Lightning Strike in Hawaii, April 4, 2003

HAWAIIAN ISLANDS SYNOPTIC DISCUSSION AND GUIDANCE
NATIONAL WEATHER SERVICE HONOLULU HI
830 PM HST THU APR 3 2003

SUMMARY...AN UPPER LEVEL LOW FAR TO OUR NORTHWEST WILL DROP SOUTH
TOWARD THE STATE OVER THE NEXT FEW DAYS. THIS UPPER LOW WILL BRING
INCREASINGLY UNSTABLE AIR OVER THE ISLANDS THROUGH THE REST OF THE
WEEK AND INTO THE WEEKEND. LOOK FOR MORE SHOWERS OVER THE NEXT FEW
DAYS...AND SOME OF THEM MAY BE QUITE HEAVY. THE BEST CHANCE OF
HEAVY SHOWERS WILL BE OVER THE INTERIOR OF THE ISLANDS DURING THE
AFTERNOONS.

DISCUSSION...THE AIRMASS AT THE KAUAI END OF THE CHAIN CONTINUES TO
DESTABILIZE...WITH THE 00Z PHLI SOUNDING SHOWING K-INDEX UP TO 31
AND A 500 MB TEMPERATURE DOWN TO -11C. THE ENVIRONMENT CONTINUES TO
BECOME INCREASINGLY FAVORABLE FOR DEEP CONVECTION TO FORM AROUND
KAUAI. LATE AFTERNOON SATELLITE DERIVED LOW LEVEL WIND FIELDS
CONTINUE TO INDICATE A SHEAR AXIS/TROUGH AROUND 162/163W...AND THIS
BOUNDARY CONTINUES TO BE THE FOCUS FOR AREAS OF SHOWERS AND
THUNDERSTORMS. THE PHTO SOUNDING SHOWS THAT THE AIRMASS AT THE
EASTERN END OF THE CHAIN CONTINUES TO BE QUITE A BIT MORE STABLE FOR
THE TIME BEING.

LOCALLY...ISLAND HEATING CONTRIBUTED TO THE DEVELOPMENT OF ISOLATED
HEAVY SHOWERS OVER OAHU TODAY. WE OFTEN REFER TO THESE AS CONVECTIVE
SHOWERS...BUT THIS IS IN FACT A MISNOMER. BY DEFINITION ALL SHOWERS
ARE CONVECTIVE...AS OPPOSED TO WIDESPREAD STRATIFORM RAINFALL WHICH
RARELY OCCURS IN HAWAII. MOST RAIN BUCKETS GOT NOTHING BUT AHUIMANU
PICKED UP OVER THREE QUARTERS OF AN INCH...WHICH AGREES WELL WITH
RAINFALL ESTIMATES FROM RADAR. OTHER HEAVY SHOWERS FORMED OVER THE
NORTHERN PART OF THE KOOLAU RANGE AND JUST OFFSHORE DURING THE
AFTERNOON. THE SHOWERS ARE ALSO BEING ENHANCED BY UPPER LEVEL
DIFFLUENCE OVER THE ISLANDS...ASSOCIATED WITH THE SUBTROPICAL JET
PASSING SOUTH OF THE BIG ISLAND.

THE SYNOPTIC PATTERN WILL CHANGE LITTLE OVER THE NEXT FEW DAYS...OF
COURSE THE MOST NOTEWORTHY FEATURE BEING THE APPROACHING UPPER LOW
WHICH IS DIVING INTO THE BASE OF THE TROUGH WEST OF HAWAII. THE
MODELS HAVE SETTLED ON THE IDEA THAT THE UPPER LOW WILL PASS JUST
NORTH OF THE ISLANDS ON SUNDAY BEFORE LIFTING OUT MONDAY. SUNDAY
LOOKS TO BE RATHER ACTIVE AS THIS WILL BE WHEN WE WILL BE MOST PRONE
TO GETTING THUNDERSTORMS. IN THE MEANTIME...THE PROXIMITY OF THE
WEAK SURFACE TROUGH...LIGHT WINDS...AND INCREASINGLY COLD AIR ALOFT
MEAN THAT ISOLATED HEAVY SHOWERS WILL BE INCREASING IN COVERAGE
THROUGH THE NEXT FEW DAYS. AS A VERY GENERAL RULE...THE SHOWERS
WILL BE MOSTLY OVER THE WATER AT NIGHT AND FORM OVER LAND DURING THE
DAY.

.HFO...NONE.

R BALLARD