Heavy Rain in Hawaii, July 20, 2007

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
1000 AM HST FRI JUL 20 2007

.SYNOPSIS...
TROPICAL DEPRESSION COSME CONTINUES TO MOVE WEST ON A TRACK THAT
WILL TAKE IT SOUTH OF THE BIG ISLAND TONIGHT. STARTING LATER
TODAY...AND CONTINUING THROUGH SATURDAY...COSME WILL PRODUCE
STRONGER WINDS AND HEAVIER RAIN...ESPECIALLY ON THE BIG ISLAND.
TRADE-WIND WEATHER WILL RETURN ON SUNDAY AND CONTINUE THROUGH NEXT
WEEK.

&&

.DISCUSSION...
AT 800 AM HST...THE CENTER OF TROPICAL DEPRESSION COSME WAS 310
MILES SOUTHEAST OF HILO...MOVING TOWARD THE WEST AT 17 MPH. MAXIMUM
SUSTAINED WINDS ARE NEAR 35 MPH WITH HIGHER GUSTS. SEE THE LATEST
BULLETINS FROM THE CENTRAL PACIFIC HURRICANE CENTER FOR DETAILS ON
COSME.

A 1605 UTC QUICKSCAT PASS SHOWS THAT COSME HAS OPENED UP INTO AN
OPEN WAVE WITH NO WESTERLY WIND COMPONENT EVIDENT AT THE SURFACE.
THERE IS STILL A VORTICITY CENTER AT CLOUD LEVEL AND ISOLATED
THUNDERSTORMS CONTINUE POPPING UP NEAR THE CENTER. THERE IS STILL A
BROAD AREA OF MOSTLY EASTERLY WINDS OF 25 TO 30 KT ON THE NORTH SIDE
OF THE SYSTEM. MUCH OF THIS IS DUE TO THE PRESSURE GRADIENT BETWEEN
COSME AND HIGH PRESSURE TO THE NORTH OF THE STATE. STRONGER THAN
NORMAL TRADE WINDS CAN BE EXPECTED OVER THE NEXT COUPLE OF DAYS
ESPECIALLY OVER PORTIONS OF THE BIG ISLAND. A WIND ADVISORY REMAINS
UP FOR THE HIGH SUMMITS ON MAUI AND THE BIG ISLAND SINCE THEY WILL
LIKELY EXPERIENCE THE STRONGEST WINDS.

FOR NOW...COSME IS NOT HAVING MUCH IMPACT ON ISLAND WEATHER.
SATELLITE IMAGERY SHOWS SCATTERED LOW CLOUDS UPSTREAM OF THE ISLANDS
FROM KAUAI TO MAUI AND RADAR SHOWS ISOLATED SHOWERS FALLING FROM
THEM. THESE SHOWERS WILL CONTINUE MOVING ACROSS THE SMALLER ISLANDS
TODAY PRIMARILY IMPACTING WINDWARD AND MAUKA AREAS...BUT SOME LIGHT
MISTY SHOWERS MAY SURVIVE OVER TO SOME LEEWARD AREAS. THE LEADING
EDGE OF THE CLOUD FIELD ASSOCIATED WITH COSME IS NOW JUST REACHING
THE EAST SIDE OF THE BIG ISLAND. AS THIS MOISTURE MOVES UPSLOPE ON
THE BIG ISLAND...HEAVY RAIN IS POSSIBLE....SO A FLASH FLOOD WATCH
CONTINUES FOR THE BIG ISLAND. IT IS NOT CLEAR HOW MUCH COSME WILL
AFFECT RAINFALL ON THE OTHER ISLANDS. HEAVIER RAINFALL MAY SPREAD AS
FAR AS MAUI COUNTY...BUT IT IS TOO SOON TO SAY VERY CONFIDENTLY IF
OAHU AND KAUAI WILL GET MUCH OF AN INCREASE FROM A NORMAL TRADE WIND
RAINFALL PATTERN.

ONCE COSME PASSES BY THE ISLANDS...A TYPICAL TRADE WIND WEATHER
PATTERN IS EXPECTED ACROSS THE STATE. CLOUDS AND PASSING SHOWERS
WILL FALL OVER TYPICAL WINDWARD AND MAUKA AREAS WITH TRADE WINDS
GENERALLY IN THE 10 TO 20 MPH RANGE.

&&

MARINE...
THE PRESSURE GRADIENT BETWEEN THE HIGH TO THE NORTH AND COSME...IS
CAUSING STRONGER THAN NORMAL TRADE WINDS ACROSS THE CENTRAL NORTH
PACIFIC. THIS WILL BRING SHORT PERIOD ROUGH SURF FOR EAST FACING
SHORES...THAT WILL LIKELY EXCEED THE HIGH SURF ADVISORY OF 8 FT. THE
BIG ISLAND WILL BEGIN TO SEE THE HIGH SURF TODAY AND THE REMAINING
ISLANDS ON SATURDAY. ALSO THE STRONGER WINDS WILL CAUSE SMALL CRAFT
ADVISORY CONDITIONS ACROSS ALL MARINE ZONES.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
HIGH SURF ADVISORY FOR EAST-FACING SHORES OF THE BIG ISLAND.
SMALL CRAFT ADVISORY FOR ALL HAWAIIAN WATERS.
WIND ADVISORY FOR SUMMITS OF BIG ISLAND AND MAUI.
FLASH FLOOD WATCH FOR THE BIG ISLAND.

&&

BURKE