Wednesday, August 27, 2014 596-SURF , 596-WAVE , 922-BONG , 638-RUSH , 572-SURF(MAUI) , 241-SURF (KAUAI) , 324-RUSH (BIG ISLAND)
   
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000
FXHW60 PHFO 270630
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
830 PM HST TUE AUG 26 2014

.SYNOPSIS...
TRADE SHOWERS CONTINUE TONIGHT WITH RAINFALL FOCUSING OVER WINDWARD
AND MOUNTAIN AREAS. THE TRADES WILL GRADUALLY WEAKEN THURSDAY
THROUGH SATURDAY AND ALLOW FOR SEA BREEZES TO DEVELOP EACH DAY.
THIS WILL BRING PERIODS OF CLOUDS AND SHOWERS OVER LEEWARD AND
INTERIOR AREAS THROUGH THE WEEKEND. THEN THE TRADES WILL STRENGTHEN
AGAIN EARLY NEXT WEEK WITH SHOWERS FOCUSING BACK OVER WINDWARD AND
MOUNTAIN AREAS.

&&

.DISCUSSION...
LATEST WATER VAPOR SATELLITE IMAGERY DEPICTS AN UPPER LVL LOW ABOUT
570 MILES WNW OF KAUAI. THE EASTERN CIRCULATION OF THIS LOW IS
PULLING SOME OF THE SCATTERED LAYERED/HIGH CLOUDS NEAR THE ITCZ INTO
THE ISLANDS. MEANWHILE...SFC HIGH PRESSURE REMAINS CENTERED FAR NNE
OF THE ALOHA STATE AND KEEPING A MODERATE TRADE WIND REGIME ACROSS
THE ISLAND CHAIN.

RADAR DATA SHOW SHOWERS JUST E/NE OF THE ISLANDS...BRINGING PERIODS
OF RAIN OVER MOST WINDWARD AND MOUNTAIN AREAS OF THE SMALLER
ISLANDS...WHICH WILL CONTINUE THROUGH THE EVENING AND OVERNIGHT
HOURS. 00Z SOUNDING DATA AND MIMIC MOISTURE ANALYSES SHOW PWATS IN
GENERAL AROUND 1.15 TO 1.30 INCHES AROUND THE MAIN HAWAIIAN
ISLANDS...AND A DRYER AIRMASS FURTHER UPSTREAM. THUS...EXPECT
SHOWERS WITH POSSIBLE LOCALIZED BRIEF DOWNPOURS TONIGHT ESPECIALLY
OVER WINDWARD AREAS...THE KOOLAU RANGE IN OAHU...THE W MAUI
MOUNTAINS AND WINDWARD HALEAKALA. THEN DRIER CONDITIONS WILL
ESTABLISH ON WED. FOR THE SECOND HALF OF THE WEEK...DESPITE THE
ARRIVAL OF A DRIER AIRMASS...THE GLOBAL MODELS SHOW FAIR AGREEMENT
REGARDING THE PASSAGE OF THE REMNANTS OF FORMER TROPICAL CYCLONE
LOWELL TO THE FAR NW OF THE ISLANDS. THIS WILL TEMPORARILY
INTERRUPT THE TRADE WIND FLOW AND ALLOW FOR SEA/LAND BREEZE
CIRCULATIONS TO DEVELOP EACH AFTERNOON THU THROUGH SAT. EXPECT
POSSIBLE PERIODS OF AFTERNOON/EARLY EVENING SHOWERS...ESPECIALLY
OVER INTERIOR AND LEEWARD AREAS.

FOR THE LONG RANGE FORECAST...THE SFC HIGH STRENGTHENS NNE OF THE
ALOHA STATE WITH THE TRADES GRADUALLY RETURN TO MODERATE LVLS SUN
INTO MON. THIS WILL BRING BACK A TRADE WIND WEATHER REGIME EARLY
NEXT WEEK WITH SHOWERS FAVORING WINDWARD AND MOUNTAIN
AREAS...ESPECIALLY AT NIGHT.

