853
FXHW60 PHFO 031439 AAA
AFDHFO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
440 AM HST TUE NOV 3 2009
UPDATE
SHOWER ACTIVITY IS BECOMING MORE WIDESPREAD OVER THE NORTHERN
PORTION OF THE FORECAST AREA...EVEN MORE THAN ANTICIPATED JUST AN
HOUR OR TWO AGO. RAISED POPS TO 50-70 PERCENT FOR KAUAI/OAHU AND
SURROUNDING COASTAL WATERS FOR THE FIRST PART OF THE DAY.
ELSEWHERE...THE FORECAST IS LOOKING IN PRETTY GOOD SHAPE.
SYNOPSIS
MODERATE TRADE WINDS WILL BRING SHOWERS TO WINDWARD AND MAUKA AREAS
TODAY...BEFORE A COLD FRONT USHERS IN A WEATHER CHANGE TUESDAY AND
TUESDAY NIGHT. THE FRONT WILL BRING ADDITIONAL SHOWERS TO MOST
ISLANDS AS IT MOVES DOWN THE ISLAND CHAIN. STRONG NORTHEAST WINDS
AND COOLER DRIER AIR WILL FOLLOW IMMEDIATELY BEHIND THE FRONT. A
RETURN TO TRADE WIND WEATHER IS EXPECTED FOR THE SECOND HALF OF THE
WEEK. ANOTHER COLD FRONT MAY APPROACH THE ISLANDS EARLY NEXT WEEK.
DISCUSSION
NO BIG CHANGES TO THE FORECAST TONIGHT. WINDWARD OAHU REMAINS THE
TARGET FOR THE HEAVIEST RAINFALL EARLY THIS MORNING. MODERATE
SHOWERS CONTINUE TO TRAIN OVER THE AREA IN THE TRADE WIND FLOW.
RADAR AND A FEW GAGES ARE INDICATING RAINFALL RATES OF 1-2 INCHES
PER HOUR IN THE HEAVIEST SHOWERS. THE FAST MOVING AND SCATTERED
NATURE OF THE SHOWERS KEEPS ANY MINOR FLOODING POTENTIAL TO A
MINIMUM...IF IT REALLY EXISTS AT ALL TONIGHT. BASED ON A QUICK
GLANCE UPSTREAM...IT LOOKS LIKE THERES MORE TO FOLLOW...POSSIBLY
EVEN FOR KAUAI A LITTLE LATER TODAY. DID MAKE A FEW TWEAKS TO THE
NEAR TERM GRIDS TO ACCOUNT FOR THIS. ELSEWHERE THERE ARE MORE
MODERATE TO HEAVY SHOWERS WEST OF KAUAI NEAR ALONG THE REMNANT
STALLED FRONT WHERE THE BOUNDARY LAYER REMAINS RICH IN
MOISTURE/THETAE.
THAT SAME STALLED BOUNDARY IS STILL EXPECTED TO PICK UP THE PACE AND
MOVE ITS WAY INTO THE AREA SOMETIME TOMORROW NIGHT. DIDNT MAKE ANY
CHANGES TO THE TIMING OTHER THAN SOME MINOR HOUSECLEANING TO THE
GRIDS. STILL EXPECTING STRONGER WINDS IN EXCESS OF 25 MPH AND THAT
COOLER MID LATITUDE AIR TO FILTER IN BEHIND THE FRONT MID WEEK.
WINDS WILL VEER EASTERLY AND DIMINISH INTO THE SECOND HALF OF THE
WORK WEEK. SHOWER FOCUS WILL RETURN MAINLY TO WINDWARD TERRAIN...
POTENTIALLY WITH HIGHER POPS FOR AREAS IN THE VICINITY OF THE
WEAKENING BOUNDARY AND REMNANT POOLED MOISTURE.
GUIDANCE CONTINUES TO AGREE ON THE SAME HEIGHT TRENDS ACROSS MOST OF
THE NORTH PACIFIC. LATE IN THE WORK WEEK INTO THE WEEKEND MODELS
STILL SUGGEST STRONG HEIGHT RISES OFF THE ASIAN EAST COAST WHICH
DOES SUPPORT DOWNSTREAM TROUGH AMPLIFICATION OVER THE CENTRAL
PACIFIC. WITH HIGH PRESSURE SHIFTING NORTHEAST OF HAWAII..FURTHER
VEERING TO THE TRADES IS LIKELY OVER THE WEEKEND INTO EARLY NEXT
WEEK..ALONG WITH A POTENTIAL FRONTAL PASSAGE IN THE MONDAY/TUESDAY
TIME FRAME. GIVEN MODERATE CONFIDENCE AND GLOBAL MODEL
AGREEMENT...DID TREND THE LATTER PART OF THE FORECAST AND ADDITION
OF DAY 7 TOWARDS THIS SOLUTION.
PREVIOUS DISCUSSION
/ISSUED 800 PM HST MONDAY NIGHT/
THE FORECAST IS LOOKING IN PRETTY GOOD SHAPE TO START THE NIGHT
SHIFT. THERE HASNT BEEN MUCH CHANGE IN THE OVERALL FORECAST
REASONING THROUGH THE SHORT TERM. WIDESPREAD SHOWERS ASSOCIATED WITH
TIGHT LOW LEVEL TROUGH MOVING EAST WITH THE TRADES CONTINUES TO
AFFECT OAHU AND SHOULD CONTINUE THROUGH MUCH OF THE NIGHT. MAY HAVE
TO MAKE A QUICK UPDATE TO THE POP/WX/QPF GRIDS OVER THE NEXT FEW
HOURS.
