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 190155
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
400 PM HST SAT APR 18 2015

.SYNOPSIS...
HIGH PRESSURE NORTH OF THE STATE WILL SUPPLY BREEZY TRADE WINDS
THROUGH THE FIRST HALF OF NEXT WEEK. THE TRADE WINDS WILL FOCUS
CLOUDS AND SHOWERS MAINLY OVER WINDWARD AREAS. TYPICAL TRADE WIND
WEATHER IS EXPECTED FOR MOST OF NEXT WEEK...ALTHOUGH A DISTURBANCE
TO THE NORTHWEST MAY BRING A WETTER PATTERN...AND SOUTHEASTERLY
WINDS...BY THE SECOND HALF OF THE WEEK.

&&

.DISCUSSION...
WATER VAPOR IMAGERY SHOWS AN UPPER LEVEL HIGH JUST NORTHWEST OF
KAUAI...WITH A TROUGH DEPARTING FAR TO THE EAST. AT THE SURFACE...
HIGH PRESSURE IS LOCATED FAR NORTHEAST OF THE STATE...WITH A RIDGE
PASSING OVER 300 MILES NORTH OF KAUAI. 00Z SOUNDINGS FROM LIHUE AND
HILO SHOW INVERSIONS OF 6-7KFT AND PRECIPITABLE WATERS JUST OVER 0.9
INCHES. EARLY AFTERNOON MIMIC TOTAL PRECIPITABLE WATER IMAGERY SHOWS
A POCKET OF MOISTURE JUST EAST OF KAUAI...WITH MUCH DRIER AIR JUST
UPSTREAM TO THE EAST AND NORTHEAST.

THE ATMOSPHERE ACROSS THE ISLANDS CONTINUES TO STABILIZE AS HEIGHTS
BUILD BEHIND THE DEPARTING TROUGH. THE AFTERNOON SOUNDINGS SHOW THE
ATMOSPHERE CONTINUING TO STABILIZE AND DRY OUT. THE SURFACE RIDGE
NORTH OF THE STATE IS ALSO STRENGTHENING...LEADING TO THE INCREASE
IN TRADE WINDS WE SAW TODAY. SURFACE PRESSURES AT AIRPORTS ACROSS
THE STATE ARE NEAR 2MB HIGHER THAN 24 HOURS AGO. THE TRADES WILL
KEEP CLOUDS AND SHOWERS FOCUSED ACROSS MAINLY WINDWARD AREAS. WITH
THE STABILIZING AIRMASS/LOWERING INVERSION AND EXPECTED OVERALL
DRYING...RAINFALL WILL BE MUCH MORE LIMITED THAN THE PAST COUPLE
NIGHTS. HOWEVER...THERE ARE ENOUGH POCKETS OF MOISTURE EMBEDDED IN
THE TRADES UPSTREAM TO KEEP AT LEAST LIKELY POPS FOR WINDWARD
AREAS...MAINLY AT NIGHT AND DURING THE EARLY MORNING.

THE HIGH NORTHEAST OF THE STATE IS EXPECTED TO WEAKEN AS A FRONT
MOVES EASTWARD INTO IT...BUT A DEVELOPING HIGH WILL QUICKLY BUILD IN
NORTH OF THE STATE BEHIND THE FRONT. NOT ONLY WILL THIS NEW HIGH
KEEP BREEZY TRADE WINDS GOING THROUGH EARLY NEXT WEEK...IT WILL
INCREASE THE GRADIENT OVER THE ISLANDS TONIGHT/SUNDAY FURTHER
STRENGTHENING THE WINDS ANOTHER NOTCH FROM WHAT WE SAW TODAY.
ADVISORY LEVEL WINDS ARE POSSIBLE IN THE TYPICALLY FUNNELED AREAS
SUNDAY/MONDAY. THE HIGH THAT WOULD DRIVE THE ADVISORY LEVEL WINDS
IS CURRENTLY FAR REMOVED FROM THE AREA THOUGH...ON THE OTHER SIDE OF
A COLD FRONT. WILL HOLD OFF ON ANY ADVISORIES FOR NOW TO SEE HOW THE
HIGH EVOLVES EASTWARD OVERNIGHT.

