Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
300 AM EDT Sat May 14 2022

Valid 00Z Sun May 15 2022 - 00Z Sun May 22 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 this weekend and
take on a little 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 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 GFS continues to
be a little faster/farther east than consensus bringing heavier
rain totals farther east towards the western main islands/Kauai
than other models would suggest. The GFS behavior can be an
occasional bias of the model, though differences remain well
within typical predictability/error ranges for forecasts several
days out in time. A general model blend for this system is
probably the best approach at this time. After this system, upper
ridging looks to build back in over the region with trades
shifting back towards normal.

Santorelli