Last Updated on Sunday, 19 May 2013 07:32
Winds Statewide in a glance ...just go HERE (this link is also the 4th drop down under weather)
May 19, 2013 4:00 AM HST
A low aloft will linger northeast of the island chain producing unsettled weather through midweek. Locally heavy rain will be possible today with a slight chance for thunderstorms on the Big Island. A sharp trough will produce light background flow resulting in a land and sea breeze pattern near the surface in the short and midterm. Trade winds will return late this week.
A complicated weather pattern persists across the state early this morning. Water vapor imagery shows a cold upper low north of the islands digging to the southeast. Meanwhile, at the surface, a sharp inverted trough has an axis across Maui and is stationary. To the north, a cold front is located about 75 miles away from Kauai and moving south towards the state at 15 mph. The front is being overrun by breezy northerly winds associated with high pressure behind it.
Current radar shows slow moving scattered showers directed in nearly a counterclockwise motion across the island chain. This is due to that sharp trough axis focused on Maui this morning. The greatest areal shower coverage is off the windward and southeast coast of the Big Island, and the least coverage around Kauai. Soundings from this morning show weak elevation inversions at 10 kft at Lihue and 14 kft at Hilo, with precipitable water values of 1.16 inches at Lihue and 1.53 inches at Hilo.
The light background flow resulting from the presence of the surface trough will allow sea breezes to build over the islands again today. Kauai will be the exception with moderate northerly winds expected. Clouds and showers associated with the approaching front should arrive in Kauai late this morning and afternoon, before washing out over Oahu tonight. For Oahu and Maui county, the sea breezes will bring clouds and showers onto the island interiors and leeward sections this afternoon and evening. The instability aloft from the upper low will cause locally heavy rainfall on all islands except Kauai today, though chances for rain will remain high on Kauai with the frontal passage. The Big Island will also be a focus for chances of heavy rain and a slight chance for thunderstorms given the pool of nearby moisture.
Land breezes will set in tonight pushing most of the clouds and rain offshore late. Oahu could still remain wet tonight as that front stalls and falls apart. The surface trough will linger near Maui through Monday, then slowly weaken and move off to the west. Aloft, a low will persist northeast of the area through midweek. Light winds associated with the surface trough and instability from the low aloft will continue this diurnal convective pattern over all the islands through Wednesday, and into Thursday for some leeward areas. There is a possibility of locally heavy showers across island interiors Monday and Tuesday given the proximity of the upper low, but not very confident in timing and location of these showers due to the complex situation. Will hold off on putting this in the forecast for now.
Long range models are in good agreement showing the trade winds becoming well-established by Friday, and locally breezy next weekend. The convective pattern will end and the trades will bring focus lighter showers to windward and mauka areas. Another trough aloft may dig down over the area next weekend and may enhance the trade wind showers.
Winds and seas are expected to remain below small craft advisory levels statewide this week. A series of swells will keep elevated surf along south facing shores through most of the week. Surf is expected to remain above the advisory threshold through at least early Monday morning, but may be extended into Tuesday if conditions persist. A marine weather statement remains posted for waves breaking near channel entrances and possible harbor surges.