Southern Puerto Rico out 10nm Marine Forecast
|Tonight...East Winds 10 To 15 Knots, Becoming Northeast After Midnight. Seas 1 To 3 Feet. Dominant Period 6 Seconds. Scattered Showers With Isolated Thunderstorms.
|Wednesday...East Winds 10 To 15 Knots. Gusts Up To 25 Knots In The Afternoon. Seas 2 To 4 Feet With Occasional Seas Around 5 Feet. Dominant Period 6 Seconds. Isolated Showers And Thunderstorms.
|Wednesday Night...Northeast Winds 10 To 15 Knots. Gusts Up To 25 Knots In The Evening. Seas 2 To 4 Feet With Occasional Seas Around 5 Feet. Dominant Period 6 Seconds. Isolated Showers.
|Thursday...East Winds 10 To 15 Knots. Gusts Up To 25 Knots In The Afternoon. Seas 2 To 4 Feet With Occasional Seas Around 5 Feet. Dominant Period 6 Seconds. Isolated Showers.
|Thursday Night...Northeast Winds 10 To 15 Knots With Gusts Up To 25 Knots, Diminishing To Northeast 10 To 15 Knots After Midnight. Seas 2 To 4 Feet With Occasional Seas Around 5 Feet. Dominant Period 6 Seconds. Isolated Showers.
|Friday...Northeast Winds 15 To 20 Knots With Gusts Up To 25 Knots. Seas 2 To 4 Feet With Occasional Seas Around 5 Feet. Dominant Period 6 Seconds. Scattered Showers.
|Saturday...East Winds 15 To 20 Knots, Becoming Northeast. Seas 3 To 5 Feet With Occasional Seas Up To 6 Feet. Dominant Period 6 Seconds. Isolated Showers.
|Sunday...East Winds 10 To 15 Knots With Gusts Up To 25 Knots. Seas 2 To 4 Feet With Occasional Seas Around 5 Feet. Dominant Period 6 Seconds. Scattered Showers.
| Area Forecast Discussion
National Weather Service San Juan PR
543pm AST Tuesday Feb 27 2024
Shower activity is expected to affect the eastern region and possibly northern PR tonight and into tomorrow, as a stationary front remains north of the region and an upper trough axis moves in from the west. By late tomorrow into Thursday conditions will gradually improve as strong high pressure builds aloft and at surface level. Moisture then returns over the weekend. ENE winds will also increase over the weekend.
.SHORT TERM...Tonight through Thursday... Active weather conditions were observed across the region today. Doppler radar monitored shower activity across most of the region this morning and afternoon. As showers moved across the islands during the morning hours a flood advisory was issued for the northern USVI. By the latter half of the morning hours light to moderate showers continue to creep into mainly the eastern half of Puerto Rico. As up to strong showers and thunderstorms moved across the island, flood advisories were issued for Bayamon and part of the eastern interior as well as for most south-central to southwestern municipalities and Mayaguez. Another flood advisory was issued for St. Thomas as well as another line of strong showers moved across. Radar preliminary rainfall totals above 2 inches today were observed over Maunabo, Patillas, Toa Alta, Coamo, Villalba, Juana Diaz, Ponce, Yauco, Penuelas, Sabana Grande, Mayaguez, Hormigueros, San German, Lajas and westernmost St. Thomas. Doppler Radar estimates that the areas with the highest accumulations since were observed in Guayanilla with values between 3 to 4.34 inches. According to various official and unofficial stations maximum temperatures ranged in the USVI were in the low to around the mid 80s across lower elevations of the islands. Highs in Puerto Rico were generally up to the low 80s across most of the lower elevations, with the exception of lower elevations in the western and southwestern coastline reaching around the mid 80s.
Unsettled weather conditions are due to the combination of a frontal boundary, now stationary to our north, a pre-frontal trough east of the islands and an upper level trough moving in from the west. The frontal boundary should meander north of the region as it gradually weakens into tomorrow. The upper-level trough axis will continue moving across the region into tomorrow. Conditions will gradually improve tomorrow onwards. Satellite derived precipitable water (PWAT) values are +1 to above +2 standard deviations above normal across the area. PWAT (Precipitable Water) values should gradually decrease tomorrow, however still being above normal values for this time of the year. Columnar moisture will continue decreasing on Thursday, reaching below normal to normal values. Although shower activity is tapering off over the region, activity tonight should mainly affect sectors along the eastern region and possibly northern PR as unsettled weather over the waters moves inland. Generally ENE surface winds will continue through the period. Under this windflow convective activity is forecast from the interior to SW Puerto Rico tomorrow afternoon while showers continue moving inland into the eastern/northern region. Conditions will further improve late Wednesday and Thursday as strong high pressure builds aloft and at surface level.
Friday through Monday
High pressure at the surface in the western Atlantic will be refreshed on Friday with another high out of the eastern United States. A persistent inverted trough that wanders between 40 and 52 degrees west longitude in the sub-tropical Atlantic will also help to maintain northeasterly flow across Puerto Rico and the U.S. Virgin Islands through the long term period. This will bring cool and fairly moist air out of the central Atlantic in the lower levels. Although mid levels will be dry, the persistent winds of 10 to 20 knots and the abundance of low level moisture will produce bands of showers that will bring night and early morning showers to the U.S. Virgin Islands and the north and northeast coastal sections of Puerto Rico and afternoon showers to the southwestern and interior portions of Puerto Rico. Amounts are not expected to be particularly heavy, but will continue to add moisture to the soils and streams. Because of the uniformity of the air flow during the period out of the cooler central Atlantic temperatures will be fairly steady from day to day, but will be warmest on the south coast.
At upper levels on Thursday and Friday, the atmosphere will recover from the cold it caught during the passage of a long wave trough today and Wednesday as high pressure builds over the Caribbean. We will begin to feel the effects of a weaker short wave trough Saturday night through Monday.
A frontal boundary and pre-frontal trough will produce continue to produce unsettled weather across the local waters tonight through Wednesday. Seas will remain somewhat choppy with seas up to 3-5 feet, with the exception of areas protected from the northeast winds, and across the northernmost regional waters with seas up to 6 feet. A surface high pressure behind the front will move northeastward across the Western Atlantic during the next few days, building over the north central Atlantic during the second part of the week to maintain northeasterly flow which will become moderate to fresh by the weekend, increasing to 15 to 20 knots across the area by Friday. By Friday night and into the weekend, marine and coastal conditions will deteriorate due to a northeasterly swell, conditions will remain deteriorated through the middle of next week.
There will be a moderate risk of Rip Currents tonight across the northern coastline of Puerto Rico, from Rincon to Fajardo, Culebra and St. Thomas. There is a low risk elsewhere. For tomorrow, several northern and easternmost beaches of St. Croix will have a moderate risk. Deteriorating coastal conditions are forecast for this weekend.
.SJU WATCHES/WARNINGS/ADVISORIES... PR...None. VI...None. AM...None.