Daily Weather

Mar 29, 2015 5:00 AM HST

Synopsis
Trade winds will increase today through Monday, bringing a slight increase in windward showers, mainly on Kauai and Oahu. A couple of upper level disturbances passing north of the islands will result in the weakening of trade winds again on Tuesday, Thursday and Friday, and may briefly enhance showers over the state.

Discussion
Stronger trade winds are staging a comeback early this morning, as indicated by both radar data as well as low cloud movements. Quite a bit of low level moisture are present in the island vicinity early this morning, with radar data showing an area of rain clouds just northeast of Oahu at time. Much of these showers will affect the windward areas under the increasing trade winds. Early morning soundings still depict a rather dry air mass in the island vicinity, though Lihue sounding has become a tad more unstable compared to Saturday afternoon. Look for passing low clouds and showers to affect mainly windward and mountain areas today, while lee areas should experience mostly fair weather.

Trade winds will be the strongest tonight and Monday over the islands, as a surface high pressure passes east far north of the state. Trade wind weather will continue Monday, with passing low clouds and showers affecting mainly windward areas.

A progressive mid-level short wave trough is forecast to pass the state on Tuesday. Its present will induce the development of a surface trough in the island vicinity. As the surface trough develops, winds will once again weaken across the islands. In fact, winds may become light and variable enough allowing land and sea breezes to develop. Forecast models indicate the atmosphere will become only slightly unstable due to this short wave. But then deeper convection can develop over the islands under the converging sea breezes in the afternoon, bringing possible locally heavier showers. This mid-level trough will track swiftly east Wednesday, with stronger trade winds returning to the state briefly.

Another mid-level short wave trough is expected to pass over the islands Thursday through Friday as indicated by the forecast models. Even though this next disturbance is forecast to be a weak feature, another surface trough is expected to develop in the island vicinity, resulting in winds becoming light across the area again. Convective weather with land and sea breezes are expected Thursday through Saturday. Furthermore, forecast models also hint the atmosphere in the island vicinity may become more unstable. Showers will therefore be enhanced. Stronger trade winds may return to the area toward early next week, though that is subject to change due to high variations between model runs.

Advisory and Warning Criteria
Location Advisory Warning
North-Facing Shores 15 Feet (8') 25 Feet
West-Facing Shores - Big Island 8 Feet (4'+) 12 Feet
West-Facing Shores - Remaining Islands 12 Feet (7') 20 Feet
South-Facing Shores 8 Feet (4'+) 15 Feet
East-Facing Shores 8 Feet (4'+) 15 Feet

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