Prognostic Meteorological Discussion
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000
FXHW01 KWNH 251233
PMDHI

HAWAII EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
732 AM EST SAT FEB 25 2017

VALID 00Z SUN FEB 26 2017 - 00Z SUN MAR 05 2017

THE CURRENT SETUP ACROSS THE CENTRAL PACIFIC CONTINUES TO SUPPORT
A BLOCKING REGIME WITH A STAGNANT UPPER RIDGE ANCHORING THE REGION
JUST SOUTH OF THE ALEUTIANS. TO ITS SOUTH, A PAIR OF CLOSED LOWS
WILL SLIDE AWAY FROM ONE ANOTHER WHICH HELPS ESTABLISH MID-LEVEL
SOUTHWESTERLY FLOW ACROSS THE HAWAI`IAN ISLAND CHAIN. MODELS
DEPICT A SHORTWAVE EVOLVING WEST OF THE STATE WITH THE FEATURE
SLOWLY MIGRATING EASTWARD WITH THE TROUGH PASSING OVERHEAD BY THE
MIDDLE OF NEXT WEEK. AFTER THIS EXITS THE REGION, A RATHER ROBUST
CLOSED LOW TRACKS EAST OF THE INTERNATIONAL DATELINE WITH MODEL
DIFFERENCES IN THE AMPLITUDE OF THIS SYSTEM. THIS INCLUDES SOME
SPREAD AMONG THE ENSEMBLE MEANS AS WELL. FORTUNATELY, MOST OF THE
ACTION SHOULD REMAIN FAR ENOUGH NORTH AND WEST TO NOT
SIGNIFICANTLY INFLUENCE THE ISLANDS.

FOR THE FIRST FEW DAYS OF THE PERIOD, EAST-NORTHEASTERLY TRADE
WINDS SHOULD BE THE NORM WITH THE INTENSITY PICKING UP BY THE
EARLY PART OF NEXT WEEK. THIS IS IN RESPONSE A LARGE SURFACE
ANTICYCLONE SETTLING OVER THE EAST-CENTRAL PACIFIC. THE LARGER
CHANGE IN THE WEATHER WILL BE AN INCREASE IN THE THREAT FOR
MODERATE TO LOCALLY HEAVY RAINFALL AS A SURFACE WAVE PASSES ACROSS
HAWAI`I. LOW-LEVEL WINDS ARE FORECAST TO SHIFT TO THE MORE
SOUTH-SOUTHWESTERLY DIRECTION WHICH WILL USHER IN RATHER HIGH
PRECIPITABLE WATER AIR TO THE SOUTHERN MOST ISLANDS. THE GUIDANCE
ARE IN AGREEMENT WITH THE POTENTIAL FOR HEAVY RAINFALL OVER THE
BIG ISLAND DURING THE TUESDAY/WEDNESDAY TIMEFRAME. AFTER THIS
SYSTEM DEPARTS, THE WINDS SHOULD GENERALLY MAINTAIN A SOUTHERLY
COMPONENT IN RESPONSE TO WARM ADVECTION AHEAD OF THE NEXT BAND OF
MID-LEVEL HEIGHT FALLS. HOWEVER, THE PATTERN SHOULD GENERALLY
REMAIN DRY AS NOTED IN MUCH OF THE GUIDANCE.


RUBIN-OSTER



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