Drought in Hawaii, August 9 to 31, 2011

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
330 AM HST TUE AUG 9 2011

.SYNOPSIS...
TRADE WINDS WILL EASE THIS WEEK AS HIGH PRESSURE TO THE NORTHEAST
GRADUALLY WEAKENS. PASSING CLOUDS AND SHOWERS WILL FAVOR WINDWARD
AND MAUKA AREAS DURING NIGHTS AND MORNINGS...BUT INCREASING HIGH
CLOUDS ARE EXPECTED FROM TONIGHT INTO FRIDAY. MOISTURE ASSOCIATED
WITH THE REMNANTS OF TROPICAL CYCLONE EUGENE IS EXPECTED TO BRING
HUMID CONDITIONS...AND ENHANCED WINDWARD SHOWERS...TO THE STATE FROM
THURSDAY NIGHT THROUGH SATURDAY. MORE TYPICAL TRADE WIND WEATHER
WILL FOLLOW FROM SUNDAY INTO NEXT WEEK.

&&

.DISCUSSION...
AFTER DROPPING SLOWLY BUT STEADILY SINCE SATURDAY...ISLAND SURFACE
PRESSURE TRENDS ARE NOW FLAT OVER THE PAST 24 HOURS. THE LOWERING
PRESSURES HAD BEEN DUE TO THE WEAKENING OF THE TRADE WIND-SUPPLYING
HIGH...CURRENTLY CENTERED ABOUT 1200 MILES NNE OF THE ISLANDS...WITH
A CENTRAL PRESSURE NEAR 1030 MB. AS THE HIGH WEAKENED...TRADE WINDS
DIMINISHED TO THEIR CURRENT MODERATE SPEEDS...AND A GRADUAL
WEAKENING TREND IS STILL ANTICIPATED THROUGH THE WORK WEEK.

SATELLITE IMAGERY SHOWS A LOOSELY ORGANIZED...NW-SE ORIENTED...BAND
OF BROKEN LOW CLOUDS OVER THE ISLANDS...AND ADJACENT WINDWARD WATERS
OUT TO 75 MILES. CLOUDS WITHIN THIS BAND INCREASED DRAMATICALLY
MONDAY EVENING...BUT ARE ON A DECIDED DOWNWARD TREND EARLY THIS
MORNING. ALTHOUGH A GOOD PORTION OF THE BAND IS COMPRISED OF STABLE
STRATOCUMULUS...ISOLATED COOL CLOUD TOPS WITHIN THE BAND NEAR KAUAI
AND OAHU REPRESENT SMALL POCKETS OF HEAVY SHOWERS...AND WINDWARD
OAHU RECEIVED THE BULK OF THE RAINFALL OVERNIGHT. THE SHORT TERM
FORECAST CALLS FOR THIS CLOUD BAND TO CONTINUE TO DIMINISH THROUGH
MID-MORNING...GIVING WAY TO A MOSTLY DRY DAY STATEWIDE.

AT THE SURFACE...HIGH PRESSURE CENTERED FAR NNE OF THE ISLANDS WILL
GRADUALLY WEAKEN THROUGH THE WEEK...EVENTUALLY GETTING SPLIT INTO
TWO WEAKER CENTERS BY THURSDAY...AS A LOW DEVELOPS BETWEEN THE TWO.
THE LARGE SCALE PRESSURE GRADIENT WILL LOOSEN SOMEWHAT OVER THE
ISLANDS IN RESPONSE...BUT A GENERALLY MODERATE TRADE WIND FLOW IS
EXPECTED...WITH A MINIMA IN WIND SPEEDS FRI-SAT. THIS WILL KEEP
PASSING CLOUDS AND SHOWERS FOCUSED OVER WINDWARD SLOPES. WINDS ARE
EXPECTED TO TREND A LITTLE STRONGER TO START NEXT WEEK AS HIGH
PRESSURE BUILDS TO THE N...BUT NOT SIGNIFICANTLY.

