Marine Weather and Tide Forecast for Utuado, PR

SHORT TERM
Tonight through Monday...

Showers have appeared around Saint Thomas and south of and downstream from Saint Croix. Elsewhere, as of 200 PM AST, no shower activity has occurred in the last several hours although scattered to broken clouds between 3 and 6 kft in the inland sections of eastern Puerto Rico have appeared. The sounding from San Juan, Puerto Rico at 07/12Z this morning showed very little buoyancy in the air column and precipitable water below normal. Also there was a weak and shallow marine layer, that, although more moist than yesterday, still went no higher than 7400 feet. This was also confirmed by the GOES TPW product which showed less than an inch of precipitable water over western parts of Puerto Rico, and San Juan this morning, and about 1.4 inches over San Juan now, with almost 1.7 inches over Saint Thomas at the moment. This area is moving west and will allow some shower formation this evening. The 850 mb GFS is also showing an area of moisture with 70-90 percent relative humidity over Puerto Rico and the U.S. Virgin Islands this afternoon till arnd 08/18Z or 2 PM Sunday. Better moisture will lead to better coverage of light to moderate showers tonight and tomorrow with total moisture peaking at just under two inches Sunday just before midnight.

High pressure at the surface is forming over the southeastern United States, and will ridge into the western Atlantic north northwest of the area Sunday. This will maintain easterly trade wind flows of 10 to 15 knots around the islands. At mid and upper levels high pressure over the central Caribbean remains the dominant influence which will maintain the atmosphere between 500 and 300 mb quite dry but the appearance of patchy altocumulus clouds give away an increase of moisture between 850-650 mb that is part of the next patch of moisture that will comprise part of the peak precipitable later Sunday night. These patches of moisture are not expected to be significant weather-makers. Showers in the lowest layers will be present as bands of better moisture roll through tonight and tomorrow night. These showers will be quick moving and unlikely to produce flooding. A drying trend will commence on Monday.

LONG TERM
Tuesday through Saturday...

Forecast confidence is increasing as model guidance continues to remain consistent across model cycles for the long-term forecast period. The polar trough and induced surface low are expected to deepen east of the Leeward Islands. The proximity of this strong trough will likely enhance local dynamics at upper levels, turning conditions slightly more favorable for convective activity.
Indicators such as 250 mb height fields, 100-500 mb thicknesses, and 500 mb temperatures are forecast to drop to near-normal levels, occasionally reaching the bottom 25th percentile during the week.

However, the northeastern Caribbean remains positioned under the area of greatest subsidence associated with the trough. As mentioned in earlier discussions, this subsidence could inhibit widespread convective activity. Another limiting factor is moisture content, which is expected to remain below 1.7 inches. Furthermore, model guidance suggests that moisture levels will plummet by the end of the week, potentially falling below 1.0 inches. This value is well below the 10th percentile of the climatological normal for this time of year.

As a result, mostly showery weather is expected across windward coastal areas during the night and morning hours as a cool advective pattern develops under a northeasterly wind flow. This will likely be followed by some convective activity in the afternoons, primarily over the interior and southwestern portions of Puerto Rico. However, limited shower activity is anticipated between Thursday and Friday, which are forecast to be the driest days of the long-term period. By the weekend, a change in this weather pattern is possible as a surge of moisture, combined with the axis of the surface-induced trough, approaches the local islands from the northeast.

This northeasterly wind pattern will also bring very pleasant temperatures across the area, with 925 mb temperatures expected to drop to nearly two standard deviations below the climatological normal.



AVIATION

(18Z TAFS)

VRF conds will prevail thru at least 08/08Z everywhere, with ocnl SHRA carrying brief MVFR conds. Likely mtn topping aft 08/08Zn in the Luquillo range of ern PR. Winds at the sfc are easterly 8-15 kts with some sea breeze influences. Land breezes are expected with lighter winds aft 07/22Z. An area of mstr will move into the area aft 08/06Z with better SHRA coverage arriving as far as ern PR by 08/15Z. Winds incrg aft 08/12Z to bcm E 10-16kt wind sea breeze influences.



MARINE

A surface high pressure exiting the eastern coast of the United States will continue to promote mostly moderate east northeasterly wind flow through tonight. On Sunday, the pressure gradient will intensify in the area promoting moderate to fresh winds. This pattern will result in choppy seas across the Atlantic and Caribbean waters through early next week. A northerly to northwesterly swell will move across the offshore Atlantic waters by Sunday into Monday.



BEACH FORECAST

A small northerly to northwesterly swell is expected to impact the northern and northwestern exposed beaches of the islands, potentially leading to hazardous beach conditions in localized areas. However, the risk of rip currents remains moderate for most coastal areas of the islands.



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