Area Forecast Discussion
Issued by NWS Honolulu, HI
FXHW60 PHFO 222000
Area Forecast Discussion
National Weather Service Honolulu HI
1000 AM HST Sat Oct 22 2016
Breezy to locally windy trade winds will persist into Sunday
followed by a gradual decline early in the work week. A stable
trade wind weather pattern will focus rainfall along windward
terrain this weekend, though showers will be periodically carried
over leeward sections on the gusty trades. Moderate trade winds
and a typical pattern of windward and mauka showers will prevail
during the work week, with pockets of moisture leading to brief
increases in shower activity.
Breezy to locally windy trade winds will continue today. A
relatively strong 1027 mb high is parked about 800 miles north-
northwest of Kauai. Overnight soundings revealed a slightly
elevated inversion around 9000 ft, and Radar VAD wind profiles
have been showing trade winds at a steady 25 to 30 kt below the
inversion. As mid level ridging builds over and north of the
islands today, the inversion should come down a couple thousand
feet, which could cause advisory level wind gusts to be more
widespread though still confined over and downwind of island
terrain. A wind advisory remains in place through the evening.
Rainfall will be focused over windward terrain today, though a
few showers will be blown across leeward portions of the smaller
islands, mainly in the late afternoon. Overnight soundings and
satellite data show precipitable water (PW) values near seasonal
normal over the state. PW values decrease upwind of the islands,
but scattered shower-bearing cumulus observed over these waters
suggests that windward slopes will continue to receive some
Trade winds will gradually decline starting Sunday. The surface
high driving the trades will be nudged westward and weakened by a
deepening trough occupying much of the northeast Pacific. Locally,
winds will still be breezy and gusty on Sunday, followed by a more
pronounced drop to moderate strength on Monday and Tuesday.
Trades will rebuild on Thursday or Friday as the northeast Pacific
trough shifts eastward, allowing stronger high pressure to move
north of the state.
Stable trade wind weather will dominate through much of the week,
though pockets of moisture will periodically lead to increases in
shower activity. One such area of moisture, the remnants of a
front, are expected to pass over the island chain Sunday night.
Strong and gusty trade winds are expected to continue through the
weekend, and as such, AIRMET TANGO for low level turbulence to
the lee of the islands will remain posted. Expect surface winds of
20 to 30 kts throughout the islands.
Clouds and showers being carried in on the trade winds brought
MVFR conditions to the mountains overnight, but have since
thinned. AIRMET SIERRA for mountain obscuration over the east
sides of Maui and the Big Island was recently canceled.
VFR conditions are expected to prevail, but expect some brief MVFR
conditions in clouds and showers.
A Gale Warning is in place for the typically windy waters around
the Big Island and Maui, while a Small Craft Advisory (SCA)
remains posted for remaining Hawaiian waters. The Gale Warning
will likely be downgraded to an SCA sometime tonight, and the SCA
should be extended through Sunday. By Monday, SCA conditions will
likely be confined to the typically windy waters around the Big
Island and Maui. Another round of widespread stronger trades is
possible by Thursday or Friday.
A high surf advisory is in effect for east facing shores through
Sunday afternoon. PacIOOS buoys have been measuring seas of 9 to
10 ft at 8 to 9 seconds across waters exposed to the rough seas
generated by the trade winds. Expect little change in these seas
through at least tonight, followed by a slow decline starting
Sunday. The only significant long period swell due this week is a
moderate northwest swell on Tuesday and Wednesday. Otherwise,
small surf will prevail on north, south and west shores.
Wind Advisory until 9 PM HST this evening for Niihau-Kauai-Oahu-
Molokai-Lanai-Kahoolawe-Maui Windward West-Maui Leeward West-
Maui Central Valley-Windward Haleakala-Leeward Haleakala-South
Big Island-Big Island North and East-Kohala-Big Island Interior.
High Surf Advisory until 6 PM HST Sunday for Kauai Windward-Oahu
Koolau-Olomana-Molokai Windward-Maui Windward West-Windward
Haleakala-South Big Island-Big Island North and East.
Gale Warning until 6 AM HST Sunday for Maalaea Bay-Pailolo
Channel-Alenuihaha Channel-Big Island Leeward Waters-Big Island
Small Craft Advisory until 6 AM HST Monday for Kauai Northwest
Waters-Kauai Windward Waters-Kauai Leeward Waters-Kauai Channel-
Oahu Windward Waters-Oahu Leeward Waters-Kaiwi Channel-Maui
County Windward Waters-Maui County Leeward Waters-Big Island
Public and Marine...Wroe