000 
FXHW60 PHFO 011345
AFDHFO

HAWAIIAN ISLANDS FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
4 AM HST WED SEP 1 2004

.SYNOPSIS...
HIGH PRESSURE TO OUR NORTH WILL WEAKEN AND A SURFACE TROUGH WILL 
DEVELOP EAST OF THE ISLANDS. AS A RESULT...OUR WINDS WILL DIMINISH 
AND SHIFT FROM EAST TO NORTHEAST. RAINFALL WILL GENERALLY BE LIGHT 
BUT A TROUGH ALOFT MAY ALLOW ISOLATED HEAVY SHOWERS TO FORM.
  
&&

.DISCUSSION...
MODELS KEEP THE SURFACE HIGH FAR TO OUR NORTH STRONG ENOUGH TO GIVE 
US TRADE WINDS THROUGH THURSDAY. THIS IS A DIFFERENT SOLUTION THAN 
THAT GIVEN SEVERAL DAYS AGO...NAMELY THAT THE HIGH AND TRADES WOULD 
WEAKEN TO A POINT THAT SMALLER SCALE SEA BREEZES AND AFTERNOON 
CONVECTION WOULD RULE ISLAND WEATHER.

MODELS ALSO HAVE A DIFFERENT SOLUTION FOR THE UPPER REACHES OF THE 
ATMOSPHERE...NAMELY THAT THE TROPICAL UPPER TROPOSPHERIC TROUGH OR 
TUTT NORTHWEST OF KAUAI WILL KEEP THE AIRMASS OVER THAT END OF THE 
ISLAND CHAIN UNSTABLE AS OPPOSED TO THE ENTIRE ISLAND CHAIN AS 
PREVIOUS MODEL RUNS DID. THIS IS BECAUSE THE MODELS NOW PLACE AN 
UPPER LEVEL HIGH AND A MORE STABLE AIRMASS OVER THE BIG ISLAND 
THROUGH FRIDAY.

FINALLY...THE MODELS SHOW A LOW ALOFT FAR NORTH NORTHEAST OF THE 
ISLANDS DIGGING SOUTHWESTWARD AND INDUCING A SURFACE TROUGH EAST OF 
THE ISLANDS. IF THIS IS CORRECT...THE TRADES WOULD WEAKEN AND SHIFT 
TO THE NORTHEAST TOWARDS THE WEEKEND.

TAKING INTO ACCOUNT ALL OF THE ABOVE...THE FORECAST CALLS FOR LIGHT 
TRADES...WITH WEAK OROGRAPHIC FORCING KEEPING WINDWARD SHOWERS 
RELATIVELY LIGHT. THE TRADES SHOULD BE STRONG ENOUGH HOWEVER TO KEEP 
AFTERNOON CONVECTION FROM BEING WIDESPREAD. AND FINALLY... ALTHOUGH 
RAINFALL WILL BE GENERALLY SPARSE...SOME SHOWERS MAY BE LOCALLY 
HEAVY NEAR KAUAI DUE TO THE INFLUENCE OF THE TROUGH ALOFT. 
CONFIDENCE IN THIS FORECAST IS SOMEWHAT LOW SINCE THE MODELS HAVE 
DIFFERENT SOLUTIONS WITH ALMOST EVERY RUN.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

$$
CRAIG