000
FXHW60 PHFO 080601
AFDHFO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
830 PM HST TUE SEP 7 2010
.SYNOPSIS...
HIGH PRESSURE FAR NORTH OF THE STATE WILL PRODUCE LIGHT TO MODERATE
TRADE WINDS OVER THE ISLANDS THROUGH THE UPCOMING WEEK. SHOWERS
WILL FAVOR WINDWARD AND MOUNTAIN AREAS WITH MAINLY LIGHT RAINFALL
TOTALS. A BRIEF INCREASE IN RAINFALL IS EXPECTED THURSDAY NIGHT AND
MORNING FRIDAY.
&&
.DISCUSSION...
LIGHT TO MODERATE TRADE WINDS WITH MODEST SHOWER ACTIVITY IS IN
STORE TONIGHT. THE CLOUD BAND THAT PASSED OVER THE STATE LAST NIGHT
HAS CLEARED THE ISLANDS TO THE WEST...AND SHOWER-BEARING CLOUDS IN
THE TRADE WIND FLOW TONIGHT WILL BE LIMITED. AS A RESULT...RAINFALL
WILL BE CONFINED TO WINDWARD AND MAUKA AREAS...WITH LIGHT RAINFALL
TOTALS...ESPECIALLY COMPARED TO LAST NIGHT...AND DRY CONDITIONS
LEEWARD.
TRADE WINDS WILL HOLD AT LIGHT TO MODERATE STRENGTH OVER THE ISLANDS
THROUGH THE WEEKEND. A NEARLY STATIONARY 1034 MB HIGH 1550 MILES
NORTH OF THE STATE NEAR 44N 156W IS GENERATING THE TRADES. A HIGH OF
THIS MAGNITUDE WOULD NORMALLY GENERATE STRONGER TRADE WINDS OVER THE
ISLANDS...BUT AN UPPER LEVEL LOW SITTING 850 MILES NORTH OF THE
MAUI IS WEAKENING THE SURFACE PRESSURE GRADIENT AND REDUCING THE
STRENGTH OF THE TRADES. THE HIGH WILL WEAKEN AND MOVE EASTWARD
THROUGH THE WEEK...WHILE SOME FORM OF UPPER LEVEL TROUGHING LINGERS
FAR NORTH OF THE STATE. AS A RESULT...EXPECT LITTLE CHANGE IN THE
WINDS. WINDS WILL BE LIGHT ENOUGH FOR AFTERNOON SEA BREEZES AND LOW
CLOUD DEVELOPMENT OVER SHELTERED...LEEWARD PORTIONS OF ALL ISLANDS.
A STABLE PATTERN OF MAINLY WINDWARD AND MAUKA SHOWERS WITH LIGHT
RAINFALL ACCUMULATION IS EXPECTED FOR THE NEXT COUPLE OF DAYS.
PRECIPITABLE WATER...PW...IN THE TRADE WIND FLOW WILL BE AT BELOW
NORMAL VALUES OF 0.75 TO 1.1 INCHES THROUGH THURSDAY AFTERNOON.
MEANWHILE...BUILDING UPPER LEVEL RIDGING WILL CREATE STABLE
CONDITIONS. THIS ALL POINTS TOWARD LIGHTER THAN NORMAL SHOWER
ACTIVITY...WITH RAINFALL CONFINED TO WINDWARD AND MAUKA AREAS...AS
WELL AS THE KONA SLOPES DURING THE AFTERNOON HOURS.
AN INCREASE IN SHOWERS IS EXPECTED THURSDAY NIGHT AND FRIDAY
MORNING...FOLLOWED BY RATHER DRY CONDITIONS FOR THE WEEKEND. THE
ABOVE MENTIONED UPPER LEVEL LOW IS GENERATING A WEAK LOW-LEVEL
TROUGH ON ITS SOUTHEAST SIDE. THIS IS CAUSING AN AREA OF CONVERGENCE
TO THE EAST OF THE TROUGH. PW VALUES OF 1.5 INCHES ARE BEING
DETECTED WITHIN THIS CONVERGENCE BAND 650 MILES NORTHEAST OF THE
STATE. AS THE UPPER LOW FILLS OVER THE NEXT COUPLE OF DAYS...THE
TROUGH AND ITS BAND OF SHOWERS WILL GET CAUGHT UP IN THE TRADE WIND
FLOW AND PASS OVER THE ISLANDS THURSDAY NIGHT AND FRIDAY MORNING.
STRONG RIDGING ALOFT WILL MAINTAIN STABLE CONDITIONS...SO EXPECT
RAINFALL SIMILAR TO LAST NIGHT/S SHOWER BAND. BEYOND THAT...A DRIER
AIRMASS SETTLING IN FOR THE WEEKEND WILL PRODUCE ONLY MODEST
WINDWARD RAINFALL.
&&
.MARINE...
TRADE WINDS OVER HAWAIIAN WATERS WILL HOLD AT MODERATE TO LOCALLY
FRESH STRENGTH THROUGH THE WEEKEND. ONLY SLIGHT FLUCTUATIONS IN
SPEED ARE EXPECTED...WITH THE TYPICALLY WINDY CHANNELS AND WATERS
AROUND THE BIG ISLAND AND MAUI FLIRTING WITH THE SMALL CRAFT
ADVISORY /SCA/ THRESHOLD. AT THIS TIME...IT LOOKS LIKE THE SMALL
CRAFT FLAG WILL REMAIN DOWN.
SEAS REMAIN WELL BELOW THE 10 FOOT SCA LEVEL. VERY SMALL...2 FT 10
SECONDS...ENERGY FROM THE NORTHWEST MAY BUILD OVERNIGHT THROUGH
WEDNESDAY...BUT NO SIGNS OF THE SWELL AT THE WAIMEA BUOY. A LONGER
PERIOD...2 FOOT SOUTH SOUTHWEST SWELL IS DUE TO ARRIVE ON FRIDAY
AND CONTINUE THROUGH THE WEEKEND.
&&
.HFO WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
WROE
THE HYDROMETEOROLOGICAL PREDICTION CENTER
CAMP SPRINGS, MD
HAWAII EXTENDED FORECAST DISCUSSION
HAWAII EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
607 AM EDT TUE SEP 07 2010
VALID 00Z WED SEP 08 2010 - 00Z WED SEP 15 2010
MODELS CONTINUE TO SHOW STRONG MID LVEL PAC RIDGING PERSISTING
NORTH OF THE ISLANDS WITH GOOD AGREEMENT ON A TRAPPED MID LEVEL
LOW MOVING WESTWARD ALONG 32N TO NORTH OF THE ISLANDS MID WEEK
WITH A SLOW DRIFT WEST. THE STRONG MID LEVEL RIDGING WILL SUPPORT
EQUALLY STRONG SFC HIGH PRESSURE AREA NORTHEAST OF THE ISLANDS TO
GRADUALLY DRIFT WESTWARD TO NORTH OF THE ISLANDS NEAR 45N LATE
PERIOD. SOME LIMITED SFC REFLECTION IN THE FORM OF AN INVERTED
TROF EXPECTED TO MOVE WEST NORTH OF THE REGION IN RESPONSE TO THE
MID LEVEL LOW. SEASONAL MODERATE TRADE FLOW OVER THE REGION WILL
CONTINUE. A DRY PERIOD WITH ANY RAIN ASSOCIATED WITH THE MID LEVEL
LOW WELL NORTH OF THE ISLANDS. ROSENSTEIN
Last Updated: 607 AM EDT TUE SEP 07 2010
