Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
813 AM EDT Sun Mar 11 2018

Valid 00Z Mon Mar 12 2018 - 00Z Mon Mar 19 2018

...Heavy rain likely midweek...

A 1032mb high just east of the Dateline will keep trades brisk for
the next few days with scattered windward showers. To the
southwest of Hawai'i, sharpening mid-level energy and an
associated weak surface low or inverted trough should lift
northeastward just west of or near Hawai'i. The GFS (farther east)
and ECMWF (farther west) still result in a surge of moisture and
precipitation for at least the central/eastern islands (~Molokai
eastward) thought the GFS amounts were 2-3 times higher than the
ECMWF. With precipitable water values rising to about 1.75 inches
but perhaps nearing 2 inches (which is about +2 to +4 standard
deviations) moderate to heavy rainfall is likely for at least part
of the region Tue-Fri. By the weekend, models/ensembles show
another upper trough or closed low near 25N/180 which should allow
heights over Hawai'i to rise, helping to diminish the heavy rain
threat as it shifts northwestward. Southeast to southerly flow
will persist next weekend with scattered showers as precipitable
water values slowly fall to under 1.5 inches. The ECMWF ensemble
mean was more amplified than the GEFS upstream again, and was the
preferred solution with support from the deterministic ECMWF/GFS.


Fracasso