THE OTHER SURFACE/LOW-LEVEL FEATURE OF INTEREST IS A WEAKENING LOW
PRESSURE SYSTEM...THE REMNANT CIRCULATION OF WHAT ONCE WAS HURRICANE
EUGENE...NOW CENTERED ABOUT 1075 MILES E OF THE BIG ISLAND...
TRAVELLING W NEAR 10 MPH. LATEST MODEL GUIDANCE WEAKENS THE SURFACE
LOW TO A TROUGH OVER THE NEXT TWO DAYS...BEFORE DISSIPATING THE
SURFACE TROUGH OVER WATERS E OF THE ISLANDS. DESPITE THIS WEAKENING
TREND...A SLUG OF LOW-LEVEL MOISTURE WILL CONTINUE TO TRACK W
WITHIN THE TRADE FLOW...AND IS EXPECTED TO TRAVERSE THE ISLAND CHAIN
FROM THURS NIGHT THROUGH SAT. TIMING AND IMPACTS OF THIS MOISTURE
WILL NEED TO BE FINE-TUNED...BUT WE CAN GENERALLY EXPECT INCREASED
WINDWARD SHOWERS AND HIGHER DEW POINTS TO COINCIDE WITH LIGHTER
TRADE WINDS...LIKELY MAKING IT FEEL MUGGY STATEWIDE. THIS MOISTURE
SHOULD BE W OF ALL ISLANDS BY SUN...WITH TYPICAL SUMMERTIME TRADE
WIND WEATHER RESUMING.

ALOFT...A BROAD AND WEAK E-W ORIENTED TROUGH AXIS IS CURRENTLY
LOCATED WELL N OF THE ISLANDS NEAR 29N. THE TROUGH WILL REMAIN IN
PLACE FOR THE NEXT COUPLE OF DAYS WITH LITTLE CHANGE...BUT A LOW
DEVELOPING WITHIN THE TROUGH IS FORECAST TO DIG S ON THU AND
FRI...MOVING INTO A POSITION NW OF KAUAI. WHILE THIS LOW MOVES NE ON
SAT AND SUN...A SHARP TROUGH AXIS ALOFT WILL PERSIST JUST NW OF
KAUAI INTO NEXT WEEK. INCREASED HIGH-LEVEL MOISTURE IS EXPECTED TO
BEGIN MOVING OVER THE ISLANDS AS EARLY AS TONIGHT...AND PERSISTING
INTO FRI...INCREASING THE POTENTIAL FOR CLOUDIER THAN NORMAL SKIES
DUE TO THICKENING HIGH CLOUDS. THE PRESENCE OF THE UPPER LOW TO THE
NW AND THE LOW-LEVEL MOISTURE INCREASE FROM THE E COULD LEAD TO
POCKETS OF HEAVY SHOWERS ON FRI/SAT...BUT AS NOTED WITHIN THE
HAWAII EXTENDED FORECAST DISCUSSION /PMDHI/ ISSUED BY HPC...NONE OF
THE CURRENT SUITE OF MODELS FORECASTS HEAVY RAIN.

&&

.AVIATION...
MASS OF LOW CLOUDS EMBEDDED IN THE TRADE WIND FLOW SPREADING ACROSS
THE AREA CONTAINS SHOWERS WITH BRIEF MVFR CEILINGS AND VIS. PHTO AND
PHLI WILL BE EXPOSED TO THESE CLOUDS AND SHOWERS. OTHERWISE...VFR
CONDS FOR THE REMAINING TERMINALS.

LOW LEVEL WINDS TOO LIGHT TO PRODUCE MODERATE TURB...AND NO AIRMETS
ARE IN EFFECT.

&&

.MARINE...
THE SURF DISCUSSION /SRDHFO/ WAS UPDATED MONDAY...AND CONTAINS AN
IN-DEPTH EXPLANATION OF EXPECTED SWELL AND SURF CONDITIONS ON
OAHU...AND CAN BE GENERALLY APPLIED STATEWIDE. GENERALLY SPEAKING...
SURF WILL BE ON THE SMALL SIDE...WITH LARGEST SURF LIKELY ALONG S
FACING SHORES.

WINDS AND SEAS WILL LIKELY REMAIN BELOW SMALL CRAFT ADVISORY LEVELS
THROUGH THE WEEKEND.

&&

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

&&

DISCUSSION/MARINE...BIRCHARD
AVIATION...LAU