Area Forecast Discussion
Issued by NWS Honolulu, HI

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000
FXHW60 PHFO 280206
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
406 PM HST THU AUG 27 2015

.SYNOPSIS...
HUMID CONDITIONS REMAIN...AND THE CHANCE OF HEAVY SHOWERS WILL
CONTINUE THROUGH FRIDAY WITH FLASH FLOODING POSSIBLE OVER THE
SMALLER ISLANDS. VARIABLE WINDS TONIGHT WILL GIVE WAY TO WEAK
TRADE WINDS FRIDAY AND MODERATE TRADES SATURDAY. ALTHOUGH SHOWERS
WILL FAVOR WINDWARD AND MAUKA AREAS... AFTERNOON CLOUDS AND SPOTTY
SHOWERS CAN BE EXPECTED OVER LEEWARD AREAS. HURRICANE IGNACIO WILL
APPROACH THE STATE LATE IN THE WEEKEND AND WILL AFFECT ISLAND
WEATHER NEXT WEEK.

&&

.DISCUSSION...

THE ATMOSPHERE AROUND THE STATE REMAINS MOIST AND UNSTABLE WITH
DEW POINTS IN THE MID 70/S AND A MID TO UPPER LEVEL TROUGH
LINGERING JUST NORTH OF THE ISLANDS. DAYTIME HEATING AND SEA
BREEZE CONVERGENCE WERE ENOUGH TO PRODUCE HEAVY SHOWERS AND
THUNDERSTORMS OVER OAHU THIS AFTERNOON WITH SPOTTY SHOWERS OVER
THE REST OF THE STATE. SHOWERS WILL TAPER OFF DURING THE EVENING
HOURS. SIMILAR CONDITIONS ARE EXPECTED OVER THE SMALLER ISLANDS
FRIDAY AND WITH THE GROUND ALREADY SATURATED...FLOODING COULD
HAPPEN QUICKLY. THE FLASH FLOOD WATCH HAS BEEN EXTENDED FOR KAUAI
COUNTY...OAHU AND MAUI COUNTY.

DRIER AIR WILL MOVE OVER THE BIG ISLAND FROM THE EAST TONIGHT AND
FRIDAY BRINGING A DROP TO HUMIDITY LEVELS. THE DECREASE IN
HUMIDITY AND WEAK RIDGING OVERHEAD SHOULD BE ENOUGH TO CAP ANY
VIGOROUS CONVECTION FRIDAY AFTERNOON. THEREFOR... THE FLASH FLOOD
WATCH HAS BEEN CANCELLED FOR THE BIG ISLAND.

LIGHT TRADE WINDS ARE EXPECTED FRIDAY WITH MODERATE TRADES FILLING
IN SATURDAY AS HIGH PRESSURE BUILDS SLOWLY NORTH OF THE STATE.
SHOWERS WILL FAVOR WINDWARD AND MAUKA AREAS AT NIGHT AND THROUGH
THE MORNING HOURS. HOWEVER...THE TRADES WILL BE WEAK ENOUGH TO
ALLOW AFTERNOON SEA BREEZES TO FORM ALONG LEEWARD COASTS FRIDAY
AFTERNOON. THE SEA BREEZES AND DAYTIME HEATING WILL SHIFT
RAINFALL FOCUS TO CENTRAL AND LEEWARD LOCATIONS WITH HEAVY SHOWERS
AND ISOLATED THUNDERSTORMS POSSIBLE. SATURDAY AND SUNDAY...TRADE
WINDS ARE EXPECTED TO BE SUFFICIENTLY STRONG ENOUGH TO PROHIBIT
WIDESPREAD AFTERNOON SEA BREEZES AND THE ASSOCIATED CONVECTIVE
ACTIVITY.

