High Surf Advisory 40, NWS Honolulu, HI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
1000 AM HST WED NOV 9 2011

.SYNOPSIS...
SHOWERS WILL DIMINISH BY AFTERNOON ACROSS THE SMALLER ISLANDS...
ALTHOUGH A SLIGHT CHANCE OF THUNDERSTORMS WILL REMAIN ALONG THE KONA
SLOPES OF THE BIG ISLAND THIS AFTERNOON. MAINLY WINDWARD AND MAUKA
SHOWERS WILL PREVAIL THURSDAY. ANOTHER ROUND OF UNSETTLED WEATHER IS
EXPECTED THURSDAY NIGHT AND FRIDAY. BUILDING HIGH PRESSURE WILL KEEP
THE TRADES STRONG FOR THE REMAINDER OF THIS WEEK.

&&

.DISCUSSION...
WATER VAPOR IMAGERY SHOWS A SHARP UPPER LEVEL TROUGH OVER THE
EASTERN HALF OF THE STATE...WITH A SHORTWAVE SOUTHWEST OF KAUAI
DIGGING DOWN BACK SIDE OF THE TROUGH. 12Z SOUNDINGS FROM HILO AND
LIHUE SHOW AN UNSTABLE AIRMASS ACROSS THE ISLANDS. THE LIHUE
SOUNDING IS THE MOST UNSTABLE...WITH OVER 1000 J/KG CAPE AND LITTLE
CIN FROM AN UNMODIFIED SURFACE PARCEL. PRECIPITABLE WATERS FROM THE
SOUNDINGS ARE JUST OVER 1.3 INCHES. THE EARLY MORNING AMSU/SSMI
IMAGERY SHOWS SIMILAR PW VALUES EXTENDING EAST OF THE BIG ISLAND...
BUT DRIER AIR WITH PW VALUES NEAR 1 INCH IS LOCATED WITHIN 100 MILES
NORTH OF THE SMALLER ISLANDS. ANOTHER BAND OF HIGHER MOISTURE IS
LOCATED ABOUT 400-500 MILES NORTHEAST OF THE STATE.

RADAR AND SATELLITE IMAGERY SHOW SHOWERS DIMINISHING ACROSS MAUI
COUNTY AND OAHU...AND STARTING TO DIMINISH ACROSS KAUAI...AS DRIER
AIR NORTH OF THE AREA MOVES ACROSS THE ISLANDS. BANDS OF SHOWERY LOW
CLOUDS CONTINUE TO FEED INTO THE BIG ISLAND...AND SHOWERS WILL
REMAIN ACTIVE ACROSS WINDWARD SECTIONS. WITH THE UNSTABLE AIRMASS...
AFTERNOON CONVECTION IS EXPECTED ACROSS LEEWARD SLOPES OF THE BIG
ISLAND...AND A SLIGHT CHANCE OF THUNDERSTORMS WILL REMAIN IN PLACE
FOR LEEWARD BIG ISLAND.

FORECAST SOUNDINGS FROM THE GFS SHOW THE DRYING OCCURING DURING THE
DAY...AND A WEAK INVERSION DEVELOPING. THIS INVERSION WEAKENS AND
BECOMES MORE ELEVATED DURING THE DAY ON THURSDAY...AS LOW LEVELS
START TO MOISTEN AGAIN. THE GREATER MOISTURE WILL MOVE THROUGH
THURSDAY NIGHT/FRIDAY. THE UPPER LOW IS FORECAST TO REMAIN OVER THE
STATE...AND MID-LEVELS ACTUALLY COOL BY A DEGREE OR SO AS THE LOW
SHIFTS WESTWARD OVER THE ISLANDS. THE COMBINATION OF MOISTURE AND
UNSTABLE CONDITIONS WILL LEAD TO GREATER SHOWER COVERAGE AND
INTENSITY. IN ADDITION TO GREATER POPS/QPF...THERE IS A POSSIBILITY
OF THUNDERSTORMS AGAIN FOR THURSDAY NIGHT AND FRIDAY.

