Southern Puerto Rico out 10nm Marine Forecast
| Rest Of Today...East Winds 10 To 15 Knots With Gusts Up To 25 Knots. Seas 3 To 5 Feet, Occasionally To 6 Feet. Wave Detail: East 5 Feet At 7 Seconds. Isolated Thunderstorms. Numerous Showers Late This Morning, Then Scattered Showers This Afternoon. |
| Tonight...East Winds 10 To 15 Knots With Gusts Up To 25 Knots. Seas 3 To 4 Feet, Occasionally To 5 Feet. Wave Detail: East 4 Feet At 7 Seconds. Numerous Showers. |
| Friday...East Winds 10 To 15 Knots With Gusts Up To 20 Knots. Seas 3 To 4 Feet, Occasionally To 5 Feet. Wave Detail: East 4 Feet At 7 Seconds. Scattered Thunderstorms In The Morning. Numerous Showers. |
| Friday Night...East 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. Scattered Showers. |
| Saturday...East Winds 10 To 15 Knots, Diminishing To 5 To 10 Knots In The Afternoon. Seas 3 To 4 Feet, Occasionally To 5 Feet. Wave Detail: East 4 Feet At 7 Seconds. Scattered Showers. |
| Saturday Night...East Winds 5 To 10 Knots With Gusts Up To 20 Knots. Seas 2 To 3 Feet, Occasionally To 4 Feet. Wave Detail: Southeast 3 Feet At 7 Seconds. Numerous Showers. |
| Sunday...East Winds 5 To 10 Knots. Seas 3 To 4 Feet, Occasionally To 5 Feet. Numerous Showers, Mainly In The Morning. |
| Sunday Night...East Winds 5 To 10 Knots. Seas 3 To 4 Feet, Occasionally To 5 Feet. Numerous Showers. |
| Monday...East Winds 5 To 10 Knots. Seas 3 To 4 Feet, Occasionally To 5 Feet. Scattered Showers. |
| Monday Night...East Winds 5 To 10 Knots. Seas 3 To 4 Feet, Occasionally To 5 Feet. Scattered Showers. Winds And Seas Higher In And Near Thunderstorms. |
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Area Forecast Discussion National Weather Service San Juan PR 518am AST Thu May 15 2025 .KEY MESSAGES... * A wet and unstable weather pattern will continue through the end of the workweek and the weekend, heightening the risk of flooding across Puerto Rico and the U.S. Virgin Islands, especially on Friday and Saturday. * Breezy winds will maintain choppy to rough seas, with a moderate risk of rip currents through at least Saturday. .SHORT TERM...Today through Saturday... A transition into a wet and unstable pattern continues to be forecast as we head towards the end of the week. A deep layered trough, currently west-northwest of our local islands, will gradually move eastward and promote more favorable conditions for widespread shower and thunderstorm activity, especially late Thursday onwards. East- southeast steering flow over the region will persist during the period and continue to bring a surge in moisture over the islands. The deep layered trough will converge with this deep tropical moisture that will arrive from the east- southeast, with current model guidance showing a completely moist atmospheric profile. Current satellite derived precipitable water values are currently at around 1.8 to more than 2.0 inches above most of the region. Current model guidance continues to indicate precipitable water (PWAT) values around 2.25 inches over the islands, above normal values for this time of the year with slight decreases in PWAT (Precipitable Water) values at times.Current model guidance also has the trough moving quicker than before, but still affecting the local islands. As they were during the early morning hours, trade wind showers (and possible isolated t-storms) will continue to affect windward sectors of the islands from the southeast during this morning, while this afternoon convection is forecast mainly over NW PR and downwind of El Yunque and the local islands but more generalized than yesterday. A broad high-pressure system over the Atlantic will continue to maintain generally breezy conditions today and tomorrow, gradually decreasing on Saturday. 