Current Conditions
Temp0.7 C
RH7 %
WindNNW 12 mph
RoadOpen
Menu of Text Products for the Hawaiian Islands and the Tropical Pacific/Atlantic Oceans:
Narrow the Menu List
Select Time Limit: 12 hours | 24 hours | 48 hours | 72 hours | No time limit
Select Product Type: All | Routine Bulletins/FCSTS | Warnings/Watches/Advisories | HAWN Weather | Tropical | Marine | Aviation | Daily Obs | Special
Hawaiian Islands Synoptic Discussion and Guidance

362
FXHW60 PHFO 011336
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
330 AM HST WED APR 1 2015

.SYNOPSIS...
THE REMNANTS OF A LOW LEVEL TROUGH OVER THE W HALF OF THE ISLAND
CHAIN WILL CONTINUE TO GRADUALLY DISSIPATE TODAY. THE TRADES WILL
RETURN ACROSS THE AREA AND BECOME LOCALLY STRONG BY THIS
AFTERNOON...WITH SHOWERS FAVORING WINDWARD AND MOUNTAIN AREAS
THROUGH FRIDAY. ENHANCED MOISTURE SOUTHEAST OF THE STATE COULD BRING
INCREASING SHOWER ACTIVITY OVER THE BIG ISLAND DURING THE UPCOMING
WEEKEND.

&&

.DISCUSSION...
THE LINGERING CLOUDY SKIES AND SHOWERS ACROSS THE ISLANDS THIS
MORNING WILL CONTINUE TO GRADUALLY DECREASE AS AN UPPER LEVEL
SHORTWAVE TROUGH NE OF THE ALOHA STATE MOVES FURTHER AWAY FROM THE
AREA. ALSO..THE REMNANTS OF A LOW LEVEL TROUGH WILL GRADUALLY
DISSIPATE NEAR OAHU TODAY. THIS IS ALLOWING FOR SFC HIGH PRESSURE
CENTERED FAR NNE OF THE STATE TO RE-ESTABLISH AND BRING A MORE
ROBUST TRADE WIND PATTERN ACROSS THE ISLANDS...WITH SHOWERS AGAIN
FOCUSING OVER WINDWARD AND MAUKA AREAS. MODEL GUIDANCE IS ALSO
SHOWING SUBSIDENCE DEVELOPING ALOFT BEHIND THE DEPARTING SHORTWAVE
TROUGH...WHICH IS HELPING IN BRINGING A MORE STABLE AIRMASS ACROSS
THE AREA.

AT 315 AM HST...THE LATEST DATA FROM THE DOPPLER WEATHER RADAR
NETWORK WAS SHOWING MOST OF THE REMAINING SHOWERS ACROSS THE ISLANDS
LINGERING OVER THE KOOLAU RANGE IN OAHU...WINDWARD MAUI AND THE SE
SLOPES OF MAUNA LOA OVER THE BIG ISLAND. MEANWHILE...CLOUD MOTION ON
LATEST INFRARED SATELLITE IMAGERY SUGGEST THAT WINDS ACROSS THE
STATE ARE SHIFTING TO A MORE E FLOW...SIGNALING THE RETURN OF THE
TRADES. WIND SPEEDS WILL GRADUALLY STRENGTHEN THROUGH THE REST OF
THE MORNING HOURS...BECOMING RATHER ROBUST BY THIS AFTERNOON. THIS
TRADE WIND PATTERN WILL FURTHER SHIFT SHOWER ACTIVITY INTO WINDWARD
AND MOUNTAIN AREAS. ONLY EXCEPTION WILL BE THE LEEWARD BIG ISLAND
WHERE ONSHORE FLOW SHOULD BRING AFTERNOON CLOUD COVER AND A FEW
SHOWERS.

