Marine Weather Net

Straits of Florida from Halfmoon Shoal to 20 NM west of Dry Tortugas out 20 NM Marine Forecast


TONIGHT

SSW
WINDS
5 - 10
KNOTS

THURSDAY

SW
WINDS
15
KNOTS

THURSDAY NIGHT

SW
WINDS
15 - 20
KNOTS

FRIDAY

WSW
WINDS
20
KNOTS

The Marine Weather Forecast In Detail:
GMZ055 Forecast Issued: 423 PM EDT Wed Oct 27 2021

Tonight...South To Southwest Winds 5 To 10 Knots, Increasing To 10 To 15 Knots. Seas 1 To 2 Feet. Scattered Showers And Isolated Thunderstorms.
Thursday...South To Southwest Winds Near 15 Knots, Increasing To 15 To 20 Knots. Seas Building To 2 To 4 Feet. Scattered Showers And Isolated Thunderstorms.
Thursday Night...Southwest Winds 15 To 20 Knots, Increasing To Near 20 Knots. Seas Building To 4 To 5 Feet. Numerous Showers And Scattered Thunderstorms In The Evening, Then Scattered Showers And Isolated Thunderstorms After Midnight.
Friday...Southwest To West Winds Near 20 Knots. Seas 4 To 7 Feet Due To West Swells. Isolated Showers.
Friday Night...West Winds Near 20 Knots. Seas 5 To 8 Feet Due To West Swells. Isolated Showers.
Saturday...West Winds 15 To 20 Knots. Seas 5 To 8 Feet Due To West Swells. Isolated Showers.
Saturday Night...West To Northwest Winds Decreasing To Near 10 Knots. Seas Subsiding To 3 To 5 Feet. Isolated Showers.
Sunday...Northwest To North Winds Near 10 Knots. Seas Subsiding To 2 To 3 Feet.
Sunday Night...North To Northeast Winds Near 10 Knots. Seas 2 To 3 Feet.
Monday...Northeast Winds Near 10 Knots. Seas 2 To 3 Feet. Isolated Showers.
Monday Night...Northeast To East Winds Near 10 Knots, Increasing To 10 To 15 Knots. Seas 2 To 3 Feet. Isolated Showers.
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Synopsis for Keys coastal waters from Ocean Reef to Dry Tortugas: GMZ005
423 PM EDT Wed Oct 27 2021

A frontal boundary will approach the Florida Peninsula overnight, resulting in freshening southwesterly to westerly breezes. The front is expected to push through the marine zones of the Keys Thursday afternoon and evening from west to east, with scattered showers and thunderstorms possible as the front passes. Small Craft Should Exercise Caution headlines and Small Craft Advisories may be required for portions or all of the Florida Keys coastal waters for Thursday through at least Saturday. Breezes will slacken Saturday night through early next week, with below normal rain and thunder chances expected.

Gulf Stream
The Approximate Shoreward Edge of the Gulf Stream as of October 27...
- 20 NM South of Dry Tortugas Light...on Loggerhead Key.
- 17 NM South of Cosgrove Shoal Light...off the Marquesas Keys.
- 17 NM South of Sand Key Light...off Key West.
- 20 NM South of Looe Key...off Big Pine Key.
- 24 NM South of Sombrero Key Light...off Marathon.
- 28 NM Southeast of Alligator Reef Light...off Islamorada.
- 20 NM Southeast of Molasses Reef Light...off Key Largo.
- 15 NM East of Carysfort Reef Light...off Ocean Reef.
Area Forecast Discussion
National Weather Service Key West FL
425pm EDT Wednesday Oct 27 2021

Under light southwesterly steering flow, visible satellite has detected weak cloud streamers in the vicinity of the island chain over the past several hours. However, owed to the formidable dry air sampled by the 12z sounding at KEY, none of these streamers has been able to produce any isolated shower activity, and KBYX radar is nearly echo free. Skies are mostly sunny across the island chain, and temperatures continue to climb to their advertised high values in the mid to upper 80s.

The main weather story in the forecast continues to be the negatively tilted, digging trough approaching the Gulf coast and the associated frontal boundary. As the front and trough approach the Florida Peninsula overnight, southwesterly flow will freshen at the same time that forecast soundings highlight a moistening atmosphere. These soundings show a period of moderate 0-6 km unidirectional shear right around the time of the closest approach of the trough axis to the Florida Keys tomorrow evening. This appears supportive of a quasilinear area of convection to push through the Florida Keys from west to east. With that being said, the strongest forcing for ascent appears it will remain to the north of the CWA, and as is typical for this time of year, the front will be waning as it loses its baroclinicity over South Florida. The general line of thinking has not changed this forecast iteration, with isolated showers and thunderstorms possible ahead of the front overnight through much of tomorrow, a decaying line of storms forecast to push through late tomorrow afternoon or tomorrow evening, and some trailing scattered stratiform showers thereafter for the overnight period.

Behind the front, freshening breezes will ensue, along with a modest cool down (with highs in the low 80s) and a more substantial drop in dew points (low to mid 60s). A broad ridge will build over the eastern third of the CONUS of the weekend through early next week. Below normal rain and thunder chances are expected for this extended period, with the forecast nudged towards climatology toward midweek.

Marine
There are no watches, warnings, or advisories currently in effect for the Florida Keys coastal waters. From synopsis, a frontal boundary will approach the Florida Peninsula overnight, resulting in freshening southwesterly to westerly breezes. The front is expected to push through the marine zones of the Keys Thursday afternoon and evening from west to east, with scattered showers and thunderstorms possible as the front passes. Small Craft Should Exercise Caution headlines and Small Craft Advisories may be required for portions or all of the Florida Keys coastal waters for Thursday through at least Saturday. Breezes will slacken Saturday night through early next week, with below normal rain and thunder chances expected.

Climate
In 1960, the daily record high temperature of 91 degrees was recorded. Temperature records in Key West date back to 1873.

NOAA Key West FL Office: Watches - Warnings - Advisories
FL...None. GM...None.