Northern US Virgin Islands and Culebra Marine Forecast
|Tonight...East Winds 10 To 15 Knots. Seas 2 To 4 Feet With Occasional Seas Around 5 Feet. Dominant Period 10 Seconds. Scattered Showers.|
|Monday...East Winds 10 To 15 Knots. Seas 3 To 5 Feet With Occasional Seas Up To 6 Feet. Dominant Period 10 Seconds. Scattered Showers.|
|Monday Night...East Winds 10 To 15 Knots With Gusts Up To 25 Knots. Seas 3 To 5 Feet With Occasional Seas Up To 6 Feet. Dominant Period 10 Seconds. Scattered Showers. Isolated Thunderstorms After Midnight.|
|Tuesday...East Winds 10 To 15 Knots. Seas 3 To 5 Feet With Occasional Seas Up To 6 Feet. Dominant Period 10 Seconds. Scattered Showers.|
|Tuesday Night...East Winds 10 To 15 Knots. Seas 3 To 5 Feet With Occasional Seas Up To 6 Feet. Dominant Period 10 Seconds. Scattered Showers.|
|Wednesday...East Winds 10 To 15 Knots. Seas 2 To 4 Feet With Occasional Seas Around 5 Feet. Dominant Period 10 Seconds, Subsiding To 8 Seconds. Scattered Showers.|
|Thursday...East Winds 10 To 15 Knots. Seas 2 To 4 Feet With Occasional Seas Around 5 Feet. Dominant Period 11 Seconds. Scattered Showers With Isolated Thunderstorms.|
|Friday...Southeast Winds 10 To 15 Knots. Gusts Up To 25 Knots. Seas 2 To 4 Feet With Occasional Seas Around 5 Feet. Dominant Period 10 Seconds. Scattered Showers With Isolated Thunderstorms.|
| Area Forecast Discussion|
National Weather Service San Juan PR
438pm AST Sunday September 25 2022
A seasonal shower pattern will prevail tonight, accentuated by trade wind showers moving into eastern Puerto Rico and the US Virgin Islands. Shower and thunderstorm development will be more favorable from Monday onwards as a strengthening TUTT Low settles to the northeast with the associated surface-induced trough and increased tropical moisture levels adding to the already unstable scenario.
.SHORT TERM...Tonight through Tuesday... Potential hazards during the short-term cycle are still lightning at limited risk levels and excessive rainfall elevating from limited hazard risk on Sunday to elevated hazard risk on Monday.
A strengthening Tropospheric Upper Tropical Trough (TUTT) low will slowly settle north of Puerto Rico, setting favorable conditions to support increased showers and thunderstorm activity through the short-term cycle. In the meantime, the associated surface-induced trough will cross the region from the east. A steady increase in tropical moisture will add to the already unstable scenario, with model-estimated precipitable water values climbing as high as 2 inches by Tuesday morning, further expanding the potential for shower and thunderstorm activity and the risk for flooding impacts across the local islands. So far, aided by local effects and diurnal heating, the highest impact is expected over the interior and western Puerto Rico, where water ponding on roads and poorly drained areas is likely. Minor to urban and small stream flooding is possible with any prolonged period of moderate to heavy rains. Until then, the shower activity will focus on portions of eastern Puerto Rico and the U.S. Virgin Islands, where isolated to scattered showers are likely tonight into early Monday morning. A typical daily temperature pattern is expected, with overnight low temperatures as low as the upper 60s across higher elevations and daytime high temperatures as high as 90 degrees across coastal areas. Surface winds will remain out of the east at 10-20 mph with higher gusts and sea breeze variations. Slightly higher gust
Wednesday through Monday... FROM PREVIOUS DISCUSSION
Another upper level low will detach from a wide Tropical Upper Tropospheric Trough localed over the central Atlantic, and then the low will approach the northeastern Caribbean on Wednesday. At the surface, moisture will increase due to patches of air with higher relative humidity induced by the upper level system that continue to be dragged across the area by the trade winds. As a result of the the upper level support and the low level moisture, active afternoons are expected across the area, with advective showers moving across eastern Puerto Rico and the United States Virgin Islands during the day, and afternoon convection developing across the interior and western Puerto Rico. The islands will be under the influence of the upper level trough through Friday. Then, on Saturday, a mid level ridge tries to build in north of the region. At the same time, moisture will be pulled out from the ITCZ (Intertropical Convergence Zone) across the northeastern Caribbean. With this deep-layered moisture, the wetter pattern will be stretching into the upcoming weekend, with an elevated risk of flooding, water surges along rivers and mudslides in areas of steep terrain.
Marine conditions will remain unchanged during the next few days, with seas at 5 feet or below and easterly winds at 10-15 knots prevailing during the next several days. A moderate risk of rip currents will persist on most local beaches.
.SJU WATCHES/WARNINGS/ADVISORIES... PR...None. VI...None.