Photo Credit: Jeni Ji Cousins

West Side

Today: Sunny with isolated showers. Highs 72 to 79. Northeast winds up to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows 63 to 69. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Tuesday: Sunny. Isolated showers in the morning. Highs 73 to 79. Northeast winds up to 10 mph in the morning becoming light. Chance of rain 20 percent.

South Side

Today: Sunny. Highs around 81. North winds 10 to 15 mph.

Tonight: Mostly clear. Isolated showers after midnight. Lows 60 to 71. North winds 10 to 15 mph. Chance of rain 20 percent.

Tuesday: Sunny. Highs around 81. North winds around 10 mph in the morning becoming light.

North Shore

Today: Mostly sunny with isolated showers. Highs 74 to 79 near the shore to around 63 near 5000 feet. East winds up to 10 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with scattered showers. Lows around 65 near the shore to around 47 near 5000 feet. East winds up to 10 mph. Chance of rain 40 percent.

Tuesday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 77 near the shore to around 63 near 5000 feet. Light winds. Chance of rain 30 percent.

Central Maui

Today: Sunny. Highs 76 to 81. Northeast winds 10 to 15 mph.

Tonight: Partly cloudy. Isolated showers after midnight. Lows 61 to 66. Northeast winds around 10 mph. Chance of rain 20 percent.

Tuesday: Sunny. Isolated showers in the morning. Highs 77 to 82. Light winds. Chance of rain 20 percent.

Upcountry

Today: Sunny. Isolated showers in the afternoon. Highs around 61 at the visitor center to around 66 at the summit. Northeast winds up to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows 40 to 51. Northeast winds up to 10 mph. Chance of rain 20 percent.

Tuesday: Mostly sunny with isolated showers. Highs around 60 at the visitor center to around 65 at the summit. Light winds. Chance of rain 20 percent.

East Maui

Today: Mostly sunny with isolated showers. Highs 74 to 79 near the shore to around 63 near 5000 feet. East winds up to 10 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with scattered showers. Lows around 65 near the shore to around 47 near 5000 feet. East winds up to 10 mph. Chance of rain 40 percent.

Tuesday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 77 near the shore to around 63 near 5000 feet. Light winds. Chance of rain 30 percent.

Lanai City

Today: Sunny. Isolated showers in the morning. Highs 68 to 76. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Mostly clear. Lows around 61. Northeast winds 10 to 15 mph.

Tuesday: Sunny. Highs 68 to 76. Northeast winds up to 10 mph in the morning becoming light.

Kaunakakai

Today: Sunny with isolated showers. Highs 64 to 82. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Mostly clear. Lows 53 to 69. Northeast winds 10 to 15 mph.

Tuesday: Sunny. Highs 65 to 81. Northeast winds up to 10 mph.

Detailed Forecast

Synopsis

Primarily dry and stable statewide conditions, with generally gentle trades, continue through Tuesday. Limited shower activity will favor windward areas and mauka slopes. A significant pattern change may develop through the middle of the week in response to an evolving northern upper trough digging south toward the islands. This will increase precipitation chances although there is a fair amount of uncertainty regarding this trough's potential impact upon regional winds and rainfall distribution. The threat for gusty southwest winds with moderate to locally heavy rain will begin to increase Wednesday into Thursday.

Discussion

A dry, stable air mass and gentle trade winds will be the main theme during the holiday. Sunrise temperatures will dip into the average middle 60s under cloudier skies with more windward and mauka slope shower activity as a band of higher moisture entering our north nearshore waters this morning passes by to the south. Regional morning soundings depict this stable, unseasonably dry air mass with near 0.9 inch precipitable waters and a pronounced near 5k ft inversion. It a rare sight to see all of the island's rain gauges remaining dry, either nil or just 0.01″ of rain (windward Big Island), these past 24 hours. With the lone exception of this ribbon of higher moisture moving south over the chain and producing a bit more upper elevation shower activity today, many of these gauges will stay dry through Tuesday. Mid to upper level ridging is nosing in from the west and this will maintain enough large scale stability to limit rainfall the next couple of days. After one more day of mainly gentle trades, Tuesday's winds will back off as a weak area of low pressure east of the state slackens the gradient produced by high pressure northeast of the islands.
Deterministic and ensemble solutions are in better agreement on the timing of a Central Pacific upper trough diving south toward the state Wednesday. Ensemble members, especially the majority of the EC members, are not as bullish on the development of a deep (near 1000 mb) surface low in the vicinity of the islands. As of this morning, the general numerical modeling consensus has a cold front passing across the island chain from Wednesday afternoon through late Thursday. Statewide rain chances ahead of the boundary will lift into the likely category as gusty southwesterlies strengthen across Oahu and Maui County Wednesday and Thursday. There is a potential for downsloping winds on Oahu Wednesday. The uncertainly lies in the potential for a cut-off low to develop within the base of this trough and, if this happens, how long the low will meander north of the state. The evolution of this low and its future movement will be the main driver of any significant periods of heavy rain possibly leading to flooding issues and/or strong damaging winds. 500 mb -10 to -13 C temperatures will certainly be cold enough to decrease mid week atmospheric stability and introduce the chance for regional thunderstorm activity. Thus, impactful weather concerns will be the focused of locally high rainfall and strong gusty winds along with proximity storms that will all be dependent upon the movement (or retrogradation) of a cut-off low meandering off to the north.
Weather conditions will begin improving on Friday as the upper level trough/low lifts north and further away from the state. Winds will likely remain light to gentle out of the west. Moderate rain chances will remain alive, especially east of Oahu, as higher mid to low level moisture lingers in the presence of weakening upper troughing. A Central Pacific trough is progged to amplify north of the region early next week. This trough may be deep enough to have its associated cold front passing over the islands next Monday or Tuesday.

Aviation

Moderate trades will continue today, then ease off tonight and Tuesday. Very dry weather will continue with VFR conditions prevailing across the state. No AIRMETs are in effect or expected today.

Marine

Surface high pressure passing just north of the waters has gradually weakened the trades to moderate to fresh speeds today and will continue to weaken Tuesday. The Small Craft Advisory (SCA) for the windier waters and channels around Maui County and the Big Island has been canceled. A cold front approaching and then moving into the islands Wednesday into Thursday will produce more variable winds along and ahead of the frontal band. The potential for unstable weather is possible with isolated thunderstorms for coastal and offshore waters along the front. Northwesterly winds will build in behind the front as it passes through each island.
The current moderate northwest swell will continue to trend down just below High Surf Advisory (HSA) criteria along exposed north and west facing shores through Tuesday. The HSA has also been cancelled this morning. Tuesday night, the next moderate to large medium period northwest swell is expected to fill in and produce High Surf Advisory (HSA) level surf along exposed north and west facing shores as it peaks Wednesday through Thursday, then slowly fades Friday into the weekend. An SCA will likely coincide with the swell for exposed coastal zones due to seas 10 feet or greater.
East facing shore surf will remain choppy today before slowly declining through the rest of the week, and background south swell will keep surf small on south facing shores through the week.

Fire weather

Dry conditions will persist through Tuesday. Today's trade winds will remain gentle to locally breezy at best then weaken Tuesday into Wednesday as the state falls downstream of an approaching cold front. This front is forecast to move down the island chain Wednesday through Thursday. This front will produce much needed statewide rain. Hence, critical fire weather conditions are not expected this week.

HFO Watches/Warnings/Advisories

None.

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Data Courtesy of NOAA.gov