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Hawaiian Islands Synoptic Discussion and Guidance

907
FXHW60 PHFO 290645 CCA
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
800 PM HST FRI AUG 28 2015

.SYNOPSIS...
VERY WARM AND HUMID CONDITIONS WILL CONTINUE DESPITE THE RETURN OF
THE TRADES THIS WEEKEND. THE TRADES WILL BE WEAK ENOUGH TO FAVOR
SOME AFTERNOON CLOUDS AND SHOWERS OVER THE LEEWARD AND INTERIOR AREAS
OF THE SMALLER ISLANDS SATURDAY. THEN A DISTURBANCE MAY RESULT IN
A FEW MORE CLOUDS AND SHOWERS SUNDAY STATEWIDE. HURRICANE IGNACIO
WILL APPROACH THE STATE LATE IN THE WEEKEND AND WILL AFFECT ALL OF
THE MAIN ISLANDS THE FIRST HALF OF NEXT WEEK.

&&

.DISCUSSION...
WE WELCOME BACK THE RETURN OF THE TRADES AND A SLIGHTLY MORE STABLE
AND DRIER AIR MASS TODAY. BELIEVE ONLY OAHU AND KAUAI HAD A FEW
MINOR CONVECTIVE SHOWERS OVER ON THEIR INTERIOR AND OR LEEWARD PARTS
OF THE ISLAND. A FEW TRADE SHOWERS ALSO BLEW ACROSS WINDWARD KAUAI
TODAY. BUT SHOWERS WERE RATHER ABSENT ACROSS MAUI COUNTY AND THE BIG
ISLAND.

THE TRADES USHERED IN A SLIGHTLY DRIER...MORE BEARABLE AIR MASS.
DEW POINTS ARE ONE TO THREE DEGREES FAHRENHEIT LESS CURRENTLY
COMPARED TO 24 HOURS AGO. A FEW MORE DEGREE DROP IS ANTICIPATED AS
SATELLITE DERIVED PRECIPITABLE WATER IMAGERY SHOWS A DRIER AIR MASS
OF 1.4 TO 1.7IN NEARING THE BIG ISLAND FROM THE EAST THIS AFTERNOON.
WE ANTICIPATE THIS AIRMASS TO CROSS THE AREA TONIGHT AND SATURDAY
BEFORE TURNING JUICIER AGAIN WITH PRECIP WATER VALUES INCREASING TO
2 INCHES OR HIGHER SUNDAY. SEA SURFACE TEMPS SURROUNDING THE ISLANDS
ARE QUITE WARM STANDING AT 82 DEGREES F. THIS AFFECT THE AIR BLOWING
ACROSS IT BY KEEPING THE AIR ON THE WARM SIDE. SO THE TRADES INSTEAD
OF BEING COOL...WILL BE WARM.

THE WEATHER BECOMES SOMEWHAT SHOWERY OR AT LEAST A BETTER CHANCE FOR
SHOWERS SUNDAY THANKS TO AN UPPER LEVEL DISTURBANCE. THE SHOWERS
BACKS OFF SLIGHTLY MONDAY...BUT BY THIS POINT...THE EFFECTS OF
HURRICANE IGNACIO TAKES OVER.

WATER VAPOR IMAGERY SHOWS AN UPPER LEVEL HIGH ABOUT 230 MILES SOUTH
SOUTHWEST OF THE BIG ISLAND. SO A WEST TO EAST WIND FLOW LIES OVER
THE HAWAIIAN ISLANDS WITH SOME CIRRUS CLOUDS EMBEDDED IN THE FLOW.
THIS FLOW BECOMES NORTH AND NORTHEAST IMMEDIATELY SOUTHEAST OF THE
BIG ISLAND TO 150W LONGITUDE. IGNACIO IS LOCATED FEW DEGREES EAST OF
150W.

