Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Honolulu HI
953 am HST Monday may 4 2015
trade winds will prevail into the foreseeable future with showers
focused over the windward slopes. Leeward locations of the smaller
islands will see a few passing showers but will experience mainly
fair weather. Leeward Big Island areas will cloud up in the
afternoons with a few showers forming over the lower slopes.
high pressure will dominate the area north of the state bringing
trade winds to the islands through the foreseeable future. Rainfall will
focus over the windward slopes with a few passing showers over
leeward locations of the smaller islands. The leeward lower slopes
of The Big Island will see mostly clear skies during the nights
and mornings with mostly cloudy skies with isolated showers in the
afternoons. Trade winds will remain almost due east through the
forecast period and winds converging on the Lee side of Molokai
may bring some quick hitting showers to east Oahu and central
areas of Honolulu.
Mimic satellite estimates of precipitable water show a few areas
of enhanced moisture moving along in the trade wind flow upstream
of the islands. One batch of moisture is pushing into the windward Big
Island this morning and will continue to bring clouds and embedded
showers to the area through the day. The second is farther
upstream and will reach the windward areas of the smaller islands
tonight...increasing showers through Tuesday morning. Only light
to moderate rain rates are expected with perhaps a brief downpour
with these showers.
Overnight soundings show the current trade wind temperature
inversion is near 9 thousand feet over Kauai and 12 thousand feet
over The Big Island.... radar data bears that out showing most
shower tops at or below the inversion height with a few isolated
tops pushing into the inversion and reaching 15 thousand feet.
Current 500 mb temperatures are about neutral for this time of
year near -8 celsius. This weekend an upper level trough pushing
by to the north is expected to decrease temperatures aloft to near
-10 celsius over the northern islands of Kauai and Oahu. The
slight drop in temperatures may allow for a bit more vertical cloud
growth and an increase in shower intensity.
high pressure NE of the state will keep a moderate east to NE trade
wind flow in place through tonight...with clouds and showers
focused primarily across mountain and north through east sections of the
islands. Predominantly VFR conditions are expected at most taf
sites...but some brief MVFR ceilings/visibilities may impact phto...phli and
Airmet Tango remains in effect for low level turbulence over and to
the south through west of the mountains. These conditions are expected
to continue through the day.
Airmet Sierra remains in effect for mountain obscuration across
portions of Oahu Molokai Maui and Big Island. Conditions should
improve later this morning.
a Small Craft Advisory remained in effect for typically windier
areas around Maui and The Big Island...and has been extended
through much of the week. Windward Maui waters may be added to the
Small Craft Advisory later today as easterly trades accelerate along the windward
coast of Molokai.
The trade winds also will maintain elevated short-period surf along
east-facing shores through the week...though heights should remain
below the advisory threshold. A long-period south-southwest swell
will build Tuesday...and then peak Wednesday into Thursday...likely
bringing advisory-level surf to south- facing shores. A tiny north
swell is expected Monday through Wednesday... and a slightly
larger north-northwest swell from Thursday into Saturday.
Small Craft Advisory until 6 PM HST Tuesday for Maalaea Bay-
Pailolo Channel-Alenuihaha Channel-Big Island leeward waters-Big
Island southeast waters.
Morrison...discussion and marine