Scientific Forecaster Discussion
fxhw60 phfo 242015
Area forecast discussion
National Weather Service Honolulu HI
1015 am HST Wed may 24 2017
breezy trades will persist today, pushing clouds and showers
across windward areas. Winds will gradually weaken through the
second half of the week, becoming light and variable through the
Memorial Day weekend. Daytime sea breezes and nighttime land
breezes will take over this weekend and bring warm and humid
weather with possible vog. A weak upper trough will pass over the
state this weekend and may provide some enhancement to afternoon
breezy trade winds are pushing showers into the windward areas of
Kauai and Oahu this morning. These conditions are likely to
continue through today with showery low clouds lined up far
upstream. Another area of showers is making its way toward the
windward Big Island with increasing showers expected this
afternoon. Maui County and the leeward Big Island are free of any
showers this morning with clear skies over most areas with
continued dry conditions expected through the day.
A strong high pressure system centered far northwest of the islands is
providing the breezy trade winds over the state today. Trades
will weaken tonight and tomorrow as a surface low forms to the NE,
diminishing the pressure gradient over the state. Winds will
remain light and variable through the weekend as an approaching
front from the northwest turns the synoptic scale winds out of the southeast.
The light southeast flow will allow for afternoon sea breezes and
nighttime downslope winds to prevail over the islands from
Saturday into early next week.
Windward and mountain areas will see the majority of showers
through Friday, but sea breezes over the weekend will bring
passing afternoon showers to interior and leeward areas. A weak
upper level low will bring some instability to the atmosphere
Saturday and Sunday. The instability will enhance showers,
allowing for some isolated heavy showers to occur.
The light southeast flow will bring volcanic haze, or vog, up over the
smaller islands by Sunday and linger into the beginning of next
week. The light winds will also bring hot and humid conditions for
the weekend, continuing into the new work week.
breezy trade winds will continue across the islands today,
particularly over the windier locations. Airmet Tango continues
for mechanical turbulence to the Lee of the mountains.
Clouds and showers moving over Kauai and Oahu will continue to
bring periods of MVFR ceilings and visibilities. Additional
clouds and showers will likely impact primarily the windward side
of the islands. Airmet Sierra remains in effect for mountain
obscuration across Kauai and Oahu.
the latest surface analysis showed a large area of high pressure
(1039 mb) encompassing much of the northern Pacific that was
centered around 1500 nm north-northwest of the waters. Remnants
of a lingering frontal boundary were analyzed from east to west
just north of the Kauai and Oahu waters. The pressure gradient
between this boundary and strong high pressure to its north
continues to support a large area of fresh to strong trade winds.
A Small Craft Advisory (sca) is in effect for locally strong
trades in the typical windy zones around Maui County and The Big
Island. The trade wind speeds and Small Craft Advisory will maintain through
tonight, then trending down through the second half of the week as
high pressure shifts northeast over the Gulf of Alaska and
weakens. The trades will also create choppy conditions across
windward shores, but this will also decrease as trades weaken.
Surf along north facing shores will steadily trend down today as
the northwest swell that peaked on Monday eases and shifts more
out of the north. For the long range, models are hinting at
another moderate north-northwest (340 deg) swell filling in early
next week due to a low tracking east of the date line over the
weekend and deepening as it passes well north of the state on
Surf along south facing shores is expected to trend down as a
small south swell eases. The largest south swell this season is
forecast to fill in Friday, peak Friday night through Saturday
night, then slowly ease into early next week. This swell is
currently impacting the Samoa buoy, where wave heights were coming
in slightly higher than predicted by guidance earlier Tuesday
(around one ft higher). A high surf advisory for south facing
shores will be likely late Friday through much of the Holiday
weekend, before steadily easing into early next week.
In addition to the expected advisory-level surf through the Memorial
Day weekend along south facing shores, coastal flooding is
anticipated due to a combination of record level Spring (king)
tides (especially for Maui County and oahu) and large surf. See
the Special Weather Statement issued this morning on our website
for more details. Similar to the April 28th through may 1st
weekend, when the highest tides on record were reported for
Honolulu, impacts will include beach flooding and standing water
on roadways and low- lying areas near the coast around the times
of high tides each day through the weekend.
High tide times for honolulu:
5/24 Wednesday 3:36 PM HST
5/25 Thursday 4:20 PM HST
5/26 Friday 5:07 PM HST (peak water levels/surf expected)
5/27 Saturday 5:55 PM HST (peak water levels/surf expected)
5/28 Sunday 6:46 PM HST
5/29 Monday 7:40 PM HST
For more detailed information on surf for Oahu, see the latest
collaborative nearshore swell and wind forecast that was issued
Monday afternoon (www.Prh.NOAA.Gov/hnl/pages/srf.Php#discussion).
Small Craft Advisory until 6 am HST Thursday for Maalaea Bay-
Pailolo Channel-Alenuihaha Channel-Big Island leeward waters-Big
Island southeast waters.