Prognostic Meteorological Discussion
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FXAK02 KWNH 241836
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ALASKA EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
236 PM EDT SUN MAY 24 2015

VALID 12Z THU MAY 28 2015 - 12Z MON JUN 01 2015

COMPARISONS AMONG INDIVIDUAL MODEL RUNS AND VERSUS THE ENSEMBLE
MEANS STILL SUGGEST LOWER THAN DESIRED CONFIDENCE WITH VARIOUS
ASPECTS OF THE FCST ACROSS THE MAINLAND AND VICINITY AS WELL AS
THE NRN PACIFIC/ALEUTIANS/BERING SEA.

WHILE THERE APPEARS TO BE SOME RESOLUTION OF PRIOR DIFFS REGARDING
CLOSED LOW ENERGY FCST TO BE NEAR THE SRN PANHANDLE AS OF EARLY
DAY 4 THU... LATEST OPERATIONAL RUNS HAVE TRENDED NOTICEABLY
STRONGER WITH SHRTWV ENERGY REACHING THE MAINLAND EARLY IN THE
PERIOD.  THIS TREND AS WELL AS AN ADJUSTMENT FOR MORE RIDGING TO
SET UP NW OF THE MAINLAND LEADS THE OPERATIONAL RUNS IN GENERAL TO
SHOW LOWER HGTS/MORE CYCLONIC FLOW OVER THE MAINLAND COMPARED TO
LATEST ENSEMBLE MEANS.  THE ENSMEANS HINT AT THESE TRENDS IN A
MORE SUBTLE FASHION AND AT THIS TIME THEIR SCENARIO WOULD BE
PREFERABLE GIVEN HOW ENTRENCHED THE NWRN NOAM RIDGE HAS BEEN
RECENTLY.

MEANWHILE GUIDANCE SPREAD AND DAY TO DAY CHANGES CONTINUE FOR THE
SYSTEM THAT HAS BEEN FCST TO TRACK OVER THE NRN PAC/ALEUTIANS/SRN
BERING SEA.  IN CONTRAST TO SWD TRENDS NOTED IN GUIDANCE LEADING
UP TO YDAYS ISSUANCE... CONSENSUS HAS REVERTED TO A MORE NWD TRACK
FOR THE SFC LOW TO VARYING DEGREES.  ONE POSITIVE NOTE COMPARED TO
24 HRS AGO IS THAT 00Z MEMBERS AMONG THE GEFS/ECMWF/CMC ENSEMBLE
PACKAGES SHOW LESS SPREAD THAN BEFORE.  FROM 12Z THU TO 12Z FRI A
COMPROMISE AMONG THE 00Z GFS/ECMWF AND NAEFS/ECMWF MEANS PROVIDES
A REASONABLE INTERMEDIATE SOLN.  AFTER 12Z FRI THE GFS STRAYS MORE
TO THE NW THAN THE 00Z ECMWF OR THE MEANS SO THE 00Z GFS IS
DROPPED AFTER EARLY FRI.  THE 12Z GFS IS NOT AS EXTREME WITH ITS
NWWD PROGRESSION.  DUE TO CONSIDERATIONS OVER THE MAINLAND...
PREFER TO EXCLUDE THE 00Z ECMWF FROM THE BLEND AFTER 00Z SAT AS
WELL.  HOWEVER IT IS REASONABLE TO EXPECT A DEEPER SYSTEM THAN
INDICATED BY THE NAEFS/ECMWF MEANS.

THE NEXT UNCERTAINTY COMES INTO THE PICTURE LATE IN THE PERIOD AS
UPSTREAM ERN ASIA/WRN PAC ENERGY MAY BRING ANOTHER SYSTEM TOWARD
THE WRN ALEUTIANS AND/OR INTERACT WITH/REINFORCE THE CNTRL
ALEUTIANS/NRN PAC SYSTEM.  THUS FAR EVEN THE ENSEMBLE MEANS HAVE
BEEN INCONSISTENT WITH THIS PART OF THE FCST AND THE 00Z ECMWF
MEAN TRENDS OUT OF PHASE RELATIVE TO LATEST GEFS MEANS AND 00Z CMC
MEAN... SO FAVOR GOING AT LEAST 2/3 IN THE 00Z NAEFS DIRECTION BY
DAY 8 MON.

DAY 4 THU TO 12Z DAY 5 FRI STARTS WITH 20 PCT EACH 00Z GFS/ECMWF
AND 30 PCT EACH 00Z NAEFS/ECMWF MEAN... REFLECTING THE DESIRE TO
INCORPORATE SOME OPERATIONAL INPUT FOR THE ALEUTIANS SYSTEM BUT NO
MORE THAN A MODEST COMPONENT OF OPERATIONAL TRENDS ALOFT OVER THE
MAINLAND EARLY IN THE PERIOD.  PHASING OUT THE 00Z GFS FIRST AND
THEN THE 00Z ECMWF LEADS TO AN EVEN ENSEMBLE MEAN BLEND DAYS 6-7
SAT-SUN WITH 70 PCT WEIGHTING OF THE NAEFS MEAN BY DAY 8 MON.  THE
BLEND IS ADJUSTED SOMEWHAT DEEPER TOWARD THE 00Z ECMWF FOR THE
ALEUTIANS SYSTEM.

RAUSCH

$$





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