FORECAST UNCERTAINTY INCREASES SIGNIFICANTLY ON MONDAY AND
TUESDAY...HINGING ON THE EVENTUAL TRACK OF HURRICANE IGNACIO.
HURRICANE IGNACIO WILL APPROACH THE BIG ISLAND LATE IN THE
WEEKEND AND MAY THREATEN THE ISLANDS EARLY NEXT WEEK. FORECAST
TRACK ERRORS AT THAT TIME ARE MORE THAN A COUPLE HUNDRED
MILES...SO IT IS TOO EARLY TO TELL WHAT THE DIRECT IMPACTS WILL
BE. EVERYONE IN THE STATE SHOULD MONITOR THE PROGRESS OF IGNACIO
DURING THE NEXT SEVERAL DAYS...AND THE NATIONAL WEATHER SERVICE
URGES INDIVIDUALS TO HAVE AN ACTION PLAN IN CASE IGNACIO...OR ANY
HURRICANE...THREATENS.

&&

.AVIATION...
THUNDERSTORMS FLARED UP ONCE AGAIN THIS AFTERNOON UNDER THE MOIST
UNSTABLE ATMOSPHERE. MOST THUNDERSTORM ACTIVITY IS CENTERED OVER
CENTRAL OAHU INCLUDING PHNL. ISOLATED THUNDERSTORMS ARE ALSO ALONG
THE BIG ISLAND SLOPES. EXPECT THUNDERSTORM AREAS TO CARRY MVFR TO
ISOL IFR CONDITIONS...INCLUDING PERIODS OF TURB AND LIGHT ICING
THE TALL CLOUDS. CB TOPS WERE REACHING FL350-450. ELSEWHERE
SCATTERED SHOWERS WITH TEMPO MVFR HAVE TOPS BETWEEN 080-120 WITH
ISOL TCU TOPS TO 15-FL220. EXPECT SHOWERS AND THUNDERSTORMS TO
DISSIPATE AFTER SUNSET AND ISLAND AREAS TO CLEAR OVERNIGHT AS LAND
BREEZES FORM.

AIRMET SIERRA IS POSTED FOR MOUNTAIN OBSCURATION OVER OAHU AND KAUAI.
THIS WILL LIKELY BE CANCELLED THIS EVENING AS CONDITIONS IMPROVE.

&&

.MARINE...
THE MAIN CONCERN WILL BE A MODERATE WEST TO WEST-NORTHWEST SWELL
DURING THE NEXT SEVERAL DAYS. THE HANALEI BUOY HAS SHOWN A STEADY
2-3 FOOT SWELL THROUGH THE DAY WHILE THE BARBERS POINT POINT IS
SHOWING A STEADY 3 FEET. WHILE THE IMPACTS OF THIS SWELL WILL BE
MODEST ON MOST ISLANDS...ADVISORY LEVEL SURF COULD DEVELOP ALONG
WEST FACING SHORES OF THE BIG ISLAND FRIDAY AND SATURDAY.

UNCERTAINTY IS VERY HIGH REGARDING THE POTENTIAL IMPACTS ON THE
STATE FROM HURRICANE IGNACIO EARLY NEXT WEEK...BUT WE ARE CONFIDENT
THAT AN EAST-SOUTHEAST SWELL WILL ARRIVE SATURDAY. THIS SWELL WILL
MAINLY IMPACT THE BIG ISLAND AND MAUI...WHERE ADVISORY LEVEL SURF
IS EXPECTED ALONG EAST FACING SHORES SATURDAY THEN LIKELY RISE TO
WARNING LEVELS SUNDAY. SOME OF THIS SWELL ENERGY WILL EVENTUALLY
IMPACT THE REST OF THE STATE.

WINDS AND SEAS WILL REMAIN BELOW SMALL CRAFT ADVISORY LEVELS THROUGH
SATURDAY.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
FLASH FLOOD WATCH THROUGH FRIDAY AFTERNOON FOR NIIHAU-KAUAI-OAHU-
MOLOKAI-LANAI-MAUI.


&&

$$

MORRISON...DISCUSSION AND MARINE
EATON...AVIATION





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