Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
402 AM EDT Sun May 15 2022

Valid 00Z Mon May 16 2022 - 00Z Mon May 23 2022

The latest guidance over Hawaii continues to agree that a
significant pattern change is on tap, leading to a wetter regime
by the middle of next week. Trades should weaken through Sunday
with more of a southeasterly component as eastern Pacific high
pressure weakens and a wavy front sharpens to the west of the
state. The combination of upper ridging and somewhat below normal
precipitable water values should keep most of the windward-focused
showers on the light side. By early next week however, guidance
shows good agreement on a central Pacific upper trough with
embedded low (part of a Bering Sea into Pacific Rex block pattern)
approaching from the northwest, likely reaching its greatest
amplitude around early Wednesday before it starts to lift out.
This system will result in stronger and more southerly winds,
especially over the western islands, which will help to advect a
significant increase of moisture by midweek. The heaviest rainfall
should stay west of the main islands, but confidence is increasing
somewhat that heavy rainfall may reach as far east as Kauai. After
this system, upper ridging looks to build back in over the region
with trades shifting back towards normal.

Santorelli