Area Forecast Discussion
Issued by NWS Honolulu, HI

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXHW60 PHFO 311338 AAA
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
400 AM HST FRI JUL 31 2015

.SYNOPSIS...
HIGH PRESSURE TO THE NORTHEAST...AND LOW PRESSURE PASSING TO THE
SOUTH...LIKELY WILL INCREASE TRADE WIND SPEEDS OVER THE WEEKEND.
WINDWARD SHOWERS ALSO WILL INCREASE SLIGHTLY...ESPECIALLY OVER THE
BIG ISLAND. EVEN WETTER CONDITIONS OVER MUCH OF THE STATE APPEAR
LIKELY BY THE MIDDLE OF NEXT WEEK. THE WIND FORECAST MAY VARY
CONSIDERABLY FROM MONDAY ONWARD.

&&

.DISCUSSION...
OBSERVATIONS AROUND THE MAIN HAWAIIAN ISLANDS REPORTED SLIGHTLY
WEAKER...BUT STILL MODERATE TRADE WINDS BLOWING. WIND SPEEDS THROUGH
THE CHANNELS WERE HIGHER...AS WOULD BE EXPECTED FOR GAP FLOW. THE
AIR MASS REMAINED ON THE MOIST SIDE OF TYPICAL...AND THE INVERSION
ROSE TO A MORE USUAL HEIGHT DURING THE PAST SIX HOURS...BUT RIDGING
PERSISTED...OR EVEN STRENGTHENED ALOFT. THUS...RAINFALL WAS MODEST
OVERALL...WITH RECORDED ACCUMULATION FALLING MAINLY OVER WINDWARD
SLOPES. CIRRUS LAYERS FROM CONVECTION NEAR THE DATELINE CONTINUED TO
ARRIVE...BUT IN FAIRLY SMALL AMOUNTS. THUS...THE SKY GRID HAS BEEN
INCREASED SLIGHTLY FOR THE EARLY PART OF THE FORECAST.

GUIDANCE AGREED IN PREDICTING ONLY GRADUAL CHANGES THROUGH THE
WEEKEND. MOST SOLUTIONS EXPANDED THE RIDGE ALOFT OVERHEAD...THUS
LIMITING SHOWER POTENTIAL. HOWEVER...THE REMNANT LOW FROM FORMER
TROPICAL DEPRESSION EIGHT-E WILL PASS TO THE SOUTH OF THE
ISLANDS...INCREASING THE PRESSURE GRADIENT...AND THUS WIND SPEEDS
ACROSS THE STATE. GREATER OROGRAPHIC FORCING IN TURN WILL OPPOSE THE
CAPPING EFFECT OF THE RIDGE ALOFT. THE MOISTER AIR MASS SURROUNDING
THE PASSING LOW ALSO SHOULD REACH AT LEAST THE BIG ISLAND. THUS...IN
THE NET...THE TRADE WINDS SHOULD INCREASE IN SPEED...AND WINDWARD
SHOWERS SHOULD BECOME SLIGHTLY MORE ACTIVE...AT LEAST OVER THE SOUTH
END OF THE STATE.

BY THE MIDDLE OF NEXT WEEK...BIG CHANGES MAY OCCUR. HURRICANE
GUILLERMO CURRENTLY WAS LOCATED ABOUT 1900 MILES EAST-SOUTHEAST OF
HONOLULU IN THE EAST PACIFIC BASIN. GUIDANCE SOLIDLY AGREED IN
PREDICTING THIS SYSTEM TO MOVE WEST-NORTHWEST FOR THE NEXT FEW DAYS.
BY SATURDAY NIGHT...THE NATIONAL HURRICANE CENTER PREDICTED
GUILLERMO TO CROSS 140W INTO THE CENTRAL PACIFIC BASIN. FORECAST
UNCERTAINTY FOR AN EVENT SO FAR IN THE FUTURE ARGUED AGAINST OVERLY
DETERMINISTIC PREDICTIONS...BUT A CLOSE APPROACH TO THE STATE COULD
NOT BE RULED OUT. SINCE IN MOST SCENARIOS GUILLERMO WILL BRING AT
LEAST A MOISTER AIR MASS TO THE STATE...THE MIDDLE OF NEXT WEEK
PROBABLY WILL BE ON THE WET SIDE OF CLIMATOLOGY. POPS AND RELATED
GRIDS HAVE BEEN TRENDED ACCORDINGLY. THE PRECISE TRACK OF THE
SYSTEM ALSO MAY TAKE THE WIND FIELD VERY FAR INDEED FROM TYPICAL
TRADE-WIND CONDITIONS.

&&

.AVIATION...
HIGH PRESSURE N OF THE STATE AND A SERIES OF LOW PRESSURE SYSTEMS
TO THE SOUTH OF THE ISLANDS WILL KEEP A BREEZY E TO NE TRADE WIND
FLOW IN PLACE THROUGH TONIGHT. CLOUDS AND SHOWERS WILL FOCUS
PRIMARILY ACROSS MTN AND N THRU E SECTIONS OF THE ISLANDS...AND SOME
BRIEF MVFR CIGS WILL BE POSSIBLE AT PHLI AND PHTO FROM TIME TO TIME.
ADDITIONALLY...MVFR CIGS WILL LIKELY IMPACT PHNY FROM MID MORNING
THROUGH EARLY THIS EVENING. ELSEWHERE...VFR CONDITIONS SHOULD
PREVAIL. AIRMET TANGO IS IN EFFECT FOR MODERATE LOW LEVEL TURBULENCE
OVER AND DOWNWIND OF THE MTS...AND THESE CONDITIONS ARE EXPECTED TO
CONTINUE THROUGH THE DAY.

&&

.MARINE...
A SMALL CRAFT ADVISORY REMAINED IN EFFECT FOR TYPICALLY WINDY AREAS
AROUND MAUI AND THE BIG ISLAND. AS THE REMNANT LOW THAT ONCE WAS
DEPRESSION EIGHT-E PASSES SOUTH OF THE STATE...THE GRADIENT MAY
TIGHTEN ENOUGH TO REQUIRE EXPANSION OF THE ADVISORY...ESPECIALLY
TOWARD OAHU AND KAUAI.

NO MAJOR SWELLS ARE EXPECTED FOR THE NEXT FEW DAYS...SO SURF SHOULD
REMAIN BELOW THE ADVISORY THRESHOLD ALONG ALL SHORES.

THE NATIONAL HURRICANE CENTER IN MIAMI HAS BEEN ISSUING BULLETINS ON
HURRICANE GUILLERMO...LOCATED ABOUT 1900 MILES EAST-SOUTHEAST OF
HONOLULU. THE CURRENT FORECAST PREDICTS GUILLERMO TO MOVE
WEST-NORTHWEST AND STRENGTHEN...LIKELY CROSSING 140W INTO THE
CENTRAL PACIFIC BASIN ON SATURDAY. ALTHOUGH THE TRACK AND INTENSITY
OF THE STORM REMAINED UNCERTAIN SO FAR IN THE FUTURE...ADVERSE
EFFECTS FOR HAWAIIAN COASTAL WATERS NEXT WEEK COULD NOT BE RULED OUT.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
SMALL CRAFT ADVISORY UNTIL 6 AM HST SUNDAY FOR MAALAEA BAY-
PAILOLO CHANNEL-ALENUIHAHA CHANNEL-BIG ISLAND LEEWARD WATERS-BIG
ISLAND SOUTHEAST WATERS.

&&

$$

DISCUSSION/MARINE...RYSHKO
AVIATION...JELSEMA





USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.