Prognostic Meteorological Discussion
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000
FXUS10 KWNH 211649
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1249 PM EDT TUE OCT 21 2014

VALID OCT 21/1200 UTC THRU OCT 25/0000 UTC

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

12Z NAM/GFS EVALUATION WITH PRELIMINARY PREFERENCES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
THERE DID NOT APPEAR TO BE ANY INITIALIZATION ERRORS WITH THE
NAM/GFS DEEMED SIGNIFICANT ENOUGH TO IMPACT THEIR FORECASTS.


WEAKENING MID-LEVEL TROUGH OVER NM TODAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL CONSENSUS
CONFIDENCE: ABOVE AVERAGE

THE MODELS SHOW SIMILARLY WITH THIS FEATURE.


COASTAL STORM AFFECTING THE NORTHEASTERN U.S. THROUGH FRIDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 12Z GFS/00Z ECMWF
CONFIDENCE: A BIT ABOVE AVERAGE

THE 12Z GFS AND 00Z ECMWF CONTINUE TO REPRESENT A GOOD COMPROMISE
WITH EXCELLENT RUN TO RUN CONTINUITY REGARDING THE 500 MB TROUGH
AND LOWER LEVEL LOW POSITIONS. THE ENSEMBLE MEANS AGREE WITH A
GFS/ECMWF BLEND WITH THE NAM/UKMET/CMC STRAYING AT VARIOUS TIMES
OF THE FORECAST THROUGH FRI EVENING.


MID-UPPER LEVEL TROUGH REACHING THE NRN PLAINS ON WED
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 12Z GFS...00Z CMC
CONFIDENCE: BELOW AVERAGE

MODEL CONSISTENCY CONTINUES TO BE POOR WITH THIS FEATURE...BUT THE
12Z GFS...00Z ECMWF AND 00Z CMC SHOW REASONABLE AGREEMENT THROUGH
THU EVENING WITH REASONABLE RUN TO RUN CONSISTENCY. DIFFERENCES
ARE GREATEST FOR DAY 3...00Z 24-25...WITH THE 00Z UKMET/ECMWF
HAVING A MORE SRN TRACK WITH THE VORT CENTER AS IT CROSSES THE
UPPER MIDWEST THU NIGHT...WHICH CAUSES THE ENERGY TO TRACK FARTHER
SOUTH IN A MORE CONSOLIDATED MANNER VERSUS THE REMAINING GUIDANCE
WHICH IS FARTHER NORTH. AT THIS TIME...THE 12Z GFS AND 00Z CMC
APPEAR TO SPLIT THE DIFFERENCE IN TRACK AND ARE IN BETTER
AGREEMENT WITH 00Z/21 ENSEMBLE SPAGHETTI HEIGHT PLOTS AT 500
MB...WITH THE 00Z UKMET AN OUTLIER.


WEST COAST UPPER TROUGHING THROUGH FRI EVENING
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 12Z GFS/00Z ECMWF
CONFIDENCE: AVERAGE

MODEL DIFFERENCES HERE ARE GREATEST THU NIGHT INTO FRI WITH THE
APPROACH OF A SHARPENING UPPER LEVEL TROUGH APPROACHING THE WEST
COAST. THE ENSEMBLE MEANS ARE IN PRETTY GOOD AGREEMENT WITH THE
DEPTH/TIMING OF THE UPPER TROUGH...WITH THE CLOSEST DETERMINISTIC
GUIDANCE BEING THE 12Z GFS AND 00Z ECMWF. THE 12Z NAM IS
SLOWER...WHILE THE 00Z UKMET/CMC ARE FASTER.


QUASISTATIONARY FRONT NEAR SOUTH FLORIDA
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON 00Z CMC BLEND
CONFIDENCE: SLIGHTLY BELOW AVERAGE

THERE ARE SOME LATITUDINAL DIFFERENCES WITH THE SWRN PORTION OF A
COLD FRONT TRANSLATING EWD ACROSS THE WRN ATLANTIC...WITH THE
BOUNDARY LYING ACROSS THE SRN PORTION OR JUST SOUTH OF THE FLORIDA
PENINSULA FOR THU/FRI. THERE IS NO CLEAR PREFERRED MODEL WITH THE
POSITION OF THE FRONT WITH THE LATEST DETERMINISTIC GUIDANCE
FORMING A REASONABLE COMPROMISE.

HOWEVER...REGARDING A POTENTIAL LOW OR TWO FORECAST TO DEVELOP
ALONG OR NEAR THE FRONT...THE 00Z CMC IS THE ONLY MODEL WHICH IS
NOT SUPPORTED BY THE REMAINING DETERMINISTIC GUIDANCE NOR THE
ENSEMBLES. CONFIDENCE IS REDUCED GIVEN THE CONVECTIVE/TROPICAL
NATURE OF THE ENVIRONMENT AND MODEST SPREAD IN THE LATEST ENSEMBLE
GUIDANCE.



...MODEL TREND GRAPHICS AT
www.wpc.ncep.noaa.gov/html/model2.shtml...
...500 MB FORECASTS AT
www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml...

OTTO

$$





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