Drought in Hawaii, August 1 to 31, 2020

Area Forecast Discussion
National Weather Service Honolulu HI
828 PM HST Fri Jul 31 2020

.SYNOPSIS...
Breezy trade wind conditions will prevail through the weekend and
much of next week as high pressure remains anchored to the north.
Clouds and showers will favor windward and mountain areas each day,
especially through the overnight and early morning periods as
pockets of moisture move through. A modest increase in moisture
combined with an upper disturbance moving through the region
will support better trade wind shower coverage Tuesday through
midweek.

&&

.DISCUSSION...
Latest surface analysis and satellite imagery showed the
subtropical ridge anchored north of the islands and patchy low-
level clouds approaching and moving through from east to west.
Some of these clouds are generating brief showers as they move
through - mainly over windward and mountain areas of Kauai and the
Big Island this evening. Rain gages around the islands reflect
this and showed peak accumulations ranging from a quarter to a
little over half of an inch in the past 6-Hrs (through 7 pm HST)
on Kauai and the Big Island. Expect this trend to persist
overnight into Saturday, especially over and just upstream of
Kauai where a band of higher low-level moisture has setup (1.2 to
1.3 inch PWs shown on satellite).

Guidance has initialized well with the current pattern and shows the
ridge holding north of the area through next week. Breezy trade wind
conditions will prevail with only subtle fluctuations in speed and
direction. Although mostly dry conditions will continue through the
weekend with PWs hovering around and just over one inch, spotty
windward showers will remain in the forecast, especially through the
overnight and early morning hours. An increase in moisture will be
possible Tuesday through the midweek period where PWs are forecast
to climb to around 1.5 to 1.75" (above normal). This combined with a
middle- to upper-level trough moving through the region from east to
west will support better trade wind shower coverage. If this setup
materializes, some showers may hold into leeward areas.

&&

.AVIATION...
High pressure far northeast of the islands will maintain a
moderate to breezy trade wind pattern, with showers focused over
the windward slopes. Satellite shows more clouds and showers over
and immediately upstream of the Big Island, and AIRMET Sierra is
in place for the windward side for mountain obscuration. Expect
this AIRMET to stay in place through the night. Small chance an
AIRMET for mountain obscuration may be needed for Kauai with some
clouds upstream, but at this time not expecting any widespread
issues. Otherwise, expect passing MVFR conditions in the trade
wind clouds and showers over the remaining islands, mainly over
the windward sides of the islands.

AIRMET Tango remains in place for mechanical turbulence to the lee
of the mountains for all islands. With the moderate to breezy
trade wind pattern expected to continue through Saturday, expect
this AIRMET to remain in place.

&&

.MARINE...
High pressure north of the waters will keep Locally strong trade
winds in place through the weekend and much of next week. A Small
Craft Advisory (SCA) remains in effect for the typically windier
waters around Maui and the Big Island through 6 pm Sunday. The SCA
will likely be required for these same zones through much of next
week.

Small background south and southeast swells will maintain small
surf along south facing shores this weekend. A reinforcing
southeast swell could produce a slight bump along the south
facing shores early next week. Around midweek, a long-period south
swell could boost south shore surf to near the summertime
average. A small north-northeast swell is possible from late this
weekend into early next week. Steady near east shore surf will
continue through early next week, with surf near to slightly below
the summertime average. East shore surf should trend up during the
middle to latter part of next week as the trades over and upstream
of the islands strengthen.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
Small Craft Advisory until 6 PM HST Sunday for Maalaea Bay-
Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big
Island Southeast Waters.

&&

DISCUSSION...Gibbs
AVIATION...M Ballard
MARINE...Jelsema