Straits of Florida from Craig Key to West End of Seven Mile Bridge out 20 - 60 NM Marine Forecast
|Today...Mainly East Winds Near 5 Knots. Seas 1 Foot Or Less. Scattered Showers And Isolated Thunderstorms.|
|Tonight Through Saturday...Mainly East Winds Near 5 Knots. Seas 1 To 2 Feet. Scattered Showers And Isolated Thunderstorms.|
|Saturday Night...Northeast To East Winds 5 To 10 Knots. Seas 1 To 2 Feet. Scattered Showers And Isolated Thunderstorms.|
|Sunday...Northeast Winds 5 To 10 Knots. Seas 1 To 2 Feet. Scattered Showers And Isolated Thunderstorms.|
|Sunday Night...Northeast To East Winds 10 To 15 Knots. Seas 2 To 3 Feet. Scattered Showers And Isolated Thunderstorms.|
|Monday...Northeast To East Winds 10 To 15 Knots. Seas 2 To 3 Feet. Scattered Showers And Isolated Thunderstorms.|
| Synopsis for Keys coastal waters from Ocean Reef to Dry Tortugas: GMZ005|
506 AM EDT Thu Sep 23 2021
A weak pressure pattern will persist across the Florida Keys and adjacent coastal waters through Saturday, with prevailing light to gentle breezes. A continental high pressure cell will build over the southeastern United States by Sunday and Sunday night, leading to a slight freshening of northeast to east breezes early next week.
The Approximate Shoreward Edge of the Gulf Stream as of September 23, 2021...
- 31 NM South of Dry Tortugas Light...on Loggerhead Key.
- 17 NM South of Cosgrove Shoal Light...off the Marquesas Keys.
- 14 NM South of Sand Key Light...off Key West.
- 7 NM South of Looe Key...off Big Pine Key.
- 6 NM South of Sombrero Key Light...off Marathon.
- 9 NM Southeast of Alligator Reef Light...off Islamorada.
- 9 NM Southeast of Molasses Reef Light...off Key Largo.
- 10 NM East of Carysfort Reef Light...off Ocean Reef.
| Area Forecast Discussion|
National Weather Service Key West FL
440am EDT Thu September 23 2021
An upper-level composite analysis this morning revealed a plume of deep, rich moisture persisting over the Florida Keys and adjacent coastal waters, within an area of very weak flow through a deep layer. Development of numerous convective cells yesterday afternoon led to large areas of rain and outflow which had worked over the lower troposphere a bit, resulting in higher values of low-level convective inhibition per data from the Key West Wednesday evening radiosonde balloon. However, recent Doppler radar base reflectivity trends suggest that gradual destabilization is once again occurring, with increasing coverage of slow-moving convective cells during the last few hours. At the moment, showers and storms remain offshore, with rain-free conditions prevailing across Florida Keys island communities. Current air temperatures are near 80F, with a few island interior locations in the mid 70s (e.g., 76F here at the WFO in mid-town Key West). Dewpoint temperatures are mainly in the mid 70s, with light and variable winds.
The basic prognostic reasoning remains unchanged from the last several forecast cycles. Forcing for significant vertical motion (either up or down) is lacking, while the presence of a plume of deep, rich moisture and plenty of mesoscale forcing (sea/land breeze circulations and migrating convective outflows) will ensure at least slightly above average rain chances for a few more days. The season's first cold front cleared the northern Gulf coast, but has begun to decelerate and frontolyze a few hundred miles north and northwest of the Florida Keys. Residents of the Conch Republic will remain entrenched in the maritime tropical "soup" for the time being. Surface winds will remain quite weak through most of the weekend. However, an eastward-moving continental high pressure cell will increase local gradient flow by late Sunday, as MSL pressures rise north of the Florida Keys, while MSL pressures remain seasonably low over the western Caribbean. Freshening northeasterly breezes rooted in autumn continental air may actually lead to dewpoints briefly dropping to near 70F in some Keys island communities early next week, enough to notice, but falling short of a true cold frontal passage. Rain and thunder chances likely will not drop below climatological values with expected moist, moderately unstable atmospheric conditions with plenty of mesoscale circulations to initiate daily convective cell growth.
No watches, warnings, or advisories are in effect for Florida Keys coastal waters zones. A weak pressure pattern will persist across the Florida Keys and adjacent coastal waters through Saturday, with prevailing light to gentle breezes. A continental high pressure cell will build over the southeastern United States by Sunday and Sunday night, leading to a slight freshening of northeast to east breezes early next week.
On this day in 1874, the daily record low temperature of 71F was recorded in Key West. Temperature records date back to 1872.
NOAA Key West FL Office: Watches - Warnings - Advisories