Area Forecast Discussion
Issued by NWS Honolulu, HI

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FXHW60 PHFO 021347
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
340 AM HST WED SEP 2 2015

.SYNOPSIS...
MUGGY CONDITIONS AND SHOWERY WEATHER WILL PREVAIL DURING THE NEXT
SEVERAL DAYS...ESPECIALLY IN THE AFTERNOON HOURS. WINDS WILL BECOME
MOSTLY SOUTHERLY THROUGH MUCH OF THE WORK WEEK...THEN BECOME LIGHT
AND VARIABLE DURING THE UPCOMING WEEKEND. THE EXTENDED FORECAST
WILL DEPEND HEAVILY ON THE TRACK OF HURRICANE JIMENA...WHICH SHOULD
REMAIN WELL TO THE NORTHEAST OF THE ISLANDS. A BRIEF RETURN TO DRIER
EASTERLY WINDS IS POSSIBLE BY EARLY NEXT WEEK.

&&

.DISCUSSION...
RAIN BANDS ASSOCIATED WITH THE OUTER CIRCULATION OF TROPICAL CYCLONE
IGNACIO WERE MOVING ACROSS THE LEEWARD WATERS OF THE BIG ISLAND AND
THE ALENUIHAHA CHANNEL. PASSING SHOWERS WERE ALSO OBSERVED OVER MAUI
COUNTY AND OAHU DURING THE OVERNIGHT HOURS.

INFRARED AND WATER VAPOR SATELLITE IMAGERY SHOW A HIGH ALOFT JUST W
OF THE MAIN HAWAIIAN ISLANDS...WHILE A TROUGH REMAINS TO THE NW.
MEANWHILE...A BROAD SFC HIGH IS CENTERED FAR N OF THE STATE.

IGNACIO IS STILL BLOCKING THE TRADES WITH THE LOW LEVEL FLOW ACROSS
THE ISLAND CHAIN REMAINING WEAK AND GENERALLY FROM THE S/SW. THE
AIRMASS REMAINS MOIST ENOUGH TO KEEP GENERATING SHOWERS TODAY AND
THROUGH THU...BUT BOTH MIMIC AND MODEL ANALYSES SUGGEST A SLIGHTLY
DRIER AIRMASS FILTERING INTO THE ISLAND CHAIN...ESPECIALLY THE
SMALLER ISLANDS. THIS IS PROBABLY RELATED TO SUBSIDENCE TAKING PLACE
S OF IGNACIO. NEVERTHELESS...ADDITIONAL SHOWERS AND ISOLATED
DOWNPOURS ARE STILL POSSIBLE LATER TODAY AND TONIGHT...ESPECIALLY
OVER THE E HALF OF THE ISLAND CHAIN WHERE HIGHER PWATS RESIDE.

OVERALL...THE LOW LEVEL FLOW WILL KEEP CHANGING AS IGNACIO MOVES
FURTHER AWAY FROM THE AREA DURING THE NEXT COUPLE OF DAYS. THIS WILL
BRING PERIODS OF SW OR S WINDS COLLIDING WITH THE MOUNTAINS...WHICH
COULD RESULT IN SOME TERRAIN ANCHORING AND LOCALIZED HEAVY RAIN AT
TIMES. THE WEAK WINDS WILL ALSO ALLOW FOR VERY HUMID CONDITIONS TO
CONTINUE...WHICH WILL TRANSLATE IN ABOVE NORMAL MAX TEMPERATURES...
POTENTIAL FOR HEAT INDEX VALUES IN THE UPPER 90S...AND OVERNIGHT
TEMPERATURES HOVERING THE UPPER 70S. THEREFORE...EXPECT GENERALLY
MUGGY AND WARM CONDITIONS TO PREVAIL.

