Area Forecast Discussion
Issued by NWS Honolulu, HI

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000
FXHW60 PHFO 032136 AAA
AFDHFO

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE HONOLULU HI
1136 AM HST THU SEP 3 2015

.UPDATE...
INCREASED RAIN CHANCES AND THUNDERSTORM COVERAGE THROUGH TONIGHT
GIVEN CURRENT RADAR AND SATELLITE TRENDS.


&&

.SYNOPSIS...
A HUMID AND UNSTABLE AIR MASS WILL SUPPORT LOCALLY HEAVY SHOWERS
AND THUNDERSTORMS THROUGH THIS EVENING...AND POSSIBLY OVER THE
NEXT COUPLE OF DAYS. WEAK EASTERLY WINDS WILL SPREAD FROM THE
EAST ON FRIDAY AND SATURDAY...THOUGH THE WEATHER WILL REMAIN
WARM AND HUMID. WINDS WILL DIMINISH AGAIN NEXT WEEK AS HURRICANE
JIMENA MOVE TO THE NORTHEAST OF THE STATE...LEADING TO STAGNANT
CONDITIONS.

&&

.PREV DISCUSSION.../ISSUED 1000 AM HST THU SEP 3 2015/

RADAR SHOWS ABUNDANT SHOWERS ACROSS OAHU AND MAUI COUNTY LATE THIS
MORNING. INFRARED AND WATER VAPOR IMAGERY INDICATE THE PRESENCE OF
SCATTERED CONVECTION SPREAD ACROSS THE CENTRAL AND WESTERN PART OF
THE STATE AS A RESULT OF AN UPPER LEVEL TROUGH JUST WEST OF KAUAI.
THE TROUGH IS PUSHING IN COLDER AIR ALOFT CAUSING AN UNSTABLE
ATMOSPHERE ACROSS THE STATE...PARTICULARLY THE SMALLER ISLANDS.
MOISTURE LEVELS REMAIN HIGH AS WEAK SOUTHERLY FLOW IS KEEPING THE
DEEP TROPICAL MOISTURE OVER HAWAII. 12Z SOUNDINGS SHOW THE
UNSTABLE PROFILE WITH PRECIPITABLE WATER VALUES OF 1.67 INCHES AT
LIHUE AND NEAR 2 INCHES AT HILO. THESE VALUES ARE 1 STANDARD
DEVIATION ABOVE NORMAL FOR SEPTEMBER. AS MENTIONED...WINDS ARE
SOUTHERLY AND LIGHT...AND WILL LIKELY RESULT IN SEA BREEZES
SETTING UP OVER THE ISLANDS TODAY.

FOR THIS AFTERNOON AND EVENING...WE ANTICIPATE THE SHOWERS TO
FOCUS OVER THE SMALLER ISLANDS AS THE SEA BREEZES CONVERGE OVER
THE INTERIORS. WITH THE MOISTURE AND INSTABILITY IN PLACE...THESE
SHOWERS MAY OCCASIONALLY BECOME HEAVY AND A FEW THUNDERSTORMS MAY
BE POSSIBLE.

THE UPPER TROUGH WILL LIFT SLIGHTLY TO THE NORTH ON FRIDAY
SHIFTING THE FOCUS OF THE CONVECTION WEST OF KAUAI...THOUGH KAUAI
WILL LIKELY STILL ON THE FRINGES OF THE ACTIVE WEATHER. WEAK
SURFACE RIDGING IS EXPECTED TO BRIEFLY NOSE IN BETWEEN IGNACIO AND
JIMENA AND SHIFT THE LIGHT WINDS EASTERLY. THE LAND AND SEA BREEZE
PATTERN WILL LIKELY CONTINUE AS MODELS PROJECT WINDS TO STAY IN
THE GENTLE RANGE. EASTERLY FLOW WILL END BY SUNDAY NIGHT ONCE
HURRICANE JIMENA MOVES FAR ENOUGH NORTH TO DISRUPT THE FLOW
ALLOWING LIGHT AND VARIABLE WINDS AND HUMID CONDITIONS TO PREVAIL.
THIS FORECAST WILL CONTINUE THROUGH AT LEAST THE FIRST HALF OF
NEXT WEEK.

&&

.AVIATION...
WIDESPREAD SHOWERS AND SCATTERED THUNDERSTORMS ARE OVER OAHU THIS
MORNING...AS A WIDE LOW LEVEL CONVERGENCE ZONE EXTENDING SOUTH FROM
TC IGNACIO TRACKS TO THE WEST. AN UPPER LEVEL TROUGH WITH ITS AXIS
JUST WEST OF KAUAI WILL ACT TO FURTHER DESTABILIZE THE ATMOSPHERE.
MVFR TO IFR CONDITIONS ARE EMBEDDED IN THESE SHOWERS AND AIRMET
SIERRA FOR MTN OBSC IS POSTED FOR OAHU. THE CONVECTION WILL LIKELY
CARRY CB TOPS BETWEEN FL350-450...AND THE POTENTIAL FOR ICING AND
TURB. THIS CONVERGENCE BAND IS FORECAST TO SLOWLY MOVE TO THE WEST
THROUGHOUT THE DAY. EXPECT CONDITIONS ON KAUAI...INCLUDING PHLI...TO
DETERIORATE THIS AFTERNOON.

THE EASTERN END OF THE CONVERGENCE ZONE IS ALSO LENDING TO SHOWER
ACTIVITY AND ISOLATED THUNDERSTORMS NEAR AND AROUND MAUI COUNTY.
AIRMET SIERRA FOR MTN OBSC IS POSTED OVER EASTERN MAUI. AS THE ZONE
TRACKS WEST EXPECT MAUI COUNTY TO IMPROVE...HOWEVER...AN UNSTABLE
ATMOSPHERE REMAINS IN PLACE AND AFTERNOON CONVECTIVE ACTIVITY CAN
NOT BE RULED OUT ALONG THE SEABREEZE CONVERGENCE. THIS WILL HOLD
TRUE OVER THE BIG ISLAND AND THE REST OF THE STATE TOO.


&&

.MARINE...
A HIGH SURF WARNING IS IN EFFECT FOR EAST-FACING SHORES OF MOST
ISLANDS. THE LARGE SURF WAS DUE TO A MIX OF DECLINING NORTHERLY
SWELL FROM IGNACIO...AND A BUILDING EAST SWELL FROM HURRICANE
JIMENA. THE IGNACIO SWELL WILL BE DROPPING OFF SIGNIFICANTLY
THROUGH TONIGHT. EAST-SHORE SURF WILL REMAIN NEAR WARNING LEVELS
THROUGH THE WEEKEND...AND LIKELY INTO EARLY NEXT WEEK. THE HIGH
SURF WARNING WILL LIKELY BE EXTENDED FOR EAST FACING SHORES.

A SMALL CRAFT ADVISORY ALSO REMAINED IN EFFECT THROUGH FRIDAY
AFTERNOON FOR HAZARDOUS SEAS PRODUCED BY THE SWELLS FROM IGNACIO AND
JIMENA. 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...
FLASH FLOOD WATCH THROUGH THIS EVENING FOR ALL HAWAII ISLANDS.

HIGH SURF WARNING UNTIL 6 PM HST THIS EVENING FOR EAST FACING
SHORES OF KAUAI OAHU MOLOKAI MAUI AND BIG ISLAND.

SMALL CRAFT ADVISORY UNTIL 6 PM HST FRIDAY 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...FOSTER
AVIATION...EATON





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