Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
348 AM EDT Thu Mar 27 2025

Valid 00Z Fri 28 Mar 2025 - 00Z Fri 04 Apr 2025

The forecast from now into the weekend has changed little in the
guidance over the past couple days. Expect east/southeasterly 
trades during this part of the forecast period. Background flow
should be sufficient to support some windward focus for showers 
over some areas while at other times/locations it may be weak 
enough to allow for sea breeze influence. Rainfall should be 
lightest late this week into the early weekend time frame as an 
upper ridge builds into and settles over the area before shifting
eastward.

For next week the guidance has been showing dramatic spread for 
pattern specifics aloft over the eastern half of the Pacific, with
some influence on the surface pattern. With improved clustering 
among the 00Z machine learning (ML) models and some hints in the 
00Z GEFS mean toward the ECMWF/CMC and their means, the 18Z/00Z 
GFS runs are looking increasingly suspect with their deep eastern 
Pacific upper trough--and front dropping down close to the main 
islands--around Tuesday/Wednesday. The majority cluster suggests
low level winds will turn somewhat more southerly ahead of the 
system evolving well to the northwest of the state. This may 
increase moisture to some degree while the band of heavier frontal
rainfall stays west of the main islands through Thursday. Recent 
ML model runs have kept the rain band farther west than some ECMWF
runs and GEFS/ECens mean while the 00Z ECMWF has shifted west to 
fit closer with the ML models. The western alignment of heavy rain
seems reasonable given the strength of the upper ridge to the 
east of the state in the majority cluster.

Rausch