Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
825 AM EDT Tue Jun 25 2019

Valid 00Z Wed Jun 26 2019 - 00Z Wed Jul 03 2019

An anomalously deep upper-level low (approximately -4 standard
deviations at 500 hPa) and surface cold front positioned a few
hundred miles northwest of the state will slowly track eastward
through the course of the week. A nearly steadily PW stream of
2-2.5 inches will be present over the Islands, with periods
nearing 3+ inches, combined with enhanced instability associated
with the upper low will support areas of deep convection. The
western islands have the best likelihood for heavy rainfall, with
amounts of 3 to 4 inches possible. Model guidance suggests that
the highest amounts will stay offshore, however very isolated
amounts of 6+ inches could be possible. Flash flooding may arise
for some areas.

Additionally, the approach of this system will likely disrupt the
trades, a period of southeasterly or southerly flow at the lower
levels likely through Wednesday. By late in the week, a return to
more typical conditions appears likely as models/ensembles
continue to show good consensus that the upper trough will lift
out as upper ridging builds overhead, allowing moderate trades and
more typical windward showers to resume.

Campbell