Saturday, July 26, 2014 596-SURF , 596-WAVE , 922-BONG , 638-RUSH , 572-SURF(MAUI) , 241-SURF (KAUAI) , 324-RUSH (BIG ISLAND)
   
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off 2/20/14; off 3/27. on 4/4. on 7/20/14
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000
FXHW60 PHFO 260151
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
400 PM HST FRI JUL 25 2014

.SYNOPSIS...
TRADE WINDS WILL FOCUS SHOWERS MAINLY ACROSS WINDWARD AND MAUKA
AREAS. AN INCREASE IN SHOWER ACTIVITY IS EXPECTED FROM EAST TO WEST
THIS WEEKEND. TRADES MAY ALSO STRENGTHEN EARLY NEXT WEEK.

&&

.DISCUSSION...
WATER VAPOR IMAGERY SHOWS A MID/UPPER LEVEL HIGH OVER/JUST SOUTH OF
THE STATE. AN UPPER LEVEL TROUGH IS LOCATED FAR TO THE NORTHWEST...
WITH A 60 KT WEST-SOUTHWESTERLY JET AHEAD OF IT JUST APPROACHING
KAUAI. AT THE SURFACE...HIGH PRESSURE IS LOCATED FAR NORTH-NORTHEAST
OF THE STATE. 00Z SOUNDINGS FROM HILO AND LIHUE SHOW INVERSIONS
SLIGHTLY HIGHER THAN 24 HOURS AGO...ALTHOUGH STILL WELL DEFINED NEAR
7KFT. PRECIPITABLE WATERS ARE 1.3-1.4 INCHES...WHICH IS NEAR NORMAL
FOR THIS TIME OF YEAR. EARLY AFTERNOON MIMIC TOTAL PRECIPITABLE
WATER IMAGERY SHOWS A SMALL POCKET OF DRIER AIR WITHIN 200 MILES
EAST OF THE BIG ISLAND...WITH A LARGER AREA OF MOISTURE FARTHER
EAST. SATELLITE DERIVED PW VALUES ARE LOWER THAN EARLIER...AND ARE
NOW 1.5-1.7 INCHES NEAR 150W.

SHOWERS HAVE BEEN SOMEWHAT LIMITED THROUGH THE AFTERNOON...WITH THE
HANDFUL OF WINDWARD GAGES THAT RECEIVED RAIN ONLY PICKING UP A
COUPLE HUNDREDTHS. KAUAI WAS SLIGHTLY WETTER THAN THE REST OF THE
STATE DUE TO A POCKET OF MOISTURE CURRENTLY PASSING TO THE NORTH.
THE SURFACE HIGH FAR TO THE NORTHEAST HAS WEAKENED...AND SURFACE
PRESSURES ACROSS THE ISLANDS HAVE DROPPED ABOUT 1-2MB OVER THE PAST
24 HOURS. TRADES SHOULD REMAIN IN THE GENERAL MODERATE CATEGORY
THROUGH THE WEEKEND.

CURRENT SATELLITE IMAGERY SHOWS SHOWERY LOW CLOUDS OVER THE EASTERN
OFFSHORE WATERS...MOVING TO THE WEST AT 20 MPH. BOTH GFS AND ECMWF
ARE RELATIVELY SIMILAR WITH THEIR TIMING BRINGING THIS MOISTURE
WESTWARD. THE CURRENT FORECAST HAS AN INCREASE IN RAINFALL CHANCES
THIS WEEKEND FROM EAST TO WEST BEGINNING NEAR THE BIG ISLAND LATE
TONIGHT. AT THE SAME TIME...THE UPPER TROUGH NORTHWEST OF THE STATE
WILL MOVE EASTWARD NORTH OF THE AREA. 12Z MODELS SHOW THE TROUGH
PASSING JUST NORTH OF KAUAI ON SUNDAY BEFORE SLOWING AND WEAKENING.
MOST SHOWERS WILL BE FOCUSED ACROSS WINDWARD AND MAUKA AREAS...BUT
SOME WILL SPREAD LEEWARD AS WELL. THE INCREASE IN MOISTURE AND RISE
IN INVERSION HEIGHT COULD LEAD TO BRIEF HEAVIER SHOWERS...BUT WITH
PERSISTENT MODERATE TRADES WE DO NOT EXPECT ANY HEAVY SHOWERS TO
BECOME ANCHORED.