925 mb temperatures will be at normal values through late Friday, when they are forecast to drop to below normal values. With moisture and instability increases (500mb temperatures dropping to around -7 to -8C), showers and thunderstorms are forecast to become more widespread as the week continues, particularly on Friday into Saturday, over southeastern and eastern Puerto Rico, Vieques, Culebra, and the U.S. Virgin Islands. There is a moderate chance (40- 60%) of receiving 2 to 4 inches across these areas with locally higher amounts of up to 6 inches each day. A Saharan Air Layer continues to approach the islands and could be a limiting factor (along with cloud coverage) for this wet pattern during the short term period. With already saturated soils and elevated streams, there is an increased risk of urban and small stream flooding, potentially isolated flash flooding, river rises and debris flow in steep terrains. Please refer to the latest Hazardous Weather Outlook and the latest Hydrologic Outlook for more information. Long Term Sunday through Wednesday... Despite recent model guidance introducing a few notable changes, a dynamic interplay between upper-level and surface features will continue to drive periods of marginal instability and variable winds across the northeastern Caribbean. A Tropical Upper Tropospheric Trough (TUTT) Low and its associated surface-induced trough will dominate on Sunday, with its divergent side supporting cooler-than-normal 500 mb temperatures and a weakened trade wind inversion, favorable for deep convection. As the TUTT Low lifts northeastward, a large upper-level trough digging into the western Atlantic will reinforce this pattern, while a developing mid- level ridge emerges far to the west. At the surface, the induced trough will continue to disrupt the trade wind flow, even after detaching from its parent feature, maintaining lighter, more variable winds through the period. Meanwhile, a broad surface high over the central North Atlantic and a weaker high near the Bahamas will help trap tropical moisture across the region. On Sunday, precipitable water values may reach up to 2.0 inches. As the weak high lifts northeastward and pushes the moisture southeastward, a gradual drying trend is anticipated, with a return of deeper moisture expected by midweek as strengthening east-southeasterly winds reestablish. During this period, Puerto Rico will experience fluctuating moisture levels and variable wind patterns early on, while generally moist and breezy conditions are expected to persist longer over Vieques, Culebra, and the U.S. Virgin Islands. Despite these variations, the overall moist and marginally unstable environment will enhance shower and thunderstorm development, particularly during the afternoon. Slackened winds will reduce ventilation, allowing convective cells to linger longer and increasing the risk of locally heavy rainfall and flooding. Marine A broad surface high pressure over the Central Atlantic will promote breezy easterly winds. As a result, small craft operators should exercise caution due to choppy conditions through Friday night across most local waters. A surface trough will gradually weaken winds over the weekend into early next week. Meanwhile, a deep trough will bring an unsettled weather pattern with a high chance of thunderstorm development beginning Thursday afternoon, leading to locally higher winds and seas. Beach Forecast Life-threatening rip currents are possible along most northern, southern, and eastern exposed beaches of the islands today and tonight. The risk will likely diminish this weekend as winds ease gradually. For more information, please refer to the latest Coastal Hazard Message (CFWSJU) and Surf Zone Forecast (SRFSJU). Shower and thunderstorm activity will likely increase by the end of the week and continue into the weekend as the region transitions back to a wet and unstable weather pattern. Reminder: Seek shelter and leave the water or beach immediately at the first sign of thunder or lightning. Hydrology Due to abundant moisture and increasing instability associated with an upper-level trough, the risk of flooding across Puerto Rico and the U.S. Virgin Islands is increasing for Friday and Saturday. The heaviest rainfall is currently expected across southeastern and eastern Puerto Rico, Vieques, Culebra, and the U.S. Virgin Islands, where 2 to 4 inches of rain are likely, with locally higher amounts possible. Saturated soils and elevated river levels will enhance the threat of urban and flash flooding, river flooding, and mudslides, particularly across central and eastern Puerto Rico. For additional details, refer to the Hydrologic Outlook (ESFSJU). If forecast confidence and risk continue to increase, a Flash Flood Watch may be issued later today or tonight. .SJU WATCHES/WARNINGS/ADVISORIES... PR...None. VI...None. AM...None. |
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