Prognostic Meteorological Discussion
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000
FXHW01 KWNH 201232
PMDHI

HAWAII EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
732 AM EST FRI JAN 20 2017

VALID 00Z SAT JAN 21 2017 - 00Z SAT JAN 28 2017

AN EXPANSIVE 588-DM MID-LEVEL RIDGE WILL FLATTEN IN RESPONSE TO
FLOW AMPLIFYING OVER THE MID-LATITUDES. THE SOUTHERN FLANK OF
THESE HEIGHT FALLS SHOULD GRADUALLY CLOSE OFF JUST WEST OF THE
ISLAND CHAIN OVER THE WEEKEND. THIS WILL ALLOW A MID/UPPER LOW TO
LINGER IN THE VICINITY OF HAWAI`I INTO EARLY NEXT WEEK BEFORE ITS
REMAINS DRIFT TOWARD THE EAST. EVENTUALLY THIS IS FORECAST TO LEAD
TO GENERAL NORTHWESTERLY FLOW FOR THE REMAINDER OF THE PERIOD. AT
THE SURFACE, A BUILDING ANTICYCLONE EAST OF THE INTERNATIONAL
DATELINE WILL FOSTER THE DEVELOPMENT OF MODERATE TO OCCASIONALLY
STRONG NORTHEASTERLY FLOW THE NEXT COUPLE OF DAYS. THIS RIDGE WILL
CONTINUE SLIDING EASTWARD RESULTING IN A SHIFT TO GENERAL EASTERLY
FLOW BY SUNDAY/MONDAY. THEREAFTER, DIFFERENCES WITH TIMING ACROSS
THE MID-LATITUDES LEADS TO SOME UNCERTAINTIES WITH THE FLOW
REGIME. ON THE QUICKEST SIDE IS THE 00Z CMC WHILE THE 06Z GFS/GEFS
MEAN REMAINED ON THE WESTERN END OF THE SPREAD. BASED ON ENSEMBLE
SPAGHETTI PLOTS, THE CMC SOLUTION LOOKED THE MOST UNREASONABLE
WITH SOME COMPROMISE BETWEEN THE 06Z GFS/00Z ECMWF AND THEIR
ENSEMBLES BEING MORE USEFUL. REGARDING THE OUTLOOK FOR
PRECIPITATION, A BAND OF SHOWERS ALONG A PASSING BAROCLINIC ZONE
MAY LEAD TO AN UPTICK IN COVERAGE EARLY THIS WEEKEND. SOME
ENHANCEMENT MAY OCCUR EARLY NEXT WEEK AS THE NEXT SYSTEM AMPLIFIES
TO THE NORTH OF THE ISLANDS WHILE DRYING IS EXPECTED TO CONCLUDE
THE PERIOD THEREAFTER.


RUBIN-OSTER

$$





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