Flash Flood and Heavy Rain in Hawaii, August 12 to 14, 2009

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
1046 PM HST TUE AUG 11 2009

.UPDATE...
SOUTHERLY FLOW AND TROPICAL MOISTURE NEAR THE BIG ISLAND HAS
TRIGGERED SHOWERS ALONG THE LOWER SLOPES OF LEEWARD BIG ISLAND AND
THE SOUTHEAST COAST. RADAR AND GAGES SHOW RAINFALL RATES OF 1
INCH PER HOUR ACROSS PORTIONS OF KONA DISTRICT...MAINLY NEAR
HONAUNAU. SOME OF THIS ACTIVITY EXTENDS TO THE SOUTH BIG ISLAND
DISTRICT AS WELL. THESE SHOWERS WILL LIKELY PERSIST FOR THE NEXT
FEW HOURS. HAVE UPDATED THE NEAR-TERM FORECAST WITH ADDED SHOWERS
AND SKY COVER FOR THESE AREAS.

&&

.SYNOPSIS...
A WEAK AREA OF LOW PRESSURE...THE REMNANT OF TROPICAL CYCLONE
FELICIA...WILL CONTINUE TO TRACK SLOWLY WEST... PASSING OVER MAUI
COUNTY TONIGHT AND OAHU ON THURSDAY. CLOUDS AND SHOWERS ASSOCIATED WITH
THE WEAK LOW WILL AFFECT THE SMALLER ISLANDS THROUGH WEDNESDAY.
LOCALLY GUSTY WINDS WILL STILL OCCUR OVER SELECT AREAS...AS WINDS
ARE ACCELERATED BETWEEN HIGH PRESSURE FAR NORTH OF THE
ISLANDS...AND FELICIA/S REMNANT LOW. ALTHOUGH TYPICAL TRADE WIND
WEATHER IS STILL EXPECTED TO RETURN IN TIME FOR THE WEEKEND...LIGHT
EAST TO SOUTHEAST WINDS WILL MAKE FOR MUGGY CONDITIONS ON THURSDAY
AND FRIDAY.

&&

.DISCUSSION...

AS OF 8 PM...THE REMNANT LOW OF FELICIA CONTINUES MOVING SLOWLY WEST
OVER THE ISLANDS WITH THE CENTER APPROACHING MAUI COUNTY. RAINFALL
OVER MAUI COUNTY HAS BEEN STEADY THIS AFTERNOON WITH THE HIGHEST 6
HOUR TOTAL OF 1.08 INCHES RECORDED AT WEST WAILUAIKI. A RECORD
RAINFALL OF 0.31 AT KAHULUI BREAKS THE OLD RECORD OF 0.19 SET IN
1981. THIS RECORD IS PRELIMINARY AS MORE RAIN IS STILL POSSIBLE
BEFORE MIDNIGHT.

FELICIA WAS REDUCED TO A REMNANT LOW EARLIER TODAY...BUT STILL
CARRIES WITH IT AN AREA OF LOWER SURFACE PRESSURE. WITH MODERATE
HIGH PRESSURE CENTERED WELL NORTH- NORTHWEST OF THE
ISLANDS...LOCALLY GUSTY WINDS ARE STILL POSSIBLE THE REMNANT LOW
FILLS AND MOVES WEST OF THE STATE ON THURSDAY. CURRENT NNE WINDS ARE
GUSTY ACROSS MAUI COUNTY AND OAHU WITH SUSTAINED SPEEDS OF 10 TO
20 MPH AND MOST GUSTS BETWEEN 30 TO 40 MPH. GUSTS ARE STRONGER
OVER HIGHER TERRAIN AND THROUGH VALLEYS AS SHOWN BY THE WAIANAE
VALLEY GAGE RECORDING A GUST OF 50 MPH EARLIER THIS EVENING.