DURING THE FIRST HALF OF NEXT WEEK...THE HIGH NORTHEAST OF THE STATE
WEAKENS...BUT A POTENTIAL SYSTEM PASSING FAR SOUTH OF THE STATE
COULD ENHANCE THE GRADIENT ACROSS THE ISLANDS. THIS MAY LEAD TO AN
INCREASE IN WINDS STARTING AS EARLY AS SUNDAY NIGHT. RECENT MODEL
RUNS HAVE BACKED OFF ON A SURGE OF TROPICAL MOISTURE THAT HAD BEEN
ADVERTISED TO SPREAD ACROSS THE STATE DURING THE MID-WEEK TIME
FRAME. HOWEVER...SPECIFICS ABOUT ANY INCREASE IN SHOWERS DURING MID
TO LATE WEEK REMAIN QUITE UNCERTAIN.

&&

.AVIATION...
VFR CONDITIONS WILL PREDOMINATE ALL AREAS THIS AFTERNOON. ISOL MVFR
CONDS IN PASSING TRADE WIND SHOWERS MAINLY ALONG WINDWARD AND MAUKA
AREAS. GUSTY TRADE WINDS ALONG EXPOSED AND THROUGH CHANNELED AREAS
WILL DIMINISH AFTER SUNSET BUT REDEVELOP DURING THE DAY TOMORROW.

&&

.MARINE...
WINDS MAY INCREASE TO SMALL CRAFT ADVISORY LEVELS AS EARLY AS SUNDAY
NIGHT FOR THE TYPICALLY WINDIER AREAS NEAR MAUI AND THE BIG ISLAND.
EVEN AS THE SURFACE HIGH FAR NORTHEAST OF THE STATE WEAKENS
SLIGHTLY...A POTENTIAL SYSTEM PASSING FAR SOUTH OF THE AREA COULD
ENHANCE THE GRADIENT ACROSS THE ISLANDS. SMALL CRAFT ADVISORY WINDS
ARE THEN POSSIBLE FOR THOSE AREAS THROUGH MUCH OF THE NEW WEEK.

NO SIGNIFICANT SWELLS ARE EXPECTED THROUGH THE NEXT SEVERAL DAYS.
SMALL LONG-PERIOD BACKGROUND SWELL FROM THE SSW AND SHORT-PERIOD
SWELL FROM THE SE REPRESENT THE SWELL SOURCES FROM THE SOUTHERN
HEMISPHERE...WHILE SHORT PERIOD WIND WAVES FROM THE EAST REPRESENT
THE ONLY SOURCE OF SWELL FROM THE NORTHERN HEMISPHERE.

&&

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

&&

$$

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


The Weather Prediction Center

College Park, MD

Hawaii Extended Forecast Discussion




Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
819 AM EDT Fri Jul 25 2014

Valid 00Z Sat Jul 26 2014 - 00Z Sat Aug 02 2014

Latest models and ensembles reasonably agree in support of
moderate to locally brezzy island trades for much of the next
week. A favored guidance composite indicates this flow well
underneath a developing higher latitude block may periodically
enhance as pressure graidents tighten with passage of a series of
tropical features to the south of the state. Windward terrain
based showers may increase slightly this weekend with any added
moisture associated with a lead tropical disturbance passing south
of the state as followed by the Central Pacific Hurricane Center.
Additional opportunities for increased moisture/showers to work
into especially the southern islands may be related to Tropical
Storm Genevieve located near 12.2N 134.4W at 09 UTC whose weakened
remnants should pass south of the islands around Thu/Fri and there
is even another tropical disturbance upstream of that near 123W.
The National Hurricane Center is now monitoring these two tropical
features.

Schichtel





Last Updated: 819 AM EDT Fri Jul 25 2014




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