC NORTHWEST COAST AT THE SAME TIME. THE 540-DM SPAGHETTI
PLOT SHOWS ENOUGH SPREAD IN THE GUIDANCE THAT A COMBINATION OF THE
MEANS WILL BE PREFERRED. WILL TAKE A SPLIT BETWEEN THE 18Z GEFS
MEAN AND 12Z ECMWF ENSEMBLE MEAN.



...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

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