THERE CONTINUES TO BE A FAIR AMOUNT OF MODEL SPREAD IN THE
EXTENDED...WITH SIGNIFICANT RUN TO RUN DIFFERENCES IN THE GFS. THE
12Z GFS AND ECMWF WERE IN MUCH BETTER AGREEMENT THAN THE 00Z RUNS
/THE 12Z GFS TRENDED TOWARD THE ECMWF SOLUTION/...BUT THE 18Z GFS
WENT BACK TO A SLOWER VERSION OF THE OLD 00Z RUN. AN UPPER LOW
CURRENTLY MOVING EAST OF JAPAN IS EXPECTED TO AMPLIFY OVER THE
CENTRAL PACIFIC IN THE TUESDAY-WEDNESDAY TIME FRAME. THERE IS A 10
DEGREE SPREAD IN THE LONGITUDE WHERE THE LOW CUTS OFF BETWEEN THE
ECMWF /FARTHER WEST...MORE CONSISTENT/ AND GFS /CLOSER TO THE
STATE...MORE VARIABLE RUN TO RUN/. THERE REMAIN ADDITIONAL AND
SIGNIFICANT SMALL-SCALE DIFFERENCES...ESPECIALLY WITH TIMING AND
LOCATION OF THE SURFACE LOW. THIS SITUATION WILL BEAR WATCHING...BUT
WE CONTINUE TO FAVOR THE MORE CONSISTENT FARTHER-WEST SOLUTION OF
THE ECMWF...WHICH ALSO IS FAVORED CLIMATOLOGICALLY. THIS FEATURES A
SLIGHT VEERING OF THE WINDS TO THE EAST-SOUTHEAST AND AN INCREASE IN
MOISTURE/SHOWERS DURING THE SECOND HALF OF THE WEEK.

&&

.AVIATION...
HIGH PRESSURE WELL NORTHEAST OF THE STATE WILL KEEP A BREEZY
EAST-NORTHEAST TRADE WIND FLOW IN PLACE THROUGH THE WEEKEND...WITH
CLOUDS AND SHOWERS FOCUSED PRIMARILY ACROSS MOUNTAIN AND NORTH
THROUGH EAST SECTIONS OF THE ISLANDS. BRIEF MVFR CIGS ARE
POSSIBLE IN PASSING SHRA AT PHTO AND PHLI...BUT PREDOMINANTLY VFR
CONDITIONS ARE EXPECTED AT ALL TERMINALS THROUGH 20/00Z.

AIRMET TANGO REMAINS IN EFFECT FOR LOW LEVEL TURBULENCE OVER AND TO
THE SOUTH THRU WEST OF THE MOUNTAINS...WITH THESE CONDITIONS LIKELY
CONTINUING THROUGH THE WEEKEND.

AIRMET SIERRA IS IN EFFECT FOR MTN OBSC ACROSS NORTH THRU EAST
SECTIONS OF KAUAI. THESE CONDITIONS ARE EXPECTED TO IMPROVE BY
19/0400Z.

&&

.MARINE...
WITH THE STRENGTHENING TRADE WINDS...SMALL CRAFT CONDITIONS ARE
EXPECTED ACROSS ALL COASTAL WATERS. A MORNING ASCAT PASS SHOWED A
SOLID AREA OF 30 KNOT WINDS THROUGH THE ALENUIHAHA CHANNEL...AND
POCKETS OF 25 KNOTS ELSEWHERE EVEN ACROSS WINDWARD MAUI COUNTY
WATERS. WINDS ARE EXPECTED TO INCREASE A NOTCH TONIGHT/SUNDAY...WITH
NEAR GALE FORCE WINDS IN CHANNELS AROUND MAUI AND THE BIG ISLAND.
THESE STRONG AND GUSTY TRADE WINDS WILL REMAIN IN PLACE THROUGH AT
LEAST MONDAY NIGHT. ADDITIONALLY...COMBINED SEAS WILL APPROACH THE
SMALL CRAFT THRESHOLD OF 10 FEET...WITH SEAS DOMINATED BY
SHORT-PERIOD WIND WAVES.

THE STRONG TRADE WINDS WILL PUSH SURF TO NEAR ADVISORY LEVELS ALONG
EAST FACING SHORES THROUGH EARLY NEXT WEEK. REGARDLESS OF WHETHER
ADVISORY CRITERIA IS MET...SURF WILL BE ROUGH ALONG EAST FACING
SHORES FOR THE NEXT SEVERAL DAYS. FOR NORTH AND WEST FACING
SHORES...NEW SMALL NORTHWEST SWELLS ARE EXPECTED ON SUNDAY AND
TUESDAY. A LONG-PERIOD SOUTH-SOUTHWEST SWELL WILL ARRIVE LATE THIS
WEEKEND AND PEAK AROUND TUESDAY...THEN SLOWLY DIMINISH THROUGH THE
WEEK. SURF ALONG SOUTH FACING SHORES IS EXPECTED TO APPROACH
ADVISORY LEVELS DURING THE PEAK OF THE SWELL.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
SMALL CRAFT ADVISORY UNTIL 6 AM HST TUESDAY FOR ALL HAWAIIAN WATERS.

&&

$$

DISCUSSION/MARINE...BRAVENDER
AVIATION...JELSEMA





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