IGNACIO SHOULD BE LIFTING N AND FURTHER AWAY FROM THE ISLANDS BY
FRI...BUT THE LOW LEVEL FLOW WILL NOT CHANGE SIGNIFICANTLY EVEN
THROUGH SAT....THUS EXPECT THE VERY HUMID CONDITIONS AND SHOWERY
WEATHER TO CONTINUE INTO THE WEEKEND. THE ONLY SIGNIFICANT CHANGE
IN THE FORECAST WILL BE THE DECREASE IN CHANCES FOR HEAVY RAIN
AFTER THU AS THE GLOBAL MODELS SHOW A BROAD RIDGE DEVELOPING ALOFT
AND FILTERING INTO THE AREA FROM THE E...WHICH WILL RESULT IN AN
INCREASE IN AIRMASS STABILITY.

DRIER EASTERLY FLOW MAY DEVELOP EARLY NEXT WEEK...BUT CONFIDENCE
REMAINS LOW IN THE EXTENDED. THIS IS MAINLY DUE TO UNCERTAINTY
REGARDING THE EVOLUTION OF HURRICANE JIMENA...WHICH IS FORECAST TO
GRADUALLY TRACK FAR E AND NE OF THE ALOHA STATE.

&&

.AVIATION...

SEE TC SIGMET SERIES TANGO FOR TROPICAL CYCLONE IGNACIO.

BANDS OF SCATTERED SHOWERS...MOVING FROM W TO E...WILL BE PASSING
OVER THE SMALLER ISLANDS THROUGH THIS COMING EVENING. SOUTHWESTERLY
FLOW ACROSS THE BIG ISLAND WILL SPREAD WIDESPREAD SHOWERS ACROSS
MOST OF THE BIG ISLAND BY MID MORNING. AN AIRMET FOR MTN OBSC HAS
BEEN ISSUED FOR THE NORTHERN LEEWARD MOUNTAINS OF THE BIG ISLAND AND
WILL LIKELY REMAIN NECESSARY THROUGH AT LEAST EARLY AFTERNOON.

THE AIRMASS OVER THE STATE REMAINS MOIST AND UNSTABLE CREATING A
POTENTIAL FOR THUNDERSTORM ACTIVITY ACROSS THE STATE. THUNDERSTORM
POTENTIAL THIS MORNING IS ONLY SLIGHT BUT WILL BE ON THE INCREASE
THROUGHOUT THE DAY DUE TO DAYTIME HEATING.

&&

.MARINE...
A HIGH SURF WARNING REMAINS IN EFFECT FOR MOST EAST FACING SHORES
OF THE ISLANDS THROUGH THURSDAY AS SWELLS FROM IGNACIO AND JIMENA
CONTINUE TO MOVE ACROSS THE WINDWARD HAWAIIAN WATERS. SOME OF THE
INCOMING EASTERLY SWELLS FROM JIMENA COULD ALSO IMPACT SOUTHEAST
SECTIONS OF THE BIG ISLAND AND MAUI. WAVEWATCH GUIDANCE SHOWS THIS
SWELL PEAKING TODAY AND TONIGHT...AND REMAINING STEADY THROUGH
THURSDAY. LATE IN THE WEEK...WE SHOULD SEE THE DIRECTION START TO
BACK TO A MORE EAST-NORTHEAST DIRECTION AS JIMENA GAINS MORE
LATITUDE...AND EVEN SEE AN INCREASE IN HEIGHT AS IT MOVES CLOSER TO
THE STATE. THE HIGH SURF WARNING COULD BE EXTENDED THROUGH THE
WEEKEND OR LONGER.

A SMALL CRAFT ADVISORY IS ALSO IN EFFECT THROUGH THURSDAY FOR
HAZARDOUS SEAS DUE TO THE SWELLS FROM IGNACIO AND JIMENA. THIS
ADVISORY MAY BE EXTENDED THROUGH THE WEEKEND OR LONGER AS SEAS
REMAIN ELEVATED. WINDS ARE EXPECTED TO REMAIN BELOW ADVISORY
LEVELS THIS WEEK.

LONG-PERIOD SWELLS FROM THE SOUTH-SOUTHWEST MAY 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...
HIGH SURF WARNING UNTIL 6 PM HST THURSDAY FOR EAST FACING SHORES OF
KAUAI...OAHU...MOLOKAI...MAUI...AND THE BIG ISLAND.

SMALL CRAFT ADVISORY UNTIL 6 PM HST THURSDAY 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...REYNES
AVIATION...BEDAL








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