Breezy trade winds today will become strong and gusty as early as tomorrow afternoon. Showers will generally favor windward and mauka areas, particularly during the overnight through early morning hours each day. Tropical Storm Lowell is about 500 miles southeast of the Big Island early this morning, and is forecast to pass south of the Big Island late Wednesday into Thursday. Winds are expected to remain strong and gusty through Friday as Lowell passes south of the islands. The forecast remains uncertain for Labor Day weekend, with the potential for Lowell and Karina in the the vicinity of the state.
No significant changes to the forecast this morning. Although the PoP grid was adjusted, little change through Thursday night. For Friday there is a marked decrease in shower activity over the islands as Lowell will have moved further from the islands.
Clouds and showers continue to be carried in on the trade wind flow, and as a result are focused over the windward and mauka areas. A surface trough about 350 miles east of the islands will continue to move towards the islands today and weaken. Moisture from that trough will reach the islands tonight, helping to boost shower activity tonight.
Tropical Storm Lowell is about 550 miles southeast of the Big Island early this morning, and the latest forecast from the National Hurricane Center (NHC) has Lowell strengthening to a hurricane within the next 12 hours. The latest track and cone for Lowell has the system passing south of the islands Wednesday night through Friday. Outer rainbands and moisture from Lowell could begin to spread across the islands today, increasing chances of passing trade wind showers, however the bulk of moisture will likely pass south of the state. Additionally dewpoint temperatures are expected to exceed 70 degrees, which will make the atmosphere muggier than normal. Trade winds will stay breezy due to a strong surface high remaining far north of the area.
Overall expect an uptick in passing showers over the next few days, due to the moisture from the trough mentioned above tonight, and moisture loosely associated with Lowell passing through the state.
The latest forecast from the NHC has Lowell passing a little over 300 miles south of the Big Island Wednesday night into Thursday as a category 3 Major Hurricane. While probabilities for tropical storm force winds remain low over the state, the tightening of the pressure gradient over the islands will likely produce very windy and gusty trade winds as early as Wednesday afternoon through Friday. Winds could reach advisory thresholds with wind gusts over 50 mph possible during this time.
As we head into the weekend, as Lowell exits, our focus will shift more to Hurricane Karina which is currently about 1500 miles east of the Big Island. The latest forecast from NHC for Karina brings it about 600 miles east of the Big Island on Saturday. We will continue to monitor Karina over the coming days to discern its potential impacts on the state.
The forecast spread drastically increases over the Labor Day weekend into early next week as an upper level trough/low develops north of the state. Several models show Lowell taking a sharp northward turn over the weekend. While confidence has increased on Lowell passing south of the state during the week, the forecast still remains very uncertain over Labor day weekend due to the northward turn in the various models. Also during this time, we could see Karina within the vicinity of the islands late this weekend. Please keep an eye out on the hurricanes.gov page for the official NHC forecast for Lowell and Karina.
Moderate to breezy trade winds will persist through this period. Occasional MVFR decks and brief organized showers riding within the trades will generally favor windward exposures and higher terrain. Otherwise, VFR conditions will prevail. Tropical Cyclone Lowell is forecast to pass far south of the island chain the next few days. On this track, late week trade winds will strengthen as the pressure gradient tightens between Tropical Cyclone Lowell and high pressure to the far north.
AIRMET Sierra is in effect for mountain obscuration for the north through east districts of Big Island due to persistent low clouds and shower coverage. AIRMET Sierra will remain in effect for Big Island through this morning.
AIRMET Tango remains in effect for moderate low level turbulence south through west downstream of high terrain. AIRMET Tango will likely be in effect for the foreseeable future.
A strong surface high will remain nearly stationary far north of the Hawaiian Islands this week, keeping moderate to locally strong trade winds in place. A Small Craft Advisory remains in effect for the typically windy waters as a result of the locally strong trades. Tropical Storm Lowell, now in the Central Pacific, is forecast to intensify into a hurricane today and will track very close to the southern offshore waters, bringing tropical storm conditions (with the core of hurricane force winds remaining outside the offshore waters) from Wednesday into Thursday. There is still some uncertainty with the forecast track of Lowell, especially closer to this weekend as the cyclone begins to gain latitude, which will have significant impacts on the wind, wave, and surf forecast for the region. Regardless of Lowell's final path, trade winds will increase by Wednesday afternoon through Friday as a result of the gradient between high pressure to the north and Lowell to the south. By this weekend, Hurricane Karina, approaching the region from the east, will increasingly be a factor in the forecast of seas and surf as well.
A moderate, long-period south swell arrives today. This swell will build through the day and overnight before peaking on Wednesday, bringing surf heights to just below advisory thresholds. This swell will then gradually decline through the rest of the week. Also by Wednesday, medium-period energy from Lowell could start filling in across south and southeast shores. South shore surf is likely to be elevated, but stay below advisory levels through at least Friday. Beyond that point, the surf forecast is highly dependent on the eventual track and intensity of Lowell, which has the potential to be a significant source of south to southwesterly swell through this weekend and into next week depending on how sharply and quickly the cyclone turns to the north.
Trade wind swell energy will keep elevated surf heights along all east-facing shores through the coming week. Tonight, a medium-period east swell arrives from Hurricane Karina that will build through the week and could push east shore surf to advisory thresholds by this weekend and into next week.
Small Craft Advisory until 6 PM HST Wednesday for Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters- Maalaea Bay-Pailolo Channel.
