Tuesday, September 30, 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 300630
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
830 PM HST MON SEP 29 2014

.SYNOPSIS...
LIGHT WINDS ACROSS THE STATE COMBINED WITH AN UNSTABLE AIRMASS WILL
RESULT IN A CHANCE OF SHOWERS AND THUNDERSTORMS THROUGH TUESDAY.
A DRIER AND MORE STABLE AIRMASS IS EXPECTED FOR THE SECOND HALF OF
THE WEEK... THOUGH LIGHT WINDS AND MUGGY CONDITIONS WILL REMAIN.

&&

.DISCUSSION...

HIGH PRESSURE FAR TO THE NORTHEAST IS BEING PUSHED AWAY FROM THE
STATE BY AN APPROACHING COLD FRONT LOCATED NORTHWEST OF THE
ISLANDS. THIS SCENARIO LEAVES HAWAIIAN IN A LIGHT EAST- SOUTHEAST
FLOW AREA BETWEEN THE TWO FEATURES. THE LOCAL SCALE AFTERNOON SEA
BREEZE AND NIGHTTIME LAND BREEZE CIRCULATIONS WILL CONTINUE
THROUGH THE NEXT SEVERAL OF DAYS. DEW POINTS WILL REMAIN IN THE
LOW 70/S AND SENSIBLE WEATHER CONDITIONS WILL REMAIN MUGGY THROUGH
THE WEEK.

ALOFT...WE HAVE A WEAK UPPER LOW THAT HAS DESTABILIZED OUR
ATMOSPHERE ALLOWING FOR ISOLATED THUNDERSTORMS TO FORM OVER THE
STATE AND COASTAL WATERS. WITHOUT A SIGNIFICANT STEERING FLOW NEAR
THE SURFACE SHOWERS AND THUNDERSTORMS WILL FORM IN PLACE AND TEND
TO REMAIN OR SLOWLY DRIFT... BEFORE RAINING ITSELF OUT. A HANDFUL
OF FLOOD ADVISORIES HAVE BEEN ISSUED FOR THESE GULLY WASHERS. A
FLASH FLOOD WARNING IS NOT OUT OF THE QUESTION... BUT THAT WOULD
BE A WORST CASE SCENARIO.

THE CURRENT FORECAST MAINTAINS A CHANCE OF THUNDERSTORMS THROUGH
TUESDAY EVENING AS THE LOW SLOWLY WEAKENS AND DRIFTS NORTHEAST.
HOWEVER...THE CHANCE OF THUNDERSTORMS COULD EXTEND INTO WEDNESDAY
AS MODELS ARE INDICATING COLD AIR ALOFT LINGERING OVER THE
ISLANDS. WILL EXAMINE THIS SCENARIO FURTHER FOR THE 4 AM FORECAST
PACKAGE. MOISTURE REMAINS ABUNDANT IN THE LOW LEVELS FOR THE NEXT
FEW DAYS. ANY FORCING DUE TO THE UPPER LOW OR CONVERGENCE AROUND
THE ISLANDS WILL LIKELY SET OFF HEAVY SHOWERS.

FOR MID TO LATE WEEK...THE UPPER TROUGH WEAKENS AND DRIFTS
NORTH...AND INSTABILITY AROUND THE ISLANDS WILL DECREASE. WEAK
EASTERLY TRADES WILL REMAIN FOR THE LAST HALF OF THE WEEK AS
ANOTHER FRONT TO THE NORTHWEST KEEPS HIGH PRESSURE AT BAY TO THE
NORTHEAST. LOCAL SEA BREEZES WITH AFTERNOON CLOUDS AND SHOWERS
WILL CONTINUE... AND NIGHT TIME LAND BREEZES WILL PARTIALLY CLEAR
SKIES.

&&

.AVIATION...
A CHANCE FOR THUNDERSTORMS REMAINS OVER THE ENTIRE AREA. CURRENTLY
THUNDERSTORMS ARE ACTIVE OVER SOUTH BIG ISLAND...20 NM SW OF
PHNL...AND IN THE NORTHERN COASTAL WATERS...WITH CB TOPS ABOVE
FL350. THESE THUNDERSTORMS AND ONES THAT MAY DEVELOP WILL CARRY
IFR CONDITIONS. SCATTERED SHOWERS WILL FAVOR WINDWARD AND MAUKA
AREAS...WITH POSSIBLE TEMPO MVFR CONDITIONS. AS OF 07Z THERE ARE
NO AIRMETS IN EFFECT...HOWEVER...AIRMET SIERRA WILL BE ISSUED AS
CONDITIONS WARRANT THROUGH THE NIGHT. OTHERWISE...TERMINALS...FOR
THE MOST PART...WILL REMAIN PREDOMINATELY VFR.


&&

.MARINE...
ISOLATED THUNDERSTORMS ARE POSSIBLE THROUGH TUESDAY OVER THE
COASTAL WATERS. OTHERWISE... LIGHT EAST TO SOUTHEAST WINDS WILL
CONTINUE THROUGH THE WEEK. ONLY SMALL SWELLS ARE ANTICIPATED TO
MOVE THROUGH THE AREA THIS WEEK. A SMALL NORTHWEST SWELL IS
EXPECTED TO ARRIVE ON TUESDAY...PEAKING ON WEDNESDAY. THIS SWELL
WILL BE REINFORCED BY A SMALL NORTHWEST FRIDAY. THE SOUTH FACING
SHORES WILL ENCOUNTER A SERIES OF SMALL SWELLS FROM THE SOUTH
THROUGH THURSDAY...THE LARGEST ARRIVING ON TUESDAY THROUGH
THURSDAY.


&&

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

&&

$$

MORRISON...DISCUSSION AND MARINE
EATON...AVIATION



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 Mon Sep 29 2014

Valid 00Z Tue Sep 30 2014 - 00Z Tue Oct 07 2014

The models/ensembles show ridging staying in place west of the
Dateline but building over/toward California which favors
troughing along the longitude of Hawai'i. With a rather deep upper
low forecast to move toward Kamchatka by early next week and
ridging remaining in the Bering Sea, a split flow in the north
central Pacific should result. The 00Z/28 ECMWF/GFS showed this
well yesterday but the 00Z/29 ECMWF appears too quick with the
flow compared to the ensembles. The 00Z GFS may have a better
handle on the flow but other contributing factors may influence
the forecast over the next few days.

Closer to the 50th state, trades should slacken as the sfc high
moves away from the state in the short term and veer more
east-southeasterly to southeasterly. PW values should hover near
to above normal through the period, supporting more scattered
showers than an otherwise average pattern. Would suggest a 00Z
GFS/ECENS mean blend which should still keep the sfc cold front NW
of the state by next Monday 6 October.


Fracasso





Last Updated: 819 AM EDT Mon Sep 29 2014




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