THE WEATHER PREDICTION CENTER

COLLEGE PARK, MD


ALASKA EXTENDED FORECAST DISCUSSION




ALASKA EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
329 PM EDT MON SEP 29 2014

VALID 12Z FRI OCT 03 2014 - 12Z TUE OCT 07 2014

SYNOPTIC PATTERN ACROSS THE HIGH LATITUDES SHOULD FEATURE
TROUGHING OVER THE SEA OF OKHOTSK THAT PROGRESSES SLOWLY
EASTWARD... RIDGING OVER THE BERING SEA... AND TROUGHING OVER THE
INTERIOR THAT WILL ONLY GRADUALLY RETREAT EASTWARD INTO NW CANADA.
OVER THE N PACIFIC... SYSTEMS SHOULD BE FAVORED TO TRAVEL IN THE
40-50N LATITUDE BELT WITH A LEAD SYSTEM TAKING AIM ON THE SOUTHERN
PANHANDLE.

POTENTIAL EXISTS FOR A RATHER DEEP CYCLONE IN THE SE GULF TO START
THE MEDIUM RANGE PERIOD... FRI 3 OCT... BUT THIS IS DEPENDENT ON
HOW THE REMNANTS OF TROPICAL STORM KAMMURI GET ENTRAINED /IF AT
ALL/ INTO THE UPPER LOW MOVING INTO THE GULF IN THE SHORT TERM.
THE 12Z GFS/ECMWF KEEP THE TWO ENTITIES JUST SEPARATED ENOUGH TO
PREVENT A DEEP / <970MB / STORM... BUT OTHER RUNS PLUS MANY
ENSEMBLE MEMBERS STILL INDICATE THAT CHANCE AND IT WOULD NOT TAKE
MUCH IN NUDGING THE TIMING/AMPLITUDE TO DEVELOP A STRONG SYSTEM.
THE 00Z ECMWF ENSEMBLE MEAN OFFERED A MOST REASONABLE SOLUTION IN
BOTH DEPTH AND PLACEMENT AND ITS FORECAST WAS USED AS A BASE FOR
THE PERIOD. HEAVY RAIN IS STILL FORECAST FOR THE CENTRAL/SOUTHERN
PANHANDLE BUT THAT WILL BE DEPENDENT ON THE DETAILS YET TO BE
RESOLVED.

THEREAFTER... FOCUS WILL TURN TO THE WESTERN BERING SEA WITH AN
APPROACHING UPPER/SFC LOW. ENSEMBLE MEANS HAVE BEEN FAIRLY
CONSISTENT FOR SEVERAL RUNS... BUT BY NEXT WEEK THE EXTRATROPICAL
TRANSITION OF TS PHANFONE /LIKELY TO BECOME A TYPHOON/ WOULD ADD
ANOTHER CURVE BALL TO THE FORECAST. FOR NOW... A BLEND OF THE
ENSEMBLE MEANS WILL SUFFICE GIVEN THE LEAD TIME. SFC LOW SHOWN ON
THE PROGS ON TUE/D8 IS THE FORECAST POSITION OF THE REMNANT LOW...
WHICH HAS BEEN FORECAST AS LOW AS THE 940S MB BY SOME MODELS
INCLUDING THE 12Z GFS AND NOW IN THE 950S MB BY THE 12Z ECMWF
/FROM BASICALLY NOTHING IN ITS 00Z RUN/.



FRACASSO





Last Updated: 329 PM EDT MON SEP 29 2014