Leeward Islands Offshore Forecast
|Today...Ne To E Winds 10 To 15 Kt. Seas 5 To 7 Ft In Ne To E Swell. Scattered Showers And Isolated Tstms.|
|Tonight...Ne To E Winds 10 To 15 Kt. Seas 6 To 8 Ft In Ne To E Swell.|
|Thu...Ne Winds 10 Kt. Seas 6 To 8 Ft In Ne To E Swell.|
|Thu Night...N To Ne Winds 10 To 15 Kt. Seas 5 To 7 Ft In Ne To E Swell.|
|Fri...Tropical Storm Conditions Possible. In The Caribbean, Variable Winds Less Than 5 Kt, Becoming Sw To W 10 Kt In The Afternoon. In The Atlc, W To Nw Winds 15 To 20 Kt, Becoming W 25 To 30 Kt In The Afternoon. Seas 5 To 7 Ft In N To Ne Swell.|
|Fri Night...Tropical Storm Conditions Possible.|
|Sat...Sw Winds 10 Kt In The Caribbean, And S To Sw 25 To 30 Kt In The Atlc. Seas 4 To 6 Ft.|
|Sat Night...In The Caribbean, Sw Winds 10 Kt In The Evening, Becoming Variable Less Than 5 Kt. In The Atlc, Se To S Winds 25 To 30 Kt. Seas 4 To 6 Ft.|
|Sun...Variable Winds Less Than 5 Kt In The Caribbean, And Se 15 To 20 Kt In The Atlc. Seas 5 To 7 Ft In Ne To E Swell.|
| Area Forecast Discussion|
National Weather Service San Juan PR
1133am AST Wednesday September 27 2023
...New Cloud cover and shower activity continued to increase across the regional waters and the north and east sections of Puerto Rico as well as around the adjacent islands, steered by the prevailing northeast wind flow. A tutt low and associated induced low level trough now crossing the eastern Caribbean will aid in enhancing the showers and thunderstormsacross the islands and coastal waters today. Recent TJSJ 27/12Z upper air sounding was fairly moist with layered precipitable water at 2.35 inches and low level winds were from the east northeast between 10 to 15 mph. Otherwise no change to the inherited short term forecast and reasoning at this time.
.Aviation...No significant changes to the previous AVN discussion. A tutt low and induced low level trough crossing the eastern Caribbeanwill enhance SHRA/TSRA over the regional waters en route btw islands today. SCT ocnl BKN lyrs nr FL025...FL050. WDLY SCT SHRA/Isold TSRA.
.From previous discussion Issued at 510am AST Wednesday September 27 2023./
A retrogressing TUTT and its surface reflection will bring unstable weather today and possibly through Thursday. Therefore, shower and thunderstorm activity will increase across Puerto Rico and the U.S. Virgin Islands. Expect a high risk of rip currents along the Atlantic Coastline and north-facing beaches today, tomorrow, and possibly Friday. Based on the latest National Hurricane Center forecast, the remnant surface low pressure associated with Philippe may result in unsettled weather conditions late this weekend and early next week.
.SHORT TERM...Today through Friday
Satellite derived precipitable water (PWAT) shows a mass of more humid air filtering into the region from the east, with values of up to around 2 inches. The dry airmass that affected the islands yesterday is filtering out of the local area. During the overnight hours, steered by northeasterly winds, passing showers moved from the local waters into sectors of north-central Puerto Rico, the metro area and eastern Puerto Rico, as well as across the local islands. Thunderstorms where observed over the Anegada Passage with some affecting St. Croix. Lows have ranged in the upper 70s to low 80s across lower elevations of the islands, and in the upper 60s to lower 70s across higher elevations of Puerto Rico. The humid air mass will affect the region today keeping PWAT (Precipitable Water) values around 2 inches across the region. This more humid air is due to a retrogressing TUTT low and its reflection in the lower levels, this feature will continue to move over the Anegada Passage and will continue to move or just south of the islands today. Showers and posible isolated thunderstorms are expected to continue during the morning hours and, under northeasterly winds, affect windward sectors of the islands, with locally stronger ones pushing further inland. These can promote ponding of water in roadways and poorly drained areas. Northeasterly winds will continue during the short term period due to the external circulation of Phillipe. In terms of PWAT, a drying trend can be observed on Thursday, as the TUTT leaves the area.
The current forecast track by the National Hurricane Center (NHC) has Philippe weakening into a post-tropical remnant low north of the lesser Antilles by Friday night or earlier. An increase in moisture could be observed on Friday evening/night and into the long term period due to Philippe. Unstable afternoons will prevail during the short-term period due to available moisture, sea breeze convergence, diurnal heating and local effects. Under NE winds, shower and thunderstorm activity should be stronger for interior to southwestern PR. Afternoon activity could also be observed downwind of El Yunque, Vieques, Culebra, and the USVI. This activity will be boosted today, with an elevated risk of rainfall, by the TUTT in comparison to Thursday and Friday. During the overnight and early morning hours on Thursday and Friday, passing showers will affect windward sectors of the islands. Excessive heat risk will persist each late morning to early afternoon across urban, coastal and lower elevation areas. From 10am to 5pm today, a Heat Advisory will be in effect due to heat indices of 108 to 111 degrees Fahrenheit for the urban and coastal sections in Puerto Rico, Culebra, Vieques and the US Virgin Islands. High temperatures should be in the upper 80s to around the low 90s across lower elevations of the islands.
Saturday through Tuesday
Philippe's final future will influence this weekend's weather forecast; therefore, significant uncertainty is present. While writing this discussion, Philippe had been weakening and will weaken further. Based on the latest NHC forecast, Philippe will weaken into a surface low pressure by the weekend. That said, model guidance suggests that we may observe inclement weather as early as Saturday due to the moisture field associated with Philippe's remnant surface low pressure. The unstable weather pattern could last into early next week as the lingering moisture of the remnants could remain over the region of Puerto Rico and the U.S. Virgin Islands.
Winds will veer from the north on Saturday to the east-southeast on Sunday, becoming southerly Tuesday into the middle of next week.
Issued at 510am AST Wednesday September 27 2023
A north-northeast swell created by Philippe is moving across the Atlantic Waters and Caribbean Passages today. Mariners can expect seas between 4 and 6 feet across the exposed waters, where small craft operator should exercise caution. Local winds will blow mainly from the northeast at 5 to 15 knots, becoming more northerly Friday into the weekend.
Beachgoers expect a high risk of rip currents along the Atlantic Coastline and north-facing beaches through the end of the workweek.
.SJU WATCHES/WARNINGS/ADVISORIES... PR...High Rip Current Risk through Thursday afternoon for PRZ001-002- 005-008-012.
Heat Advisory until 5pm AST this afternoon for PRZ001>005-007- 008-010>013.
VI...High Rip Current Risk through Thursday afternoon for VIZ002.
Heat Advisory until 5pm AST this afternoon for VIZ001-002.