Prognostic Meteorological Discussion
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000
FXUS02 KWBC 211555
PMDEPD

EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1154 AM EDT TUE OCT 21 2014

VALID 12Z FRI OCT 24 2014 - 12Z TUE OCT 28 2014

...OVERVIEW AND GUIDANCE EVALUATION/PREFERENCES...

MEAN FLOW IS FCST TO BE MODERATELY PROGRESSIVE WITH THE MOST
PROMINENT FEATURES BEING AN ERN PAC TROUGH/ROCKIES-PLAINS RIDGE
THAT SHOULD REACH THE PLAINS AND EAST COAST RESPECTIVELY BY DAY 7
TUE.  FARTHER UPSTREAM THE FCST EXTRATROPICAL TRANSITION OF
CURRENT TROPICAL STORM ANA BY AROUND DAY 5 SUN AND SUBSEQUENT NERN
PAC EVOLUTION WILL BE CLOSELY MONITORED.  MEANWHILE AHEAD OF THESE
FEATURES THE SHORT RANGE SYSTEM AFFECTING THE NORTHEAST WILL LIFT
AWAY EARLY IN THE PERIOD AND UNCERTAINTIES PERSIST WITH THE
PRECISE EVOLUTION TO THE S AND E OF FLORIDA.


BY THE LATTER HALF OF THE PERIOD THE 00Z ECMWF BECOMES THE LOWEST
CONFIDENCE SOLN FROM THE ERN PAC INTO WRN NOAM.  ISSUES IN THAT
RUN ORIGINATE FROM FASTER THAN CONSENSUS PROGRESSION ACROSS THE
BERING SEA/ALEUTIANS LATE SUN INTO MON LEADING TO FAST/NWD
INCORPORATION OF ANA DOWNSTREAM.  THIS DIFFERENCE MAY INDIRECTLY
PLAY A PART IN THE UPR LOW WHICH THE 00Z ECMWF BRINGS INTO THE SRN
ROCKIES.  THIS LATTER FEATURE IS NOT AN OUTLIER RELATIVE TO THE
FULL 00Z ENSEMBLE SPREAD BUT DOES BECOME FAIRLY EXTREME BY DAY 7
TUE.  OTHERWISE THERE IS FAIR AGREEMENT THAT LOW PRESSURE OFF THE
BC COAST LATE IN THE PERIOD MAY INCLUDE A COMPONENT OF
EXTRATROPICAL ANA.

WITH RESPECT TO THE INITIAL ERN PAC TROUGH ALOFT... THERE IS
DECENT AGREEMENT ASIDE FROM THE 00Z UKMET TOWARD A RATHER VIGOROUS
COMPACT SFC LOW REACHING A POSN JUST OFF THE PAC NW COAST BY EARLY
DAY 4 SAT.  AN AVG OF THE 00Z ECMWF AND 00Z-06Z GFS PROVIDES A
REASONABLE STARTING POINT TO REFLECT OPERATIONAL MODEL STRENGTH
AND AN INTERMEDIATE TRACK.  AS THE UPR TROUGH CONTINUES INLAND
CONFIDENCE IN THE DISTRIBUTION OF EMBEDDED ENERGY GRADUALLY
DECREASES AS PER SPREAD IN OPERATIONAL/ENSEMBLE SOLNS.  AMONG
RECENT 12-HRLY RUNS THE GFS HAS GENERALLY BEEN MORE STABLE THAN
THE ECMWF WITH TROUGH DETAILS BY NEXT MON-TUE.  ENSEMBLE MEANS ARE
FAIRLY SIMILAR THROUGH DAY 7 AND ARE PREFERRED TO RESOLVE THE
DETAILS THAT HAVE LOW PREDICTABILITY AT THAT TIME FRAME.

GUIDANCE SEEMS TO BE DEVELOPING SOME COMMON IDEAS REGARDING SFC
EVOLUTION FROM THE BAY OF CAMPECHE/NWRN CARIBBEAN NEWD... THOUGH
GUIDANCE SPREAD STILL TEMPERS CONFIDENCE.  THE NON-00Z UKMET
CONSENSUS IS SUGGESTING THAT AMPLIFICATION OF ERN CONUS ENERGY TO
THE SERN COAST/ERN GULF BY DAY 4 SAT SHOULD ENCOURAGE NEWD
PROGRESSION OF A FRONTAL WAVE TO OR BEYOND THE NRN BAHAMAS BY SAT
AND THEN NOT FAR FROM BERMUDA BY SUN.  AT THE SAME TIME CONSENSUS
IS SHOWING A SEPARATE FEATURE LINGERING OVER THE NWRN CARIBBEAN
FOR A TIME.

BASED ON ABOVE PREFERENCES THE STARTING FCST BLEND EMPHASIZES THE
00Z-06Z GFS/00Z ECMWF DAY 3 FRI WITH A GRADUAL INCORPORATION OF
06Z GEFS/00Z ECMWF MEAN GUIDANCE THROUGH DAY 5 SUN... FOLLOWED BY
AN EVEN BLEND OF THE MEANS FOR DAYS 6-7 MON-TUE.


...SENSIBLE WEATHER HIGHLIGHTS...

UPR TROUGH/SFC SYSTEM PROGRESSING EWD FROM THE ERN PAC WILL BRING
A PERIOD OF ENHANCED RNFL TO PARTS OF THE CNTRL-NRN WEST COAST
FRI-SAT WITH LESSER AMTS OF MSTR SPREADING INLAND.  RNFL SHOULD
THEN REACH PORTIONS OF THE NRN-CNTRL PLAINS INTO GRTLKS BY EARLY
NEXT WEEK.  UNCERTAINTY OVER THE EXACT DISTRIBUTION OF ENERGY
ALOFT/RESULTING SFC EVOLUTION AT THAT TIME LOWERS CONFIDENCE IN
DETERMINING RNFL COVERAGE/INTENSITY FROM THE PLAINS NEWD.  FROM
LATE THIS WEEK INTO THE START OF NEXT WEEK THE WARM SECTOR AHEAD
OF THIS SYSTEM SHOULD CONTAIN A BROAD AREA OF PLUS 10-20F TEMPS
AND ISOLD HIGHER ANOMALIES... DIMINISHING BY TUE.  PACIFIC ORIGIN
OF AIR BEHIND THE COLD FRONT SHOULD KEEP NEGATIVE ANOMALIES MORE
MODERATE.  THE PAC NW SHOULD SEE A RETURN OF MSTR BY NEXT MON OR
TUE IN ASSOC WITH A NERN PAC SYSTEM THAT MAY INCLUDE SOME INPUT
FROM EXTRATROPICAL ANA.  ALONG THE EAST COAST... THE SRN FL
PENINSULA STILL HAS POTENTIAL TO SEE SOME HVY RNFL EARLY IN THE
PERIOD DUE TO DEEP TROPICAL MSTR INTERACTING WITH A WAVY SFC FRONT
JUST S/E OF THE STATE.  MEANWHILE THE NORTHEAST SHOULD BEGIN A
DRYING TREND AS LOW PRESSURE LIFTS AWAY THOUGH NWLY FLOW ALOFT AND
A PASSING COLD FRONT MAY KEEP UNSETTLED CONDS OVER NWRN NEW
ENGLAND INTO SUN.

RAUSCH

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