Last Updated on Monday, 21 July 2014 07:44
Winds Statewide in a glance ...just go HERE(this link is also the 4th drop down under weather)
Jul 21, 2014 4:00 AM HST
Small craft advisory from 6 pm HST this evening to 6 pm HST Tuesday for Pailolo and Alenuihaha channels and Big Island leeward waters.
Small craft advisory from 6 am HST to 6 pm HST Tuesday for Kaiwi Channel, Maalaea Bay and Big Island southeast waters.
Synopsis Ample tropical moisture in the island vicinity coupled with an upper level trough just west of the state will continue to elevate the threat of locally heavy rainfall today. More typical trade wind weather is expected to return by the middle of the week.
Discussion Locally heavy rain have tampered off over windward Maui and the Big Island overnight. The activity has now shifted to Oahu along the koolaus early this morning. At least the heavier showers along the koolaus are moving. The situation certainly needs a closer monitoring. Ample tropical moisture is spreading across the island chain early this morning and will linger in the island vicinity through the next couple of days. An upper level trough west of the islands early this morning continues to move away slowly and weaken. This trough will still be close enough to influence the island weather today. Coupled with the present of ample tropical moisture in the area, conditions are still favorable for locally heavy rain to develop. On the other hand, the widespread threat of thunderstorms across the state has diminished quite a bit, though shall not be surprised if a thunderstorm develops over the Big Island later this afternoon. The moderate trade winds that the islands experience yesterday have eased a bit overnight as expected. The surface high pressure that is responsible for the winds remains far north of the state today, providing trade winds to the islands.
The upper level trough will shift further west and weaken by Tuesday. In turn, atmospheric conditions will be slowly improving across the islands, though lingering low level moisture will remain in the island vicinity, bringing possible showers to much of the area Tuesday. As a surface high pressure persists far north of the state, trade winds will continue across the state. In fact, a slight boost in the trades is expected as the surface pressure gradient tightens a tad in the area. Forecast models still indicate drier conditions to return to the state by Wednesday through Friday, as a drier and more stable air mass returns to the islands. Therefore, more typical summer trade wind weather is expected for the later part of the week.
Latest GFS and ECMWF continue to indicate another area of tropical moisture reaching the state by the weekend into early next week. Models do not indicate the air mass in the island vicinity to become too unstable at this time. The end result may be a slight increase in the trade showers and clouds for the state.
Marine Winds may increase enough tonight into Tuesday for small craft wind conditions to return to the windier coastal waters around Maui and the Big Island. Expect the moderate trade winds to prevail through much of the week. In turn, the small craft advisory for those windier coastal waters will probably remain in effect as well.
There will be a series of small south and southeast swells through this week. Trade winds will remain strong enough to bring short period choppy surf along east facing shores.