THE NEARLY STATIONARY AXIS OF HIGH PRECIPITABLE WATER OF UP TO 2.0
INCHES...IS SHOWING ONLY LITTLE PROGRESSION TOWARD THE STATE RIGHT
NOW. THE FRONT IS STILL EXPECTED TO REACH KAUAI SOMETIME TOMORROW
NIGHT BRINGING SCATTERED TO NUMEROUS SHOWERS IS CONTINUES TO CRAWL
SOUTHWARD ACROSS THE STATE. STILL HAVE A SLIGHT CHANCE OF
THUNDERSTORMS IN THE GRIDS RIGHT NOW AS WELL. LOOKING
NORTHWEST...SEEING NO LIGHTNING ACTIVITY WITH HIGHEST TOPPED
CONVECTION WELL TO THE NORTH WHERE THE DYNAMICS ARE MORE FAVORABLE.
NOT SEEING MAJOR FALLS IN 500 MB TEMPS OR IMPRESSIVE 700-500 MB
LAPSE RATES. AM CONSIDERING REMOVING THE THUNDERSTORMS FROM THE
GRIDS AT THIS POINT. GUSTY WINDS AROUND 20 TO 25 KT OR MORE ARE
EXPECTED IMMEDIATELY FOLLOWING THE FRONT ALONG WITH COOLER DRIER MID
LATITUDE AIR ADVECTING OVER THE STATE WEDNESDAY NIGHT AS THE FRONT
SAGS SOUTHWARD WHILE SLOWLY WASHING OUT THROUGH MID WEEK.
INTO THE LONGER TERM THERE ISNT TOO MUCH CHANGE FROM THE DAY SHIFT
EITHER. AS THE AFOREMENTIONED COLD FRONT DROPS SOUTHWARD ACROSS THE
STATE THE ATTENDANT LOW WILL LIFT NORTHEAST. WINDS WILL VEER BACK TO
THE EAST-NORTHEAST AS HEIGHTS/PRESSURES STEADILY RISE TO THE NORTH
AND NORTHEAST OF THE STATE. ANOTHER SHALLOW REMNANT FRONTAL BAND MAY
APPROACH THE STATE LATE THURSDAY...BUT CONFIDENCE IN THIS FEATURE IS
LOW RIGHT NOW. ITS AFFECTS WOULD LIKELY JUST BE MORE SHOWERS FOR
WINDWARD TERRAIN. THE GFS AND ECMWF DOING THEIR BEST TO MAINTAIN
AGREEMENT IN THE LARGER SCALE HEIGHT PATTERN ACROSS THE NORTH
PACIFIC PINCHING OFF A CUT-OFF LOW JUST WEST OF THE STATE TUESDAY
EVENING...THEN MOVING IT SLOWLY WESTWARD. ITS EFFECTS ON SENSIBLE
WEATHER LOCALLY LOOK MINIMAL AS OF NOW. GLOBAL GUIDANCE IS
SUGGESTING HEIGHT FALLS AGAIN NORTHWEST OF THE STATE OVER THE
CENTRAL NORTH PACIFIC DURING THE SECOND HALF OF THE WEEK. THERE IS
DIVERGENCE AMONG MODEL SOLUTIONS IN THE AMPLITUDE AND EASTWARD
PROGRESSION OF THE TROUGHING. HOWEVER...THIS WOULD SUGGEST VEERING
TRADES AGAIN OVER THE WEEKEND...ALONG WITH ANOTHER FRONTAL APPROACH
POSSIBLE SOMETIME VERY EARLY NEXT WEEK.
MARINE
THE CURRENT NORTHWEST SWELL WILL CONTINUE TO DIMINISH. A MIX OF
SHORT AND LONG PERIOD NORTH PACIFIC SWELL WILL BUILD OVER THE FEW
DAYS AGAIN INTO MID WEEK. SOUTH FACING SHORES WILL ALSO SEE AN
INCREASE IN SOUTHERN HEMI SWELL AGAIN DURING THE SECOND HALF OF THE
WEEK. MORE SWELL LOOKS LIKELY AROUND THE 10TH. PLEASE CHECK OUT THE
FRESHLY UPDATED SURF FORECAST FOR MORE DETAILS ON THE LONG RANGE.
A SMALL CRAFT ADVISORY IS IN EFFECT FOR THE TYPICALLY WINDIER
LOCATIONS NEAR THE BIG ISLAND. GIVEN THE SLOWER APPROACH OF THE
FRONT...HAVE DELAYED THE INCREASE IN WIND SPEEDS ACROSS THE
NORTHWEST COASTAL WATERS UNTIL TUESDAY/TUESDAY NIGHT. HOWEVER...A
SOLID 25 KNOTS OF WINDS ARE EXPECTED WITH THE FRONT. HAVE EXPANDED
THE SMALL CRAFT TO INCLUDE WATERS NEAR KAUAI BEGINNING ON TUESDAY.
HFO WATCHES/WARNINGS/ADVISORIES
SMALL CRAFT ADVISORY UNTIL 6 AM HST WEDNESDAY FOR ALENUIHAHA
CHANNEL-BIG ISLAND LEEWARD WATERS-BIG ISLAND SOUTHEAST WATERS.
SMALL CRAFT ADVISORY FROM 6 AM TODAY TO 6 AM HST WEDNESDAY FOR
KAUAI NORTHWEST WATERS-KAUAI WINDWARD WATERS-KAUAI LEEWARD
WATERS-KAUAI CHANNEL.
DEJESUS
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