Southern US Virgin Islands, Vieques and Eastern Puerto Rico out 10nm Marine Forecast
| Rest Of Today...Southwest Winds 5 To 10 Knots. Seas 1 To 3 Feet. Dominant Period 11 Seconds. Isolated Showers. |
| Tonight...West Winds 5 To 10 Knots. Seas 1 To 3 Feet. Dominant Period 10 Seconds. Isolated Showers. |
| Thursday...West Winds 5 To 10 Knots. Seas 2 To 4 Feet With Occasional Seas Around 5 Feet. Dominant Period 10 Seconds. Numerous Showers. |
| Thursday Night...North Winds 10 To 15 Knots. Seas 4 To 6 Feet With Occasional Seas Up To 8 Feet. Dominant Period 11 Seconds. Scattered Showers. |
| Friday...North 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 11 Seconds. Isolated Showers. |
| Saturday...Southeast Winds 5 To 10 Knots. Seas 3 To 5 Feet With Occasional Seas Up To 6 Feet. Dominant Period 12 Seconds. Isolated Showers. |
| Sunday...South Winds 5 To 10 Knots, Becoming East. Seas 3 To 5 Feet With Occasional Seas Up To 6 Feet. Dominant Period 12 Seconds. |
| Area Forecast Discussion National Weather Service San Juan PR 516am AST Wednesday September 11 2024 Synopsis A wet and unstable weather pattern will persist through the end of week, maintaining an elevated flood threat across the islands. Although the upper trough that has been affecting our region will start to move away today through tomorrow, a tropical wave will reach the islands late Friday and into Saturday. However, light to moderate southeasterly winds and high moisture content will promote hot conditions during the day before the onset of showers and thunderstorms each day. A notable decrease in columnar moisture will be observed to start the next workweek. .SHORT TERM...Today through Friday The tropical upper tropospheric trough (TUTT) will continue to meander and sag southwards between eastern Puerto Rico and the Virgin Islands through today. This along with a broad surface trough spread across the eastern Caribbean and moisture trailing a tropical wave will aid in maintaining a moist and unstable environment across the region through most of the period. These expected conditions will support variably cloudy skies and favor periods of scattered to numerous showers with isolated thunderstorm development each day due to the combination of the warm and moist east southeast low level winds and the cooler 500mb advective temperatures. By Thursday and Friday the TUTT is still forecast to weaken and fill as it lifts north and slightly west of the region. This is in response to a high pressure ridge which will build and spread across the region. However, recent model guidance continued to suggest an abundance of tropical moisture is to linger across the region through the short term period, with above normal layered precipitable water values ranging between 2.00 inches and 2.16 inches between now and Friday. The moderate east southeast winds will persist through today, then become more easterly on Thursday, and more southeasterly by late Friday when additional moisture transport is forecast due to the arrival of the next tropical wave (psbl remnants of AL92). Overnight skies became partly cloudy over Puerto Rico and variably cloudy to the east and over the U.S. Virgin Islands as showers and thunderstorm activity diminished over the islands. A few showers however continued over the coastal waters and passages with only one or two isolated thunderstorms noted well east the U.S. Virgin Islands. Overnight low temperatures were between the mid 70s to near 80 degrees across lower elevations of the islands, and in the upper 60s across high elevations of Puerto Rico. Surface winds were calm to light and variable. For the rest of today another unstable weather pattern is forecast especially by late morning and through the afternoon hours, as sea breeze convergence and good daytime heating will aid in the development of some enhanced convection. As a result, the risk of excessive rainfall and lightning will remain elevated in some areas as strong thunderstorms may again produce frequent lightning and gusty winds with heavy rains leading to possible flooding impacts, particularly across the interior, western, and northern areas and also downwind from El Yunque and the U.S. Virgin Islands. In addition, already saturated soils could lead to localized flash flooding and mudslides, particularly in small streams, creeks, and areas of steep terrain that experienced heavy rains from recent days. In the U.S. Virgin Islands, minor ponding of water on roads and poor drainage areas will be more isolated as afternoon showers activity will remain possible. By Thursday although activity is expected to be less widespread due to the weakening Tutt, there will be still be an abundance of low level moisture across the region which will continue to support late morning and afternoon showers and isolated thunderstorm development, with still elevated risk of urban and flash flooding in isolated areas, but mainly over the central interior and west to northwest sections of Puerto Rico. Regardless of the expected rains today, the humid conditions and warm east southeast winds, will cause heat indices along portions of the coastal, and urban areas to reach above 108 degrees Fahrenheit, before the start of the afternoon convection. Therefore a heat Advisory is in effect today for most of the southern, and northwest to north central sections of Puerto Rico from 10am at least until 2pm AST. Long Term Saturday through Wednesday Weak mid to upper level ridging will promote more stable conditions aloft this weekend. However, southeasterly winds will continue to bring high end normal to above normal columnar moisture to the region through Sunday. Invest 92L, is also forecast to reach our area during the start of the weekend, likely as a weak disturbance but increasing the coverage and intensity of showers. It's not until next Monday, and onwards, that columnar moisture becomes more normal and patch, mostly contained to below 850 mb. This will result in a drier weather pattern with precipitable water (PWAT) ranging between 1.50-1.80 inches. Shower and thunderstorm activity will follow the typical pattern, with higher chance of t- storms developing during the afternoons over the western half of PR steered by E-SE winds, and isolated to locally scattered showers streaming over the USVI and eastern sections of PR during the night and early morning hours. East-southeast winds can also help promote high heat indices in coastal, urban and lower elevation areas, reaching above 108 degrees Fahrenheit. According to the 2am Tropical Weather Outlook (TWO), the NHC monitors two disturbances over the tropical Atlantic: Invest 92L, with a low chance of development through 7 days, and Invest 93L, with a high chance of development through 7 days. Invest 92L is expected to reach an area of stronger upper-level winds tomorrow, likely ending its chances for development and, as previously mentioned, ultimately reaching our area this weekend as a weak disturbance. Invest 93L is forecast to stay over the open Atlantic waters. Please continue to monitor future forecast updates from the NHC and from WFO San Juan. Marine A surface high pressure over the far northeastern Atlantic will promote gentle to moderate easterly winds over the next few days. A lingering upper-level trough will continue to affect the area through midweek although above normal moisture will persist through Sunday. Thunderstorms will also affect the coastal waters of western Puerto Rico each afternoon. Another tropical wave, Invest 92L, will bring active weather around Saturday. Beach Forecast A moderate risk of rip currents will continue for the northern beaches of Puerto Rico through at least tomorrow. There is a moderate risk of rip currents for eastern Puerto Rico, Culebra and St. Croix as well. Low risk elsewhere. Isolated thunderstorms with occasional lightning strikes are expected today across most coastal areas of the islands. .SJU WATCHES/WARNINGS/ADVISORIES... PR... Heat Advisory from 10am this morning to 2pm AST this afternoon for PRZ003-005-007-008-010-011. VI...None. AM...None. |
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