Area Forecast Discussion
Issued by NWS Honolulu, HI

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FXHW60 PHFO 040608
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
830 PM HST SUN MAY 3 2015

.SYNOPSIS...
TRADE WINDS WILL PREVAIL THROUGH THE WEEK...STRENGTHENING SOMEWHAT
INTO MID-WEEK...AND THEN DIMINISHING AGAIN BY FRIDAY. CLOUDS AND
SHOWERS WILL BE MOST ACTIVE OVER WINDWARD SLOPES...THOUGH A FEW MAY
DRIFT LEEWARD AT TIMES.

&&

.DISCUSSION...
OBSERVATIONS AROUND THE MAIN HAWAIIAN ISLANDS REPORTED MODERATE TO
LOCALLY STRONG TRADE WINDS. CLOUD MOTIONS UPWIND OF THE STATE...AND
SOUNDING DATA FROM LIHUE...SUGGESTED THAT THE WINDS EXTENDED THROUGH
MOST OF THE MIXED LAYER BELOW THE INVERSION. LIGHTER WINDS OVER HILO
PROBABLY REPRESENTED LOCAL STAGNATION OF THE FLOW UPWIND OF THE HIGH
PEAKS...RATHER THAN THE GENERAL ENVIRONMENT.

THE INVERSION ITSELF WAS SOLID...BUT NOT EXCEPTIONALLY STRONG...AND
SLOPED FROM SLIGHTLY BELOW ITS USUAL HEIGHT AT LIHUE TO SLIGHTLY
ABOVE AT HILO. PRECIPITABLE WATER OVER THE STATE WAS ON THE LOW SIDE
EARLIER IN THE AFTERNOON...BUT A LOOSE CLUSTER OF SHOWERY CUMULI AND
STRATOCUMULI LIKELY WILL BRING SOME MODESTLY ORGANIZED RAIN TO
WINDWARD SLOPES LATER THIS EVENING. INDIVIDUAL SMALL SHOWERS ALSO
WILL CONTINUE TO ENHANCE OVER WINDWARD SLOPES THROUGH THE WEEK.

ALOFT...BROAD ZONAL RIDGING ACROSS MOST OF THE CENTRAL PACIFIC OCEAN
KEPT THE MAIN PART OF THE STORM TRACK WELL TO THE NORTH OF THE
ISLANDS...BUT SHALLOW EXTENSIONS OF PASSING TROUGHS AND RIDGES
REACHED THE STATE. THESE WAVES...AND THEIR INFLUENCE ON THE
SUBTROPICAL RIDGE AT THE SURFACE...WILL BRING MOST OF THE CHANGES TO
LOCAL WEATHER THROUGH THE WEEK.

FROM THIS EVENING INTO WEDNESDAY...CRESTING RIDGING ALOFT...AND THEN
AT THE SURFACE IN REACTION...WILL TEND TO SUPPORT GRADUAL INCREASES
IN WIND SPEED. THEN...FROM WEDNESDAY INTO FRIDAY...FOLLOWING
TROUGHING ALOFT...AND A FEEBLE FRONT ERODING THE SUBTROPICAL RIDGE
AT THE SURFACE... WILL TEND TO REDUCE WIND SPEEDS. ALTHOUGH IT MAY
BE TEMPTING TO PREDICT TRENDS IN TRADE-WIND SHOWERS SIMPLY FROM
MODEL CONSENSUS PRECIPITABLE WATER...IN PRACTICE THE CORRELATION IS
LESS THAN IDEAL. THUS...POPS AND RELATED FIELDS IN THE OFFICIAL
FORECAST LIKELY WILL BE TRENDED SLIGHTLY BACK TOWARD CLIMATOLOGY.

&&

.MARINE...
A SMALL CRAFT ADVISORY REMAINED IN EFFECT FOR TYPICALLY WINDIER
AREAS AROUND MAUI AND THE BIG ISLAND...AND LIKELY WILL BE EXTENDED
THROUGH MUCH OF THE WEEK. ITS AREA OF EFFECT ALSO MAY EXPAND BY
TUESDAY...AND THEN AGAIN FROM FRIDAY INTO SATURDAY.

THE TRADE WINDS ALSO WILL MAINTAIN ELEVATED SHORT-PERIOD SURF ALONG
EAST-FACING SHORES THROUGH THE WEEK...THOUGH HEIGHTS SHOULD REMAIN
BELOW THE ADVISORY THRESHOLD. A LONG-PERIOD SOUTH-SOUTHWEST SWELL
WILL BUILD GRADUALLY ON TUESDAY...AND THEN PEAK FROM WEDNESDAY INTO
THURSDAY...LIKELY BRINGING ADVISORY-LEVEL SURF TO SOUTH-FACING
SHORES. A TINY NORTH SWELL IS EXPECTED MONDAY THROUGH WEDNESDAY...
AND A SLIGHTLY LARGER NORTH-NORTHWEST SWELL FROM THURSDAY INTO
SATURDAY.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
SMALL CRAFT ADVISORY UNTIL 6 PM HST TUESDAY FOR MAALAEA BAY-
PAILOLO CHANNEL-ALENUIHAHA CHANNEL-BIG ISLAND LEEWARD WATERS-BIG
ISLAND SOUTHEAST WATERS.

&&

$$

RYSHKO




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