Prognostic Meteorological Discussion
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FXHW01 KWNH 151204
PMDHI

HAWAII EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
804 AM EDT MON SEP 15 2014

VALID 00Z TUE SEP 16 2014 - 00Z TUE SEP 23 2014

THE 15/00Z GEFS/ECENS ENSEMBLE MEANS WERE VERY REPRESENTATIVE OF
THE FLOW PATTERN ACROSS THE PACIFIC OCEAN THROUGH DAY 5
(20/12Z)---BEFORE DIFFERENCES `CROP UP` ALONG THE WESTERN TIP OF
THE ALEUTIANS AND DOWNSTREAM IN THE GULF OF ALASKA.

THE FORECAST FOR THE CENTRAL PACIFIC REMAINS ESSENTIALLY
UNCHANGED---WITH THE WESTERN PORTION OF THE SUBTROPICAL RIDGE
REBUILDING AND MIGRATING EASTWARD TO A POSITION NEAR 35N 160W BY
WEDNESDAY (17/12Z).

THE RIDGE THEN FLATTENS---MIGRATING EAST-SOUTHEASTWARD TO
APPROXIMATELY 33N 142W HEADING INTO FRIDAY (19/12Z). THE `FLATTER`
SUBTROPICAL RIDGE AXIS SOLUTION IN THE CENTRAL PACIFIC ALONG
30N-35N LATITUDE RESULTS IN A BRIEF RETURN OF THE MORE TYPICAL
`NORTHEAST TRADES` FROM WEDNESDAY `TIL THE FRIDAY/SATURDAY TIME
FRAME. THE LOW-LEVEL FLOW PATTERN THEN BEGINS TO GAIN
AMPLITUDE---THE RESULT OF MID-LATITUDE ENERGY FROM THE SOUTHERN
BERING SEA TRANSFERRING DOWNSTREAM TO THE GULF OF ALASKA AND THE
PRESENCE OF ANOTHER `ENERGIZED` ALEUTIAN LOW IN THE GULF OF ALASKA.

THE BIGGEST DIFFERENCES---IN THE 15/00Z MEANS AND DETERMINISTIC
RUNS---WERE TIED TO A RE-POSITIONING (A LATITUDE AND LONGITUDE
ISSUE) OF THE BROAD CYCLONIC GYRE IN THE NORTHEAST PACIFIC. THE
CONSEQUENCE OF THIS WILL BE TO THE DETRIMENT OF THE SUBTROPICAL
RIDGE. RECOMMEND A 50/50 BLEND OF THE 15/00Z ECENS-GEFS AFTER DAY
4 (FRIDAY) TO HANDLE THE CHANGES OVER THE MID-LATITUDE PACIFIC AND
CHARACTER OF THE SUBTROPICAL RIDGE AXIS.

FOR HAWAI`I, TRADES SHOULD BE ON THE INCREASE AROUND WEDNESDAY
WITH THE POSITIONING OF THE SUBTROPICAL RIDGE AXIS NORTHEAST OF
THE ISLANDS TO GIVE THE ITCZ AND CLOUD DEBRIS EMBEDDED WITHIN IT A
CHANCE TO SPREAD NORTHWARD AND NORTHWESTWARD OVER THE
ISLANDS---PRIMARILY BETWEEN DAY 2 AND DAY 4.

VOJTESAK

$$




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