Area Forecast Discussion
Issued by NWS Honolulu, HI

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000
FXHW60 PHFO 041330
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
400 AM HST FRI SEP 4 2015

.SYNOPSIS...
A HUMID AND UNSTABLE AIR MASS WILL SUPPORT SPOTTY...BUT LOCALLY
VERY HEAVY...SHOWERS AND THUNDERSTORMS INTO THIS AFTERNOON. WEAK
TRADE WINDS AND SOMEWHAT MORE STABLE CONDITIONS WILL SPREAD FROM THE
EAST TONIGHT AND SATURDAY...THOUGH THE WEATHER WILL REMAIN HOTTER
AND MORE HUMID THAN USUAL. PREVAILING WINDS WILL DIMINISH INTO NEXT
WEEK...LEADING TO STAGNANT CONDITIONS AND INCREASED AFTERNOON
SHOWERS AGAIN.

&&

.DISCUSSION...
THE AIR MASS MOISTENED AGAIN OVERNIGHT...ALTHOUGH THE SHALLOW
MID-LEVEL TROUGH EXTENDING SOUTH FROM TROPICAL CYCLONE IGNACIO
GRADUALLY WEAKENED AND SHIFTED WEST OF THE STATE. IMPRESSIVE DEEP
CONVECTION CONTINUED TO FIRE OVER THE COASTAL AND OFFSHORE WATERS.
SOME FORMED QUITE CLOSE TO SHORE...INCLUDING SUCH COASTS AS EAST
KAUAI...EAST OAHU...AND WEST BIG ISLAND. HOWEVER...AS OCCURRED 24
HOURS AGO...VIRTUALLY ALL OF THIS ACTIVITY REMAINED OVER THE
WATER...AVERTING POTENTIALLY SIGNIFICANT FLOODING. NONETHELESS...THE
POTENTIAL FOR SERIOUS CONSEQUENCES REMAINED...AND THUS SO DID THE
FLASH FLOOD WATCH.

LATER TODAY AND TONIGHT...A SHIFT IN THE PATTERN OF TROPICAL
CYCLONES DRIVING REGIONAL WEATHER MAY BRING A NOTICEABLE CHANGE TO
THE HUMID AND STAGNANT CONDITIONS. ALTHOUGH TROPICAL CYCLONE JIMENA
WILL REMAIN FAR ENOUGH AWAY NOT TO AFFECT THE ISLANDS DIRECTLY...A
SWATH OF NORTHEAST WINDS WILL EXTEND PAST THE NORTH EDGE OF THE
STORM AND OVER THE STATE. GUIDANCE PREDICTED FAIRLY MODEST WIND
SPEEDS...BUT THEY STAND A CHANCE OF BEING STRONGER THAN THE
PREVAILING FLOW EARLIER THIS WEEK. MOST SOLUTIONS ALSO PREDICTED A
SLIGHTLY DRIER AIR MASS TO ADVECT IN ON THE WINDS. CONVERGENCE ALONG
THE LEADING EDGE OF THE NEW AIR MASS MAY ENCOURAGE A BRIEF BURST OF
SHOWERS AT FIRST...BUT SUBSIDENCE CLEARLY VISIBLE IN SATELLITE
IMAGES TO THE WEST OF JIMENA WILL HELP TO STABILIZE CONDITIONS.

THIS PERIOD OF TRADE WINDS WILL END BY SUNDAY NIGHT ONCE JIMENA
MOVES FAR ENOUGH NORTH...LEAVING FEEBLE NORTHERLIES IN PLACE.
STAGNANT FLOW INTO NEXT WEEK WILL PERMIT EVAPORATION TO MOISTEN THE
AIR MASS AGAIN...AND DIURNAL EFFECTS WILL PREVAIL. CONDITIONS DURING
THE LATTER PART OF NEXT WEEK DEPENDED HEAVILY ON THE PRECISE TRACK
OF JIMENA.

&&

.AVIATION...
AN AREA OF LOW LEVEL CONVERGENCE DRIFTING WESTWARD OVER THE CENTRAL
AND WESTERN PART OF THE STATE....COMBINED WITH AN UPPER LEVEL TROUGH
AND COPIOUS TROPICAL MOISTURE...WILL GENERATE SCATTERED HEAVY
SHOWERS AND ISOLATED THUNDERSTORMS ONCE AGAIN TODAY. AREAS OF MVFR
AND LOCALIZED IFR WILL PROBABLY DEVELOP OVER THE ISLANDS DURING THE
DAY. LOCALIZED TURBULENCE AND ICING WILL BE POSSIBLE WITH ANY
THUNDERSTORMS.

NO AIRMETS ARE CURRENTLY IN EFFECT...BUT AIRMET SIERRA FOR MOUNTAIN
OBSCURATION WILL LIKELY BE NEEDED FOR SOME OF THE ISLANDS DURING THE
DAY.

&&

.MARINE...
INCOMING EAST SWELL FROM HURRICANE JIMENA CONTINUED TO REQUIRE A
HIGH SURF WARNING FOR EAST-FACING SHORES OF MOST ISLANDS. EAST-SHORE
SURF WILL REMAIN NEAR WARNING LEVELS THROUGH THE WEEKEND...AND
LIKELY INTO EARLY NEXT WEEK.

A SMALL CRAFT ADVISORY ALSO REMAINED IN EFFECT THROUGH THIS
AFTERNOON FOR HAZARDOUS SEAS PRODUCED BY THE SWELLS FROM IGNACIO AND
JIMENA. WINDS ARE EXPECTED TO REMAIN BELOW THE ADVISORY THRESHOLD
THIS WEEK.

A LONG-PERIOD SWELL FROM THE SOUTH-SOUTHWEST WILL PRODUCE
ADVISORY-LEVEL SURF ALONG SOUTH-FACING SHORES THIS WEEKEND. PLEASE
REFER TO THE LATEST COLLABORATIVE NEARSHORE SWELL AND WIND FORECAST
/SRDHFO/ FOR MORE DETAILS ON THE SWELLS.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
FLASH FLOOD WATCH THROUGH THIS AFTERNOON FOR ALL HAWAII ISLANDS.

HIGH SURF ADVISORY FROM 6 AM THIS MORNING TO 6 PM HST SATURDAY
FOR NIIHAU-KAUAI LEEWARD-OAHU SOUTH SHORE-WAIANAE COAST-LANAI
MAKAI-KAHOOLAWE-MAUI LEEWARD WEST-LEEWARD HALEAKALA-KONA.

HIGH SURF WARNING UNTIL 6 PM HST SATURDAY FOR KAUAI WINDWARD-
OAHU KOOLAU-OLOMANA-MOLOKAI-MAUI WINDWARD WEST-MAUI CENTRAL
VALLEY-WINDWARD HALEAKALA-SOUTH BIG ISLAND-BIG ISLAND NORTH AND
EAST.

SMALL CRAFT ADVISORY UNTIL 6 PM HST THIS EVENING FOR KAUAI
NORTHWEST WATERS-KAUAI WINDWARD WATERS-KAUAI CHANNEL-OAHU
WINDWARD WATERS-KAIWI CHANNEL-MAUI COUNTY WINDWARD WATERS-
PAILOLO CHANNEL-ALENUIHAHA CHANNEL-BIG ISLAND WINDWARD WATERS-
BIG ISLAND SOUTHEAST WATERS.

&&

$$

DISCUSSION/MARINE...RYSHKO
AVIATION...JACOBSON





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