Marine Weather Net

Straits of Florida from Craig Key to West End of Seven Mile Bridge Out 20 NM Marine Forecast




20 - 25





The Marine Weather Forecast In Detail:
GMZ053 Forecast Issued: 428 AM EDT Sun Sep 22 2019

Today...Northeast To East Winds Near 25 Knots. Seas 7 To 11 Feet. Widespread Showers And Isolated Thunderstorms.
Tonight...Northeast To East Winds 20 To 25 Knots. Seas 6 To 10 Feet. Numerous Showers And Isolated Thunderstorms.
Monday...Northeast Winds Near 20 Knots. Seas 5 To 8 Feet. Numerous Showers And Isolated Thunderstorms.
Monday Night...Northeast Winds Near 20 Knots, Decreasing To 15 To 20 Knots After Midnight. Seas 4 To 7 Feet. Scattered Showers And Isolated Thunderstorms.
Tuesday...Northeast Winds Near 15 Knots. Seas Subsiding To 2 To 5 Feet. Scattered Showers And Isolated Thunderstorms.
Tuesday Night...Northeast To East Winds 10 To 15 Knots. Seas 2 To 3 Feet. Isolated Showers.
Wednesday...Northeast To East Winds Near 10 Knots. Seas 1 To 3 Feet. Isolated Showers.
Wednesday Night...East Winds 10 To 15 Knots. Seas 2 To 3 Feet. Isolated Showers.
Thursday...East Winds Near 10 Knots. Seas 1 To 2 Feet. Isolated Showers.
Thursday Night...East Winds 10 To 15 Knots. Seas 2 To 3 Feet. Scattered Showers And Isolated Thunderstorms.
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Synopsis for Keys coastal waters from Ocean Reef to Dry Tortugas: GMZ005
428 AM EDT Sun Sep 22 2019

Strong northeast to east breezes will continue across the Florida Keys coastal waters today, between high pressure over the Southeast United States and lower pressure over the western Caribbean. The high pressure will gradually weaken tonight through Tuesday, allowing easterly breezes to slowly diminish. Gentle to moderate east breezes will prevail from Tuesday night through Thursday night, as weak high pressure lingers over the Florida peninsula.

Gulf Stream
The Approximate Shoreward Edge of the Gulf Stream as of September 21, 2019...
- 55 NM South of Dry Tortugas Light...on Loggerhead Key.
- 33 NM South of Cosgrove Shoal the Marquesas Keys.
- 27 NM South of Sand Key Key West.
- 21 NM South of Looe Big Pine Key.
- 18 NM South of Sombrero Key Marathon.
- 21 NM Southeast of Alligator Reef Islamorada.
- 20 NM Southeast of Molasses Reef Key Largo.
- 13 NM East of Carysfort Reef Ocean Reef.
Area Forecast Discussion
...UPDATED National Weather Service Key West FL
753am EDT Sunday September 22 2019

Updated Aviation section only. Remainder from previous discussion.

Mostly cloudy and windy conditions prevail across the Florida Keys on this early Sunday morning, with frequent fast-moving showers and isolated thunderstorms passing through. Temperatures along the island chain are hovering in the upper 70s to near 80, and winds on land are from the ENE around 20 mph with peak gusts over 30 mph. Radar shows numerous showers extending from the Atlantic waters east of the Upper Keys, along the island chain and the Straits of Florida, and into the Lower Straits to the south of the Dry Tortugas.

Surface analysis depicts strong high pressure extending from the western Atlantic across the Southeastern states, while lower pressure is located over the western Caribbean Sea. The tight pressure gradient between these features is producing the strong winds over the Keys and surrounding waters. Aloft, a strong lower/mid level ridge is centered over the Southeast United States, while a weak upper level trough extends from off the Carolina coast across Florida and into the southeastern Gulf of Mexico. The 00Z Key West sounding shows copious moisture present within a very strong ENE flow pattern in the low levels, with PW of 2.27 inches which is above the 90th percentile for this date. MIMIC-TPW satellite imagery depicts a similarly moist airmass extending from the Keys eastward through Andros Island, while a much drier airmass lies not far to our northeast just to the north of Miami and over the northernmost Bahamas.

For today, expect a mostly cloudy, windy and rather wet pattern to continue across the Keys, as high pressure holds firm to our north and deep tropical moisture remains over our area. A weak inverted trough moving slowly westward across Cuba will also aid the wet pattern over the Keys, and have maintained well above normal 70 percent rain chances for today.

The much drier airmass to our north will begin to infiltrate southward, first at the mid levels, into the Keys tonight. This will lead to a gradual reduction in shower activity from north to south across the area, but it appears that sufficient low level moisture will remain within the still strong ENE flow to support 60 percent Probability of Precipitation along the island chain for tonight. Thereafter, rain chances will continue to trend downward Monday and Monday night as the drier airmass continues to deepen over the Keys and low level flow slackens. For Tuesday through Thursday, a strong low/mid level ridge over the eastern Gulf and Florida will bring mostly clear skies and mainly dry conditions to the Keys, with deep dry air aloft precluding any thunderstorm activity. Have maintained only slight 10-20 percent rain chances for these periods. Longer range guidance indicates a possible return to wetter weather toward the end of the week, and have trended the forecast toward climatology during that time.

Very strong ENE winds in the 25-30 kt range have continued across the Keys coastal waters overnight, with peak gusts over 40 knots with some of the fast-moving squalls racing through the area. Sustained ENE winds near 25 knots are expected to continue today, slowly decreasing to 20-25 knots tonight, although stronger wind gusts in excess of 30 knots will remain possible at any time. The Small Craft Advisory has been extended for all waters through tonight, and will probably be needed for much or all of the area on Monday as well. Improving marine conditions are expected beginning late Monday night into Tuesday, when winds/seas should finally drop below advisory levels.

NOAA Key West FL Office: Watches - Warnings - Advisories
FL...None. GM...Small Craft Advisory for GMZ031>035-042>044-052>055-072>075.