textproduct: Honolulu

SYNOPSIS

Drier trade winds will prevail early this week with light showers on the windward side of the islands. Low level convergence along a surface trough will bring a modest increase in clouds and showers late Monday into Tuesday. More rain is expected through the second half of the week as remnants of Tropical Storm Norbert pass by.

DISCUSSION

Evening satellite imagery shows mostly cloudy skies over the Big Island with mostly clear skies elsewhere. Light trade winds and isolated light showers will continue today.

A broad upper level low currently northeast of the islands is forecast to track westward over the next several days. Moisture associated with a disturbance currently near 13N 148W may be pulled northward into the eastern half of the state as both it and the trough move westward. Low level convergence will bring a modest increase in clouds and showers late Monday into Tuesday, initially reaching the Big Island with showers becoming more diffuse as the trough moves west.

Tropical Storm Norbert is currently around 1530 miles east of Hilo, moving west at 12 mph. This system is forecast to continue to move westward, weakening to a tropical depression by Tuesday morning and becoming post-tropical later that day. Trade winds will strengthen as the residual trough of Norbert passes Thursday into Friday. Rainfall will also increase east to west across the state from Wednesday night through Friday night. Large-scale forcing from an upper trough over the region and forecast precipitable water near 2" will increase the flooding risk, especially for areas where the soil is still saturated from recent heavy rainfall.

AVIATION

Satellite imagery indicates mostly clear conditions for Hawaii, however there are a few areas of low clouds with MVFR conditions this morning. A large upper level low well northeast of the islands is weakening the pressure gradient and therefore the trade winds near Hawaii. These weak to moderate trades will continue through Sunday. Winds may become light enough within more wind- protected leeward areas to initiate local topographically- driven breezes. These trades are also relatively dry, and will limit shower activity.

MARINE

Moderate to locally fresh trades will continue through the week before gradually strengthening through the latter half of the week. Moisture associated with a weak trough moving in on the trade wind flow may bring a slight uptick in shower activity to the coastal waters Tuesday into Wednesday. While the current forecast has Tropical Storm Norbert dissipating before it nears the Hawaiian coastal waters from the east, remnant moisture from this system is expected to arrive potentially by Thursday, likely bringing more showers.

Surf along south-facing shores will gradually decline through Monday as the small, medium-period energy slowly fades. A series of long-period swells are expected during the second half of the week. The first pulse will gradually fill in Tuesday into Wednesday out of the southwest, followed by larger south-southwest swells Friday into the weekend. Surf could get near advisory thresholds over the weekend, but at this time it looks like it would peak just below advisory thresholds.

A small short-period northeast swell filled in overnight and will peak today and fade out on Monday. Surf along east-facing shores should see an increase during the second half of the week as the trades strengthen and the remnants of Norbert moves through the islands. Some small energy is expected along northern exposures today from the northeast swell, but otherwise flat to tiny surf along north facing shores is expected through the forecast period.

FIRE WEATHER

Fire weather risk will remain low the next several days due light to moderate winds and the effects of recent rainfall. Inversion heights are expected to remain elevated or weak through Monday. Moisture increases for the middle to latter part of the week with a bump in the trade winds as remnants from Tropical Storm Norbert potentially approach the area.

HFO WATCHES/WARNINGS/ADVISORIES

None.