Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
822 AM EDT Thu Oct 23 2014
Valid 00Z Fri Oct 24 2014 - 00Z Fri Oct 31 2014
Into the weekend, expect trades to strengthen moderately as T.S.
Ana continues to track away from the islands and high pressure
initially to the north of Ana slides southeastward. Then by next
week the surface pressure gradient should slacken for a time as
the high drifts farther into the eastern Pacific.
From about Tue onward the forecast for the state becomes more
uncertain due to significant model/ensemble spread that develops
with respect to timing and amplitude of large scale Pacific
systems. These differences originate from eastern Asia and
extreme northwest Pacific already by day 3 Sun. Currently there
is strong clustering among the ECMWF/CMC/UKMET/NAVGEM and
ECMWF/CMC ensemble means toward faster progression than the
00Z/06Z GFS runs and the 00Z GEFS mean, leading to much less
troughing hanging back to the northeast of the islands than the
operational GFS runs. Based on a preferred non-GFS scenario
trades should strengthen a little Wed-Thu as Pacific high pressure
reaches a position around 42-45N and 150-160W as of 12Z Thu.
Showers may be enhanced for a period late this week into the
weekend as a pocket of higher deep moisture crosses the region.
Somewhat more modest precipitable water maxima may reach the
islands there after as well.