Hawaii Weather Synopsis: Showers will diminish by afternoon across the smaller islands, although a slight chance of thunderstorms will remain along the Kona slopes of the Big Island this afternoon. Mainly windward and mauka showers will prevail Thursday. Another round of unsettled weather is expected Thursday night and Friday. Building high pressure will keep the trades strong for the remainder of this week.
A Small Craft Advisory is in effect through Thursday afternoon for all Hawaiian waters.
A High Surf Advisory is in effect through Saturday afternoon for east facing shores of Kauai, Oahu, Molokai, Maui and the Big Island.
Click on the following link for the latest National Weather Service advisories and warnings: Wind/Surf/Flood related advisories or warnings
Broad Overview of Hawaii’s Weather
Based on the NWS Area Forecast Discussion for Hawaii, issued 9 Nov 2011 at 1000am HST
Water vapor imagery shows a sharp upper level trough over the eastern half of the state. Data soundings from Hilo and Lihue this morning show an unstable air mass across the islands. Precipitable waters from the soundings are just over 1.3 inches. Similar values extend east of the Big Island, but drier air with values near 1 inch is located within 100 miles north of the smaller islands. Another band of higher moisture is located about 400-500 miles northeast of the state.
Radar and satellite imagery show showers diminishing across Maui County and Oahu, and starting to diminish across Kauai, as drier air north of the area moves across the islands. Bands of showery low clouds continue to feed into the Big Island, and showers will remain active across windward sections. With the unstable air mass, afternoon convection is expected across leeward slopes of the Big Island, and a slight chance of thunderstorms will remain in place for leeward Big Island.
Increased moisture is expected to move through the state Thursday night and Friday. The upper low is forecast to remain over the state, and mid-levels actually cool by a degree or so as the low shifts westward over the islands. The combination of moisture and unstable conditions will lead to greater shower coverage and intensity. In addition to an increased chance of precipitation, there is the possibility of thunderstorms again for Thursday night and Friday.
High pressure far north of the state will keep strong trade winds over the islands this week. Surface wind speeds of 30 knots were measured in Honolulu this morning. Locations exposed to funneling under a northeast wind (such as Lanai) will be quite gusty. The tight pressure gradient, and consequently the strong and gusty winds will continue through the work week, and then begin to diminish over the weekend.
Over the weekend, the upper low near the state will slowly move northeast, allowing conditions over the islands to stabilize somewhat. Forecast soundings show a weak inversion developing Friday night, although low-levels remain rather saturated. Shower coverage will remain higher than normal on Saturday, and then diminish to more normal levels for Sunday into next week. With trade winds weakening to more moderate levels, rainfall will still be focused mainly across windward and mauka areas.
Marine Forecast: A Small Craft Advisory remains in effect for all coastal waters due to the strong winds of 25 knots or greater and combined seas of 10 feet or greater. Winds are strongest through the Pailolo and Alenuihaha Channels, where funneled winds may lead to gale force wind gusts. These conditions will continue through Thursday before starting to slowly diminish. Surf observations from Kauai came in at 4-8 feet for east facing shores. Combined seas at the Mokapu buoy have also ramped up another 2 feet this morning. With the trade swell expected to build further through Thursday, in addition to a longer period north-northeast swell expected on Friday, we will update to issue a High Surf Advisory for east facing shores.
The following numbers represent the strongest wind gusts (mph), along with directions Wednesday morning:
29 Lihue Apt, Kauai – NE
32 Honolulu Apt, Oahu – NE
32 Molokai – NE
28 Kahoolawe – N
43 Kapualua-West, Maui- NE
48 Lanai – NE
38 South Point, Big Island – NE
Here are the 24-hour precipitation totals (inches) for each of the islands as of Wednesday morning:
1.57 Mt. Waialeale, Kauai
0.51 Waiawa C.F., Oahu
3.02 Puu Kukui, Maui
2.17 Waiakea Uka, Big Island
Here is the latest NWS rainfall forecast
Here are the latest available satellite images:
SURF ZONE FORECAST – OAHU
NATIONAL WEATHER SERVICE HONOLULU HI
1030 AM HST WED NOV 9, 2011
Surf along north facing shores will be 6 to 8 feet through Thursday.
Surf along south facing shores will be 3 to 5 feet through Thursday.
Surf along west facing shores will be 1 to 3 feet today, rising to heights of 2 to 4 feet Thursday.
Surf along east facing shores will be 2 feet or less through Thursday.
Outlook through Tuesday Nov 15: Trade winds will maintain head high short period chop along windward reefs and beaches over the next several days. An incoming longer period north northeast swell on Saturday and Sunday will maintain high surf advisory level surf for east facing and possibly north facing shores.