Area Forecast Discussion
Issued by NWS Honolulu, HI
FXHW60 PHFO 251222
Area Forecast Discussion
National Weather Service Honolulu HI
222 AM HST MON JUL 25 2016
Quick forecast update to cancel the Tropical Storm Warning for
Oahu, Kauai, and Niihau, along with most of the adjacent coastal
waters as Tropical Storm Darby has shifted off to the west-
northwest of Kauai.
.PREV DISCUSSION.../ISSUED 852 PM HST SUN JUL 24 2016/
The 8 pm HST advisory from the Central Pacific Hurricane Center
(CPHC), indicated that Tropical Storm Darby was located 20 miles
east-northeast of Lihue. Infrared satellite imagery shows cloudy
or mostly cloudy skies in place across the state, with radar
imagery showing some intense bands of showers and thunderstorms
primarily impacting Oahu. Main short term concern for tonight
revolves around the potential for heavy rainfall and flash
Rest of tonight...
The latest track from CPHC takes Darby northwestward near or over
Kauai to a location around 125 miles northwest of Kauai by 8 am
Monday. Deep southerly flow on the eastern side of Darby will
continue to transport tropical moisture with precipitable water
values in excess of 2.0 inches across the island chain through the
overnight hours. The combination of moisture along with large
scale synoptic forcing provided by an upper level trough to the
northwest of the state and the right rear quad of an upper level
jet will promote numerous to widespread showers and thunderstorms
overnight. These features will best align over central and
western portions of the state, particularly Oahu and Kauai, where
the potential for locally heavy rainfall and flash flooding will
continue. Deep layer ridging will begin to build westward over the
Big Island overnight, so conditions are expected to improve here.
Monday through Friday night...
Darby will continue to track northwestward and away from the Aloha
state, with conditions steadily improving from east to west during
the day on Monday. As high pressure builds well northeast of the
island chain, a more typical trade wind pattern is expected
through the remainder of the week, with clouds and showers
focused primarily over windward and mauka locales.
Model guidance is in good agreement showing the trade wind flow
moistening up in response to a lowering of upper level heights
over the state. There is also some indication that moisture
associated with the remnants of what is now Hurricane Georgette in
the eastern Pacific, will get caught up in the trade wind flow. As
a result, there should be an increase in trade wind showers
across the state, with the majority of the activity impacting
windward and mauka locales.
Tropical Storm Darby continues to bring clouds and rain to most
areas of the state, with the heaviest rainfall with thunderstorms
over Oahu this evening. Tropical SIGMET Whiskey remains in effect
for Darby which covers most of the state.
AIRMET Sierra is in effect for IFR conditions across Kauai and
Oahu, and mountain obscuration for the rest of the state. AIRMET
Sierra is likely to remain up most of the night.
AIRMET Tango continues for both mechanical turbulence downwind of
the mountains on all islands, and for strong surface winds over
Kauai and Oahu.
Darby is expected to continue a northwest track, so expect
clearing from east to west over the next 24 hours.
Flash Flood Watch until noon HST today for Oahu.
Flash Flood Watch through this afternoon for Niihau-Kauai.
High Surf Advisory until 6 AM HST early this morning for Kauai
Windward-Oahu Koolau-Olomana-Windward Haleakala.
Flash Flood Watch until 6 AM HST early this morning for Molokai-
Tropical Storm Warning for Kauai Northwest Waters-Kauai Windward