Prognostic Meteorological Discussion
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FXUS10 KWNH 051847
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
146 PM EST THU MAR 05 2015

VALID MAR 05/1200 UTC THRU MAR 09/0000 UTC

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

12Z MODEL EVALUATION...INCLUDING THE NAM/GFS/UKMET/GEM AND ECMWF


...SHORTWAVE TROUGH CROSSING THROUGH THE NORTHEAST...
...WAVY FRONTAL ZONE EXITING THE EASTERN SEABOARD...

PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: ABOVE AVERAGE

THE MODELS ARE IN VERY GOOD AGREEMENT MASS FIELD WISE WITH THE
SHORTWAVE TROUGH THAT WILL BE EJECTING ACROSS THE OH VALLEY AND
NORTHEAST THROUGH TONIGHT. THIS ENERGY WILL CONTINUE TO DRIVE A
WAVY COLD FRONT EAST AND OFFSHORE THE EAST COAST. A GENERAL MODEL
COMPROMISE WILL BE PREFERRED.


...SHORTWAVE CROSSING THE MIDDLE MS VALLEY TO THE MID-ATLANTIC
THROUGH FRI...

PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: ABOVE AVERAGE

IN THE WAKE OF THE CURRENT TROUGH MOVING INTO THE EASTERN
U.S....THE MODELS ADVERTISE A LOW AMPLITUDE SYSTEM CROSSING THE
MIDDLE MS VALLEY BY EARLY THIS EVENING AND THEN CROSSING THE
MID-ATLANTIC REGION ON FRI. THE MODELS ARE IN VERY GOOD AGREEMENT
WITH THIS FEATURE AND SO A GENERAL MODEL COMPROMISE WILL BE
PREFERRED.


...ADDITIONAL SHORTWAVES REACHING THE NORTHERN TIER THIS WEEKEND...
...WEAK SURFACE LOW MOVING ACROSS THE GREAT LAKES...

PREFERENCE: BLEND OF THE 12Z GFS AND 12Z ECMWF...THROUGH 60 HOURS
            BLEND OF THE 12Z ECMWF AND 00Z ECENS MEAN...THEREAFTER
CONFIDENCE: AVERAGE

BROAD UPPER CYCLONIC FLOW WILL CONTINUE THROUGHOUT THE PERIOD AS
ADDITIONAL SHORTWAVE IMPULSES MOVE FROM CENTRAL CANADA THROUGH THE
NORTHERN TIER OF THE U.S. THERE ARE FEWER DIFFERENCES NOTED
OVERALL COMPARED TO PREVIOUS MODEL CYCLES WITH RESPECT TO THE
TIMING AND DEPTH OF EACH IMPULSE. ONE IMPULSE WILL DRIVE A SURFACE
WAVE AND ASSOCIATED FRONT THROUGH THE GREAT LAKES REGION ON SAT
AND THEN INTO NEW ENGLAND ON SUN. GRADUALLY THE NAM BECOMES A
WEAKER OUTLIER WITH THIS SYSTEM. AN ADDITIONAL IMPULSE WILL
APPROACH THE GREAT LAKES BY LATER SUN ALONG WITH A WEAK FRONT. THE
12Z UKMET/12Z GEM AND 12Z ECMWF TEND TO BE A BIT MORE AGGRESSIVE
WITH THE ENERGY AND SHOW LOWER SURFACE PRESSURES VS THE 12Z NAM
AND 12Z GFS. GIVEN THE FAST DEEPER LAYER NORTHWEST FLOW OVER THE
REGION...THE AMPLITUDE OF EACH IMPULSE SHOULD BE RATHER SMALL.
WILL FAVOR A GFS AND ECMWF BLEND THROUGH ABOUT 60 HRS...AND THEN
FAVOR A BLEND OF THE ECMWF AND ECENS MEAN THEREAFTER WITH THE
LARGER SCALE FLOW.


...SLOW MOVING CLOSED LOW IN THE VICINITY OF NORTHERN BAJA CA...

PREFERENCE: NON-UKMET CONSENSUS
CONFIDENCE: AVERAGE

SOME FORM OF A REX BLOCK IS NOTED IN THE GUIDANCE ACROSS THE
WESTERN U.S. AS THE PERSISTENT UPPER RIDGE REMAINS IN PLACE ACROSS
THIS SIDE OF THE COUNTRY. BOUNDED TO ITS SOUTH WILL BE A COMPACT
CLOSED LOW WHICH IS FORECAST TO SLIDE EASTWARD ACROSS NORTHERN
BAJA CA BY MIDDAY FRIDAY. THE LATEST GUIDANCE THEN SUGGESTS THE
ENERGY WILL WEAKEN AND OPEN UP INTO A TROUGH AXIS THAT WILL BEGIN
SHEARING TOWARD THE SOUTHERN HIGH PLAINS BY LATER SUN. THE 12Z
UKMET HANGS ONTO A STRONGER TROUGH THROUGH THE END OF THE PERIOD
WITH MORE ENERGY CONCENTRATED OVER NORTHERN MX. THE GLOBAL MODEL
CONSENSUS IS FOR A SOMEWHAT MORE SHEARED AND POSITIVELY TILTED
TILTED TROUGH THAT WILL BE ADVANCING OUT INTO WEST TX. THIS IS
SUPPORTED BY THE ENSEMBLE MEANS AND SO A NON-UKMET CONSENSUS WILL
BE PREFERRED.


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

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

ORRISON

$$




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