THE REST OF THE FORECAST HINGES ON THE TRACK OF IGNACIO WITH THE
FORECAST OF UNCERTAINTY INCREASING SIGNIFICANTLY ON MONDAY AND
TUESDAY. PLEASE SEE THE LATEST DISCUSSION ISSUED BY THE CENTRAL
PACIFIC HURRICANE CENTER FOR SPECIFICS RELATED TO THE TRACK AND
INTENSITY...ISSUED UNDER AWIPS HEADER TCDCP3 AND WMO HEADER WTPA43
PHFO.

THE CONE OF UNCERTAINTY...WHICH IS THE POTENTIAL TRACK GIVEN
HISTORIC TRACK ERROR...INCLUDES THE ENTIRE STATE. IF IGNACIO SHIFTS
TO THE RIGHT...WE COULD SEE LIGHT WINDS...MORE HUMID
CONDITIONS...AND LOCALIZED HEAVY RAIN. ON A MORE LEFTWARD TRACK
CLOSER TO THE ISLANDS...WE COULD SEE STRONGER/DAMAGING WINDS AND
MORE WIDESPREAD HEAVY RAIN/FLOODING. EVERYONE SHOULD CONTINUE TO
MONITOR THE PROGRESS OF IGNACIO DURING THE NEXT SEVERAL DAYS.

&&

.AVIATION...
VFR CONDITIONS WILL PREVAIL THROUGH THE OVERNIGHT HOURS. THE TRADE
WINDS WILL CARRY IN A FEW SHOWERS FAVORING THE WINDWARD AND
MOUNTAIN AREAS OF ALL THE LARGER ISLANDS. SO EXPECT SOME BRIEF MVFR
CIGS AND VIS WITH THESE SHOWERS. AN ISOLATED SHOWER OR TWO MAY
APPEAR ALONG THE KONA COAST OF THE BIG ISLAND IN THE NEXT FEW HOURS
AS WELL.

NO AIRMETS CURRENTLY AND NO AIRMETS EXPECTED FOR THE REST OF THE
NIGHT.

&&

.MARINE...
LITTLE CHANGE WITH THE MARINE ASPECTS. ALL MARINERS SHOULD MONITOR
THE PROGRESS OF HURRICANE IGNACIO DURING THE NEXT SEVERAL DAYS.

WINDS AND SEAS SHOULD REMAIN BELOW SMALL CRAFT ADVISORY LEVELS INTO
SATURDAY...WITH ELEVATED SEAS BECOMING A CONCERN BY SUNDAY FOR
PORTIONS OF THE STATE.

IN THE SHORT TERM...A WEST TO WEST-NORTHWEST SWELL WILL BE THE MAIN
CONCERN. BOTH THE WAIMEA AND HANALEI BUOYS ARE REPORTING A WNW SWELL
OF 3.6 FEET AND 15 SEC PERIOD AS OF 7 PM HST. THE BARBERS POINT BUOY
OFF OAHU IS COMING IN AT 3.9 FOOT SWELL AT 15 SECONDS. WITH THIS
SAID...THE HIGH SURF ADVISORY IS ON TRACK FOR LEEWARD BIG ISLAND...
GOOD TO 6 PM HST SATURDAY.

A HIGH SURF ADVISORY WILL GO INTO EFFECT AT 6 AM HST SATURDAY
FOR THE EAST FACING SHORES OF THE BIG ISLAND...FROM A SWELL
GENERATED BY HURRICANE IGNACIO. THE ADVISORY MAY BE EXTENDED TO THE
EAST FACING SHORES OF MAUI SATURDAY NIGHT. TIMING FOR THE OTHER
ISLANDS WILL BE DELAYED DUE TO SHADOWING/BLOCKING FROM THE BIG
ISLAND AND MAUI. WARNING LEVEL SURF IS LIKELY FOR THE BIG ISLAND IN
THE DAYS AHEAD. THE SURF FORECAST THEREAFTER REST ON THE TRACK AND
STRENGTH OF IGNACIO.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
HIGH SURF ADVISORY UNTIL 6 PM HST SATURDAY FOR WEST FACING SHORES OF
THE BIG ISLAND.

HIGH SURF ADVISORY FROM 6 AM SATURDAY TO 6 PM HST SUNDAY FOR EAST
FACING SHORES OF THE BIG ISLAND.

&&

$$

LAU