Area Forecast Discussion
Issued by NWS Honolulu, HI

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000
FXHW60 PHFO 250643
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
842 PM HST SUN MAY 24 2015

.SYNOPSIS...
COOL AND RELATIVELY DRY NORTHEASTERLY WINDS WILL CONTINUE THROUGH
TUESDAY...WITH WINDS GRADUALLY WEAKENING. THESE WINDS WILL CARRY
LOW CLOUDS AND A FEW LIGHT SHOWERS OVER THE ISLANDS...WITH THE
SHOWERS FOCUSING ALONG NORTHEAST FACING SLOPES. THE LOW CLOUDS
HOWEVER WILL SPREAD TO LEEWARD AREAS ON THE SMALLER ISLANDS. WINDS
ARE EXPECTED TO BE SUFFICIENTLY LIGHT TO ALLOW ISLAND SCALE LAND AND
SEA BREEZES TO PREVAIL FROM WEDNESDAY INTO NEXT WEEKEND...WITH A
SOMEWHAT CLOUDY AND UNSETTLED WEATHER PATTERN EXPECTED.

&&

.DISCUSSION...
LATEST GUIDANCE OFFERS LITTLE CHANGE TO THE ONGOING FORECAST
PHILOSOPHY...AND THUS THIS FORECAST DISCUSSION OFFERS LITTLE
SIGNIFICANT CHANGE FROM WHAT WAS TRANSMITTED EARLIER.

WATER VAPOR IMAGERY SHOWS AN UPPER LEVEL LOW TO THE NE OF THE
ISLANDS...WITH AN ASSOCIATED TROUGH EXTENDING BACK OVER THE STATE.
AT THE SURFACE...A PAIR OF RELATIVELY WEAK LOWS ARE LOCATED NE OF
THE ISLANDS...WITH AN ASSOCIATED FRONT EXTENDING TO AN AREA JUST SE
OF THE BIG ISLAND. HIGH PRESSURE IS LOCATED FAR TO THE NW. 00Z
SOUNDINGS SHOW INVERSIONS RANGING FROM 6KFT AT LIHUE TO 8KFT AT
HILO. PRECIPITABLE WATERS ARE ALSO 1.0 AND 1.2 INCHES RESPECTIVELY.

ALL ISLANDS ARE NOW IN A POST-FRONTAL WEATHER REGIME...WITH BROKEN
TO OVERCAST STABLE LOW CLOUDS STREAMING OVER THE AREA FROM THE NNE.
WHILE LIGHT SHOWERS ASSOCIATED WITH THE CLOUDS ARE FAVORING N AND E
FACING SLOPES...THE CLOUDS ARE EASILY SPREADING TO LEE AREAS OF THE
SMALLER ISLANDS. A SIMILAR PATTERN IS EXPECTED ON MEMORIAL DAY.

THE UPPER LOW NE OF THE STATE WILL BEGIN TO SHIFT E...BUT A WEAK
UPPER LEVEL TROUGH WILL REMAIN NEAR THE STATE THROUGH TUESDAY.
AT THE SURFACE...THE FRONT SE OF THE BIG ISLAND WILL WEAKEN AS THE
LOW TO THE NE SHIFTS N. HOWEVER...THIS DEPARTING LOW WILL ALSO LEAVE
A SURFACE TROUGH NE OF THE ISLANDS. WINDS WILL CONTINUE TO DIMINISH
OVER THE E HALF OF THE STATE ON MONDAY AND EVERYWHERE BY TUESDAY...
ALLOWING FOR LOCALLY DRIVEN LAND AND SEA BREEZES. THE PATTERN DOES
NOT APPEAR TO BE AS PURE CONVECTIVE AS IT WAS BRIEFLY LAST WEEK WITH
THE RIDGE OVERHEAD. INSTEAD...THERE WILL BE ENOUGH OF A WEAK NE
GRADIENT TO KEEP SOME CLOUDS FOCUSED ACROSS WINDWARD SECTIONS AT
NIGHT...BUT WITH MOST BUILDUPS OCCURING DURING THE DAY ACROSS
INTERIOR AND LEEWARD SECTIONS.

