Prognostic Meteorological Discussion
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FXHW01 KWNH 161209
PMDHI

HAWAII EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
808 AM EDT WED AUG 16 2017

VALID 00Z THU AUG 17 2017 - 00Z THU AUG 24 2017

A SLOW MOVING UPPER-LEVEL INVERTED TROUGH WILL GRADUALLY SLIDE
WEST ACROSS THE STATE. DESPITE SOME WEAK INSTABILITY ALOFT, A
LARGE DOME OF SURFACE HIGH PRESSURE OVER THE PACIFIC AND NORTH AND
EAST OF THE STATE SHOULD YIELD LIGHT TO MODERATE EASTERLY TRADES
WITH SOME WINDWARD SHOWERS FOR HAWAII. THE OPERATIONAL VERSIONS OF
THE GFS AND ECMWF INDICATE PRECIPITABLE WATER VALUES TO REMAIN
BELOW AVERAGE THROUGH A GOOD PART OF THIS COMING WEEKEND, VALUES
AT OR ABOUT 1 INCH.

HOWEVER BY LATE THIS WEEKEND INTO EARLY NEXT WEEK, THE MOISTURE
CONTENT WILL BE ON THE INCREASE AND BECOME ANOMALOUS (PRECIPITABLE
WATER VALUES 3 TO 4 TIMES ABOVE AVERAGE). OPERATIONAL AND ENSEMBLE
GUIDANCE INDICATE A POSSIBLE TROPICAL DISTURBANCE AND INFLUX OF
MOISTURE ALONG THE ITCZ (INTER TROPICAL CONVERGENCE ZONE) TO
ADVECT IN FROM THE EAST AND SOUTHEAST. THE CENTRAL PACIFIC
HURRICANE CENTER GIVES THIS FEATURE AN 80 PERCENT PROBABILITY TO
DEVELOP OVER THE NEXT 5 DAYS. DESPITE THIS POTENTIAL IN
DEVELOPMENT, THERE IS NOT MUCH MODEL SUPPORT FOR A TRUE AREA OF
LOW PRESSURE TO REACH THE ISLANDS, OTHER THAN PERHAPS THE BIG
ISLAND. THE BIGGEST POTENTIAL IMPACTS WILL BE PERHAPS SOME MORE
ORGANIZED AND PERSISTENT SHOWER ACTIVITY AND INCREASE IN WAVE
ACTION.

MUSHER


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