Drought in Hawaii, May 1 to 31, 2012

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
830 PM HST MON APR 30 2012

.SYNOPSIS...
MODERATE TRADE WINDS WILL DIMINISH SLOWLY THROUGH THE WEEK. MOST
CLOUDS AND SHOWERS WILL BE LIMITED TO WINDWARD SLOPES...BUT RAINFALL
WILL REMAIN LIGHT. AFTERNOON CLOUD BUILDUPS ALSO WILL OCCUR OVER LEE
SLOPES OF THE BIG ISLAND.

&&

.DISCUSSION...
OBSERVATIONS AROUND THE MAIN HAWAIIAN ISLANDS REPORTED MODERATE TO
STRONG TRADE WINDS. MOMENTUM WAS SOMEWHAT LIMITED ABOVE THE
IMMEDIATE SURFACE...BUT PRESSURE TRENDS SUGGESTED LITTLE CHANGE
THROUGH THE SHORT RUN.

ALOFT...A BROAD AND STRONG RIDGE PREVAILED OVERALL...BUT A COMPACT
LOW WITHIN THE GREATER RIDGE WOBBLED OVER AND JUST SOUTH OF THE
STATE. A SHARP LOCAL GRADIENT BETWEEN THE RIDGE AND LOW CONTRIBUTED
TO INTERMITTENT HIGH WIND SPEEDS ACROSS THE BIG ISLAND SUMMITS.

THE LOW ALOFT WAS NOT STRONG ENOUGH TO COUNTERACT LARGE-SCALE
SUBSIDENCE ASSOCIATED WITH THE DOMINATING RIDGE...BUT SOUNDINGS
REVEALED A SLIGHTLY MORE COMPLEX INVERSION STRUCTURE THAN IS
USUAL...THOUGH THE INVERSION REMAINED AT A FAIRLY TYPICAL HEIGHT.
SATELLITE ESTIMATES SHOWED A FAIRLY DRY AIR MASS...AND TOGETHER WITH
THE SUBSIDENCE SUBSTANTIALLY EXPLAINED VERY LOW RAINFALL
ACCUMULATION ACROSS THE STATE.

GUIDANCE DIFFERS SOMEWHAT WITH RESPECT TO PREDICTING THE TRACK OF
THE LOW ALOFT...THOUGH BROADLY SPEAKING SOLUTIONS EXPECT IT TO
WANDER AROUND WITHIN THE RIDGE AS BOTH WEAKEN GRADUALLY OVER THE
NEXT FEW DAYS. BY THE WEEKEND...A STRONG MID-LEVEL TROUGH PASSING
FURTHER NORTH IS EXPECTED TO FINISH OFF THE RIDGE. THOUGH THE
GRADUAL DECREASE IN SUPPORT FROM ALOFT WILL DIMINISH THE SUBTROPICAL
RIDGE...AND THUS THE TRADE WINDS...THROUGH THE WHOLE WEEK...THIS
EFFECT WILL BECOME FAR MORE NOTICEABLE BY AROUND FRIDAY NIGHT.

THUS...IN PRACTICAL TERMS...MODERATE BUT DIMINISHING TRADE WINDS
WILL DRIVE THE WEATHER THIS WEEK. CLOUDS AND SHOWERS WILL BE LIMITED
MAINLY TO WINDWARD SLOPES. THOUGH PLENTIFUL SUNSHINE WILL DRIVE
SHALLOW CONVECTION OVER LEE SLOPES OF THE BIG ISLAND EACH
AFTERNOON...SUBSIDENCE AND A LACK OF MOISTURE WILL LIMIT
ACCUMULATION SIGNIFICANTLY.

&&

.MARINE...
STRONG TRADES CONTINUE TO BRING SMALL-CRAFT-ADVISORY CONDITIONS TO
MOST OF THE COASTAL WATERS...AND THESE CONDITIONS ARE EXPECTED TO
CONTINUE INTO WEDNESDAY MORNING. SOME AREAS MAY REMAIN ABOVE THE
THRESHOLD BEYOND WEDNESDAY MORNING.

SMALL SWELLS FROM THE SOUTH AND THE NORTH NORTHWEST WILL FADE
TUESDAY. SURF ALONG SHORES FACING SOUTH...NORTH...AND WEST WILL
REMAIN VERY SMALL THROUGH AT LEAST FRIDAY.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
WIND ADVISORY UNTIL 6 AM HST TUESDAY FOR HALEAKALA SUMMIT-BIG
ISLAND SUMMITS.

SMALL CRAFT ADVISORY UNTIL 6 AM HST WEDNESDAY FOR ALL CHANNELS...
WINDWARD WATERS...LEEWARD BIG ISLAND...AND MAALAEA BAY.

&&

RYSHKO