Photo Credit: James Grenz

Hilo

Today: Frequent showers and possibly a thunderstorm. Some of the storms could produce heavy rainfall. High near 73. West wind around 5 mph becoming east in the afternoon. Chance of precipitation is 90%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

Tonight: Frequent showers and possibly a thunderstorm. Some of the storms could produce heavy rainfall. Low around 63. East wind around 6 mph. Chance of precipitation is 90%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

Tuesday: Frequent showers and possibly a thunderstorm. Some of the storms could produce heavy rainfall. High near 76. South wind around 5 mph becoming light and variable in the afternoon. Chance of precipitation is 100%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

Kona

Today: Scattered showers and thunderstorms. Some of the storms could produce heavy rainfall. Widespread haze. Mostly cloudy, with a high near 79. Southeast wind around 5 mph becoming northwest in the afternoon. Chance of precipitation is 50%. New rainfall amounts between a quarter and half of an inch possible.

Tonight: Showers likely and possibly a thunderstorm. Some of the storms could produce heavy rainfall. Widespread haze. Mostly cloudy, with a steady temperature around 68. North wind around 5 mph. Chance of precipitation is 60%. New rainfall amounts between a half and three quarters of an inch possible.

Tuesday: Showers likely and possibly a thunderstorm. Some of the storms could produce heavy rainfall. Widespread haze. Mostly cloudy, with a high near 79. West wind around 5 mph becoming calm in the afternoon. Chance of precipitation is 60%. New rainfall amounts between a half and three quarters of an inch possible.

Waimea

Today: Showers likely and possibly a thunderstorm. Some of the storms could produce heavy rainfall. Mostly cloudy, with a high near 72. East wind around 11 mph. Chance of precipitation is 70%. New rainfall amounts between 1 and 2 inches possible.

Tonight: Showers likely and possibly a thunderstorm. Some of the storms could produce heavy rainfall. Cloudy, with a low around 52. Breezy, with an east wind 13 to 16 mph, with gusts as high as 22 mph. Chance of precipitation is 70%. New rainfall amounts between 1 and 2 inches possible.

Tuesday: Frequent showers and possibly a thunderstorm. Some of the storms could produce heavy rainfall. High near 73. East northeast wind 6 to 8 mph. Chance of precipitation is 80%. New rainfall amounts between 1 and 2 inches possible.

Kohala

Today: Showers likely and possibly a thunderstorm. Some of the storms could produce heavy rainfall. Mostly cloudy, with a high near 68. Breezy, with an east wind around 15 mph, with gusts as high as 21 mph. Chance of precipitation is 70%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

Tonight: Showers likely and possibly a thunderstorm. Some of the storms could produce heavy rainfall. Cloudy, with a low around 45. Breezy, with an east wind 15 to 22 mph, with gusts as high as 31 mph. Chance of precipitation is 70%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

Tuesday: Frequent showers and possibly a thunderstorm. Some of the storms could produce heavy rainfall. High near 69. Breezy, with an east southeast wind 12 to 17 mph decreasing to 5 to 10 mph in the morning. Winds could gust as high as 24 mph. Chance of precipitation is 90%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

South Big Island

Today: Frequent showers and possibly a thunderstorm. Some of the storms could produce heavy rainfall. Widespread haze. High near 79. Windy, with an east wind 24 to 26 mph, with gusts as high as 34 mph. Chance of precipitation is 80%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

Tonight: Frequent showers and possibly a thunderstorm. Some of the storms could produce heavy rainfall. Widespread haze. Low around 69. Windy, with an east northeast wind around 24 mph, with gusts as high as 31 mph. Chance of precipitation is 90%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

Tuesday: Frequent showers and possibly a thunderstorm. Some of the storms could produce heavy rainfall. Widespread haze. High near 79. Breezy, with an east northeast wind 16 to 21 mph, with gusts as high as 26 mph. Chance of precipitation is 90%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

Puna

Today: Frequent showers and possibly a thunderstorm. Some of the storms could produce heavy rainfall. High near 75. East northeast wind 6 to 8 mph. Chance of precipitation is 90%. New rainfall amounts between three quarters and one inch possible.

Tonight: Frequent showers and possibly a thunderstorm. Some of the storms could produce heavy rainfall. Low around 61. East northeast wind 8 to 11 mph. Chance of precipitation is 90%. New rainfall amounts between three quarters and one inch possible.

Tuesday: Frequent showers and possibly a thunderstorm. Some of the storms could produce heavy rainfall. High near 76. Northeast wind 3 to 5 mph. Chance of precipitation is 90%. New rainfall amounts between 1 and 2 inches possible.

