Southern Puerto Rico out 10nm Marine Forecast
| Today...East Winds 10 To 15 Knots With Gusts Up To 25 Knots. Seas 3 To 5 Feet, Occasionally To 6 Feet. Wave Detail: Southeast 4 Feet At 7 Seconds. Isolated Showers Until Late 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 6 Seconds. |
| Tuesday...East Winds 10 To 15 Knots With Gusts Up To 25 Knots. Seas 3 To 4 Feet, Occasionally To 5 Feet. Wave Detail: East 3 Feet At 6 Seconds. |
| Tuesday Night...East Winds 10 To 15 Knots With Gusts Up To 25 Knots. Seas 2 To 4 Feet, Occasionally To 5 Feet. Wave Detail: East 3 Feet At 6 Seconds. |
| Wednesday...East Winds 10 To 15 Knots With Gusts Up To 20 Knots. Seas 2 To 3 Feet. Wave Detail: East 3 Feet At 7 Seconds. Scattered Showers In The Morning. |
| Wednesday Night...East Winds 10 To 15 Knots With Gusts Up To 20 Knots. Seas 2 To 3 Feet. Wave Detail: Southeast 3 Feet At 5 Seconds. |
| Thursday...East Winds 10 To 15 Knots, Increasing To 15 To 20 Knots In The Afternoon. Seas 2 To 4 Feet, Occasionally To 5 Feet. Scattered Showers In The Morning. |
| Thursday Night...East Winds 15 To 20 Knots, Diminishing To 10 To 15 Knots After Midnight. Seas 3 To 5 Feet, Occasionally To 6 Feet. |
| Friday...East Winds 10 To 15 Knots, Increasing To 15 To 20 Knots In The Afternoon. Seas 4 To 5 Feet, Occasionally To 6 Feet. |
| Friday Night...East Winds 15 To 20 Knots, Diminishing To 10 To 15 Knots After Midnight. Seas 3 To 5 Feet, Occasionally To 6 Feet. Scattered Showers. |
| Area Forecast Discussion National Weather Service San Juan PR 237pm AST Monday August 17 2026 .Short Term(This evening through Wednesday)... Issued at 233pm AST Monday August 17 2026 Tranquil and generally fair weather conditions will continue across most of the region through this evening and much of Tuesday as a relatively dry and stable air mass remains in place. Precipitable water (PWAT) values will remain near 1.25 to 1.50 inches through Tuesday, near the lower end of climatological values for this time of year. This dry air is particularly evident in the mid-levels, where 700-500 mb relative humidity remains well below normal. Therefore, shower activity should remain limited despite sufficient low-level moisture and daytime heating. Nevertheless, local and diurnal effects could promote isolated to locally scattered showers across western Puerto Rico each afternoon. Otherwise, mostly fair weather is expected across the U.S. Virgin Islands and eastern Puerto Rico. Hot conditions will remain the main concern across coastal and urban areas, where elevated heat indices are expected. A transition to wetter and more unsettled weather remains possible from late Tuesday night into Wednesday as a vigorous tropical wave, previously designated as Invest 94L, interacts with a deep-layer trough. The trough is expected to pull the wave and its associated tropical moisture northward toward the region. However, uncertainty remains regarding how much of this moisture reaches the local islands. The GFS (Global Forecast System) has remained consistent in bringing the bulk of the moisture across the forecast area, while the ECMWF (European Centre for Medium-Range Weather Forecasts) keeps the deepest moisture north of the region. If the wetter solution materializes, PWAT (Precipitable Water) values could increase to around 2.0-2.3 inches, with a substantial increase in moisture through the mid-levels. This would favor periods of moderate to locally heavy showers across the U.S. Virgin Islands and eastern Puerto Rico, followed by additional afternoon activity across interior and western Puerto Rico. Localized urban and small-stream flooding could occur where persistent heavy rainfall develops. Stronger thunderstorms could also produce frequent lightning and locally strong, gusty winds. Rainfall associated with this wave would be beneficial given the worsening drought conditions across portions of the region, particularly if the wetter GFS solution materializes. Nevertheless, while this event could provide some temporary relief, it is not expected to be sufficient to end the ongoing drought conditions. Continue to monitor subsequent forecasts, as relatively small changes in the evolution of the wave and trough could significantly affect Wednesday's rainfall coverage and amounts. .Long Term(Thursday through next Sunday)... Issued at 317am AST Monday August 17 2026 A generally quiet weather pattern is expected through most of the period, with no significant rainfall hazards anticipated. Moisture should gradually decrease Thursday into Friday, favoring brief passing showers and limited afternoon convection over western Puerto Rico. Heat will likely remain the main concern, with elevated heat risk possible where sufficient sunshine occurs. Forecast confidence decreases toward the end of the period as some guidance suggests an open tropical wave approaching the northeastern Caribbean by Sunday or the following weekend. At this range, however, the signal remains highly uncertain and may partly reflect climatological influences in the model solutions rather than a well- defined system. Trends will continue to be monitored. Marine Issued at 233pm AST Monday August 17 2026 A subtropical surface high-pressure ridge centered across the western Atlantic will remain the dominant feature controlling the regional pattern. This system will maintain gentle-to-moderate easterly trade winds across the local waters for the next few days. Tranquil to moderate marine conditions will prevail through much of the workweek, with seas generally ranging between 2 and 5 feet across the Atlantic and Caribbean waters. Moisture from an approaching tropical wave is forecast to build by Wednesday, bringing a higher potential for scattered showers and thunderstorms over coastal waters, which will elevate the localized lightning hazard. Beach Forecast Issued at 233pm AST Monday August 17 2026 There is a moderate risk of rip currents across the northern, eastern, and southern coastal areas of Puerto Rico, Culebra, and Vieques, as well as the eastern tip of St. Croix. Meanwhile, a low risk of rip currents is expected along the western sections of the region. Similar marine conditions, with a low-to-moderate risk of rip currents, will remain in place for the rest of the workweek. In addition, an increase in showers and thunderstorms is expected by Wednesday afternoon. This weather shift will raise the potential lightning threat across the coastal areas. Beachgoers and residents should remain cautious and stay informed on changing weather updates throughout the week. Fire Weather Issued at 233pm AST Monday August 17 2026 Critical fuel conditions continue across the islands, with extreme drought affecting portions of eastern Puerto Rico and the southern coastal plains. Dry conditions have prevailed through much of today, with low relative humidity, stressed vegetation, and dry fuels continuing to support elevated fire danger. The greatest concern remains across southern and southwestern Puerto Rico, where fuels are exceptionally dry and recent fire activity has been frequent. Breezy easterly winds with occasional higher gusts this afternoon could support rapid fire spread and make any ongoing fires more difficult to control. Elevated fire danger also continues elsewhere across Puerto Rico, Vieques, Culebra, and the U.S. Virgin Islands. Some relief remains possible by Wednesday as a tropical wave could bring an increase in showers and beneficial rainfall. However, uncertainty remains regarding rainfall coverage and amounts, and drought-stressed fuels will likely persist in areas that receive limited rainfall. .SJU WATCHES/WARNINGS/ADVISORIES... PR... Heat Advisory until 5pm AST this afternoon for PRZ001>005-007- 008-010>013. VI... Heat Advisory until 5pm AST this afternoon for VIZ001-002. AM...None. |
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