THERE IS A GENERAL CONSENSUS AMONG THE EXTENDED MODELS AS TO THE
OVERALL PATTERN THROUGH THE WEEK AND INTO NEXT WEEKEND...BUT WITH
SOME DIFFERENCES WITH RESPECT TO TIMING AND STRENGTH. THE CONSENSUS
IS FOR A SURFACE TROUGH TO DEVELOP NEAR THE E HALF OF THE STATE...
THEN GRADUALLY MOVE W ACROSS THE CHAIN...WITH A CLOUDY AND SOMEWHAT
DAMP PATTERN IN THE WORKS. THIS TROUGH WILL MAINTAIN THE LIGHT WIND
PATTERN...AND ALSO PROVIDE A FOCUS FOR MOISTURE THAT MAY ENHANCE
AFTERNOON SHOWERS. MODEL FORECAST SOUNDINGS SHOW AN INCREASE IN
MOISTURE DEPTH/INVERSION HEIGHT BY MID/LATE WEEK...IN PART DUE TO
THE MOISTURE POOLED ALONG THE SURFACE TROUGH...AND IN PART DUE TO A
SHARPENING MID-LEVEL TROUGH OVERHEAD. BY LATE IN THE WEEKEND A
NEW SURFACE HIGH BUILDING NW OF THE ISLANDS SHOULD HELP TO
STRENGTHEN THE TRADE FLOW...AND RETURN US TO A MORE TYPICAL RAINFALL
PATTERN.

&&

.AVIATION...
STABLE STRATOCUMULUS CLOUDS...THE REMNANTS OF AN EXITING COLD
FRONT...WILL LINGER THROUGH THE NIGHT AND INTO MONDAY MORNING.
CLOUDS AND SCATTERED LIGHT SHOWERS WILL FAVOR NORTH AND NORTHEAST
SLOPES. PARTIAL CLEARING WILL BEGIN LATER TONIGHT ALONG LEEWARD
COASTS AND TOWARDS MID MORNING ALONG WINDWARD SLOPES AND COASTS.
AIRMET SIERRA FOR MTN OBSC NORTHEAST BIG ISLAND WILL LIKELY REMAIN
NECESSARY THROUGH MID MORNING MONDAY.

&&

.MARINE...
SMALL CRAFT ADVISORY LEVEL WINDS OR SEAS ARE NOT EXPECTED THROUGH
THE UPCOMING WEEK...EVEN THOUGH SWELLS FROM THE S...SSW...NNE...AND
WNW ARE EXPECTED. OPEN OCEAN SWELL HEIGHTS ARE EXPECTED TO BE 3 FEET
OR LESS...AND WITH LOCAL WINDS REMAINING LIGHT TO MODERATE...
COMBINED SEAS WILL REMAIN BELOW THE 10 FOOT THRESHOLD.

SURF WILL REMAIN SOMEWHAT ELEVATED ALONG S FACING SHORES INTO THE
BEGINNING OF JUNE...AS THE DEVELOPING EL NINO FAVORS LOW PRESSURE
DEVELOPMENT NEAR...AND E OF...NEW ZEALAND. A PEAK IN S SHORE SURF
HEIGHTS IS EXPECTED ON MONDAY AND TUESDAY...WITH THE CONTINUED
POTENTIAL FOR ADVISORY LEVEL HEIGHTS ALONG EXPOSED S FACING SHORES.
WHILE LATEST BUOY OBSERVATIONS DO NOT SUPPORT ISSUANCE OF AN
ADVISORY AT THIS TIME...THE FACT THAT TWO SEPARATE SWELLS OF VARYING
PERIODS WILL BE ARRIVING MEANS THAT SURF WILL BE MORE CONSISTENT
THAN USUAL ALONG S FACING SHORES. LATEST SURFACE ANALYSES AND WAVE
WATCH MODEL OUTPUT INDICATE THAT A NEAR-STORM FORCE LOW NOW BREWING
E OF NEW ZEALAND IS PRODUCING A SWELL THAT WILL ARRIVE NEXT
WEEKEND...WITH INITIAL INDICATIONS THAT THIS SWELL WILL PRODUCE SURF
NEAR ADVISORY LEVELS.

&&

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

&&

$$

DISCUSSION...BRAVENDER/BIRCHARD
MARINE...BIRCHARD
AVIATION...BEDAL




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