000 
FXHW60 PHFO 091952
AFDHFO

HAWAIIAN ISLANDS FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
1000 AM HST FRI SEP 9 2005

.SYNOPSIS...
WITH JET STREAM SUPPORT ALOFT AND PLENTIFUL MOISTURE NEAR THE 
SURFACE...THIS COULD BE A RATHER WET WEEKEND ESPECIALLY FOR WINDWARD 
AND MAUKA SECTIONS OF THE ISLANDS. THE STRONG HIGH FAR NORTH OF THE 
STATE WILL REMAIN IN PLACE THROUGH THE WEEKEND...KEEPING MODERATE TO 
LOCALLY FRESH TRADE WINDS BLOWING...BUT THE REAL CULPRIT IS THE 
MOISTURE BEING SPREAD NORTHWARD BY THE NORTHWARD DISPLACED AND 
RATHER ACTIVE TROPICAL CONVERGENCE ZONE JUST EAST OF OUR LONGITUDE.

&&

.DISCUSSION...
THE SUBTROPICAL JET STREAM HAS SLIPPED NORTHWARD...NORTH OF THE MAIN 
HAWAIIAN ISLANDS. THIS HAS ALLOWED ITS ASSOCIATED CIRRUS CLOUD 
BAND...ALONG THE SOUTHEAST SIDE OF THIS JET...TO MOVE NORTHWARD AND 
OVER THE ISLANDS. IT HAS ALSO TAKEN SOME OF THE SHEAR PRESSURE OFF 
THE INCIPIENT TROPICAL SYSTEM TRYING TO DEVELOP SOUTHEAST OF 
HILO...AND ALLOWED IT TO BECOME RE-ENERGIZED OVERNIGHT. WHILE THE 
CIRRUS CLOUD BAND NOW OVER THE ISLANDS IS FORMING FROM JET ENHANCED  
EXHAUST FROM THUNDERSTORM DEVELOPMENT TO THE SOUTH AND SOUTHWEST OF 
THE MAIN HAWAIIAN ISLANDS...THESE THUNDERSTORMS HAVE INCREASED IN 
AREAL COVERAGE AND INTENSITY OVERNIGHT ALL THE WAY FROM NEAR 140W... 
WHERE THE TROPICAL DISTURBANCE SITS NEAR 16N...TO WEST OF 170W... 
WHERE THE STORMS ARE CONFINED TO THE PROXIMITY OF THE ITCZ...SOUTH 
OF 12N. BUT BENEATH THE CIRRUS CLOUD...THE INCREASED LIFT FROM THE 
NEARBY JET STREAM APPEARS TO BE ENHANCING THE CLOUDS SLIPPING IN IN 
THE TRADE WIND FLOW. THIS IS PRODUCING SOME BRIEF LOCALLY HEAVY 
BURSTS OF RAIN OVER THE ISLANDS THIS MORNING. WITH WEAK TROUGHING... 
AT 500MB AT LEAST...CONTINUING OVER THE ISLANDS THROUGH THE WEEKEND 
AND SIGNIFICANT LOW-LEVEL MOISTURE MOVING INTO THE ISLANDS FROM THE 
EAST...EXPECT SHOWERY WEATHER TO CONTINUE.

MODELS ARE STILL HAVING A DIFFICULT TIME WITH THE TROPICAL SYSTEM TO 
THE SOUTHEAST OF HILO...ALTHOUGH THEY APPEAR TO BE COMING TO 
AGREEMENT ON MOVING THE SYSTEM WESTWARD AT THIS POINT. THE QUESTION 
WILL BE TO WHAT EFFECT MOISTURE FROM THIS DISTURBANCE ENHANCES OUR 
SHOWERS AND TO WHAT DEGREE THE LOWERED PRESSURE OF THE SYSTEM WILL 
ENHANCE OUR TRADE WINDS. THESE REMAIN UNCERTAIN IN MODEL FORECASTS 
AND SO THE SYSTEM WILL CONTINUE TO BE WATCHED FOR ITS EFFECTS ON OUR 
WEATHER...EVEN THOUGH SIGNIFICANT DEVELOPMENT OF THIS SYSTEM IS NOT 
EXPECTED AT THIS TIME.

&&

.MARINE...
WILL KEEP THE SMALL CRAFT ADVISORY IN EFFECT FOR AREAS WHERE THE 
TRADE WINDS WILL BE ENHANCED BY TERRAIN EFFECTS TODAY...AND WITH 
PRESSURE GRADIENT FORCES REMAINING QUITE STRONG THROUGH THE 
WEEKEND...MAY HAVE TO KEEP THESE UP THROUGH SUNDAY AS WELL. 
HOWEVER...INDICATIONS ARE THAT A WEAKENING OF THE STRONG HIGH NORTH 
OF THE ISLANDS EARLY NEXT WEEK...ALONG WITH LOWERING PRESSURES DUE 
TO THE PASSAGE OF THE TROPICAL SYSTEM TO OUR SOUTH...MAY ALLOW US 
TO DROP THESE ADVISORIES BY MONDAY.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
SMALL CRAFT ADVISORY FOR MAALAEA BAY AND WATERS SOUTH OF THE BIG 
ISLAND REMAIN IN EFFECT.

&&

$$

FARRELL