Prognostic Meteorological Discussion
Issued by NWS

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8
000
FXUS10 KWNH 061857
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
157 PM EST FRI MAR 06 2015

VALID MAR 06/1200 UTC THRU MAR 10/0000 UTC

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

==============================================
12Z MODEL EVALUATION AND PREFERENCES
==============================================
NAM/GFS INITIALIZATION ERRORS DO NOT APPEAR TO
SIGNIFICANTLY AFFECT THEIR LARGE SCALE OUTPUT.
==============================================

...FRONTAL ZONE PUSHING THROUGH SOUTH FLORIDA FRIDAY NIGHT...

PREFERENCE: BLEND OF THE OPERATIONAL MODELS
CONFIDENCE: ABOVE AVERAGE

SOME CONVECTIVE PRECIPITATION IS EXPECTED AS A FRONT SLIPS THROUGH
SOUTH FLORIDA FRIDAY EVENING AND AS POST-FRONTAL EASTERLY ONSHORE
FLOW STRENGTHENS SATURDAY. MODELS ARE HANDLING THE SCENARIO
SIMILARLY...INCLUDING IN THEIR PRECIPITATION OUTPUT. THE ECMWF
CONTINUES...HOWEVER...AS ONE OF THE DRIEST SOLUTIONS.


...BROAD TROUGH DEVELOPING IN THE CENTRAL AND SOUTHWEST U.S...

PREFERENCE: 12Z ECMWF...SUPPORTED BY THE GEFS AND ECMWF ENSEMBLE
MEAN
CONFIDENCE: AVERAGE

A CLOSED LOW OVER NORTHWEST MEXICO WILL MOVE EAST AND AWAY FROM A
BLOCKING RIDGE...ALLOWING THE LOW TO OPEN UP AS IT PHASES WITH
NORTHERN STREAM TROUGHING. THE ANTICIPATED RESULT WILL BE A
POSITIVELY TILTED TROUGH EXTENDING FROM THE MIDWEST STATES TO
SOUTHWEST TEXAS BY SUNDAY EVENING...WITH A SOUTHERN STREAM JET AND
ASSOCIATED GRADIENTS CONCENTRATED OVER TEXAS AND THE LOWER
MISSISSIPPI VALLEY.

THE MODELS SHOW MODERATELY GOOD AGREEMENT ALOFT...BUT OFFER A
VARIETY OF SOLUTIONS NEAR THE SURFACE. THERE ARE NO STRONG
OUTLIERS...BUT THE ECMWF APPEARS TO BE THE MOST REPRESENTATIVE OF
CONSENSUS. ECMWF MASS FIELDS AND PRECIPITATION OUTPUT CLOSELY
MATCH THAT OF THE GEFS MEAN AND ECMWF ENSEMBLE...ALL OF WHICH
REPRESENT A COMPROMISE BETWEEN THE MORE SUPPRESSED OPERATIONAL GFS
AND THE MORE AMPLIFIED LOW LEVEL SOLUTIONS / ASSOCIATED NORTHWARD
EXTENSION OF HEAVY PRECIPITATION / SEEN IN THE UKMET/CANADIAN.
RELATIVE TO CONSENSUS THE NAM IS DISPLACED NORTH BUT ALSO WEST
WITH ITS PRECIPITATION.


...WEST-NORTHWESTERLY FLOW OVER THE GREAT LAKES AND NEW ENGLAND...

PREFERENCE: BLEND OF THE 12Z OPERATIONAL MODELS...DROPPING THE NAM
ON DAY 3
CONFIDENCE: AVERAGE

BENEATH FAST WEST TO NORTHWESTERLY FLOW ALOFT...FRONTAL WAVES WILL
OCCUR ALONG THE INTERFACE BETWEEN ARCTIC AIR IN THE GREAT
LAKES/NORTHEAST...AND MILDER CONTINENTAL POLAR AIR OVER THE
MISSOURI VALLEY.

AT MID LEVELS THE MODELS FEATURE MINOR TIMING AND AMPLITUDE
DIFFERENCES...WHICH WILL LIKELY CONTINUE GIVEN FAST FLOW WITH WEAK
SURFACE REFLECTION. GENERALLY THE SPREAD IS MINIMAL. THERE WAS A
TREND TOWARD QUICKER PROGRESSION OF A WAVE OFF THE COAST OF NEW
ENGLAND ON DAY 3. THE GFS LAGS BEHIND THERE. BUT STRONGER
DIFFERENCES APPEAR IN THE LOW LEVELS TOWARD DAY 3 WHEN THE NAM IS
PARTICULARLY FAST UPSTREAM OVER CANADA AND THE GREAT LAKES.


...DEEP LOW TRACKING THROUGH CENTRAL CANADA MONDAY...

PREFERENCE: BLEND OF THE 12Z OPERATIONAL MODELS...EXCLUDING THE NAM
CONFIDENCE: AVERAGE

MOST OF THE MODELS ARE POINTING TOWARD DEEP SURFACE LOW
DEVELOPMENT SUN/MON OVER CENTRAL CANADA AS A STRONG AND STRAIGHT
JET PUNCHES IN FROM THE WEST-NORTHWEST. THE UKMET JOINED THE
GLOBAL MODEL CONSENSUS WITH ITS 12Z RUN. THE ECMWF ENSEMBLE MEAN
AND GEFS MEAN HAVE BEEN FAIRLY STEADY FROM RUN TO RUN...AND THEIR
HEIGHT PATTERN WOULD PLACE THE GREATEST DIFLUENCE IN SUPPORT OF
SURFACE LOW DEVELOPMENT OVER CENTRAL MANITOBA BY MONDAY AFTERNOON.
THE GFS/GEFS SURFACE SOLUTIONS ARE SLIGHTLY FASTER THAN THE HEIGHT
PATTERN WOULD SUGGEST...BUT ARE SIMILAR ENOUGH TO THE
ECMWF/UKMET/CANADIAN TO BE BLENDED WITH THOSE MODELS. THE 12Z NAM
WAS A FAST OUTLIER. THIS SYSTEM MAY NOT BE A PRECIPITATION
PRODUCER FOR THE U.S. THROUGH DAY 3...BUT IT WILL INFLUENCE OTHER
SENSIBLE WEATHER SUCH AS WINDS OVER THE NORTHERN PLAINS AND UPPER
MIDWEST.

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

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

BURKE
$$





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