Photo Credit: Laila Reiss

West Side

Today: Sunny and breezy. Isolated showers in the morning. Highs 82 to 89. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Tonight: Breezy. Partly cloudy with isolated showers. Lows 68 to 75. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Sunday: Mostly sunny with isolated showers. Highs 82 to 89. East winds 10 to 15 mph. Chance of rain 20 percent.

South Side

Today: Sunny and breezy. Highs 86 to 91. North winds 10 to 20 mph.

Tonight: Mostly clear. Breezy. Lows around 69. North winds 10 to 20 mph.

Sunday: Mostly sunny. Breezy. Highs 86 to 91. North winds 10 to 20 mph.

North Shore

Today: Partly sunny. Showers likely in the morning, then scattered showers in the afternoon. Highs 81 to 87 near the shore to around 69 near 5000 feet. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then showers likely after midnight. Lows 65 to 72 near the shore to around 56 near 5000 feet. East winds 10 to 15 mph. Chance of rain 70 percent.

Sunday: Breezy. Partly sunny with numerous showers in the morning, then mostly sunny with scattered showers in the afternoon. Highs 81 to 87 near the shore to 64 to 69 near 5000 feet. East winds 10 to 20 mph. Chance of rain 70 percent.

Central Maui

Today: Sunny and breezy. Isolated showers in the morning. Highs around 89. North winds 10 to 20 mph. Chance of rain 20 percent.

Tonight: Breezy. Partly cloudy with isolated showers. Lows 67 to 73. North winds 10 to 20 mph. Chance of rain 20 percent.

Sunday: Breezy. Mostly sunny with isolated showers. Highs around 89. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Upcountry

Today: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 65 at the visitor center to around 62 at the summit. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Partly cloudy with scattered showers. Lows around 52 at the visitor center to around 50 at the summit. East winds 10 to 15 mph. Chance of rain 50 percent.

Sunday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 62 at the visitor center to around 59 at the summit. East winds 10 to 15 mph. Chance of rain 50 percent.

East Maui

Today: Partly sunny. Showers likely in the morning, then scattered showers in the afternoon. Highs 81 to 87 near the shore to around 69 near 5000 feet. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then showers likely after midnight. Lows 65 to 72 near the shore to around 56 near 5000 feet. East winds 10 to 15 mph. Chance of rain 70 percent.

Sunday: Breezy. Partly sunny with numerous showers in the morning, then mostly sunny with scattered showers in the afternoon. Highs 81 to 87 near the shore to 64 to 69 near 5000 feet. East winds 10 to 20 mph. Chance of rain 70 percent.

Lanai City

Today: Mostly sunny. Breezy. Isolated showers in the afternoon. Highs 73 to 82. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Tonight: Mostly clear. Breezy. Lows around 66. Northeast winds 10 to 20 mph.

Sunday: Mostly sunny. Isolated showers in the afternoon. Highs 73 to 82. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Kaunakakai

Today: Sunny and breezy. Isolated showers in the morning. Highs 79 to 89. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Tonight: Breezy. Partly cloudy with isolated showers. Lows 61 to 72. Northeast winds 15 to 20 mph. Chance of rain 20 percent.

Sunday: Breezy. Mostly sunny with isolated showers. Highs 79 to 89. East winds 15 to 20 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Tropical cyclone Calvin is expected to be gradually weakening as it passes very close to, and possibly over, the islands from Tuesday night through Wednesday night, bringing the potential for locally strong wind gusts, flooding rain, and high surf. Stay tuned for forecast updates as Calvin moves closer to Hawaii over the next couple of days. Otherwise, moderate to breezy trade winds will prevail, bringing limited showers to windward areas during nights and mornings.

