Breezy east-northeast trade winds will gradually veer to the east and then east-southeast this weekend into the upcoming week as Hurricane Lowell approaches from the southwest. Lowell is forecast to pass west of Kauai's coastal waters as a major Hurricane (category 3). Impacts such as high surf and heavy rain are forecast to extend hundreds of miles from the center, potentially impacting any of the islands.
Radar and satellite imagery this morning shows a fairly typical summertime trade wind pattern with scattered showers over windward and mountain areas. Increasing moisture upstream is also evident and will contribute to increasing showers this evening into tomorrow mostly for windward and mountain areas. Weather conditions then deteriorate Sunday evening into the upcoming week.
Hurricane Lowell is currently sitting about 540 nautical miles south-southwest of Kauai moving west at 6 kt as a category 4 (150 mph maximum sustained winds). Lowell is forecast to make a sharp turn to the north and then north-northeast at some point later today into tonight. It's forward speed will increase once it begins moving north and will make its closest approach to the main Hawaiian Islands Monday night as a category 2 to 3 hurricane. Lowell is forecast to pass west of Kauai's coastal waters, and will bring several hazards to the state. The hazards are expected to be flooding, strong southerly winds, and high surf.
The greatest risk for flooding at this time appears to be Sunday evening through Tuesday morning, and could potentially linger into Wednesday, as deep tropical moisture associated with Lowell is drawn up from the south. The environment will begin destabilizing Sunday afternoon as GFS model CAPE values increase, along with moisture depth. The winds will also veer to the east- southeast and increase starting Sunday evening. The threat of heavy rainfall and thunderstorms will be present anywhere in the state, and flooding could occur as a result. Exact details on where the heaviest of rain will fall remain uncertain, as any heavy showers and thunderstorms that develop will likely be disorganized. Therefore everyone in the state should be prepared for flooding. The issuance of a flood watch is anticipated later this afternoon.
Winds will increase and veer out of the east-southeast by Sunday night into Monday morning with Kauai County having the strongest winds. Winds will also increase out of the southeast for the rest of the islands to a lesser extent, and could be amplified by island terrain.
For surf and other marine impacts, please see the marine section of the discussion below.
Any deviation in track or intensity could also change how these hazards effect the islands.
High pressure is forecast to build back in Thursday through Saturday, bringing in drier and more stable conditions. Long range models then indicate a tropical wave potentially moving over the islands next Sunday into Monday, although confidence is very low this far out.
A stable, moderate to locally fresh trade wind flow will focus scattered showers and produce areas of MVFR conditions over windward slopes today, while VFR will prevail leeward. AIRMET Sierra for mountain obscuration may be needed over some windward areas. AIRMET Tango remains in effect for low-level mod turb over and south through west of all island mountains.
Expect winds to hold at current strength and veer more easterly on Sunday. The atmosphere will slowly destabilize through the day, and deepening moisture along the far periphery of Hurricane Lowell may overspread the state and lead to isolated heavy showers and thunderstorms in the afternoon.
A surface high persists north of the Hawaiian Islands and will slowly drift east through the weekend. Currently, Hurricane Lowell is around 540 nm south-southwest of the islands as it continues to track west. The trade winds are beginning to ease slightly as Lowell gains a bit of distance from the island chain, and the Small Craft Advisory (SCA) has been trimmed back to only the windier waters and channels around Maui County and the Big Island through this afternoon. Lowell is expected to turn northward on Sunday, which will cause winds to veer to the southeast to south with the strongest winds over the western end of the state.
Confidence has grown with the latest updates from the National Hurricane Center for the potential for hurricane conditions in the offshore waters west of 160W Sunday night through Tuesday. While confidence is increasing in the track forecast of the cyclone, a deviation in track of 50 nm west or east from the current predicted path will have significant differences in impact for the coastal waters around Kauai County. As for Hurricane Karina, it is expected to weaken and pass northeast of the state.
Southerly swell generated by Hurricane Lowell will keep surf along south facing shores at High Surf Advisory criteria today. As Lowell begins to turn north on Sunday, its swell will gradually veer from south to southwest and begin a rapid upward trend. Very large surf exceeding warning criteria appears increasingly likely for south and west facing shores on Monday. Coinciding also with monthly high tides, this will create the potential for impacts to harbor entrances, channels, as well as coastal properties and infrastructure including roadways. Surf will then rapidly decrease on Tuesday after the hurricane passes north of the island chain. A pulse of northwesterly swell could then bring a bump to north shore surf on Tuesday and fade through Thursday.
East facing shores will see continued advisory level surf from a large, medium-period east swell generated by Hurricane Karina to the east of the islands. This swell will gradually fade early next week as Karina weakens into a tropical storm. Late next week, surf along east facing shores could be bolstered by some medium-period swell generated by Hurricane Marie in the East Pacific. Otherwise, expect choppy conditions from easterly trade wind swell through the week.
High Surf Advisory until 6 PM HST Sunday for Niihau-Kauai Leeward-Waianae Coast-Olomana-Kahoolawe-Maui Leeward West-Kona- Kauai East-Kauai South-East Honolulu-Honolulu Metro-Ewa Plain- Koolau Windward-Molokai Windward-Molokai Southeast-Molokai West- Molokai Leeward South-Lanai Leeward-Lanai South-Maui Central Valley South-Windward Haleakala-Kipahulu-South Maui/Upcountry- South Haleakala-Big Island South-Big Island Southeast-Big Island East-Big Island North.
Small Craft Advisory until 6 PM HST this evening for Maalaea Bay- Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters.
