Flash Flood and Heavy Rain in Hawaii, October 5 to 6, 2015

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
347 PM HST MON OCT 5 2015

.SYNOPSIS...
MODERATE TRADES WILL CONTINUE AS THE ISLANDS REMAIN
BETWEEN A HIGH PRESSURE SYSTEM LOCATED FAR TO THE NORTHWEST...AND
TROPICAL STORM OHO SOUTH OF THE ISLANDS. A NORTHEAST TO SOUTHWEST
BAND OF SHOWERS OVER OAHU THIS MORNING IS EXPECTED TO SINK
SOUTHWARD...SPREADING SHOWERS TO MAUI COUNTY THIS AFTERNOON AND
THE BIG ISLAND TONIGHT. THE TRADE WIND FLOW WILL FOCUS MOST OF
THOSE SHOWERS OVER WINDWARD AND MAUKA AREAS.

&&

.DISCUSSION...
THE NORTHEAST TO SOUTHWEST ORIENTED CLOUD BAND THAT HAS SAT OVER
OAHU MOST OF THE DAY HAS FINALLY BEGUN TO SHIFT TO THE SOUTH LATE
THIS AFTERNOON. THIS BAND...ASSOCIATED WITH AN OLD FRONT OR
TROUGH...HAS BROUGHT PLENTY OF LOW CLOUDS TO OAHU...AND SOME RAIN.
FOR THE MOST PART THE RAIN OVER THE EAST SIDE OF THE ISLAND WAS
LIGHT ALL DAY...BUT SOME OF THE GAGES IN THE MOUNTAINS DID PICK UP
BETWEEN .50 AND 1 INCH IN 3 HOURS. THE BAND IS STARTING TO MOVE
TO THE SOUTH AND IS EXPECTED TO BRING AN UPTICK IN SHOWERS TO MAUI
COUNTY TONIGHT.

THE AFTERNOON SOUNDINGS FROM HILO AND LIHUE HAD 1.35 AND 1.19
ICHES OF PRECIPITABLE WATER /PW/ RESPECTIVELY. THESE VALUES ARE
WITHIN NORMAL FOR THIS TIME OF YEAR...AS ARE THE 500 AND 700 MB
TEMPERATURES. AS SUCH DO NOT EXPECT ANY PROBLEMS WITH HEAVY RAIN.

TROPICAL STORM OHO REMAINS TO THE SOUTH OF THE ISLANDS...AND IS
EXPECTED TO CONTINUE MOVING TO THE NORTHEAST OVER THE NEXT BIT.
THE STORM IS EXPECTED TO REMAIN FAR ENOUGH SOUTH TO HAVE A MINIMAL
IMPACT ON WINDS OVER THE MAIN HAWAIIAN ISLANDS. SOME OF THE
MOISTURE ASSOCIATED WITH OHO MAY REACH THE BIG ISLAND TONIGHT
THROUGH MIDWEEK. HOWEVER...AS WITH THE SHOWER ACTIVITY MENTIONED
ABOVE...DO NOT EXPECT ISSUES WITH HEAVY RAIN.

HIGH PRESSURE BUILDING TO THE NORTHWEST OF THE STATE WILL CONTINUE
TO BRING TRADES TO THE ISLANDS FOR MUCH OF THE WEEK. THROUGH THE
WEEK...THE HIGH IS EXPECTED TO REMAIN TO THE NORTHWEST...WITH THE
ASSOCIATED RIDGE NORTH OF THE ISLANDS. EXPECT TRADE WIND SHOWERS
TO PERSIST WITH SHOWERS FOCUSED OVER THE WINDWARD SIDES OF THE
ISLANDS. HEADING INTO THE WEEKEND...THE GFS WANTS TO BRING IN SOME
ADDITIONAL LOW LEVEL MOISTURE FROM THE SOUTHEAST. IT DOESN/T
APPEAR TO BE AN ORGANIZED SYSTEM...BUT RATHER SOME LEFT OVER
MOISTURE BEING CARRIED NORTHWARD...WHICH COULD BOOST SOME POPS.

&&

.AVIATION...
THE DECAYING FRONTAL BOUNDARY AS OF 02Z IS CENTERED BETWEEN OAHU AND
MOLOKAI WITH LOW CLOUDS SPREADING OVER OAHU THROUGH MAUI. AIRMET
SIERRA FOR MTN OBSC IS POSTED FOR NORTH THROUGH EAST SECTIONS OF
THESE ISLANDS AND OVER THE NORTH THROUGH EAST SECTIONS ON KAUAI.
THIS WILL LIKELY BE DROPPED AT THE 04Z ROUTINE ISSUANCE FOR
KAUAI...ELSEWHERE EXPECT MTN OBSC TO CONTINUE INTO THE NIGHT.

THE FRONTAL BOUNDARY  WILL CONTINUE TO DISSIPATE AND DRIFT EAST WITH
WHAT REMAINS OF THE FRONT REACHING THE BIG ISLAND LATE TONIGHT. THE
MVFR TO IFR CONDITIONS ALONG THE WINDWARD SIDE OF OAHU SHOULD
IMPROVE TONIGHT AND SLOWLY FOLLOW SUITE OVER MOLOKAI AND MAUI.
AIRMET SIERRA MAY BE NEEDED OVER THE BIG ISLAND TONIGHT.

MODERATE TO GUSTY N WINDS CAN ALREADY BE SEEN AT TERMINALS FROM MAUI
WEST. EXPECT THESE MODERATE TO GUSTY N TO NE WINDS OVER THE ISLAND
TUESDAY.

&&

.MARINE...
CURRENTLY NO MARINE HAZARDS IN EFFECT. TROPICAL STORM OHO COULD
PRODUCE SOME SOUTHERLY AND EASTERLY SWELLS THAT ARE MOST LIKELY TO
IMPACT THE BIG ISLAND. BOTH SOUTH AND EAST SHORES OF THE BIG
ISLAND COULD APPROACH ADVISORY LEVELS. THE SOUTH SHORES COULD SEE
A BUMP AS EARLY AS TONIGHT...BUT THE BUMP ON THE EAST SIDE WILL
LIKELY BE TOMORROW. THE REMAINING ISLANDS WILL LIKELY BE SHADOWED
FROM ANY OF THIS SURF.

ELSEWHERE...THE CURRENT NORTH NORTHEAST SWELL CONTINUES TO
DECLINE. ANOTHER MODERATE SWELL IS EXPECTED TO ARRIVE SATURDAY
NIGHT.

&&

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

&&

DISCUSSION/MARINE...M BALLARD
AVIATION...EATON