Prognostic Meteorological Discussion
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FXHW01 KWNH 011215
PMDHI

HAWAII EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
715 AM EST WED MAR 01 2017

VALID 00Z THU MAR 02 2017 - 00Z THU MAR 09 2017

LATEST MODEL AND ENSEMBLE GUIDANCE SHOWS GOOD LARGE SCALE
AGREEMENT INTO THE WEEKEND.  A VIGOROUS UPPER LEVEL TROUGH NOW
APPROACHING THE STATE WILL MAINTAIN THE THREAT FOR AREAS OF
HEAVY/STRONG CONVECTION WEDNESDAY-WEDNESDAY NIGHT WHILE DEVELOPING
SURFACE LOW PRESSURE PASSES BY THE NORTHWESTERN ISLANDS AROUND 00Z
THURSDAY.  EXPECT A DECREASE IN RAINFALL AS THIS SYSTEM CONTINUES
NORTHWARD THURSDAY BUT WITH SOME LINGERING RAINFALL POTENTIAL
GIVEN MOIST SOUTHERLY LOW LEVEL FLOW.  A FRONT WILL APPROACH/REACH
THE STATE DURING THE WEEKEND AND SUPPORT AREAS OF RAIN, MOST
LIKELY OVER NORTHWESTERN/CENTRAL ISLANDS.  BY NEXT
MONDAY-WEDNESDAY THERE IS STILL UNCERTAINTY WITH FORECAST DETAILS
AS GUIDANCE VARIES WITH THE EVOLUTION OF ANOTHER DEEP TROUGH
DEVELOPING TO THE NORTHWEST OF THE STATE, INFLUENCING
TIMING/PROGRESSION OF A LEADING SURFACE FRONT.  AS OF WEDNESDAY
THE 00Z GFS STRAYS TO THE FASTER SIDE OF THE ENVELOPE, INCLUDING
THE GEFS MEAN, IN STARTING TO EJECT UPPER TROUGH ENERGY.  ON THE
OTHER HAND DURING TUESDAY-WEDNESDAY THE 00Z ECMWF/CMC SHOW GREATER
TROUGH DEPTH/AMPLITUDE THAN THEIR ENSEMBLE MEANS OR THE GEFS MEAN.
 RESULTING EXTREME HEIGHT ANOMALIES AND CHANGES FROM PREVIOUS RUN
THAT WAS ACTUALLY EVEN MORE EXTREME BUT FARTHER WEST OF THE
ISLANDS WITH THE TROUGH, SUGGEST HEDGING A BIT AWAY FROM THE 00Z
ECMWF/CMC AS WELL.  EVEN WITH THE UNCERTAINTIES ALOFT THERE IS A
COMMON SIGNAL AMONG THE MODELS AND ENSEMBLE MEANS, CONSISTENT WITH
THE OVERALL PATTERN, TOWARD INCREASING RAINFALL POTENTIAL OVER THE
NORTHWESTERN ISLANDS IN THE MONDAY-WEDNESDAY TIME FRAME.

RAUSCH

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