FOR THE REST OF THE WORK WEEK...THE TRADE WIND WEATHER REGIME IS
EXPECTED TO PREVAIL THROUGH FRI...A SOLUTION STILL SUPPORTED BY THE
ECMWF AND CANADIAN MODELS. GFS...ON THE OTHER HAND...REMAINS AS THE
OUTLIER BY BRINGING ANOTHER COLLAPSE OF THE TRADES STARTING LATE THU
AND INTO FRI...WITH A VERY MOIST AIRMASS FILTERING AT THE MID LEVELS
FROM SW AND S OF THE ISLANDS. THE REASON FOR THIS SYNOPTIC SCENARIO
IS AN APPROACHING MID/UPPER TROUGH FROM THE NW...WHICH GFS SEEMS TO
BE HAVING TROUBLE HANDLING ITS EVOLUTION AND EVENTUAL SOLUTION
DURING THE LATE THU TO FRI TIME FRAME. THIS RESULTS IN A
CONSIDERABLY MORE AGGRESSIVE RAIN EVENT FOR THE UPCOMING WEEKEND
COMPARED TO THE REST OF THE GUIDANCE. THUS...IT SEEMS REASONABLE TO
KEEP FOLLOWING THE ECMWF SOLUTION ATTM...WITH A LESS AGGRESSIVE
WEAKENING TREND OF THE TRADES ON FRI...AND WAIT FOR UPCOMING MODEL
GUIDANCE BEFORE MAKING ANY SIGNIFICANT ADJUSTMENTS TO THE ONGOING
FORECAST PHILOSOPHY.

FOR THE UPCOMING WEEKEND...IT IS LIKELY THAT ENHANCED MOISTURE SE OF
THE STATE WILL BRING INCREASING SHOWERS ACROSS THE BIG ISLAND LATE
SAT AND INTO SUN. TRADE WIND SHOWERS SHOULD CONTINUE EARLY NEXT WEEK
WITH MODEL GUIDANCE SHOWING STRONGER TRADES DEVELOPING ACROSS THE
AREA AS A STRENGTHENING HIGH PRESSURE SYSTEM REMAINS CENTERED FAR
NNE OF THE ALOHA STATE.

&&

.AVIATION...
REBUILDING TRADE WINDS AND INCREASED STABILITY ARE EXPECTED TODAY.
LIMITED MOISTURE WITHIN THE TRADE WIND FLOW WILL FOCUS SHRA ALONG
WINDWARD SLOPES AND COASTS...WHERE ISOL MVFR VIS/CIG CAN BE EXPECTED.
AIRMET TANGO FOR LOW LEVEL TURBULENCE TO THE W AND SW OF TERRAIN IS
LIKELY TO BE ISSUED. VFR WILL BE THE PREVAILING CONDITION AT THE
TERMINALS...ALTHOUGH PERIODS OF MVFR CIG ARE EXPECTED AT PHNY AROUND
MID-DAY...WITH BRIEF MVFR VIS/CIG IN SHRA POSSIBLE AT PHLI AND PHTO.

&&

.MARINE...
LATEST READINGS FROM THE ASCAT SCATTEROMETER PRODUCT SHOW WINDS IN
THE ALENUIHAHA CHANNEL ALREADY AT ADVISORY LEVELS. THUS...A SMALL
CRAFT ADVISORY HAS BEEN ISSUED FOR THE WINDIER WATERS AROUND THE
BIG ISLAND AND MAUI COUNTY. THE STRONG E WINDS SHOULD CONTINUE
THROUGH AT LEAST THURSDAY EVENING...AND THE ADVISORY COULD BE
EXTENDED BEYOND THURSDAY IF THE STRONG WINDS PERSIST.

A SMALL NORTHWEST SWELL WILL GRADUALLY DISSIPATE TODAY. A SMALL
SOUTH-SOUTHWEST SWELL IS EXPECTED TO ARRIVE DURING THE SECOND HALF
OF THE WORK WEEK.

&&

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

&&

$$

DISCUSSION...REYNES
AVIATION...BIRCHARD










Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office