Photo Credit: Tyler Rooke

West Side

Today: Partly sunny with isolated showers. Highs 82 to 88. East winds up to 15 mph. Chance of rain 20 percent.

Tonight: Breezy. Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows 70 to 77. East winds up to 15 mph increasing to 10 to 20 mph after midnight. Chance of rain 30 percent.

Monday: Breezy. Mostly sunny with isolated showers. Highs 82 to 88. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

South Side

Today: Mostly sunny. Highs 86 to 91. Northwest winds up to 15 mph.

Tonight: Partly cloudy. Lows around 70. North winds up to 15 mph.

Monday: Mostly sunny. Breezy. Highs 86 to 91. Northeast winds up to 20 mph.

North Shore

Today: Mostly cloudy. Breezy. Occasional showers in the morning, then scattered showers in the afternoon. Highs around 82 near the shore to around 68 near 5000 feet. East winds up to 20 mph. Chance of rain 70 percent.

Tonight: Breezy. Mostly cloudy with showers likely. Lows 68 to 74 near the shore to around 55 near 5000 feet. East winds 10 to 20 mph decreasing to up to 15 mph after midnight. Chance of rain 70 percent.

Monday: Mostly cloudy. Breezy. Occasional showers in the morning, then scattered showers in the afternoon. Highs around 82 near the shore to around 69 near 5000 feet. East winds 10 to 20 mph decreasing to up to 20 mph in the afternoon. Chance of rain 70 percent.

Central Maui

Today: Breezy. Partly sunny with isolated showers in the morning, then mostly sunny in the afternoon. Highs 85 to 91. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 20 percent.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Breezy. Isolated showers. Lows 68 to 74. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Monday: Mostly sunny. Breezy. Isolated showers in the morning. Highs 85 to 91. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Upcountry

Today: Mostly sunny in the morning then becoming partly sunny. Scattered showers. Highs around 60 at the visitor center to around 58 at the summit. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Breezy. Partly cloudy with scattered showers. Lows around 47 at the visitor center to around 43 at the summit. East winds up to 20 mph. Chance of rain 50 percent.

Monday: Mostly sunny in the morning then becoming partly sunny. Breezy. Scattered showers. Highs 59 to 73. East winds up to 20 mph. Chance of rain 50 percent.

East Maui

Today: Mostly cloudy. Breezy. Occasional showers in the morning, then scattered showers in the afternoon. Highs around 82 near the shore to around 68 near 5000 feet. East winds up to 20 mph. Chance of rain 70 percent.

Tonight: Breezy. Mostly cloudy with showers likely. Lows 68 to 74 near the shore to around 55 near 5000 feet. East winds 10 to 20 mph decreasing to up to 15 mph after midnight. Chance of rain 70 percent.

Monday: Mostly cloudy. Breezy. Occasional showers in the morning, then scattered showers in the afternoon. Highs around 82 near the shore to around 69 near 5000 feet. East winds 10 to 20 mph decreasing to up to 20 mph in the afternoon. Chance of rain 70 percent.

Lanai City

Today: Mostly sunny in the morning, then mostly cloudy with isolated showers in the afternoon. Highs 76 to 83. Light winds becoming northeast up to 15 mph in the afternoon. Chance of rain 20 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Lows around 67. Northeast winds up to 15 mph increasing to 10 to 15 mph after midnight.

Monday: Breezy. Mostly sunny in the morning, then mostly cloudy with isolated showers in the afternoon. Highs 76 to 83. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Kaunakakai

Today: Partly sunny. Isolated showers in the morning. Highs 75 to 89. East winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 20 percent.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Breezy. Isolated showers. Lows 62 to 73. East winds 10 to 20 mph. Chance of rain 20 percent.

Monday: Breezy. Mostly sunny with isolated showers in the morning, then partly sunny in the afternoon. Highs 75 to 89. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Showers will expand across the state today as an area of moisture drifts across the region. An area of deep low pressure exiting well northwest of Hawaii will re-establish the ridge north of the state and strengthen trade wind flow through the middle of this week. This will reinforce a typical trade wind weather pattern through Wednesday. Trade winds will weaken slightly and veer southeast Thursday and Friday, as another area of low pressure develops northwest of the state.

Discussion

Radar trends this morning show the areal coverage of showers expanding westward across the islands, with the most persistent showers around the Big Island and windward areas of the smaller islands. Satellite trends show a similar pattern, with moisture and cloud cover drifting westward across the state while jet dynamics enhance upper clouds west of Kauai.
The areal coverage of showers will continue to increase across the eastern and central islands this morning, spreading westward across the remainder of the islands by this afternoon. CIMSS satellite based imagery continues to show increased RH with layered precipitable water values nearing 1.80 inches, streaming in from the east. This matches well with the morning HTO sounding showing a PW value of 1.73 inches. Rainfall early this morning has been limited, however a few locations around the Big Island have already seen amounts in excess of one half inch. These locally enhanced showers will continue across the islands through this afternoon, as model data shows moisture depths increasing to over 13k feet today. The most persistent showers will remain across windward areas of the central and eastern islands where moisture depths will be greatest. An upper level ridge building across the state through early next week, should help generate moderately stable conditions and limit widespread heavy rainfall threats for most locations. Tonight through Wednesday, a return to more shallow layered moisture will combine with persistent trade wind flow to maintain showers across mainly windward zones, with overnight and early morning hours seeing the most persistent rainfall.
Another low pressure system developing northwest of the islands later in the week, will slowly drop southward, though maintaining a track west of the Kauai. This pattern will slightly weaken the surface pressure gradient and trade winds some, as the winds trend more southeastward Thursday and Friday. Expect another potential uptick in the areal coverage of rainfall to end the work week, as models indicate another band of deeper layered moisture drifting across the state from the east. There continues to be some differences in model solutions late next week, though trends suggest high pressure trying to reestablish a drier typical trade wind pattern next weekend.

Aviation

Trade winds will gradually strengthen today as high pressure begins to build in north of the state. VFR conditions prevail at all TAF sites and are expected to continue through the forecast period. Clouds and a few passing showers will favor windward and mauka areas. No AIRMETS are in effect and none are expected this morning. However, if trade winds strengthen sufficiently later today, AIRMET Tango for terrain-induced turbulence may be needed.

Marine

The upper level low and associated trough north of the islands that has been producing recently light western water winds and more moderate eastern water east southeast winds will lift north northwest through the day. Upper ridging will take hold over the state the next couple days as surface high pressure re-establishes itself far northeast of the region. As this occurs, local near and offshore water east trade winds will restrengthen back to more moderate to fresh magnitudes, locally strong across the windy zones by this evening. A Small Craft Advisory will be in effect within the notoriously windier bays and channels around Maui County and Big Island, as well as south of Big Island, from tonight through Tuesday afternoon.
A small, short period southeast swell will fade through the day as a small, medium period south swell continues to decline into Tuesday. A small, long period reinforcement south swell arrives late Tuesday and will pass around the islands through next weekend. A moderate size, short period north swell will peak today before a slightly longer period northwest swell arrives late Monday and fills in through Tuesday. Choppy wind wave surf will continue along east-facing shores the next several days.

HFO Watches/Warnings/Advisories

Small Craft Advisory from 6 PM this evening to 6 PM HST Tuesday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

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Data Courtesy of NOAA.gov