High Surf in Hawaii, March 30 to 31, 2011

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
340 AM HST WED MAR 30 2011

.SYNOPSIS...
A SURFACE RIDGE NORTH OF THE STATE WILL MAINTAIN LOCALLY BREEZY
TRADE WINDS THROUGH THE WEEK. WINDS ARE EXPECTED TO GRADUALLY SHIFT
TO EAST-SOUTHEASTERLY ACROSS THE SMALLER ISLANDS DURING THE
WEEKEND...AS A WEATHER SYSTEM APPROACHES FROM THE NORTHWEST. THIS
SYSTEM WILL BRING THE THREAT OF LOCALLY HEAVY RAINFALL AND CHANCE
FOR THUNDERSTORMS NEXT WEEK.

&&

.DISCUSSION...
DIDNT MAKE ANY BIG CHANGES TO THE ONGOING FORECAST REASONING. E
TRADES WILL PERSIST WITH ISOLATED TO SCATTERED SHOWERS ALONG
WINDWARD TERRAIN INTO THE WEEKEND. INCREASING SUBSIDENCE OVER THE
STATE WILL STRENGTHEN/LOWER THE INVERSION FURTHER LIMITING SHOWER
DEVELOPMENT KEEPING IT FOCUSED ON WINDWARD TERRAIN THU-FRI. A
DEVELOPING CENTRAL NPAC SHORT WAVE TROUGH WILL DRIVE A SFC COLD
FRONT TOWARDS HAWAII FRI INTO THE WEEKEND. THIS WILL DISPLACE THE
SFC RIDGE TO OUR N CLOSER TO THE STATE VEERING THE TRADE WINDS AND
THE LOW LEVEL FLOW ESE SAT-SUN. THIS WILL ALLOW FOR SHALLOW
AFTERNOON CLOUDS AND A FEW LIGHT SHOWERS FOR LEEWARD SECTIONS EACH
AFTERNOON WITH SCATTERED POPS FOR WINDWARD TERRAIN...HIGHEST AT
NIGHT. DID MAKE SOME MINOR ADJUSTMENTS TO THE WEEKEND GRIDS TO
REFLECT THIS...BUT OVERALL CHANGES WERE QUITE MINOR WITH BENIGN
WEATHER EXPECTED THROUGH SUN.

GLOBAL SOLUTIONS STILL HAVE THE SAME FLAVOR FOR NEXT WEEK WITH
SIGNIFICANT HEIGHT FALLS AND INCREASED CYCLONIC FLOW ALOFT MON-WED
AS A MID/UPR LEVEL DISTURBANCE DEVELOPS. HAVE MODERATE CONFIDENCE IN
A WETTER PATTERN OVERALL...HOWEVER PREDICTABILITY IN THE EVENTUAL
INTENSITY OF THE LOW ALOFT AND SURFACE REFLECTION REMAIN LOW SO ITS
DIFFICULT TO MAKE LASTING CHANGES TO THE GRIDS. KEPT CHANGES BROAD
AND WILL FINE TUNE THINGS AS THE FORECAST EVOLVES. MAINTAINED E
FLOW WITH SLIGHT HINTS OF A SFC TROF IN THE VICINITY MON-WED AND
INCREASE POPS SLIGHTLY TO ACCOUNT FOR THE STRONG SIGNALS OF A
MID/UPR LOW. ALSO COVERED A WIDER AREA FOR SLIGHT CHANCE OF
TSTORMS FOR THE SAME TIME FRAME GIVEN THE UNCERTAINTY IN THE
ORIENTATION/LOCATION OF THE MID LEVEL COLD POOL AND DYNAMICS.

&&

.PREVIOUS DISCUSSION.../ISSUED 755 PM HST TUE EVENING MAR 29/
TRADES WILL KEEP SHOWERS FOCUSED ON WINDWARD TERRAIN OVERNIGHT. THE
30/00Z PHTO SOUNDING DEPICTS A HIGHER WEAKER INVERSION AND SLIGHTLY
DEEPER MOISTURE IN THE VICINITY AND S OF THE BIG ISLAND. COOLER
TEMPS ALOFT BETWEEN TWO UPPER LOWS IS KEEPING THE INVERSION
LIFTED/WEAK. POPS WILL REMAIN HIGHEST ALONG THE WINDWARD BIG ISLAND
OVERNIGHT WITH A SLIGHT DIURNAL INCREASE OVERNIGHT FOR THE ENTIRE
STATE. AS INCREASING SUBSIDENCE ASSOCIATED WITH A STRENGTHENING MID
LEVEL RIDGE SETTLES OVER THE AREA...STABLE TRADE WEATHER WILL
PREVAIL INTO THE WEEKEND. WILL BE ISSUING A ZONE UPDATE FOR THE
HEADLINES AS WE WILL BE ADDING EXPOSED N AND W FACING SHORES OF MAUI
COUNTY TO THE HIGH SURF ADVISORY. PLEASE SEE THE DETAILS BELOW.

