Prognostic Meteorological Discussion
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FXUS10 KWNH 250643
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
242 AM EDT FRI APR 25 2014

VALID APR 25/0000 UTC THRU APR 28/1200 UTC

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

...AN EVALUATION OF THE 00Z CMC/UKMET/ECMWF 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.


...PAIR OF SYSTEMS MOVING IN UNISON TOWARD THE GREAT
LAKES/NORTHEASTERN U.S...
...COASTAL LOW DEVELOPMENT OFF OF THE DELMARVA BY LATE FRIDAY...
...RESULTANT DEEP UPPER LOW ANCHORING THE NORTHWESTERN ATLANTIC BY
LATE SUNDAY/EARLY MONDAY...

FINAL PREFERENCE: BLEND OF THE 00Z ECMWF/12Z UKMET
FORECAST CONFIDENCE: SLIGHTLY BELOW AVERAGE

WATER VAPOR IMAGERY SHOWS TWO DISTINCT UPPER LOWS TRACKING THROUGH
THE MIDDLE MS VALLEY AND UPPER MIDWEST...RESPECTIVELY. BOTH APPEAR
TO BE MIGRATING EASTWARD IN UNISON ALTHOUGH SOME CHANGES UNFOLD
DURING THE FOLLOWING 24 HOURS. THE SOUTHERN MOST SYSTEM IS
EXPECTED TO SHEAR OUT WHILE MOVING INTO THE OH VALLEY/MID-ATLANTIC
REGION WHILE THE DISTURBANCE TO THE NORTH DEVELOPS A CLOSED LOW
AND SLOWS CONSIDERABLY ACROSS THE UPPER GREAT LAKES. EARLY IN THE
PERIOD...THERE IS QUITE A BIT OF SPREAD WITH THE PLACEMENT OF THE
PAIR OF SURFACE LOWS MOVING THROUGH THE LOWER GREAT LAKES/UPSTATE
NY...RESPECTIVELY. THE LATTER CYCLONE HAS MORE UNCERTAINTY WITH
THE NCEP GUIDANCE BEING MORE TO THE NORTH RELATIVE TO THE OTHER
MODELS. BY FRIDAY NIGHT...THERE IS AGREEMENT THAT A SURFACE WAVE
WILL DEVELOP OFF THE DELMARVA COAST WITH MODELS IN SOLID AGREEMENT
WITH THE LOW POSITION. IN TERMS OF INTENSITY...THE SOLUTIONS HAVE
DEFINITELY TRENDED DEEPER RELATIVE TO YESTERDAY ALTHOUGH THE 00Z
MODELS HAVE BACKED OFF ON WHAT THE PRECEDING GUIDANCE SHOWED. NOW
THE 00Z NAM IS THE ONLY MODEL ADVERTISING A SUB-1000 MB LOW AT
26/1200Z. MOREOVER...THE 00Z NAM ALSO BECOMES THE MOST WESTERN
SOLUTION AS THE CYCLONE LIFTS EAST OF CAPE COD...MA ON SATURDAY
EVENING. THE PREFERENCE WILL REMAIN SIMILAR TO BEFORE ALTHOUGH
WILL KEEP THE OLD 12Z UKMET IN THE MIX VERSUS THE CURRENT 00Z RUN
AS THIS VERSION OF THE UKMET SHIFTED EAST AND IS ON THE FAR
EASTERN SIDE OF THE ENSEMBLE LOW SPREAD. HOWEVER...THE 00Z ECMWF
APPEARED STABLE SO FEEL COMFORTABLE INCORPORATING THE NEW RUN INTO
THE BLEND. THIS PREFERENCE WILL BE UTILIZED FOR ALL ASPECTS OF THE
DEVELOPMENT INCLUDING THE RESULTANT PLACEMENT OF THE CLOSED LOW
OFFSHORE OF NEW ENGLAND LATE IN THE FORECAST.


...STRONG UPPER TROF CROSSING THE DESERT SOUTHWEST ON SATURDAY
MORNING...
...EVENTUAL CLOSED LOW CENTER POSITIONED OVER THE CENTRAL HIGH
PLAINS BY 28/0000Z...
...DEEP SURFACE CYCLONE AFFECTING THE CENTER OF THE U.S...

FINAL PREFERENCE: BLEND OF THE 00Z GFS/ECMWF
FORECAST CONFIDENCE: AVERAGE

MODELS AGREE THAT THE MID-LATITUDE PATTERN WILL GAIN SIGNIFICANT
AMPLITUDE AS A DEEP UPPER TROF SETS UP ACROSS THE SOUTHWESTERN
U.S. BY SATURDAY MORNING. THE SYSTEM IS EXPECTED TO EVENTUALLY
LIFT NORTH AND EAST AS A CLOSED LOW WHILE BECOMING
NEGATIVELY-TILTED ACROSS THE FOUR CORNERS REGION BY SUNDAY
MORNING. THE MODEL AGREEMENT THROUGH 27/0000Z IS MUCH BETTER WITH
THIS SET OF GUIDANCE VERSUS YESTERDAY WHERE TIMING DIFFERENCES
WERE NUMEROUS. BY SUNDAY MORNING...THE MOST NOTABLE DIFFERENCES
ARE THE 00Z NAM IS FURTHER TO THE SOUTH WITH THE CORE OF ITS LOWER
HEIGHTS OVER THE TX/OK PANHANDLES WHILE THE 00Z UKMET IS WELL TO
THE NORTH. AS TIME PROCEEDS FORWARD...THE 00Z UKMET CONTINUES TO
BE QUICKER AT LIFTING THE COMPACT CLOSED LOW UP TOWARD THE LOWER
NORTHERN PLAINS WHILE THE 00Z NAM STAYS WELL TO THE SOUTH.
CENTERED CLOSER TO THE MIDDLE ARE THE 00Z GFS/ECMWF/CMC. THE
CURRENT SPAGHETTI PLOTS AT ALL CRITICAL HEIGHTS ARE IN HALF-DECENT
AGREEMENT FOR AN 84 HOUR FORECAST SO FEEL COMFORTABLE NOT
UTILIZING ANY ENSEMBLE MEANS IN THE BLEND. WITH THAT IN MIND...THE
SOLUTION WHICH BEST RESEMBLES THE STABLE MEANS AND FITS THE CENTER
OF THE SPREAD ARE THE 00Z GFS/ECMWF. SUCH AN IDEA FITS REASONABLY
WELL AT THE SURFACE AS WELL ALTHOUGH THERE ARE SOME DIFFERENCES
WITH THE PLACEMENT OF THE FRONTAL ZONE. WILL LOWER THE CONFIDENCE
TO AVERAGE AS THERE IS A LITTLE MORE MODEL SPREAD NOW THAN BEFORE
THE 00Z GUIDANCE ALL ARRIVED.


...ADDITIONAL MID-LEVEL ENERGY SETTLING INTO THE PACIFIC NORTHWEST
LATE IN THE PERIOD...

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

ON THE WINGS OF THE INITIAL SYSTEM RAPIDLY INTENSIFYING ACROSS THE
CENTRAL PLAINS...ADDITIONAL ENERGY UPSTREAM WILL GATHER ACROSS THE
NORTHEASTERN PACIFIC AND INTO THE PACIFIC NORTHWEST DURING THE
WEEKEND. OVERALL THERE IS ENOUGH MODEL SPREAD AT HAND TO AFFORD A
COMBINATION OF ENSEMBLE MEANS. WILL FAVOR A BLEND OF THE 00Z
GEFS/12Z ECMWF ENSEMBLE MEANS.


...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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