Waikoloa

Today: Scattered showers and thunderstorms. Some of the storms could produce heavy rainfall. Mostly cloudy, with a high near 78. East northeast wind around 5 mph. Chance of precipitation is 50%. New rainfall amounts between a quarter and half of an inch possible.

Tonight: Showers likely and possibly a thunderstorm. Some of the storms could produce heavy rainfall. Mostly cloudy, with a low around 62. East wind 5 to 7 mph. Chance of precipitation is 60%. New rainfall amounts between three quarters and one inch possible.

Tuesday: Showers likely and possibly a thunderstorm. Some of the storms could produce heavy rainfall. Mostly cloudy, with a high near 79. North northeast wind around 5 mph. Chance of precipitation is 70%. New rainfall amounts between three quarters and one inch possible.

Detailed Forecast

Synopsis

Cloudy and showery weather is expected for the first half of the week as an upper level disturbance interacts with tropical moisture moving in from the east and south. Breezy trade winds will give way to lighter winds by mid-week as a surface trough moves over the islands. Strong and gusty northeast winds are in the forecast for next weekend.

Discussion

The combination of cold temperatures aloft and a deep tropical air mass will result in an extended period of widespread heavy showers and possible thunderstorms through mid week. A Flash Flood Watch is currently in effect for the Big Island and Maui County through Tuesday night. This watch could be extended to the other islands if the conditions warrant. This moisture will also bring a potential for winter weather to the Big Island summits above 11k feet through mid week. A Winter Weather Advisory is effect through early Tuesday morning with the likelihood of additional extensions.
The latest ECMWF model run has nudged toward the GFS solution. Not completely but closer by placing the surface trough over the central islands on Thursday. The trough presented by the EC, although not as strong as the GFS, will still cut off the trades. This surface trough not expected to clear the Big Island until Saturday afternoon.
There is no disagreement with the models in addressing the upper level low/trough. Both models have the low southwest of Kauai opening up to a trough Wednesday. The upper trough then pushes eastward across the island chain, finally moving past the Big Island by Friday morning. With the upper level trough moving east of the surface trough, there will only be limited support for heavy rains. So, expect an improving trend Thursday through Friday, from west to east.
Heavy showers ended across the Hilo and Puna districts just before midnight. This dry period will help the ground recover from the drenching it took earlier. Now, the leading edge of a new area of clouds and showers has just moved ashore into the Puna and Kau districts. Hopefully, the land breeze will slow down its progress inland, and/or weaken the showers. Passing showers have been observed with the remaining islands. Satellite imagery shows mid and high clouds streaming across the eastern half of the island chain that will get thicker through the rest of today.
Following the trough, strong northeast winds are expected to spread down the island chain from east to west, that is between Friday and Saturday. It won’t be until Sunday night and Monday when the northeast winds weakens.

Aviation

VFR conditions prevail at all TAF sites except PHTO where MVFR to IFR conditions are expected through the night due to low clouds and showers. As increasing moisture moves in from the southeast tonight, conditions will deteriorate mainly over windward slopes of the Big Island and Maui County. AIRMET Sierra for mountain obscuration is currently in effect for the NE slopes of the Big Island and will likely be expanded to Maui County.
AIRMET Tango is currently in effect over and immediately south thru west of mountain ranges on all islands due to low level mechanical turbulence.

Marine

A high far north of the main Hawaiian Islands will slowly drift southeast over the next few days as it drives moderate to locally strong trades across Hawaiian waters through 6 am HST Tuesday morning. Trade wind waves, combined with northerly swell, will maintain elevated seas over exposed waters. A Small Craft Advisory is in effect through early Tuesday morning for all Hawaiian waters. Models develop a surface trough east the area in the coming days and slowly drag it across the state through the week. This would disrupt mid to late week trade flow.
Strong trade winds will cause surf to remain elevated along east- facing shores today and tonight. A High Surf Advisory for eastern exposures remains in effect through tonight. North swell will continue to decline through today. However, reinforcing north and northwest swells, in tandem with a trade wind wave/east swell wrap, will generate medium surf heights along most north and west- facing shores through today. Diminishing northerly swells will cause surf heights along north and west shore to decrease from Tuesday into next weekend. Small, long period south and southwest swells, along with some trade wrap, will provide enough background to support near seasonable surf along most south-facing shores.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 AM HST Tuesday for Kauai Windward, Oahu Koolau, Olomana, Molokai Windward, Maui Windward West, Windward Haleakala, South Big Island, Big Island North and East.
Flash Flood Watch through late Tuesday night for Big Island.
Flash Flood Watch through late Tuesday night for Molokai, Lanai, Kahoolawe, Maui.
Winter Weather Advisory until 6 AM HST Tuesday for Big Island Summits.
Small Craft Advisory until 6 AM HST Tuesday for all Hawaiian waters,

Data Courtesy of NOAA.gov