&&

.AVIATION...
A MODERATE TRADE WIND FLOW WILL PRODUCE PERIODS OF MVFR CIGS AND VIS
OVER WINDWARD SLOPES AS SHOWERS COME IN. PHTO AND PHLI WILL BRIEFLY
EXPERIENCE THESE CONDITIONS AT TIMES TONIGHT...AND PHKO WILL SEE
SOME NEARBY SHOWER ACTIVITY BEFORE MIDNIGHT. OTHERWISE...VFR WILL
PREVAIL. NO AIRMETS ARE ANTICIPATED.

&&

.MARINE...
AN INCREASING EASTERLY LONG-PERIOD SWELL FROM HURRICANE MARIE IS
EXPECTED TO ARRIVE LATE WEDNESDAY AND CONTINUE TO BUILD THROUGH
THURSDAY NIGHT. THIS SWELL WILL BRING ADVISORY LEVEL SURF TO EAST
FACING SHORES. ALSO...AN INCREASING SOUTH-SOUTHWEST SWELL IS
ANTICIPATED FOR WEDNESDAY NIGHT INTO THURSDAY...BRINGING NEAR
ADVISORY LEVEL SURF OVER SOUTH FACING SHORES THROUGH FRIDAY. STRONG
CURRENTS COULD ALSO DEVELOP WITH THE ARRIVAL OF THESE SWELLS. THE
SURF SHOULD BEGIN SUBSIDING SATURDAY AND CONTINUE TO DECLINE THROUGH
EARLY NEXT WEEK.

WITH WINDS EXPECTED TO DIMINISH FURTHER...NO SMALL CRAFT ADVISORY
CONDITIONS ARE EXPECTED THROUGH THE HOLIDAY WEEKEND. HOWEVER...THE
LONG PERIOD EASTERLY SWELL MENTIONED ABOVE COULD PRODUCE UNUSUAL
CONDITIONS IN EAST FACING CHANNELS AND HARBORS.

&&

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

&&

$$

DISCUSSION/MARINE...REYNES
AVIATION...WROE



The Weather Prediction Center

College Park, MD

Hawaii Extended Forecast Discussion




Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
811 AM EDT Tue Aug 26 2014

Valid 00Z Wed Aug 27 2014 - 00Z Wed Sep 03 2014

Aloft, 26/00Z ECENS/GEFS cycle and their deterministic runs
remained in very good agreement concerning the movements of a
broad upper-level ridge in the north central and eastern Pacific
heading into day 6 (1/12Z).

At the surface, the 26/00Z GFS MOS data (extended version)
indicated a slackening of the current trade wind intensity for a
slightly longer period of time (Friday through Sunday) versus the
ECMWF solution.  

After day 6, the 26/00z GEFS/ECENS part ways at 500 millibars
along the Dateline---with the deterministic ECMWF containing a
flatter flow over the mid-latitude Pacific and stronger
Subtropical Ridge solution vs the GFS and its cutoff 500mb low
solution. The GFS carries a well-defined low invof 39N 175W (@
2/12Z) and a weaker downstream Subtropical Ridge axis between
California and Hawai'i.

In turn, these differences translate to widening model/ensemble
spread with respect to latitude--and where tropical moisture
associated with 'Marie' and the remnants of 'Lowell' is displaced
across the southeast Pacific. Both runs displace the moisture and
vorticity along a westward path but do not agree with the
latitude. The GFS suggests the moisture and vorticity reach 30N
150W while the ECMWF suggests more organization of the moisture
westward to ~ 25N 155W.

Recommend a blend of the GFS/ECMWF deterministic runs and their
means through day 5, then reverting to the means and a straight
GEFS/ECENS blend for day 6-7 to mitigate the changes emerging
along the Dateline--and to dampen the sensible weather impacts of
any 'tropicals'--ie 'Marie' and 'Lowell'.

Vojtesak





Last Updated: 811 AM EDT Tue Aug 26 2014




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