Area Forecast Discussion
Issued by NWS Honolulu, HI

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FXHW60 PHFO 202343
AFDHFO

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE HONOLULU HI
143 PM HST SUN APR 20 2014

.UPDATE...
UPDATED FOR HIGH SURF ADVISORY IN WWA BLOCK AT THE BOTTOM.

&&

.SYNOPSIS...
TRADE WINDS WILL INCREASE TODAY AND TONIGHT...THEN REMAIN STRONG
ON MONDAY...BEFORE DROPPING BACK TO MODERATE LEVELS BY MIDWEEK.
SHOWERS WILL CONTINUE TO FOCUS ACROSS WINDWARD AND MAUKA
AREAS...WITH SHOWERS SPILLING OVER INTO SOME LEEWARD AREAS AS
WELL.

&&

.DISCUSSION...
MAIN CONCERNS FOR THIS FORECAST CENTER ON STRENGTH OF THE TRADE
WINDS. ALTHOUGH MOST AREAS REMAIN WELL BELOW ADVISORY CRITERIA AS
OF MID-MORNING...KAMUELA AIRPORT DID REPORT A SUSTAINED WIND OF 26
KT EARLIER. A 1032 MB HIGH ANALYZED 850 MILES N OF KAUAI AT 12Z
IS FORECAST TO SLIDE SLOWLY ESE AND REMAIN NEAR ITS CURRENT
INTENSITY OVER THE NEXT COUPLE OF DAYS. AT THE SAME TIME...RIDGING
ALOFT IS EXPECTED TO BUILD OVER THE HIGH TONIGHT AND TOMORROW. THE
GUIDANCE RESPONDS TO THIS UPSTREAM RIDGING BY LOWERING AND
STRENGTHENING THE INVERSION A TAD OVER THE ISLANDS. MOS GUIDANCE
REFLECTS WINDS ABOUT 2 TO 4 KT STRONGER ACROSS THE STATE TONIGHT
AND MONDAY THAN TODAY...AND THE HIGH RES MODEL CROSS SECTIONS SHOW
STRONGER WINDS AT 925 MB AND 850 MB...SO CONFIDENCE IN REACHING
ADVISORY CRITERIA IN SELECT LOCATIONS IS A BIT HIGHER DURING THAT
TIME.

A FAIRLY TYPICAL DISTRIBUTION OF LOW CLOUDS AND SHOWERS IS SEEN
IN THE VISIBLE SATELLITE IMAGERY. THE GUIDANCE INDICATES WE WILL
CONTINUE TO SEE TYPICAL TRADE WIND SHOWERS OVER WINDWARD AND MAUKA
AREAS...EASILY SPILLING OVER TO ADJACENT AREAS TO THE LEE OF THE
SMALLER MOUNTAINS...FOR THE NEXT COUPLE OF DAYS. RAINFALL AMOUNTS
OVERALL WILL BE ON THE LIGHT SIDE...WITH SOMEWHAT HIGHER TOTALS
OVER WINDWARD BIG ISLAND WHERE OROGRAPHIC FORCING IS MAXIMIZED
DURING TRADES.

NOT MUCH CHANGE IS EXPECTED THIS WEEK. THE CURRENT HIGH WILL SLIDE
OFF TO THE EAST AWAY FROM THE ISLANDS AND THE WINDS WILL MODERATE
A BIT. A NEW HIGH...A BIT WEAKER THAN THE CURRENT ONE...WILL PASS
NORTH OF THE ISLANDS DURING THE MIDDLE OF THE WEEK...KEEPING THE
TRADES FAIRLY BREEZY. AFTER THE SLIGHTLY HIGHER INVERSION HEIGHTS
YIELDING EXTRA CLOUDS AND SHOWERS TODAY...THE MULTI-MODEL ENSEMBLE
IS SHOWING NEAR-NORMAL INVERSION HEIGHTS RETURNING AND SLIGHTLY
WARMER THAN NORMAL MID-LEVEL TEMPERATURES THROUGH THE WEEK...SO
SHOWERS SHOULD BECOME A LITTLE MORE SCARCE ONCE AGAIN.

&&

AVIATION...
MODERATE TO STRONG TRADE WINDS FROM SFC TO ABOUT 10 KFT WITH
SUBSIDENCE INVERSIONS BETWEEN 5 KFT AND 8 KFT ALOFT EXPECTED
THROUGH 24 HOURS AND BEYOND. WILL BE KEEPING AIRMET TANGO FOR MT
WAVE TURB TO THE LEE OF ALL ISLANDS IN EFFECT INDEFINITELY.

CLOUDS AND SHOWERS WILL FAVOR THE TYPICAL WINDWARD AND MOUNTAIN
AREAS TODAY AND TONIGHT WITH A FEW OF THESE SHOWERS DRIFTING INTO
THE LEEWARD PORTIONS OF THE SMALLER ISLANDS. MVFR CIGS IN SHOWERS
ARE PRESENTLY ISOLATED BUT TREND IS FOR INCREASED MOISTURE IN THE
LOWER LEVELS SO AN AIRMET FOR MT OBSC FOR NE SECTIONS OF ALL ISLANDS
COULD BECOME NECESSARY THIS AFTERNOON OR EVENING. WILL NEED TO
MONITOR CLOSELY.

WEAK SEA BREEZES...AND SEA BREEZE DRIVEN VFR CLOUDS AND SHOWERS...
ARE EXPECTED ALONG THE KONA COAST THIS AFTERNOON AND EARLY
EVENING.

&&

.MARINE...
WINDS ARE EXPECTED TO INCREASE TO SMALL CRAFT ADVISORY /SCA/
LEVELS EVERYWHERE LATER TODAY. THERE IS THE POSSIBILITY WINDS
COULD REACH GALE FORCE IN THE ALENUIHAHA CHANNEL TONIGHT OR
MONDAY...AND WE WILL BE KEEPING AN EYE ON THIS.

STRENGTHENING TRADE WINDS WILL PRODUCE SHORT PERIOD...CHOPPY SURF
ALONG EAST FACING SHORES...LIKELY REACHING ADVISORY LEVELS FOR
MONDAY THROUGH TUESDAY. OTHERWISE...A SMALL TO MODERATE NORTHWEST
SWELL WILL CONTINUE TODAY...THEN DECLINE TONIGHT AND MONDAY.
ANOTHER MODERATE NORTHWEST SWELL IS EXPECTED TO ARRIVE WEDNESDAY...
PEAK ON THURSDAY...THEN SLOWLY DECLINE ON FRIDAY. RESULTING SURF
ON NORTH AND WEST FACING SHORES WILL REMAIN WELL BELOW ADVISORY
LEVELS.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
WIND ADVISORY TIL 6 PM HST MON FOR WAIANAE COAST-OAHU KOOLAU-
OLOMANA-WAIANAE MOUNTAINS-LANAI-KAHOOLAWE-MAUI WINDWARD WEST-MAUI
LEEWARD WEST-MAUI CENTRAL VALLEY-SOUTH BIG ISLAND-BIG ISLAND NORTH
AND EAST-KOHALA-BIG ISLAND INTERIOR.

SCA TIL 6 PM HST MON ALL HAWAIIAN WATERS.

HIGH SURF ADVISORY UNTIL 6 PM HST TUESDAY FOR EAST FACING SHORES OF
KAUAI-OAHU-MOLOKAI-MAUI-BIG ISLAND.

&&

$$

R BALLARD/ASB





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