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fxus62 kkey 211927 
afdkey

Area forecast discussion
National Weather Service Key West Florida
327 PM EDT Sat Sep 21 2019

Discussion...
the weather today across the Florida Keys has been warm, humid,
and windy, with occasional showers and some stronger squalls
offshore. The Keys archipelago is positioned beneath a deep
current of easterly flow along the southern flank of a deep layer
mean anticyclone centered over the southeastern United States.
Meanwhile. Seasonably low mean sea level pressures persist over
the Caribbean basin. Currently, Key West Doppler radar base
reflectivity scans show numerous fast-moving showers with
scattered heavier squalls and isolated thunderstorms. Northeast to
east winds are blowing close to a steady 25 knots at automated
stations along the Florida reef tract, with gusts in and around
passing showers near or exceeding gale force (34 knots).
Meanwhile, ashore northeast winds have been much more variable in
speed, averaging 10-25 mph depending on exposure, air temperature,
and rainfall. Currently, air temperatures in most Keys island
communities are in the mid 80s, with dewpoint temperatures in the
mid to upper 70s.

A wet and windy weather pattern is expected tonight through Sunday
night due to a combination of several favorable factors. #1: a
deep tropical moist layer which migrated northward during the last
24 hours is expected to persist; #2: strong near-surface air flows
will promote healthy upward fluxes of heat and water vapor from
the warm seas adjoining the Florida Keys and Bahamas upstream; #2;
a weak trough/cyclonic vorticity maximum in the lower troposphere
over the old Bahama channel will migrate westward, with increasing
influence across The Straits and keys; and #5: an anticyclonic
wave break over the eastern United States will induce a re-
positioning of an upper jet streak over the western North Atlantic
and southern Florida, placing the Florida Keys/Straits of Florida
in a favorable right-rear quadrant region. The upshot: well-above
average cloud cover, rain chances, and qpf are forecast through
Sunday, with gradual clearing Sunday night through Monday night. A
much drier and more stable pattern will set in during the
Tuesday-Thursday time frame, with clearing skies, only slight
shower chances, an near nil chances for thunder. A more moist,
unstable, northeast to east flow regime likely will set in by next
Friday or Saturday.
&&

Marine...
a Small Craft Advisory is in effect for all Florida Keys coastal
waters zones. Strong northeast to east breezes will blow across
Florida Keys coastal waters tonight, as a sprawling high pressure
cells maintains intensity and position from the western North
Atlantic to the Gulf of Mexico. The high pressure cell will weaken
very slowly, between Sunday night and Wednesday. Consequently,
breezes will diminish slowly during this time.
&&

Aviation...
gusty and squally weather will persist at the eyw and mth terminals
through the evening. After each squall passage, winds may collapse
to 10 knots or less. This scenario would result in a speed shear
impact for those planes on approach. Surface winds near 10 knots, with
winds at 2 kft near 30 knots, would result in 20 knots of speed
shear.

&&

Climate...
on September 21, 1948, a hurricane intensified as it moved north-
northeastward off Cuba, crossing Boca Chica Key as a category
three storm. At the U.S. Weather Bureau airways station at Boca
Chica Key, a one-minute sustained wind of 122 mph was measured
before the anemometer blew away, with a 15-minute period of near
calm noted as the western portion of the hurricane's eye moved
across. Other measured sustained winds include 120 mph at the
Sombrero Key light station, 80 mph at the Carysfort Reef light
station, 78 mph at Dry Tortugas, and 75 mph at the Weather Bureau
office in Key West. A total of 6.33 inches of rain was recorded
at Key West, with a station in Tavernier recording 6.02 inches as
well as a 5-foot storm tide. An unusual feature of this hurricane
was its apparent large, distorted eye, resulting in a distinct
wind lull occurring in Tavernier, around 80 miles away from Boca
Chica.
&&

Preliminary point temps/pops...
Key West 78 87 78 88 / 80 80 70 60
Marathon 78 88 78 89 / 80 80 70 50
&&

Key watches/warnings/advisories...
Florida...none.
GM...Small Craft Advisory in effect for
gmz031-gmz032-gmz033-gmz034-gmz035-gmz042-
gmz043-gmz044-gmz052-gmz053-gmz054-gmz055-
gmz072-gmz073-gmz074-gmz075.
&&

$$

Public/marine/fire...kasper
aviation/nowcasts....clr
data collection......bt

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