Flash Flood Warning 4, NWS Honolulu, HI

HAWAIIAN ISLANDS FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
400 PM HST THU JAN 26 2006

.SYNOPSIS...
SHOWERS ENHANCED BY A MID-LEVEL KONA LOW JUST SOUTH OF THE ISLANDS
WILL KEEP THE ISLANDS WET FOR THE NEXT 24 HOURS. THE COLD UPPER LOW
WILL ALSO BRING SOME MORE SNOW TO THE BIG ISLAND SUMMITS...AS IT
CREEPS SLOWLY EASTWARD. EXPECT THIS LOW TO CONTINUE ITS SLOW
EASTWARD MOVEMEMENT...GRADUALLY IMPROVING CONDITIONS OVER THE
WESTERNMOST ISLANDS...BUT MODEL FORECASTS SWEEP A REMNANT OF THIS
UPPER LEVEL FEATURE BACK OVER THE ISLANDS OVER THE WEEKEND...
KEEPING THE BIG ISLAND WET.

&&

.DISCUSSION...
SATELLITE WATER VAPOR IMAGERY CONFIRMS MODEL TREND OF TAKING WET
UPPER AIR KONA SYSTEM CURRENTLY SOUTH OF THE ISLANDS SLOWLY EASTWARD
AND GRADUALLY DRYING OUT ISLAND WEATHER OVER THE NEXT COUPLE OF
DAYS. THE LATEST VERSIONS OF THE MODELS BRING A REMNANT OF THE LOW
BACK OVER THE BIG ISLAND OVER THE COMING WEEKEND HOWEVER...KEEPIING
THE BIG ISLAND WET AT LEAST THROUGH SUNDAY. MEANWHILE...HEAVY
SHOWERS CONTINUE IN THE MOIST ENVIRONMENT GENERATED BY THE MID-LEVEL
LOW PRESSURE SYSTEM TO OUR SOUTH. INDIVIDUAL SHOWERS ARE TENDING TO
BE FAIRLY FAST MOVING IN THE 20,000 FOOT DEEP MOIST LAYER FLOW FROM
THE SOUTHEAST...BUT TRAINING OF HEAVY SHOWERS OVER THE KAU SECTION
OF THE BIG ISLAND OF HAWAII DID PROVIDE ENOUGH RAINFALL FOR FLOODING
OF ROADS IN THAT AREA...THUS A FLASH FLOOD WARNING WAS ISSUED.
HEAVY RAIN ELSEWHERE ON THE BIG ISLAND OF HAWAII ALSO CREATED
NUISANCE FLOODING OF ROADWAYS...PROMPTING THE ISSUANCE OF A FLOOD
ADVISORY ELSEWHERE ON THIS ISLAND. SNOW FALLING ON THE HIGHER
VOLCANO SUMMITS HAS CONTINUED THROUGH THE DAY. THIS IS WET SNOW...
MIXED WITH RAIN AT TIMES...BUT A WINTER WEATHER ADVISORY REMAINS IN
EFFECT FOR THESE SUMMITS THROUGH TONIGHT.

WHILE ALL ISLANDS HAVE SEEN PERIODIC HEAVY RAINS...THE ISLAND MOST
AFFECTED BY THE HEAVY RAINFALL HAS BEEN THE BIG ISLAND OF HAWAII.
HERE 24 HOUR RAINFALL TOTALS OF AS MUCH AS 8 INCHES HAVE BEEN NOTED.
COMPUTER MODELS ARE STILL INDICATING A SLOW EASTWARD MOVEMENT OF THE
MID-LEVEL KONA LOW SYSTEM SOUTH OF THE ISLANDS OVER THE NEXT COUPLE
OF DAYA...BUT THEY ARE ALSO BRINGING A REMNANT OF THIS MID-LEVEL
DISTURBANCE BACK OVER THE BIG ISLAND AGAIN OVER THE WEEKEND. THUS
WILL BE TEMPERING THE IMPROVING FORECAST TO ALLOW FOR THIS PVA
RETURN OVER THE BIG ISLAND THIS WEEKEND. OTHERWISE...THE FOREAST
REFLECTS ACCEPTANCE OF A FLOW OF DRYER AIR FROM THE NORTHEAST OVER
THE WEEKEND TO EVENTUALLY FILTER INTO THE ISLAND ATMOSPHERE...
REPLACING THE MOISTURE LADEN AIR PRESENTLY IN PLACE OVER THE
HAWAIIAN ISLANDS WITH BETTER WEATHER FOR THE WEEKEND.

&&

.MARINE...
WHILE THE MEAN WIND FLOW OVER THE ISLANDS CONTINUES TO BE FROM THE
EAST OR EAST-SOUTHEAST AT 20 TO 25 MPH AT THE SURFACE...BLOCKING OF
THE WIND BY THE ISLANDS THEMSELVES IS MAKING FOR LIGHTER WINDS OVER
THE LAND AREAS. WILL KEEP SMALL CRAFT ADVISORIES OVER THE WATERS
HOWEVER DUE TO THE LARGER SCALE WIND FIELD AND SOME ADDITIONAL
CHANNELLING THROUGH THE ISLAND CHANNELS.

THESE FAIRLY STRONG WINDS WILL ALSO KEEP SURF ALONG EAST FACING
SHORES NEAR THE 8 FOOT ADVISORY LEVEL THROUGH SATURDAY. A NORTHWEST
SWELL WILL BE ARRIVING ON FRIDAY...RAISING SURF ALONG NORTH AND
WEST FACING SHORES TO ABOVE ADVISORY LEVELS ALSO.

&&

.HYDROLOGY...
A FLASH FLOOD WARNING WAS ISSUED FOR THE BIG ISLAND OF HAWAII...
FOR HEAVY RAINFALL CAUSING EXCESSIVE RUNOFF...ESPECIALLY IN THE
PAHALA AREA ALONG THE KAU COAST. HOWEVER...HEAVY RAINS CONTINUE
ELSEWHERE AS WELL...SO THE ENTIRE ISLAND IS INCLUDED IN THE
WARNING. AN URBAN SMALL STREAM AND FLOOD ADVISORY HAS BEEN ISSUED
FOR THE ISLAND OF OAHU AND WILL BE CONSIDERED FOR OTHER ISLANDS AS
NEEDED WHERE HEAVY RAINS ARE CAUSING WATER TO POND ON ROAD SURFACES.
A WINTER WEATHER ADVISORY HAS ALSO BEEN CONTINUED FOR INTERMITTANT
SNOWFALL ON THE SUMMITS OF MAUNA KEA AND MAUNA LOA.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...

HIGH SURF ADVISORY UNTIL 6 PM HST FRIDAY FOR EAST NORTH AND WEST
FACING SHORES.

WINTER WEATHER ADVISORY UNTIL 6 AM HST FRIDAY FOR BIG ISLAND
SUMMITS.

SMALL CRAFT ADVISORY UNTIL 6 PM HST FRIDAY FOR MOST COASTAL WATERS.

&&

FARRELL