Straits of Florida from Ocean Reef to Craig Key out 20 - 60 NM Marine Forecast
|Today...Northeast To East Winds 5 To 10 Knots. Seas 1 To 2 Feet. Scattered Showers And Isolated Thunderstorms.|
|Tonight...Northeast To East Winds 5 To 10 Knots. Seas 1 To 2 Feet. Scattered Showers And Isolated Thunderstorms.|
|Monday...East Winds Near 10 Knots. Seas 1 To 2 Feet. Scattered Showers And Isolated Thunderstorms.|
|Monday Night...Northeast To East Winds Increasing To 10 To 15 Knots. Seas Building To 2 To 3 Feet. Scattered Showers And Isolated Thunderstorms.|
|Tuesday...East Winds 10 To 15 Knots. Seas 2 To 3 Feet. Scattered Showers And Isolated Thunderstorms.|
|Tuesday Night...Northeast To East Winds 10 To 15 Knots. Seas 2 To 3 Feet. Scattered Showers And Isolated Thunderstorms.|
|Wednesday...Northeast To East Winds Decreasing To 5 To 10 Knots. Seas Subsiding To 1 To 2 Feet. Scattered Showers And Isolated Thunderstorms.|
|Wednesday Night...Variable Winds 5 To 10 Knots. Seas 1 To 2 Feet. Scattered Showers And Isolated Thunderstorms.|
|Thursday...Variable Winds Near 5 Knots. Seas Around 1 Foot. Scattered Showers And Isolated Thunderstorms.|
|Thursday Night...Variable Winds Near 5 Knots, Becoming East To Southeast. Seas Around 1 Foot. Scattered Showers And Isolated Thunderstorms.|
| Synopsis for Keys coastal waters from Ocean Reef to Dry Tortugas: GMZ005|
417 AM EDT Sun Sep 19 2021
A ridge will continue to build westward across the Florida Peninsula today, bringing gentle northeast to east breezes. Northeast to east breezes will peak and lull tonight through Wednesday, before becoming light and variable at times Wednesday night through Friday.
The Approximate Shoreward Edge of the Gulf Stream as of September 18...
- 49 NM South of Dry Tortugas Light...on Loggerhead Key.
- 29 NM South of Cosgrove Shoal Light...off the Marquesas Keys.
- 37 NM South of Sand Key Light...off Key West.
- 45 NM South of Looe Key...off Big Pine Key.
- 39 NM South of Sombrero Key Light...off Marathon.
- 26 NM Southeast of Alligator Reef Light...off Islamorada.
- 17 NM Southeast of Molasses Reef Light...off Key Largo.
- 7 NM East of Carysfort Reef Light...off Ocean Reef.
| Area Forecast Discussion|
National Weather Service Key West FL
420am EDT Sunday September 19 2021
A mostly quiet overnight across the Florida Keys. There were a couple of isolated showers that develop, one over the Florida Bay, and another over portions of the lower Keys. Neither one was terribly impressive, though some island communities did pick up to one to two-tenths of an inch based on radar estimates. Otherwise, just some high level cirrus streaming in from the northeast from earlier convection over the mainland overnight.
The north to northeast steering flow aloft is thanks to a low and mid level ridge situated across the eastern Gulf of Mexico. The combination of these features will help to establish a surface high pressure just to our north. This in turn will allow for northeast winds to dominate across the island chain today. Moisture-wise, last night's 00Z RAOB (Radiosonde Observation or Upper-Air Observation) sounding showed a PWAT (Precipitable Water) of 1.94 inches, which is still slightly above our climatological norm. As we go through the day today, the low and mid levels should further moisten up. This, when combined with the deeper northeast flow, will allow for a weak cloudline to develop. In addition to the threat of thunderstorms, a few waterspouts are possible.
As we start the new work week, deep layer ridging will push further west. This will allow for winds to veer to the east and draw in even more moisture. As a result, models continue to depict a more active weather pattern with the best or highest chances being Tuesday. With that said, there's no discernible feature in the easterly flow and therefore mesoscale processes will be the dominant factor. By mid-week the flow will collapse and we will go light and variable and chances for showers and thunderstorms will fall slightly for the end of the week. For now will maintain a middle of the road approach with 40% probability of precipitation for the later half of the forecast period given that models are hinting at a mixed bag of rain chances.
Light northeast breezes prevail this morning across all of the Florida Keys coastal waters. Given the northeast winds, a cloudline will develop across the Keys, especially the lower and middle Keys. Mariners should be cautious as a few waterspouts may form under flat dark cloud bases today in association with the cloudline. Otherwise, ridge will build and push westward starting Monday with freshening northeast to east breezes. Expect gentle to moderate breezes by Monday night, continuing into Tuesday night. Then winds collapse and become light and variable at times Wednesday through Thursday night.
In 1963, the daily record rainfall of 4.23" was recorded in Key West. Precipitation records date back to 1871.
NOAA Key West FL Office: Watches - Warnings - Advisories