HIGH PRESSURE FAR NORTH OF THE STATE WILL KEEP STRONG TRADE WINDS
OVER THE ISLANDS THIS WEEK. RADAR VAD WIND PROFILES AND ACARS
SOUNDINGS INTO HONOLULU SHOW UP TO 30 KNOTS OF WIND IN THE
LOW-LEVELS. LOCATIONS EXPOSED TO A FUNNELING UNDER A NORTHEAST WIND
/SUCH AS LANAI/ WILL BE QUITE GUSTY. THIS TIGHT GRADIENT AND
CONSEQUENTLY THE STRONG AND GUSTY WINDS WILL CONTINUE THROUGH THE
WORK WEEK...THEN BEGIN TO DIMINISH OVER THE WEEKEND.

OVER THE WEEKEND...THE UPPER LOW NEAR THE STATE WILL SLOWLY MOVE
NORTHEAST...ALLOWING CONDITIONS OVER THE ISLANDS TO STABILIZE
SOMEWHAT. FORECAST SOUNDINGS SHOW A WEAK INVERSION DEVELOPING FRIDAY
NIGHT...ALTHOUGH LOW-LEVELS REMAIN RATHER SATURATED. SHOWER COVERAGE
WILL REMAIN HIGHER THAN NORMAL ON SATURDAY...THEN DIMINISH TO MORE
NORMAL LEVELS FOR SUNDAY INTO NEXT WEEK. WITH TRADE WINDS WEAKENING
TO MORE MODERATE LEVELS...RAINFALL WILL STILL BE FOCUSED MAINLY
ACROSS WINDWARD AND MAUKA AREAS.

&&

.AVIATION...
DUE TO STRONG TRADE WINDS...AIRMET TANGO REMAINS IN PLACE FOR LOW
LEVEL TURBULENCE BLW 100...S AND W OF THE TERRAIN ON ALL ISLANDS.
ALTHOUGH THE TYPICAL LOW LEVEL INVERSION IS NON-EXISTENT...THE
AIRMET WILL REMAIN IN EFFECT AS TRADES WILL BE ESPECIALLY STRONG
THROUGH THURSDAY. AIRMET SIERRA IS CURRENTLY IN EFFECT FOR MT OBSC
OVER THE NE FACING SLOPES OF THE BIG ISLAND...BUT IMPROVING
CONDITIONS WILL LIKELY ALLOW IT TO BE DROPPED BY THIS AFTERNOON.

DRIER AIR MOVING OVER MOST ISLANDS WILL MEAN A DECREASE IN SHRA...
AND THE MAJORITY OF THE TERMINALS WILL HAVE VFR CONDITIONS. BRIEF
MVFR CIGS/VIS WILL AFFECT PHTO THROUGH THE MORNING...WITH IMPROVING
CONDITIONS EXPECTED BY THIS AFTERNOON.

&&

.MARINE...
A SMALL CRAFT ADVISORY REMAINS IN EFFECT FOR ALL COASTAL WATERS DUE
TO THE STRONG WINDS OF 25 KNOTS OR GREATER AND COMBINED SEAS OF 10
FT OR GREATER. WINDS ARE STRONGEST THROUGH THE PAILOLO AND
ALENUIHAHA CHANNELS...WHERE FUNNELED WINDS MAY LEAD TO GALE FORCE
WIND GUSTS. THESE CONDITIONS WILL CONTINUE THROUGH THURSDAY BEFORE
STARTING TO SLOWLY DIMINISH.

SURF OBSERVATIONS FROM KAUAI CAME IN AT 4-8 FEET FOR EAST FACING
SHORES. COMBINED SEAS AT THE MOKAPU BUOY HAVE ALSO RAMPED UP ANOTHER
2 FEET THIS MORNING. WITH THE TRADE SWELL EXPECTED TO BUILD FURTHER
THROUGH THURSDAY...IN ADDITION TO A LONGER PERIOD NORTH-NORTHEAST
SWELL EXPECTED ON FRIDAY...WE WILL UPDATE TO ISSUE A HIGH SURF
ADVISORY FOR EAST FACING SHORES.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
SMALL CRAFT ADVISORY THROUGH THURSDAY AFTERNOON FOR ALL HAWAIIAN
WATERS.

HIGH SURF ADVISORY THROUGH SATURDAY AFTERNOON FOR EAST FACING SHORES
OF KAUAI...OAHU...MOLOKAI...MAUI..AND THE BIG ISLAND.
&&

PUBLIC/MARINE...BRAVENDER
AVIATION...BIRCHARD