Marine Weather Net

Mona Passage Southward to 17N Marine Forecast


10 - 15


15 - 20


15 - 20


15 - 20

The Marine Weather Forecast In Detail:
AMZ741 Forecast Issued: 1053 AM AST Thu Dec 07 2023

Rest Of Today...East Winds 10 To 15 Knots, Becoming Northeast With Gusts Up To 25 Knots This Afternoon. Seas 2 To 4 Feet With Occasional Seas Around 5 Feet. Dominant Period 10 Seconds. Isolated Showers.
Tonight...Northeast Winds 15 To 20 Knots, Becoming East After Midnight. Seas 3 To 5 Feet With Occasional Seas Up To 6 Feet. Dominant Period 10 Seconds. Isolated Showers.
Friday...East Winds 15 To 20 Knots With Gusts Up To 25 Knots. Seas 4 To 6 Feet With Occasional Seas Up To 8 Feet. Dominant Period 10 Seconds.
Friday Night...East Winds 15 To 20 Knots With Gusts Up To 30 Knots. Seas 5 To 7 Feet With Occasional Seas Up To 9 Feet. Dominant Period 10 Seconds. Isolated Showers.
Saturday...East Winds 20 To 25 Knots With Gusts Up To 30 Knots. Seas 6 To 8 Feet With Occasional Seas Up To 10 Feet. Dominant Period 10 Seconds. Isolated Showers.
Sunday...East Winds 15 To 20 Knots With Gusts Up To 30 Knots. Seas 6 To 8 Feet With Occasional Seas Up To 10 Feet. Dominant Period 10 Seconds, Decreasing To 8 Seconds. Scattered Showers.
Monday...East Winds 15 To 20 Knots With Gusts Up To 25 Knots. Seas 5 To 7 Feet With Occasional Seas Up To 9 Feet. Dominant Period 8 Seconds. Scattered Showers.
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Area Forecast Discussion
...CORRECTED National Weather Service San Juan PR
1146am AST Thu Dec 7 2023

Anticipate generally stable weather conditions today, characterized by mostly clear skies and limited shower activity under a light breeze. A transition is likely from Friday into the weekend as a building surface high pressure generates increased wind speeds across the region and a cold front settles north of the islands. While an enhanced frequency of showers moving into windward areas from the local waters is likely with these conditions, the remnants of a cold front will contribute to this wet trend during the weekend into early next week. Starting on Friday, hazardous seas for small craft and life-threatening rip currents for beachgoers are anticipated due to the impact of northwesterly swells and increasing winds.

.SHORT TERM...Today through Saturday... A stable weather pattern is forecast over the next few days as a mid- upper level ridge remains over the eastern Caribbean. This will maintain dry and stable conditions aloft, while suppressing convection. The presence of drier air today across the northeastern Caribbean will also continue to limit shower development over the islands and regional waters. An induced pre-frontal trough is resulting in the weakening of the local pressure gradient and trade wind flow today, allowing light winds to exist for most areas with the exception of higher speeds across coastal areas due to seabreeze enhancement. Under this expected pattern there will be the potential for shower development mainly over the interior and west-southwest sections of Puerto Rico.

Late tonight into Friday, a polar trough will move eastward across the west Atlantic, with it's moisture field approaching the northwestern corner of the region. By Friday the winds will begin to prevail from the east-northeast, increasing in strength as a surface high pressure builds across the western Atlantic. This will result in a cooler advective pattern and better chance for quick passing overnight and early morning showers that will continue into Saturday. This acceleration of the trade winds will also assist the advection of a moist airmass into eastern Caribbean, with the northern boundary moving into the southern half of the region. This will increase the rate of passing showers on Saturday afternoon into the night across eastern Puerto Rico and the USVI. However, due to stronger winds, showers should be fast moving without any significant rainfall accumulations.

Long Term
Sunday through Thursday... While there is a possibility of limited afternoon convective development, a cool advective pattern, typically the primary source of shower development during the local fall season, will prevail. A dominant mid-level ridge will persist over the northern Caribbean, sustaining a trade wind cap inversion and dry air aloft, suppressing shower development. However, weak upper-level troughs will briefly weaken the trade wind cap and facilitate the influx of deep moisture into the region. Meanwhile, at the surface, a subtropical surface high pressure system building over the western-central Atlantic will maintain a tightened local pressure across the Northeastern Caribbean and, thus, breezy to locally windy conditions are likely across the forecast area. These increased winds will frequently steer patches of shallow moisture, including moisture related to the remnants of a cold front and an easterly disturbance early in the forecast period.

According to model guidance, precipitable water values are anticipated to remain within typical seasonal levels (between 1.2 and 1.6 inches). However, above-normal moisture levels (1.6 inches or higher) are likely on Sunday into Monday and later in the workweek, aligning with the timing of the remnants and easterly disturbances and a weakened trade wind cap. These brief transitions will be evident in the increased frequency of showers moving inland from the waters, especially during nighttime over eastern Puerto Rico and the U.S. Virgin Islands. Despite this, hazard risks through the long-term forecast period should center on winds-related threats, mainly across coastal areas and lower elevations.

Recent observations from the CariCOOS buoy network near Puerto Rico and the U.S. Virgin Islands have shown consistent marine conditions with wave heigheights below 3 feet.

Marine conditions are forecast to deteriorate as a long-period northwesterly swell and increasing winds impact the regional waters starting Friday and continuing through the weekend. Seas are anticipated to reach up to 8 feet, with occasional seas up to 10 feet, while winds will gradually reach 15-20 knots on Friday and escalate to 20-25 knots with gusts up to 30 knots over the weekend. Small Craft Advisories are currently in place for the offshore Atlantic waters and coastal waters of northern Puerto Rico. With hazardous conditions expected to expand across the local waters, additional Small Craft Advisories will be required from Friday evening onward. For more information on current marine risks, refer to the Marine Weather Message (MWWSJU).

.SURF ZONE...A moderate risk of rip currents remains for most northern beaches of Puerto Rico and the eastern beaches of Saint Croix today. However, deteriorating marine conditions will also impact beach conditions, with breaking waves increasing to 6-7 feet, likely generating life-threatening rip current conditions from Friday onward. If the forecasted conditions persist, a Rip Current Statement will be issued later today, covering beaches from Rincon eastward to Fajardo across northern Puerto Rico and the beaches of Culebra, Vieques, and the U.S. Virgin Islands. For details on current surf zone risks, refer to the Coastal Hazard Message (CFWSJU).

.SJU WATCHES/WARNINGS/ADVISORIES... PR...None. VI...None. AM...Small Craft Advisory from 2am Friday to 8pm GMT Sunday for AMZ711.

Small Craft Advisory from 2pm Friday to 8pm GMT Sunday for AMZ712.