Prognostic Meteorological Discussion
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FXHW01 KWNH 261213
PMDHI

HAWAII EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
811 AM EDT TUE AUG 26 2014

VALID 00Z WED AUG 27 2014 - 00Z WED SEP 03 2014

ALOFT, 26/00Z ECENS/GEFS CYCLE AND THEIR DETERMINISTIC RUNS
REMAINED IN VERY GOOD AGREEMENT CONCERNING THE MOVEMENTS OF A
BROAD UPPER-LEVEL RIDGE IN THE NORTH CENTRAL AND EASTERN PACIFIC
HEADING INTO DAY 6 (1/12Z).

AT THE SURFACE, THE 26/00Z GFS MOS DATA (EXTENDED VERSION)
INDICATED A SLACKENING OF THE CURRENT TRADE WIND INTENSITY FOR A
SLIGHTLY LONGER PERIOD OF TIME (FRIDAY THROUGH SUNDAY) VERSUS THE
ECMWF SOLUTION.

AFTER DAY 6, THE 26/00Z GEFS/ECENS PART WAYS AT 500 MILLIBARS
ALONG THE DATELINE---WITH THE DETERMINISTIC ECMWF CONTAINING A
FLATTER FLOW OVER THE MID-LATITUDE PACIFIC AND STRONGER
SUBTROPICAL RIDGE SOLUTION VS THE GFS AND ITS CUTOFF 500MB LOW
SOLUTION. THE GFS CARRIES A WELL-DEFINED LOW INVOF 39N 175W (@
2/12Z) AND A WEAKER DOWNSTREAM SUBTROPICAL RIDGE AXIS BETWEEN
CALIFORNIA AND HAWAI`I.

IN TURN, THESE DIFFERENCES TRANSLATE TO WIDENING MODEL/ENSEMBLE
SPREAD WITH RESPECT TO LATITUDE--AND WHERE TROPICAL MOISTURE
ASSOCIATED WITH `MARIE` AND THE REMNANTS OF `LOWELL` IS DISPLACED
ACROSS THE SOUTHEAST PACIFIC. BOTH RUNS DISPLACE THE MOISTURE AND
VORTICITY ALONG A WESTWARD PATH BUT DO NOT AGREE WITH THE
LATITUDE. THE GFS SUGGESTS THE MOISTURE AND VORTICITY REACH 30N
150W WHILE THE ECMWF SUGGESTS MORE ORGANIZATION OF THE MOISTURE
WESTWARD TO ~ 25N 155W.

RECOMMEND A BLEND OF THE GFS/ECMWF DETERMINISTIC RUNS AND THEIR
MEANS THROUGH DAY 5, THEN REVERTING TO THE MEANS AND A STRAIGHT
GEFS/ECENS BLEND FOR DAY 6-7 TO MITIGATE THE CHANGES EMERGING
ALONG THE DATELINE--AND TO DAMPEN THE SENSIBLE WEATHER IMPACTS OF
ANY `TROPICALS`--IE `MARIE` AND `LOWELL`.

VOJTESAK

$$





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