Weather Service Report


473 
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



Return to Home page


Western Regional Climate Center, wrcc@dri.edu