805 

FXHW01 KWNH 190751

PMDHI 



Hawaii Extended Forecast Discussion

NWS Weather Prediction Center College Park MD

351 AM EDT Tue May 19 2026



Valid 00Z Wed 20 May 2026 - 00Z Wed 27 May 2026



Early in the forecast period, the broad and relatively flat 

mid/upper level trough will linger, maintaining modest mid-level 

instability. This combined with the slightly veered 

(Southeasterly) low-level flow will maintain higher PWAT values 

(1.5 to 2.0") through early Wed. As a result PoPs will remain 

elevated (generally 50-70%) Tue through early Wed across windward 

slopes. Later Wed afternoon, diurnal activity will become more 

infrequent and isolated as high pressure builds in from the north 

and surface winds back towards the more typical E-NE trade wind 

pattern. 



The stable and persistent E-NE trades will remain locked in Thu

through early next week, as the broad 1032+ mb surface high 

centered well N-NE of the islands will maintain moderate to 

locally strong trades (15-25 mph with higher gusts). Deep- 

tropospheric stability and seasonably drier airmass (PWAT values 

near 1.0-1.2") will persist as well, maintaining PoPs near

climatological norms with the highly-predictable spatial and 

diurnal distribution of fast-moving trade showers. PoPs will range

from 30-60% over windward and mauka locations and generally less 

than 15% across leeward areas.



Hurley