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Hawaiian Islands Synoptic Discussion and Guidance |
FXHW60 PHFO 150636
Area Forecast Discussion
National Weather Service Honolulu HI
836 PM HST Tue Jul 14 2020
Gradually decreasing trade winds are in the forecast for the rest
of this week. Enhanced shower activity tonight and Wednesday
morning will also decrease in coverage over the next few days as
the low level trough moves westward away from the island chain.
Another low level disturbance moves into the region from the east
on Friday bringing another round of enhanced rain showers to the
islands. Stronger trade winds return from Saturday into the first
half of next week as high pressure builds in from the north.
No big changes to the weather pattern for the next seven days with
just a few adjustments based on changes in the mid range model
forecasts. On the satellite picture we continue to see an upper
level low roughly 600 miles north of Kauai drifting slowly
westward away from the islands, and a low level 700 mb trough
moving through the western islands this evening. A subtropical jet
continues to stream this high level cirrus clouds over the state.
Expect enhanced shower activity to continue through Wednesday
morning with a decreasing trend in showers forecast from Wednesday
afternoon through Thursday.
Friday through Sunday...Another low level trough will drift into
the islands from the east on Friday. Shower and cloud cover trends
will increase into Saturday as the system passes through the
region. However, Saturday might be your best day for outdoor
activities on the leeward side of the islands. Sunday looks
fairly wet in the model cross sections as yet another low level
trough moves from east to west through the state. This trough
tracks further south as compared to the Friday disturbance
allowing a deeper tropical moisture tap.
Monday and Tuesday...Breezy trade winds are forecast for the start
of next week with scattered to numerous windward and mountain
showers. Monday appears to trend a bit more stable and drier as
compared to Tuesday due to an approaching upper level disturbance.
However, windward and mauka areas may not see much difference in
shower coverage due to the stronger trade winds forcing available
moisture up the mountain slopes.
Elongated high pressure north of the state will allow for
moderate trades to persist across the islands tonight. Scattered
to numerous showers are expected to occur along the windward
coasts and slopes with isolated shower elsewhere. The highest
coverage of this activity will be over the western smaller
islands, including Kauai and Oahu. MVFR ceiling and visibility
could accompany this activity at times.
AIRMET SIERRA remains in effect for north thru east sections of
Oahu and Kauai above 2500 feet for tempo mountain obscuration from
low clouds and showers.
No changes to the forecast this evening, and no significant
changes are expected overnight. High pressure to the far northeast
of the state will maintain a moderate to locally fresh trade wind
pattern through Thursday. Winds are expected to remain just below
Small Craft Advisory levels. A weak disturbance is forecast to
move to the northeast of the islands Thursday and Friday, which
will help to weaken our winds a bit for later Thursday and Friday.
Winds may become light enough for afternoon sea breezes over
select leeward waters Thursday and Friday afternoons. Expect the
trades to ramp back up over the weekend as that disturbance
dissipates and the high pressure strengthens to the north of the
Overall, no significant swells are expected through the forecast
period. Small background surf will continue along south facing
shores over the next several days. A small south-southwest swell
is possible over the weekend. East facing shores will continue to
experience small to moderate short period surf produced by the
trade winds locally and upstream of the state. An increase is
expected over the weekend as the breezy trade winds return. Surf
along north facing shores will remain nearly flat through the
Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office