Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
353 AM EDT Sun May 14 2023

Valid 00Z Mon May 15 2023 - 00Z Mon May 22 2023

A cold front passing through the islands in the near term should
clear the islands on Sunday while dissipating. Behind this front
and with a surface high to the northwest of the state, moderate
(to perhaps breezy at times) trades with some northerly component
are likely through the early part of the week. Trades are forecast
to trend more easterly by around Tuesday-Wednesday and weaken a
bit as the high shifts north. Not too many showers are expected
given a relatively dry airmass in place.

By around midweek, model guidance continues to indicate an upper
trough axis setting up to the west of the state, which would then
track east eventually over Hawaii Thursday and Friday. The upper
trough should draw in higher moisture levels and provide for
increasing shower coverage with heavy rain becoming more likely.
Even the ensemble means from the GEFS and the ECMWF are showing
climatological precipitable water anomalies over the 90th
percentile, with the individual deterministic GFS and ECMWF
indicating PW anomalies over the 95th percentile and 4 standard
deviations above average. This pattern would also turn winds more
southerly, helping tropical moisture stream in. Models are all
becoming agreeable with this overall pattern, though with
remaining differences in the details. But confidence is increasing
for this wetter pattern later this week, perhaps lasting into the
weekend as amplified moisture levels stick around, though the
upper levels may become less supportive for heavy rain.


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