A POTENT SHORT WAVE TROUGH MOVING OFF THE NE ASIAN COAST WILL
AMPLIFY NPAC FLOW INTO THE WEEKEND. THIS WILL DRIVE A FRONT TO
WITHIN A FEW HUNDRED MILES NW OF KAUAI BY SUN NIGHT. THE FALLING
HEIGHTS/PRESSURES NW OF THE AREA WILL EASE AND VEER THE LLVL FLOW
ESE OVER THE WEEKEND. THIS MAY ALLOW FORA AFTERNOON LEEWARD CLOUDS
AND ISOLATED LIGHT SHOWERS. OVERALL THE WEATHER LOOKS BENIGN THROUGH
THE WEEKEND.

GLOBAL SOLUTIONS BEGIN TO DIVERGE SUN NIGHT. GFS/ECMWF SUGGEST
FALLING HEIGHTS AND STRONG CYCLONIC FLOW ALOFT ASSOCIATED WITH A
DEVELOPING UPPER TROUGH OR CLOSED LOW MON-WED. REGARDLESS OF THE
DIFFERENCES YET TO BE RESOLVED THE LARGE SCALE PATTERN DOES SIGNAL
WETTER WEATHER NEXT WEEK. GIVEN HIGH UNCERTAINTY...WILL KEEP THE
GRIDS ON THE WETTER SIDE FOR MOST OF THE AREA NEXT WEEK WITH ERLY
FLOW PREVAILING AT THE SURFACE.

&&

.MARINE...
WNW SWELL IS SHOWING ON BUOY 51101 ON TIME. VERY LARGE SURF...NEAR
WARNING LEVELS...WILL BUILD ACROSS THE STATE FROM KAUAI TO MAUI
COUNTY TODAY...THEN PERSIST THROUGH THU BEFORE DROPPING THU NIGHT.
THE SWELL HAS A STRONG W COMPONENT SO THE SWELL WILL PRODUCE HIGH
SURF ALONG THE KONA COAST OF THE BIG ISLAND. THE SURF WILL BEGIN
BUILDING THERE LATE TODAY LIKELY PRODUCING SURF OF 8 FT OR GREATER
BEFORE SUNRISE THU MORNING THROUGH SOMETIME FRI AFTERNOON. WILL
CARRY THIS PORTION OF THE ADVISORY THROUGH 6 PM HST FRI.

THE SMALL CRAFT ADVISORY HAS BEEN EXPANDED TO ALL COASTAL ZONES DUE
TO THE INCOMING WNW SWELL WHICH WILL BOOST COMBINED SEAS TO 10 FT OR
GREATER. WINDS WILL ALSO REMAIN AT SCA CRITERIA AT LEAST THROUGH
TODAY.

&&

.AVIATION...
AT THE TERMINALS...VFR CONDITIONS WILL BE THE RULE...WITH ONLY BRIEF
MVFR CIGS/VIS EXPECTED AT WINDWARD SITES PHLI AND PHTO...DUE TO
PASSING SHRA. THE ONLY OTHER EXCEPTION IS LANAI...WHERE SEA BREEZE
CONVERGENCE WILL LIKELY LEAD TO MVFR CIGS FROM LATE MORNING THROUGH
MID-AFTERNOON TODAY.

NO AIRMETS ARE CURRENTLY IN EFFECT. TRADE WINDS ARE LIGHT ENOUGH
THAT AN AIRMET FOR LOW LEVEL TURB IS NOT REQUIRED...AND THE EARLIER
AIRMET FOR TURB ALOFT NEAR THE BIG ISLAND HAS BEEN CANCELLED.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
HIGH SURF ADVISORY FROM NOON TODAY TO 6 AM HST FRIDAY FOR NIIHAU-
KAUAI WINDWARD-KAUAI LEEWARD-WAIANAE COAST-OAHU NORTH SHORE-OAHU
KOOLAU-MOLOKAI-MAUI WINDWARD WEST-WINDWARD HALEAKALA.

HIGH SURF ADVISORY FROM 2 AM THURSDAY TO 6 PM HST FRIDAY FOR
KONA.

SMALL CRAFT ADVISORY UNTIL 6 AM HST FRIDAY FOR MAALAEA BAY-
PAILOLO CHANNEL-ALENUIHAHA CHANNEL-BIG ISLAND LEEWARD WATERS-BIG
ISLAND SOUTHEAST WATERS.

SMALL CRAFT ADVISORY FROM NOON TODAY TO 6 AM HST FRIDAY FOR
KAUAI NORTHWEST WATERS-KAUAI WINDWARD WATERS-KAUAI LEEWARD
WATERS-KAUAI CHANNEL-OAHU WINDWARD WATERS-OAHU LEEWARD WATERS-
KAIWI CHANNEL-MAUI COUNTY WINDWARD WATERS-MAUI COUNTY LEEWARD
WATERS-BIG ISLAND WINDWARD WATERS.

&&

PUBLIC...DEJESUS
MARINE...DEJESUS
AVIATION...BIRCHARD