Heavy Rain in Hawaii, April 1 to 3, 2014

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE HONOLULU HI
1040 PM HST MON MAR 31 2014

.UPDATE...
INCREASED CHANCES FOR PRECIPITATION OVER THE BIG
ISLAND...PARTICULARLY OVER THE UPPER WINDWARD SLOPES AND SUMMITS.
ISSUED A WINTER WEATHER ADVISORY THROUGH TUESDAY FOR THE BIG
ISLAND SUMMITS FOR SNOWFALL ACCUMULATION.

&&

.SYNOPSIS...
TRADE WINDS WILL PREVAIL THROUGH THE UPCOMING WEEK...BECOMING BREEZY
WEDNESDAY...THEN DIMINISHING OVER THE WEEKEND. THE ISLAND ATMOSPHERE
WILL BE SOMEWHAT UNSTABLE THROUGH WEDNESDAY MORNING...ALLOWING PASSING
SHOWERS TO BECOME BRIEFLY HEAVY. IN ADDITION...THUNDERSTORMS WILL
BE POSSIBLE OVER THE BIG ISLAND SLOPES THE NEXT COUPLE OF AFTERNOONS.
A DRIER TRADE WIND WEATHER REGIME WILL PREVAIL FOR THE SECOND HALF
OF THE WEEK BEFORE SHOWERS PICK UP AGAIN OVER THE WEEKEND.

&&

.PREV DISCUSSION.../ISSUED 834 PM HST MON MAR 31 2014/

TRADE WINDS ARE PUSHING PERSISTENT MODERATE SHOWERS INTO WINDWARD
BIG ISLAND SLOPES THIS EVENING. WINDWARD SIDES OF THE SMALLER
ISLANDS ALSO HAVE SOME PASSING SHOWERS THIS EVENING BUT THE
SHOWERS ARE A BIT MORE DIFFUSE. ISOLATED SHOWERS ARE ALSO PASSING
ONTO SOME OF THE UPPER LEEWARD SLOPES OF THE SMALLER ISLANDS. ALL
OF THE RAIN IS BEING ENHANCED BY AN UPPER TROUGH TO THE EAST-
NORTHEAST OF THE STATE...AND ANOTHER DIGGING UPPER TROUGH TO THE
NORTHWEST. ABUNDANT MOISTURE NEAR THE SURFACE AND A RELATIVELY
COLD POOL ALOFT PROVIDED BY THE TROUGHS IS PRODUCING SUFFICIENT
INSTABILITY IN THE ATMOSPHERE TO ENHANCE THE SHOWERS...MAKING THEM
A BIT MORE HEAVIER THAN USUAL.

SOUNDINGS FROM THIS AFTERNOON SHOW LITTLE IF ANY INVERSION IN
PLACE OVER THE STATE WITH HIGH PRECIPITABLE WATER VALUES OF 1.78
INCHES AT HILO AND 1.47 INCHES AT LIHUE. RADAR ECHO TOPS SHOW
CLOUD TOPS OF AROUND 20 KFT AT THIS TIME...INDICATIVE OF THE
ENHANCED RAINFALL. EXPECT THE CURRENT WEATHER PATTERN TO CONTINUE
THROUGHOUT THE NIGHT. MINOR PONDING AND FLOODING WILL BE POSSIBLE
ACROSS THE WINDWARD BIG ISLAND...BUT THE TRADE WINDS WILL AID IN
PREVENTING THE SHOWERS FROM LINGERING OVER THE SAME LOCATIONS FOR
TOO LONG AND CAUSING MORE FLOODING PROBLEMS.

THE TROUGHS WILL REMAIN IN THE ISLAND VICINITY THROUGH WEDNESDAY
MORNING...AND TRADE SHOWERS WILL REMAINED ENHANCED AS A RESULT. IN
ADDITION...THE POTENTIAL FOR AFTERNOON THUNDERSTORMS OVER THE
LEEWARD AND INTERIOR BIG ISLAND SLOPES WILL CONTINUE ON TUESDAY.
THE TRADE WINDS WILL ALSO STRENGTHEN TO FRESH TO LOCALLY STRONG
BREEZES BY WEDNESDAY MORNING CONTINUING THROUGH THE WEEKEND.

BY LATE WEDNESDAY...WEAK RIDGING ALOFT WILL PUSH IN FROM THE WEST AND
SHOWER INTENSITY AND COVERAGE IS EXPECTED TO DIMINISH FOR THE
SECOND HALF OF THE WEEK.

ANOTHER ROUND OF UNSETTLED WEATHER IS EXPECTED THIS WEEKEND AS A
FRONT MOVES ACROSS THE STATE. AN ASSOCIATED UPPER TROUGH WILL ALSO
PASS TO THE NORTH OF THE STATE. MODELS ARE HAVE SOME CONSISTENCY
ISSUES WITH THIS SYSTEM AND WILL RE-ASSES THE SITUATION TONIGHT
WITH THE LONG RANGE MODELS.

&&

.AVIATION...
ENHANCED SHOWER ACTIVITY ASSOCIATED WITH A TROUGH ALOFT LOCATED JUST TO THE
EAST OF THE ISLANDS IS EXPECTED TO PERSIST THROUGH WEDNESDAY MORNING.
LOWEST CEILINGS AND VISIBILITIES ARE EXPECTED ALONG WINDWARD COASTS
AND SLOPES...ESPECIALLY THOSE OF THE BIG ISLAND. AIRMET SIERRA FOR
MTN OBSC WILL LIKELY BE EXTENDED THROUGH AT LEAST TUESDAY MORNING.
THUNDERSTORMS ARE LIKELY TO REDEVELOP ALONG BIG ISLAND WINDWARD
SLOPES TUESDAY AFTERNOON.

&&

.MARINE...
A MODERATE NW SWELL IS EXPECTED TO BUILD WEDNESDAY NIGHT AND PEAK
BELOW ADVISORY LEVELS THURSDAY. A STORM FORCE LOW EAST OF JAPAN
WILL GENERATES A WEST-NORTHWEST SWELL THAT ARRIVES BY THE END OF THE
WEEK...WITH PEAK SURF HEIGHTS AT ADVISORY LEVELS ALONG NORTH AND
WEST FACING SHORES SATURDAY. A PULSE OF SWELL FROM THE SOUTH IS ALSO
EXPECTED FROM WEDNESDAY THROUGH FRIDAY.

GRADUALLY STRENGTHENING TRADE WINDS OVER THE NEXT FEW DAYS WILL
BRING SMALL CRAFT ADVISORY /SCA/ CONDITIONS FOR THE
THE WINDY ZONES AROUND MAUI AND THE BIG ISLAND BY TUESDAY
NIGHT...WITH THE POTENTIAL FOR SCA WINDS/SEAS TO SPREAD TO MOST
OTHER ZONES FROM WEDNESDAY THROUGH SATURDAY AS A LONG FETCH OF
FRESH TRADE WINDS EXTENDS E FROM THE ISLANDS. THIS FETCH COULD
RESULT IN SURF ALONG E FACING SHORES REACHING ADVISORY LEVELS
AROUND THE MIDDLE OF THE WEEK.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY UNTIL 6 PM HST TUESDAY FOR BIG ISLAND
SUMMITS.

&&

UPDATE/DISCUSSION/MARINE...FOSTER
AVIATION...BEDAL