423
FXHW60 PHFO 161434
AFDHFO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
350 AM HST WED OCT 16 2013
.SYNOPSIS...
AN INCLEMENT WEATHER PATTERN IS EXPECTED TO RULE THE MAIN HAWAIIAN
ISLANDS FOR THE NEXT COUPLE OF DAYS AS AN UPPER LEVEL TROUGH REMAINS
OVER THE AREA. A DRIER WEATHER PATTERN MAY RETURN ON SATURDAY.
&&
.DISCUSSION...
A CHALLENGING FORECAST AS WE APPROACH THE WEEKEND. CHALLENGING DUE
TO HOW MUCH OF THE INCLEMENT WEATHER THERE WILL BE.
OVER NIGHT ACTIVITY INCLUDED A COUPLE OF DIE HARD THUNDERSTORMS WITH
ONE CLUSTER HAVING FORMED OVER WAIKOLOA OF LEEWARD BIG ISLAND...THEN
SHIFTED INTO THE COASTAL WATERS...AFFECTING THE NORTHERN END OF THE
BIG ISLAND/S LEEWARD WATERS. THE SECOND THUNDERSTORM AFFECTED MAINLY
THE SOUTH END OF THE KAUAI CHANNEL. ANOTHER CELL PASSED SOUTH OF
OAHU. WIDELY SCATTERED SHOWERS...ON THE OTHER HAND...PEPPERED THE
WINDWARD AND MOUNTAIN AREAS OF MOST ISLANDS WITH SOME OF THESE
CLOUD TOPS REACHING 25000 FEET. THESE SHOWERS AND STORMS PRETTY MUCH
ABATED BY 3 AM HST.
THE LATEST INFRARED SATELLITE IMAGERY SHOWS VERY LITTLE LOW LEVEL
CLOUDINESS FROM THE BIG ISLAND WESTWARD. HOWEVER...LURKING JUST
BEYOND THE BIG ISLAND/S EASTERN HORIZON IS AN AREA OF CLOUDS AND
THUNDERSTORMS. THIS IS A PART OF A SURFACE TROUGH THAT WILL REACH
THE BIG ISLAND THIS AFTERNOON. THUNDERSTORMS HAS BEEN REINTRODUCED
INTO THE FORECAST PACKAGE FOR THE BIG ISLAND SINCE IT WILL BE
INTERACTING WITH THE UPPER LEVEL TROUGH THAT IS STILL OVER THE
ISLANDS...ALTHOUGH WEAKER.
WITH THIS SAID...HE SMALLER ISLANDS MAY SEE LIMITED INTERIOR AND
LEEWARD SHOWERS THIS AFTERNOON.
THE SURFACE TROUGH SETTLES ACROSS THE CENTRAL ISLANDS THURSDAY...
REPLACING THE TRADES WITH LIGHT AND VARIABLE WINDS IN THE PROCESS.
THIS WILL LEAD TO SOME SPOTTY AFTERNOON SHOWERS ESPECIALLY OVER
INTERIOR AND LEEWARD AREAS. THESE SHOWERS WILL LIKELY HAVE THE
SUPPORT OF A DEEPER UPPER LEVEL TROUGH. THUS WE ARE LOOKING AT MORE
WIDESPREAD AFTERNOON SHOWERS THURSDAY INTO FRIDAY AND A CONTINUED
SLIGHT CHANCE FOR A THUNDERSTORM OVER THE KONA SLOPES.
THEREAFTER,..THE SURFACE TROUGH SLIDES EAST OF THE BIG ISLAND WITH A
DRIER NORTHERLY WIND FLOW FOLLOWING IN. CONFIDENCE IS VERY LOW WITH
THIS ASSESSMENT HOWEVER. SO STAY TUNE. THIS IS DUE TO THE FACT THAT
THE GFS AND ECMWF KEEP THEIR DIFFERENCES...ESPECIALLY SURFACE WINDS
WHERE THE EC IS ADVERTISING NORTHERLIES...WHICH IS THE PREFERRED
CHOICE...AND THE GFS IS SHOWING SOUTHERLIES.
&&
.AVIATION...
A LIGHT BACKGROUND TRADE WIND FLOW COMBINED WITH MARGINALLY UNSTABLE
ATMOSPHERIC CONDITIONS WILL PREVAIL INTO THIS EVENING. LOCAL NIGHT
TIME LAND BREEZES HAVE RESULTED IN IFR CONDITIONS OVER MOST LAND
AREAS AS OF EARLY THIS MORNING...EXCEPT FOR ISOL MVFR CIG/VIS DUE TO
LOW CLOUDS AND -SHRA ALONG SOME WINDWARD FACING SECTIONS OF THE
ISLANDS. THERE HAVE ALSO BEEN A FEW TSRA OVER COASTAL WATERS SOUTH
OF THE ISLANDS. NOT MUCH CHANGE IS EXPECTED IN THESE CONDITIONS
THROUGH MID-MORNING.
THE DEVELOPMENT OF LOCAL SEA BREEZE CIRCULATIONS OVER THE INDIVIDUAL
ISLANDS STARTING LATE THIS MORNING AND CONTINUING THROUGH THIS
AFTERNOON WILL LIKELY ALLOW TEMPO MVFR CIG/VIS IN SHRA AND ISOL IFR
CIG/VIS IN +SHRA OVER INTERIOR AND LEEWARD PORTIONS OF THE SMALLER
ISLANDS...WITH A SLIGHT CHANCE OF +TSRA OVER THE BIG ISLAND INTERIOR
AND LEEWARD SLOPES. AS DAYTIME HEATING DIMINISHES THIS EVENING...SO
WILL MOST OF THE LOW CLOUDS AND +SHRA...WITH GENERAL CLEARING
EXPECTED OVER MOST LAND AREAS AGAIN LATER TONIGHT AS LOCAL LAND
BREEZES ONCE AGAIN DOMINATE THE CIRCULATION PATTERN NEAR EACH
ISLAND.
&&
.MARINE...
NO CHANGE ON THE MARINE SIDE. THE WINDS WILL BE BELOW SMALL CRAFT
ADVISORY CRITERIA THROUGH THE REST OF THE WEEK. THE CURRENT
NORTHWEST SWELL HAS PEAKED AND WILL BE LOWERING SLOWLY THROUGH
TODAY. ANOTHER MIXED NORTHWEST SWELL IS SLATED TO PEAK DURING THE
WEEKEND. THE GFS MODEL IS HAVING A DIFFICULT TIME RESOLVING THE
EVOLUTION OF THE LOW THAT WILL GENERATE THE WEEKEND SWELL. SINCE
THIS DATA FEEDS INTO THE WAVEWATCH III MODEL...THERE IS SOME
UNCERTAINTY IN THE SIZE OF THE WEEKEND SURF.
&&
.HFO WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
DISCUSSION/MARINE...LAU
AVIATION...HOUSTON