Prognostic Meteorological Discussion
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FXHW01 KWNH 221215
PMDHI

HAWAII EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
814 AM EDT SAT APR 22 2017

VALID 00Z SUN APR 23 2017 - 00Z SUN APR 30 2017

HIGH PRESSURE ON ITS WAY TO SETTLING OVER THE EASTERN PACIFIC, AND
ITS RIDGE EXTENDING WESTWARD, WILL SUPPORT AT LEAST MODERATE
TRADES THROUGH MIDWEEK.  BASED ON CHANGES IN THE PRESSURE GRADIENT
THERE SHOULD BE A MODEST WEAKENING TREND BETWEEN NOW AND EARLY
MONDAY, AND A SLIGHTLY STRONGER TREND MONDAY INTO EARLY WEDNESDAY.
 MOISTURE INITIALLY OVER THE NORTHWESTERN HALF OF THE STATE WILL
LIFT AWAY TO YIELD DRIER CONDITIONS EARLY IN THE WEEK WITH ANY
RAINFALL TENDING TO FAVOR WINDWARD LOCALES.  THERE MAY BE SOME
INCREASE IN PRECIPITABLE WATER VALUES AROUND MIDWEEK.

DURING THE LATTER HALF OF THE WEEK INTO THE WEEKEND MODEL/ENSEMBLE
GUIDANCE CONTINUES TO SHOW A LOT OF SPREAD FOR AN AMPLIFIED TROUGH
FORECAST TO APPROACH AND POSSIBLY REACH THE STATE.  THERE WILL
LIKELY BE A WAVY SURFACE FRONT AHEAD OF THIS TROUGH.  IN VARYING
WAYS LATEST GFS/CMC RUNS ARE NOT AS EXTREME ALOFT COMPARED TO
YESTERDAY.  THE 00Z GFS RUN IS STILL ON THE DEEPER PART OF THE
SPREAD WITH THE TROUGH WITH THE 06Z GFS A LITTLE WEAKER AND
EASTWARD WITH ITS CORE, AND WHILE THE 00Z GEFS MEAN IS THE MOST
AMPLIFIED AMONG THE MEANS THE OPERATIONAL 00Z ECMWF OFFERS
POTENTIAL FOR SOMEWHAT GREATER AMPLITUDE FOR THE SOUTHERN PART OF
THE UPPER TROUGH THAN THE 00Z ECMWF MEAN.  THE 00Z ECMWF SHOWS A
WESTWARD TREND FROM ITS PRIOR 12Z RUN.  OVERALL BASED ON THE FULL
ARRAY OF GUIDANCE AND EMBEDDED TRENDS A COMPROMISE BETWEEN THE 06Z
GFS AND 00Z ECMWF APPEARS TO BE THE BEST STARTING POINT AT THIS
TIME.  IN ASSOCIATION WITH THIS EVOLUTION, BY FRIDAY-SATURDAY
THERE MAY BE A NORTH-SOUTH BAND OF ENHANCED MOISTURE ALIGNED
OVER/NEAR THE ISLANDS WITH INCREASED RAINFALL POTENTIAL.

RAUSCH

$$





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