Current Conditions
Temp6.3 C
RH10 %
WindENE 42 mph
RoadOpen (4x4)
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Hawaiian Islands Synoptic Discussion and Guidance

254
FXHW60 PHFO 250126
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
326 PM HST Fri May 24 2019

.SYNOPSIS...
Humid easterly trade winds will again give way to afternoon sea
breezes in some leeward areas. Showers will favor windward slopes,
though afternoon clouds and a few showers are expected over
leeward terrain this afternoon. Moderate easterly trade winds and
stable conditions will prevail this weekend and through most of
next week. Showers will mainly be confined to windward slopes.

&&

.DISCUSSION...
An easterly trade wind flow is building across the island chain
this afternoon. The islands lie under the western periphery of a
broad area of surface high pressure centered far northeast of the
state, while a slow moving and front is weakening roughly 350
miles northwest of Kauai. As the front weakens, the ridge has
exerted greater influence over the state, causing easterly trade
winds to increase several mph compared to this time yesterday. A
diffuse band of low level moisture moved across the Big Island and
Maui last night and recently fell apart over Oahu. This feature
dropped less than 1/4 inch of rainfall on windward Oahu around mid
day and triggered a brief period of leeward shower activity
before largely dissipating. Lingering moisture from this feature
has kept humidity up, but increasing trades are providing some
relief in spite of above normal high temps of around 90.

Easterly trade winds are expected to continue to temporarily
strengthen tonight. This will occur as the front northwest of
Kauai begins to dissipate and surface high pressure to the
northeast exerts greater influence. Expect dew points to fall
a few degrees back to seasonal normal. Stable conditions will
continue, keeping modest rainfall focused over windward slopes.

Little change is in store through next week. After the initial
surge, easterly trade winds will decrease slightly as the area of
high pressure to the northeast weakens and its associated ridge
remains disrupted north of the state. In fact, the easterly winds
could be weak enough to allow another round of extensive leeward
sea breezes on Memorial Day and Tuesday afternoons. Models are
hinting at stronger trades building in on Wednesday or Thursday.
Overall, conditions will remain stable as a mid level ridge holds
overhead. Showers will favor windward slopes, though small pockets
of moisture will lead to periodic and brief increases in shower
activity.

&&

.AVIATION...
TAFs should remain mostly VFR through Saturday. A weak band of
showery clouds will continue to dissipate as it moves westward
through Kauai this evening. Winds will increase slightly through
tonight, so clouds and any showers will favor the typical windward
coasts and slopes, as well as fewer afternoon clouds over leeward
areas for the next few days.

&&

.MARINE...
East trade winds are expected to surge tonight, bringing in
moderate to fresh speeds across the state, with a bit more
acceleration across through the typically windier waters around
the Big Island and Maui County. A moderate to locally fresh east
trade pattern is then expected to continue into next week.

A series of south-southwest swells will keep surf up along south
facing shores well into next week. The current south-southwest
swell will fade Saturday as forerunners from a larger south-
southwest swell will fill in. Surf from this second swell is
expected to peak around the 8-foot advisory level Sunday and
Memorial Day. Surf should then stay in the shoulder to head high
range into midweek along the south facing shores.

The north facing shores will see a bump in surf this weekend as a
moderate, short period northwest swell continues to fill in and
peak Saturday and hold Sunday. This will also put surf along
north facing shores in the head high range over the weekend. This
swell will gradually subside into midweek.

Along east facing shores, trade wind swell will pick up as the
trades winds increase this weekend, but will remain below advisory
levels.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

DISCUSSION...Wroe
AVIATION...TS
MARINE...Eaton

Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office