High Surf Warning 10, NWS Honolulu, HI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
400 AM HST TUE NOV 12 2013

.SYNOPSIS...
A COOL NORTHEASTERLY FLOW WILL FOCUS LOW CLOUDS AND SHOWERS MAINLY
OVER NORTH AND NORTHEAST FACING SLOPES OF THE SMALLER HAWAIIAN
ISLANDS TODAY. WET AND SLIGHTLY UNSTABLE CONDITIONS ARE EXPECTED TO
LINGER OVER PARTS OF THE BIG ISLAND. OUR WINDS ARE FORECAST TO
WEAKEN ON WEDNESDAY...WITH LOW CLOUDS AND SHOWERS SPREADING SLOWLY
WESTWARD FROM THE BIG ISLAND TO THE WESTERN END OF THE ISLAND CHAIN
DURING THE SECOND HALF OF THE WORK WEEK. A LARGE NORTH SWELL
ARRIVING LATER TONIGHT IS EXPECTED TO PRODUCE SIGNIFICANT SURF ALONG
MOST NORTH AND EAST FACING SHORES OF THE ISLAND CHAIN THROUGH
MID-WEEK.

&&

.DISCUSSION...
A STRONG 1047 MB SURFACE HIGH LOCATED FAR NORTHWEST OF THE MAIN
HAWAIIAN ISLANDS IS MOVING SLOWLY TOWARD THE SOUTH. HOWEVER...THE
LOCAL PRESSURE GRADIENT SOUTH OF THIS HIGH IS BEING PARTIALLY
DISRUPTED BY A STORM LOW LOCATED ABOUT 850 MILES NORTH NORTHEAST OF
HONOLULU. AS A RESULT...THE GUSTY NORTHEASTERLY WINDS WE HAVE BEEN
EXPERIENCING DURING THE PAST COUPLE OF DAYS HAVE DIMINISHED
OVERNIGHT. THE LEADING EDGE OF A FRONTAL BAND IS LOCATED ABOUT 120
MILES NORTH NORTHWEST OF LIHUE. THIS 60 MILE WIDE BAND IS MOVING
TOWARD THE SOUTH SOUTHEAST AT LESS THAN 20 MPH. ELSEWHERE...THE
REMNANT CLOUD AND SHOWER BAND ASSOCIATED WITH A FORMER SHEAR LINE
ARE LOCATED SOUTHEAST OF THE BIG ISLAND.

ALOFT...WATER VAPOR IMAGERY SHOWS THE AXIS OF A BROAD UPPER LEVEL
TROUGH EXTENDING FROM NEAR 35N 155W THROUGH A POINT ABOUT 340 MILES
WEST NORTHWEST OF LIHUE. THIS TROUGH ALOFT IS PROPAGATING SLOWLY
EASTWARD. THERE IS ALSO A MID-LEVEL TROUGH OVER THE MAIN HAWAIIAN
ISLAND CHAIN. WATER VAPOR IMAGERY INDICATES THERE IS SIGNIFICANT
SUBSIDENCE ALOFT OVER ALL OF THE SMALLER HAWAIIAN ISLANDS...WHICH IS
CONTRIBUTING TO THE STABLE ATMOSPHERIC CONDITIONS WEST OF THE BIG
ISLAND. THE MID- AND UPPER LEVEL TROUGHING HAVE ALLOWED A SMALL LINE
OF CLOUDS...HEAVY SHOWERS AND EVEN A THUNDERSTORM TO DEVELOP NEAR
KAILUA-KONA ALONG THE LEEWARD BIG ISLAND COAST DURING THE PAST HOUR.

NOTE THAT THE MID-LEVEL TROUGH HAS BEEN PRODUCING STRONG
SOUTHWESTERLY WINDS ON THE HIGHEST SUMMITS OF THE BIG ISLAND.
HOWEVER...THE WINDS ON THE SUMMITS DROPPED BELOW THE WIND ADVISORY
CRITERIA EARLIER THIS MORNING...SO THE WIND ADVISORY HAS BEEN
CANCELLED.

DIMINISHING AMOUNTS OF MOISTURE FROM THE FORMER SHEAR LINE WILL
LIKELY REMAIN IN THE VICINITY OF THE BIG ISLAND THROUGH TODAY.
THEREFORE...EXPECT CONTINUED SHOWERS ALONG WINDWARD FACING SLOPES OF
THE BIG ISLAND TODAY. THE MID- AND UPPER LEVEL TROUGHING WILL
MAINTAIN SLIGHT INSTABILITY OVER THE BIG ISLAND...SO LEEWARD SLOPES
WILL CONTINUE TO SEE AFTERNOON AND EVENING CLOUDS AND SHOWERS.

THE COOL AND DRY NORTHEASTERLY FLOW WILL CONTINUE TO DOMINATE THE
WEATHER OVER THE SMALLER ISLANDS...WHERE PRECIPITABLE WATER /PW/
VALUES ARE NEAR ONE INCH...AND SURFACE DEW POINTS RANGE FROM THE MID
50/S TO NEAR 60. THE APPROACHING FRONTAL BAND WILL LIKELY INCREASE
LOW CLOUDS AND SHOWERS ONCE IT ARRIVES. THEREFORE...SOME CLOUDS AND
LIGHT SHOWERS WILL LIKELY CONTINUE ALONG NORTH AND NORTHEAST FACING
SLOPES OF THE SMALLER ISLANDS INTO MID-WEEK. GENERALLY CLEAR
CONDITIONS ARE EXPECTED OVER MOST LEEWARD SECTIONS OF THE SMALLER
ISLANDS. NOTE THAT THE REMNANTS OF THE FRONT MAY ALSO CAUSE A BRIEF
INCREASE IN THE WINDS IN THE VICINITY OF KAUAI AND OAHU FROM LATER
THIS MORNING INTO THIS AFTERNOON.

