Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
802 AM EDT Sun Mar 25 2018

Valid 00Z Mon Mar 26 2018 - 00Z Mon Apr 02 2018

An upper low currently located about 250 miles north of Hawaii is
moving eastward while a cold front moves across the eastern
islands. A surge of high precipitable water values (perhaps
exceeding 2.00 inches) ahead of the front will begin to move east
of the islands over the next 12-24 hours. However, models continue
to indicate that the front should stall and gradually wash out
over the next few days, keeping some degree of moisture lingering
across the eastern islands. This will keep the potential for
showers in the picture perhaps into midweek before drier air
overtakes the region. ECENS probabilities indicate that the best
chance for any additional locally heavy rains would be along the
southern coast of the Big Island.

Models/ensembles continue to show general agreement that heights
will gradually rise across Hawai'i after Mon with drier air
advecting across the state by mid-week. Low-level flow during this
time period should be very light through mid-week, with light
easterlies resuming by late in the week. A trough/upper low is
expected to amplify along 170W by late next week, and the
GFS/ECMWF continue to show a front approaching by next weekend.
The GFS remains a bit quicker to move the front east, bringing an
increased threat of showers into the western islands by next Sat,
while the ECMWF would hold the showers a couple hundred miles
farther west. Ensemble means seem to suggest that perhaps the
GFS/GEFS are too fast with the front, with the ECENS/NAEFS means
more in line with the ECMWF.

Ryan