Marine Weather Net

Mona Passage Southward to 17N Marine Forecast


TODAY

SE
WINDS
10 - 15
KNOTS

TONIGHT

SE
WINDS
10 - 15
KNOTS

FRIDAY

SE
WINDS
5 - 10
KNOTS

FRIDAY NIGHT

E
WINDS
5 - 10
KNOTS

The Marine Weather Forecast In Detail:
AMZ741 Forecast Issued: 329 AM AST Thu May 23 2024

Today...Southeast Winds 10 To 15 Knots With Gusts Up To 20 Knots. Seas Around 4 Feet, Occasionally To 5 Feet. Wave Detail: Southeast 4 Feet At 6 Seconds And North 1 Foot At 7 Seconds. Isolated Thunderstorms. Scattered Showers Early This Morning, Then Numerous Showers Late This Morning And Afternoon.
Tonight...Southeast Winds 10 To 15 Knots With Gusts Up To 25 Knots. Seas 3 To 4 Feet, Occasionally To 5 Feet. Wave Detail: Southeast 4 Feet At 7 Seconds And North 1 Foot At 9 Seconds. Scattered Showers.
Friday...Southeast Winds 5 To 10 Knots. Seas 3 To 4 Feet, Occasionally To 5 Feet. Wave Detail: Southeast 4 Feet At 7 Seconds And North 1 Foot At 9 Seconds. Numerous Showers.
Friday Night...East Winds 5 To 10 Knots. Seas 2 To 3 Feet, Occasionally To 4 Feet. Wave Detail: Southeast 3 Feet At 7 Seconds And North 1 Foot At 9 Seconds. Numerous Showers.
Saturday...Southeast Winds 5 To 10 Knots. Seas 2 To 3 Feet, Occasionally To 4 Feet. Wave Detail: Southeast 3 Feet At 6 Seconds. Numerous Showers In The Morning.
Saturday Night...East Winds 5 To 10 Knots. Seas 2 To 3 Feet, Occasionally To 4 Feet. Wave Detail: Southeast 3 Feet At 7 Seconds. Scattered Showers.
Sunday...East Winds 10 To 15 Knots, Diminishing To 5 To 10 Knots In The Afternoon. Seas 2 To 3 Feet, Occasionally To 4 Feet. Scattered Showers In The Morning.
Sunday Night...East Winds 10 To 15 Knots. Seas 2 To 3 Feet, Occasionally To 4 Feet.
Monday...East Winds 10 To 15 Knots, Diminishing To 5 To 10 Knots In The Afternoon. Seas 3 To 4 Feet, Occasionally To 5 Feet. Scattered Showers In The Afternoon.
Monday Night...East Winds 5 To 10 Knots, Increasing To 10 To 15 Knots After Midnight. Seas Around 3 Feet, Occasionally To 4 Feet. Scattered Showers. Winds And Seas Higher In And Near Thunderstorms.
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Area Forecast Discussion
National Weather Service San Juan PR
330am AST Thu May 23 2024

Synopsis
Unsettled, squally weather is expected to prevail through the end of the workweek, with elevated risks for flooding, rapid river rises, and mudslides. Wet weather conditions will persist throughout next week as a tropical wave approaches from the southeast by Monday, maintaining above-normal moisture across the northeastern Caribbean. Additionally, some Saharan dust is expected by early next week, along with an elevated heat risk.

.SHORT TERM...Today through Saturday... Numerous showers and thunderstorms continued across the eastern Puerto Rico out to the USVI, providing a rainy night. The best rainfall overnight was seen across St. Thomas and John with multiple thunderstorms passing by during these early morning hours.

Unstable, wet conditions will prevail into the weekend as a deep layered trough moves through the Caribbean basin then lifting into the southwestern Atlantic by Saturday. As the mid to upper jet of the trough sits over Hispaniola over the next 24 hours, a surface induced trough begins to form to the southwest of the region causing the veering of the surface winds to a southerly flow by Friday. A moist airmass entered the region yesterday and as winds veer, another plume of moisture sourced from northern South America will move into the area, keeping precipitable water values high in the upper 2nd percentile. This moisture, unstable dynamics aloft due to the proximity of the mid to upper-level jets, and moderate surface wind flow will maintain a pattern of numerous passing showers, especially for the eastern half of the region, including eastern mainland Puerto Rico, Vieques, Culebra, and the USVI. Squally weather with thunderstorms are possible at times which can bring strong winds and heavy downpours.

This afternoon convection will increase shower activity with the eastern sections most likely to receive the bulk of rain. Thunderstorms are also likely to spawn across northwestern Puerto Rico, however due to cloud coverage convection over land may be reduced. However, expect a 70 to 90 percent chance of rain for all of the island through this afternoon. Passing showers will continue through the night into Friday and Saturday with a similar pattern prevailing. The greatest threat during this time is flooding due to consecutive showers and thunderstorms capable of producing frequent lightning and strong winds. Conditions do look slightly less unstable Friday through Saturday, yet the previous days of rainfall and ongoing activity will keep an elevated risk of flooding for most of the area. Also if cloud coverage begins to lighten on Saturday, heavy afternoon convection is very likely.

Long Term
Sunday through Thursday... Model guidance indicates that the wet period will persist through the long-term forecast. Sunday remains very moist, with precipitable water values above 2.0 inches and ample instability aloft. A mid- level ridge just east of the forecast area is expected to move over us by late Sunday into early Monday, coinciding with a slight reduction in low-level moisture, which will cause precipitable water values to drop to almost 1.8 inches. However, this "reprieve" won't last long as a tropical wave moves from the southeast over the islands by late Monday, causing moisture content to surge above 2.0 inches once again, persisting through the long-term forecast. Instability aloft will be marginal, as weak ridging will alternate with a series of weak short-wave troughs throughout the week. Therefore, the combination of above-normal moisture and marginal instability will maintain the flood risk across the area.

The National Blend of Models indicates approximately a 3-in-5 (60%) chance for thunderstorm activity and a 1-in-5 (20%) chance for 24- hour rainfall accumulations to exceed an inch each day of the long- term forecast, particularly across western/northwestern Puerto Rico under an east-southeast steering flow. The Galvez-Davison Index also suggests a similar scenario, with a high potential for observing isolated to scattered thunderstorms capable of producing heavy rainfall. With saturated soils and elevated streamflows from previous rainfall, the flooding risk will remain elevated. Therefore, we could expect urban and small stream flooding, as well as flash flooding and landslides in areas of steep terrain.

Another hot episode is expected on Sunday and Monday, accompanied by suspended Saharan dust particulates by early next week. Therefore, in areas with limited showers, hot and hazy conditions will prevail. The combination of high moisture content and high temperatures will produce hazardous heat index values, particularly in coastal and urban areas, possibly reaching Heat Advisory criteria once again.

Marine
The interaction of an induced surface trough and a surface high pressure to the northeast will promote moderate to locally fresh east-southeast winds. In addition, the proximity of a deep layered trough close to the Dominican Republic will continue to enhance thunderstorm development with the potential for squally conditions across the regional waters and local passages through at least Friday. Winds are forecast to diminish once again by Friday night.

Beach Forecast

Low to moderate rip current risk will persist throughout the period. In the presence of moderate rip current risk, there is still the possibility of life-threatening rip currents in the surf zone. Please remember to heed the advice of the local beach patrol and flag warning systems.

.SJU WATCHES/WARNINGS/ADVISORIES... PR...None. VI...None. AM...None.