LOW-TOPPED SHOWERS REMAIN ACTIVE ALONG WINDWARD PORTIONS OF MAUI
COUNTY...OAHU...AND KAUAI THIS EVENING...AS NNE WINDS WEST OF
FELICIA DRIVE MOISTURE INTO ISLAND TERRAIN. HOWEVER... RAIN RATES
HAVE MAINTAINED AT LIGHT TO MODERATE LEVELS AND NO FLOOD PRODUCTS
HAVE BEEN NECESSARY AS OF YET. RAIN RATES HAVE BEEN KEPT IN CHECK BY
AN UPPER LEVEL RIDGE WHICH HAS MAINTAINED A STABLE ATMOSPHERE
ABOVE THE LOWER LEVELS. CLOUDY AND SHOWERY CONDITIONS ARE STILL
EXPECTED FROM MAUI TO KAUAI OVER THE NEXT TWO DAYS AS THE REMNANT
LOW PLODS WESTWARD.

WINDS OVER THE SMALLER ISLANDS WILL TRANSITION OUT OF THE SOUTHEAST AND
SOUTH WEDNESDAY AND THURSDAY...AND THEN BACK TO LIGHT EASTERLIES
ON FRIDAY. THESE WINDS WILL BRING MUGGY CONDITIONS OVER THE
STATE FOR THE SECOND HALF OF THE WEEK.

HIGH PRESSURE IS EXPECTED TO REMAIN WELL NORTH OF THE STATE
THROUGH THE ENTIRE FORECAST PERIOD. ONCE THE REMNANTS OF FELICIA
MOVES WEST OF ALL ISLANDS BY FRIDAY...THE HIGH PRESSURE WILL AGAIN
BE THE MAIN FEATURE DRIVING OUR WEATHER. LIGHT TO MODERATE TRADE
WINDS ARE EXPECTED OVER THE WEEKEND AS FELICIA MOVES AWAY WITH
CLOUDS AND PASSING SHOWERS FAVORING WINDWARD AND MAUKA AREAS...INTO
NEXT WEEK.

LONG RANGE FORECAST MODELS CONTINUE TO SHOW TROPICAL CYCLONE FORMATION
IN THE EAST PACIFIC BASIN. HOWEVER...LOCATION AND TRACKS OF THESE
SYSTEMS VARY WIDELY FROM EACH MODEL RUN...SO UNCERTAINTY REMAINS
AT A HIGH LEVEL.

&&

.MARINE...
A HIGH SURF ADVISORY REMAINS IN EFFECT FOR EAST FACING SHORES OF
MOST ISLANDS...DOWNGRADED FROM A WARNING EARLIER THIS AFTERNOON.
SURF IS EXPECTED TO DROP MARKEDLY ON WEDNESDAY... LIKELY BELOW
ADVISORY LEVELS.

A SMALL CRAFT ADVISORY /SCA/ HAS BEEN EXTENDED TO VIRTUALLY ALL
HAWAIIAN WATERS...DUE TO WINDS AND SEAS MEETING CRITERIA. THE SCA
WILL LIKELY NEED TO BE EXTENDED FOR SELECT MARINE ZONES ON
WEDNESDAY.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
HIGH SURF ADVISORY UNTIL 6 AM HST WEDNESDAY FOR NIIHAU-KAUAI
WINDWARD-OAHU SOUTH SHORE-OAHU KOOLAU-OLOMANA-MOLOKAI WINDWARD-
MAUI WINDWARD WEST-WINDWARD HALEAKALA-SOUTH BIG ISLAND-BIG
ISLAND NORTH AND EAST.

SMALL CRAFT ADVISORY UNTIL 6 AM HST WEDNESDAY FOR OAHU LEEWARD
WATERS-KAIWI CHANNEL-MAUI COUNTY WINDWARD WATERS-MAUI COUNTY
LEEWARD WATERS-MAALAEA BAY-PAILOLO CHANNEL-ALENUIHAHA CHANNEL-
BIG ISLAND WINDWARD WATERS-BIG ISLAND LEEWARD WATERS.

SMALL CRAFT ADVISORY UNTIL 6 PM HST WEDNESDAY FOR KAUAI
NORTHWEST WATERS-KAUAI WINDWARD WATERS-KAUAI LEEWARD WATERS-
KAUAI CHANNEL-OAHU WINDWARD WATERS.

&&

MORRISON