textproduct: Honolulu

SYNOPSIS

Moderate to locally breezy trade winds will persist through the rest of the week. Bands of low clouds and showers will periodically push across the islands, focusing primarily over windward and mauka areas during the overnight and early morning hours. A couple bands of enhanced moisture will move through the islands tonight through Thursday morning, bringing an increase in shower coverage and intensity, with some locally heavy rainfall possible. In addition, humidity levels will rise, bringing muggier conditions across the island chain through the middle of this week.

DISCUSSION

Currently at the surface, a 1038 mb high is centered around 1750 miles north-northeast of Honolulu, driving moderate to locally breezy trade winds across the island chain this evening. Infrared satellite imagery shows mostly cloudy to overcast conditions in windward and mauka areas, while partly to mostly cloudy skies prevailing in leeward locales. Radar imagery shows numerous showers moving into windward slopes and coasts, with leeward spillover on the increase. Main short term focus revolves around trade wind trends and rain chances.

High pressure will meander north and northeast of state during the next 7 days, keeping moderate, to at times locally breezy, trade winds solidly in place. Somewhat wetter than normal, summertime trade wind weather is expected through the period, with showers favoring windward and mauka areas, particularly during the night and early morning hours. A couple bands of enhanced moisture will affect the state this week, bringing an increase in shower coverage and intensity. The first batch of enhanced moisture is already affecting Maui County and the Big Island, and will spread to the Oahu and Kauai later tonight, remain over all islands on Monday, then exit to the west Monday night. The next area of enhanced moisture is located around 700 miles east-northeast of the state in the vicinity of 145W. Portions of this area of enhanced moisture will begin to affect the islands Tuesday night and linger into early Thursday, increasing shower coverage and intensity once again.

Both these bands will raise precipitable water values into the 1.5 to 2.0 inch range and elevate inversion heights to between 10 and 12 kft. Some locally heavy rainfall can't be ruled out as these bands of moisture move through, particularly the second batch of moisture affecting the islands during the middle of the week. That said, with the trades in place, a widespread flash flood threat is not expected, but some minor flooding could very well necessitate flood advisories over windward and mauka areas during this time. Additionally, dewpoints are forecast to increase to around 70 or the lower 70s Monday through the middle of the week, making it feel more muggy across the island chain.

AVIATION

An easterly wave moving through the islands will produce MVFR conditions and showers across the state through Monday morning. MVFR conditions could decrease in coverage and frequency by Monday afternoon. Another low level disturbance will move through the islands bringing another round of MVFR conditions and showers from Tuesday night into Thursday.

AIRMET Sierra remains in effect for mountain obscuration above 020 along northern and eastern mountain slopes of most islands. These conditions will persist through Monday morning, then decrease in coverage by Monday afternoon.

AIRMET Tango is in effect for moderate turbulence downwind of terrain due to breezy trade winds and will continue through the forecast period.

MARINE

A high pressure ridge far north of the Hawaiian Islands will remain nearly stationary this week and keep trade winds blowing across the region. The Small Craft Advisory (SCA) will continue through Monday for much of the waters around Oahu, Maui County and Big Island, as well as the Kaiwi Channel. This is due to brief boost in wind speeds expected to move in tonight into Monday.

The current long period south swell will maintain through Monday then gradually decline over the next few days. Another larger south swell energy pulse will arrive next weekend.

Surf along east facing shores will remain rough and choppy through the week. Surf heights along north facing shores will remain nearly flat.

HFO WATCHES/WARNINGS/ADVISORIES

Small Craft Advisory until 6 PM HST Monday for Oahu Windward Waters-Kaiwi Channel-Maui County Windward Waters-Maalaea Bay- Pailolo Channel-Alenuihaha Channel-Big Island Windward Waters- Big Island Leeward Waters-Big Island Southeast Waters.