Small Craft Advisory 23, NWS Honolulu, HI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
1000 AM HST WED APR 15 2015

.SYNOPSIS...
A SURFACE RIDGE TO THE NORTH WILL MAINTAIN TRADE WINDS OVER THE
ISLANDS THROUGH NEXT WEEK. A TROUGH ALOFT WILL PASS NORTH OF THE
AREA THROUGH FRIDAY. THE TROUGH WILL MAKE SHOWERS MORE ACTIVE AND
WEAKEN THE TRADES AS IT PASSES. THE TRADE WINDS WILL STRENGTHEN AND
RAINFALL WILL DECREASE OVER THE WEEKEND AS THE TROUGH MOVES AWAY.

&&

.DISCUSSION...
A STRONG 1035 MB HIGH IS ABOUT 1900 MILES NORTHEAST OF OAHU WITH A
1031 MB HIGH ABOUT 1400 MILES TO THE NORTHWEST. THERE IS A FRONT...
SUPPORTED BY A TROUGH ALOFT...BETWEEN THE TWO HIGHS ABOUT 650 MILES
NORTHWEST OF OAHU. THE HIGH PRESSURE AT THE SURFACE IS MAINTAINING
TRADE WINDS OVER THE ISLANDS BUT THE WINDS HAVE WEAKENED SINCE
YESTERDAY DUE TO THE FRONT TO THE NORTHWEST. THE TRADE WINDS ARE
CARRYING LOW CLOUDS OVER THE WINDWARD SIDES OF THE ISLANDS. THE
ATMOSPHERE OVER THE AREA IS A BIT MOIST AND UNSTABLE THANKS TO THE
TROUGH ALOFT...SO THE CLOUDS MOVING OVER THE ISLANDS ARE RATHER
SHOWERY.

THE MODELS ARE IN PRETTY GOOD AGREEMENT SHOWING THE ATMOSPHERE
REMAINING MOIST AND UNSTABLE THROUGH FRIDAY AS THE TROUGH ALOFT
PASSES NORTH OF THE AREA. THE WEATHER WILL TURN DRIER BY THE WEEKEND
AND THE DRIER WEATHER IS EXPECTED TO CONTINUE THROUGH THE FIRST HALF
OF NEXT WEEK. MEANWHILE...HIGH PRESSURE NORTH OF THE ISLANDS WILL
STRENGTHEN AS THE TROUGH ALOFT MOVES AWAY. THAT WILL TIGHTEN THE
PRESSURE GRADIENT OVER THE ISLANDS AND THE TRADE WINDS WILL
STRENGTHEN. THE TRADES WILL BECOME QUITE BREEZY BY EARLY NEXT WEEK.

&&

.AVIATION...
AIRMET SIERRA FOR MTN OBSC IS IN EFFECT FOR THE WINDWARD SIDES OF
THE BIG ISLAND AND MAUI. VFR CONDITIONS WILL PREVAIL OVER MOST
LEEWARD AREAS...BUT AFTERNOON CONVECTION MAY PRODUCE MVFR CONDITIONS
OVER THE LEEWARD AREAS OF THE BIG ISLAND AND MAUI.

AIRMET TANGO IS IN EFFECT FOR MOD TURB BETWEEN FL280 AND FL350 DUE
TO A JET STREAM ALOFT AND FOR MOD TURB BLW 090 IN THE LEE OF THE
ISLANDS.

&&

.MARINE...
WIND SPEEDS AND SEAS ARE FORECAST TO REMAIN BELOW THE ADVISORY
THRESHOLDS TODAY. TRADE WINDS WILL STRENGTHEN AGAIN LATER THIS WEEK
AND SMALL CRAFT ADVISORIES...SCA...MAY BE REQUIRED AGAIN BY TOMORROW
NIGHT FOR THE WINDY AREAS AROUND THE BIG ISLAND AND MAUI. THE WINDS
WILL LIKELY STRENGTHEN FURTHER OVER THE WEEKEND AND THE SCA
CONDITIONS MAY BECOME MORE WIDESPREAD.

SURF IS BUILDING ALONG NORTH AND WEST FACING SHORES AS A NEW
NORTHWEST SWELL ROLLS IN...BUT THE SURF IS EXPECTED TO REMAIN BELOW
THE ADVISORY THRESHOLD. THIS SWELL WILL PEAK OVERNIGHT...THEN
GRADUALLY SUBSIDE THROUGH THE WEEKEND.

TRADE WINDS WILL CONTINUE TO PRODUCE ROUGH SURF ALONG EAST FACING
SHORES. SURF HEIGHTS WILL LIKELY INCREASE SLIGHTLY ALONG EAST FACING
SHORES THIS WEEKEND AS THE TRADE WINDS STRENGTHEN AGAIN. ONLY SMALL
SURF IS EXPECTED ALONG SOUTH FACING SHORES THROUGH THE WEEKEND. SURF
ALONG THE SOUTH FACING SHORES MAY BUILD TO MODERATE LEVELS NEXT WEEK.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

DONALDSON