Discussion

The stable and locally breezy trade wind weather pattern currently in place will change little over the next couple of days, although wind speeds may increase slightly this weekend. The trade winds will be supported by a pair of high pressure cells, one to the NE and one NW of the islands, with the stronger high to the NW. This configuration, and the presence of a 700 mb trough E of the islands, has veered the trade wind flow to the NE over the past 24 hours or so. The trough will move W through Sunday, bringing a modest increase in low cloud coverage and trade showers, with low-level winds gradually veering to a more typical E direction by tomorrow night.
A mid-level ridge extends over the islands from the E, and will remain in place for at least the next several days, keeping a strong subsidence inversion in place. Any trade showers that arrive will be brief, primarily falling over windward areas during nights and mornings. Only isolated showers are expected over leeward areas, with the exception of leeward Big Island, which will see typical afternoon cloud buildups and scattered showers each afternoon.
The National Hurricane Center (NHC) in Miami, Florida is issuing advisories on Hurricane Calvin, located about 1800 miles ESE of the Big Island, moving WNW at 16 mph. When Calvin crosses 140W (expected Sunday night), the Central Pacific Hurricane Center (CPHC) in Honolulu, Hawaii will assume forecast responsibility. The official forecast track has been fairly consistent in bringing Calvin very close to, or over, the main Hawaiian Islands Tuesday night and Wednesday. Some questions remain as to the intensity, but vertical wind shear is expected to increase as it nears the islands, with Calvin on a gradual weakening trend during its closest point of approach. Like most systems approaching Hawaii from the E, strongest winds are expected to be in the northern semicircle.
Considering typical forecast track errors, it remains too soon to be specific as to where (and what – if any) impacts occur over land, which will be highly dependent on the track. If the center were to pass N of the islands, most of the strong winds would remain offshore, with a more southerly track potentially putting the islands in a stronger wind field. As a reminder, tropical cyclones can bring the triple threat of strong winds, heavy rainfall and high surf. The forward speed of the tropical cyclone (forecast to be near 18 mph) should preclude widespread flooding impacts for an extended period of time, hence we've decided that a Hydrologic Outlook (ESFHFO) is not warranted, although a Flash Flood Watch (FFAHFO) may be issued for parts (or all of) the state early next week.
A return to a typical trade wind weather pattern is expected from Thursday into next weekend as the remnants of Calvin move quickly W away from the islands, likely as a trough.
As the public and marine forecasts for Hawaii will be highly dependent on bulletins from NHC/CPHC issued at 11 am/pm and 5 am/pm HST, our regularly scheduled forecast issuances will soon be modified, with updates issued shortly after these bulletins.

Aviation

Moderate to locally breezy trade winds and stable atmospheric conditions will likely persist today. There are scattered to locally broken low clouds with isolated showers embedded within the low- level trade wind flow. This may produce brief periods of MVFR conditions along some north through east facing sections of the islands this morning. Otherwise, expect VFR conditions to prevail across most of the state today.
AIRMET Tango remains in effect for Tempo moderate low-level turbulence leeward of the higher terrain on all islands. This AIRMET will likely be required into this evening based on the latest forecast. No additional AIRMETs are anticipated at this time.

Marine

A surface ridge far north of the state will likely maintain moderate to locally strong trade winds into Monday. A Small Craft Advisory (SCA) remains in effect for the typically windier waters adjacent to the islands of Maui County and the Big Island this weekend. This SCA will likely need to be extended into early next week for these same areas.
Based on the latest advisory issued by the NHC in Miami, Florida at 11 PM HST Friday evening, Hurricane Calvin is forecast to enter the CPHC's area of responsibility Sunday night as a weakening tropical storm. Tropical storm conditions associated with Calvin may reach the eastern Hawaiian Offshore Waters starting on Tuesday. After that, Calvin is expected move near the main Hawaiian Islands starting Tuesday night or Wednesday. If so, tropical storm conditions may develop over the waters adjacent to the Big Island. and possibly Maui, from Tuesday night into Wednesday. Given uncertainties about the track, size, and intensity of Calvin as it approaches the state, all marine interests in the Hawaiian Islands should monitor the latest forecast advisory product issued by NHC under WMO header WTPZ23 KNHC.
A small southeast swell and background swell energy from the south- southwest will likely maintain small surf along exposed south facing shores this weekend. Modest, choppy surf will persist along east facing shores this weekend due to the trade winds. An upward trend in surf is expected along east facing shores early next week due to the arrival of a medium-period easterly swell, which is being generated by the captured fetch associated with Hurricane Calvin. Depending on the track, size and intensity of Calvin, surf will likely reach the High Surf Advisory threshold along east facing shores of most islands starting Tuesday night or Wednesday. There is a possibility that some east facing shores, such as the Big Island or Maui, may have a brief period of surf reaching the High Surf Warning criteria in the Tuesday night / Wednesday morning time frame based on the latest wave model guidance.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 AM HST Monday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

Maui Now Weather is brought to you by Blue Hawaiian Helicopters.

Check out their Maui Helicopter Tours today!

Data Courtesy of NOAA.gov