Marine Weather and Tide Forecast for Santo Domingo, PR

SHORT TERM
Today through Tuesday...

Mostly fair conditions prevailed once again tonight across the CWA, with passing showers mainly over the regional waters and some moving over windward sections. Winds continue slowing down, with a few stations such as Cabo Rojo and Vieques reached 20 maximum wind gusts of 20 mph. Similar to yesterday, minimum temperatures remained seasonal with stations in urban and lower elevations ranging in the mid 70s to lower 80s and higher elevations in the low to mid 60s.

The short-term forecast remains on track but with slight changes.
The broad surface high pressure is still expected to promote easterly-southeasterly winds throughout the forecast period, with a slight reduction today and an increase by Tuesday. The upper-level love located north of the CWA is now expected to linger through Monday and then migrate east by Tuesday. Based on the latest GEOS- 5/GMAO dust extinction product, the arrival of a Saharan Air Layer (SAL) is expected by this afternoon through at least Tuesday. The difference compared to the previous analysis is that moderate concentrations should reach the local islands earlier than expected (originally, by Monday afternoon), which introduces uncertainty regarding the shower activity expected this afternoon and later tonight. Nevertheless, deterministic guidance from the GFS and ECMWF continues suggesting the increase to above-normal PWAT values (1.9 - 2.0 inches) due to the increase in mid-to- upper-level moisture over the CWA, which can be observed in the latest satellite-derived products. Additionally, the presence of the upper-level low will coll 500 mb (around -8 Celsius), increasing instability aloft and supporting deep convection activity. The Galvez-Davison Index (GDI) also continues highlighting the potential of isolated-to-scattered thunderstorms over the region during the forecast period.

Overall, the hazards and impacts remain the same for the short-term forecast. The afternoon convection is expected each day, mainly over interior and western/northwestern portions of Puerto Rico. The frequency of showers and isolated thunderstorms will increase slowing down tonight into early Monday, affecting mainly portions of eastern Puerto Rico and the U.S. Virgin Islands. The flooding risk will remain limited to elevated over the aforementioned areas, including possible slippery pavement, reduced visibility, and possible urban and small stream flooding. Over periods without significant rainfall activity, suspended Saharan Dust will likely promote hazy skies, reduced visibility, and deteriorate air quality, affecting those sensitive to these particles.

LONG TERM
Wednesday through Sunday...

Model guidance indicates changes in the forecast, as the TUTT low is now expected to move away from the region much faster than suggested in previous model cycles. By Wednesday, the TUTT low is forecast to be positioned northwest of Puerto Rico, with upper-level dynamics showing reduced favorability for deep convective activity compared to earlier runs. 500 mb temperatures are now projected to range between -5 and -6 Celsius, which is slightly warmer than the climatological normal. This will result in marginal instability, which is expected to persist through the remainder of the long- term forecast period. As a result, POPs have been slightly reduced to reflect the expected decrease in convective potential.
However, further adjustments may be necessary as models come into better agreement.

The determining factor for shower activity will be moisture availability, with significant fluctuations in precipitable water values. These values are expected to range from as low as 1.45 inches on Wednesday to nearly 2.0 inches by Thursday, with a similar pattern expected to repeat from Friday through Sunday. Moisture will remain mostly concentrated south of the local islands, with intermittent patches of drier and more humid air streaming across the region.

Surface high pressure over the central Atlantic will maintain an east-southeast wind flow across the northeastern Caribbean. The local pressure gradient is also expected to tighten, resulting in the return of breezy to locally windy conditions across coastal areas through the long-term forecast period. As a result, the weather pattern will favor shower and thunderstorm activity that follows a typical diurnal cycle, with overnight and morning showers over windward coastal areas, followed by afternoon convection developing over interior and western Puerto Rico. The areal coverage of this activity will largely depend on available moisture.

The prevailing east-southeast wind flow will also contribute to warmer temperatures across the local islands. The heat threat will largely depend on moisture content, with the greatest risk occurring on days with high humidity, as this will significantly increase heat index values and the potential for heat-related impacts. Residents and visitors are advised to take precautionary measures during peak heating hours, including staying well-hydrated, wearing light and breathable clothing, limiting direct sun exposure, and taking regular breaks when engaging in outdoor activities.



AVIATION
(06z TAFs)

Mostly VFR conds across all terminals. E-SE winds will bring TSRA over western-northwestern Puerto Rico , most likely VCTS over TJBQ which can also bring around 14/17z. Winds will slightly decrease, exptd btwn 12 - 17 kt, and gsty winds btwn 20 - 22 kt after 14/13z, reducing btwn 8 - 10 kt for most TAF sites and VRB for JPS around 14/23z.

MARINE

The surface high pressure north of the region will continue to gradually shift east over the coming days. While some fluctuations in the wind pattern are expected, winds will generally remain from the east to east-southeast through the period, gentle to moderate through Tuesday, then increasing to moderate to locally fresh by Tuesday night across the regional waters. As winds increase, seas will become choppy, especially in exposed areas. A plume of suspended Saharan dust is expected to reach the region today and linger through midweek, potentially causing a slight reduction in visibility.
Meanwhile, increasing moisture and instability associated with an upper-level trough will likely lead to a rise in thunderstorm activity from today into early in the week.



BEACH FORECAST

Moderate rip current risks will continue over the next few days, particularly at beaches exposed to prevailing winds and open ocean conditions. While some western beaches tend to be more sheltered, caution is still advised near jetties, piers, and channels where stronger currents may still develop.

Scattered showers and isolated thunderstorms remain possible, mainly during the afternoon over interior and western Puerto Rico.
Beachgoers should remain alert, as any thunderstorm can produce dangerous lightning and rapidly changing conditions. Increasing moisture and upper-level instability may continue to support periods of thunderstorm activity through early this week.

Visitors are encouraged to swim near lifeguards when possible, avoid strong surf, and stay informed on the latest weather updates.

SJU WATCHES/WARNINGS/ADVISORIES
PR...None.
VI...None.
AM...None.