THE WINDS ALONG THE EASTERN PERIPHERY OF THE MID-LEVEL TROUGH...
WHICH IS EXPECTED TO SLOWLY RETROGRADE...WILL LIKELY INCREASE AGAIN
OVER THE BIG ISLAND SUMMITS. IF SO...EXPECT A SIGNIFICANT INCREASE
IN WIND SPEEDS ON THE BIG ISLAND SUMMITS BY WEDNESDAY...SO THE
CURRENT FORECAST SHOWS WINDS NEAR THE WIND ADVISORY CRITERIA THAT
DAY. NOTE...THE SUMMIT WINDS MAY REACH THE HIGH WIND WARNING
THRESHOLD...SO MONITOR FUTURE FORECASTS FOR UPDATES ON THE MOUNTAIN
TOP WIND SPEEDS.

ANOTHER ROUND OF WET WEATHER IS POSSIBLE OVER PARTS OF THE ALOHA
STATE FROM LATE WEDNESDAY THROUGH THE END OF THE WORK WEEK AS THE
MID-LEVEL TROUGH REMAINS NEAR THE ISLANDS. THE REMNANT MOISTURE
ASSOCIATED WITH THE FORMER SHEAR LINE...WHICH IS NOW NEAR THE
SOUTHEASTERN BIG ISLAND...IS EXPECTED TO START SLOWLY SHIFTING BACK
OVER THE ISLANDS. BASED ON THE LATEST GUIDANCE...IT APPEARS THE
HIGHEST CHANCES FOR RAINFALL WILL BE ON THE BIG ISLAND AND MAUI FROM
WEDNESDAY NIGHT INTO THURSDAY. THIS RAINFALL MAY THEN SHIFT TO THE
CENTRAL ISLANDS...INCLUDING OAHU...BY THURSDAY NIGHT AND FRIDAY.
CURRENTLY...THE STRONGEST DYNAMICS WILL BE LOCATED TO THE NORTHEAST
OF THE ISLANDS...SO WE DO NOT HAVE ENOUGH CONFIDENCE TO MENTION
HEAVY SHOWERS IN THE FORECAST AT THIS TIME.

&&

.AVIATION...
LARGE...STRONG SURFACE HIGH REMAINS CENTERED ABOUT 1500 MILES NNW OF
THE STATE. A SURFACE LOW CURRENTLY 825 NM N OF HONOLULU WILL MEANDER
IN THAT AREA TODAY. RESULTANT NORTHERLY WINDS ARE SENDING SPORADIC
BATCHES OF LOW CLOUDS DOWN INTO THE STATE WHICH WILL AFFECT MAINLY
KAUAI AND OAHU WITH SOME MVFR CEILINGS ALONG THE NORTH COASTS AND
SLOPES. SOME OF THESE CLOUDS ARE ALIGNED WITHIN A WEAK FRONTAL
BOUNDARY ASSOCIATED WITH THE LOW. THIS WEAK FRONTAL CLOUD BAND IS
CURRENTLY 125 NM NORTH OF KAUAI AND MOVING SOUTH NEAR 20 MILES AN
HOUR.

THE BIG ISLAND SHOULD SEE A MIXTURE OF HIGH AND LOW CLOUDS DUE TO A
JETSTREAM FLOWING OVERHEAD FROM SOUTHWEST TO NORTHEAST THROUGH
TODAY. THE JET ALOFT WILL PRODUCE CREATE MORE INSTABILITY OVER THAT
ISLAND THROUGH TODAY.

&&

.MARINE...
THE SMALL CRAFT ADVISORY /SCA/ HAS BEEN CANCELLED SINCE WINDS AND
SEAS HAVE DROPPED BELOW THE SCA CRITERIA OVER ALL HAWAIIAN WATERS. A
SCA WILL LIKELY BE ISSUED LATER TODAY FOR ALL HAWAIIAN WATERS DUE
TO A LARGE NORTH SWELL THAT WILL BE BUILDING ACROSS THE AREA LATER
THIS EVENING.

A STORM LOW LOCATED NORTH OF THE ISLANDS HAS BEEN MOVING SLOWLY
SOUTHWARD SINCE YESTERDAY. AS A RESULT...THE CAPTURED FETCH ALONG
THE WESTERN CIRCULATION AROUND THIS STORM LOW WILL SEND A VERY LARGE
NORTH SWELL TOWARD THE ISLANDS. BASED ON THE LATEST OUTPUT FROM THE
WAVE WATCH III MODEL...THIS SWELL MAY GENERATE SURF NEAR THE HIGH
SURF WARNING CRITERIA ALONG NORTH AND EAST FACING BEACHES OF MOST
ISLANDS FROM LATE TONIGHT THROUGH WEDNESDAY. THIS SWELL WILL ALSO
LIKELY CAUSE HARBOR SURGES...ALONG WITH THE POSSIBILITY OF LARGE
BREAKING WAVES IN CHANNEL ENTRANCES...OF NORTH FACING HARBORS SUCH
AS KAHULUI AND HILO. THIS NORTH SWELL WILL SLOWLY DROP FROM THURSDAY
INTO THIS WEEKEND.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

DISCUSSION/MARINE...HOUSTON
AVIATION...FUJII