Hurricane Season runs from June 1-November 30
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000 FXCA62 TJSJ 230821 AFDSJU Area Forecast Discussion National Weather Service San Juan PR 421 AM AST Tue Apr 23 2024 .SYNOPSIS... A surface trough continue to impact the local islands, bringing periods of showers and thunderstorms. Slight concentrations of Saharan dust are expected today as well, so skies could be hazy. The wet weather pattern will persist through the end of the workweek, but drier conditions are anticipated late in the weekend and early next week. && .SHORT TERM...Today through Thursday... The axis of the surface trough was located just west of Puerto Rico during the early night hours. However, the most active part of the trough was situated over the USVI, Vieques, and Culebra. Heavy showers and strong thunderstorms pulsed throughout the night across this region, with some reaching eastern portions of Puerto Rico. Despite this area of activity, the night was much calmer than the previous night. The greatest rainfall accumulations estimated by the radar were over western and eastern St. John and Puerto Rico, respectively, with slightly above 1 inch each. Satellite and radar data indicate an elongated convergence zone promoting heavy showers persisting west of St. Croix. As this active area is advected westward, expect cloudy skies and showery weather across the eastern third of Puerto Rico during the morning hours, with some localized areas possibly experiencing heavy showers. According to TAFB surface analysis, the axis of the surface trough is expected to persist over and near the CWA through at least the end of the week. This is attributed to the deepening and approach of a mid-level short-wave trough and surface frontal boundary from the west, which will combine with the surface trough that has been impacting us over the last day or so. This weather pattern will maintain unsettled conditions for the rest of the short-term forecast. The 1000-500mb thickness will gradually decrease throughout the week, with steep 850-700 mb lapse rates. Additionally, this setup will promote enhanced moisture convergence across the region. Model guidance suggests precipitable water content will remain within the range of 1.9 to above 2.0 inches for most of the period, with slightly lower amounts across the eastern half of the CWA by Thursday afternoon onwards. USGS river sensors still indicate that most rivers over the eastern half of Puerto Rico are exceeding the 75th percentile, with half of them surpassing the 90th percentile or well above normal. Soil saturation is also high, increasing the potential for excess runoff and landslides in steep terrain. Therefore, the flood risk over the eastern half of Puerto Rico will remain elevated for the rest of the short-term forecast, as any additional rainfall could exacerbate these factors. For the rest of the area, a limited to elevated flooding risk will persist. Suspended Saharan dust particulates will be present, promoting hazy skies in areas with limited shower activity. .LONG TERM...Friday through Tuesday... As a shortwave trough digs into the western Caribbean, high clouds are expected to get established over Puerto Rico and over the Virgin Islands. At the surge, a high pressure over the central Atlantic drives the trade winds from the east at speeds below 15 knots. Moisture from a surface trough/old frontal boundary will linger into the region, maintaining that pattern of showers reaching the region at times. The moisture will finally be pushed south of the islands late on Friday and early Saturday, as a high pressure exits the eastern coast of the United States. This feature will push a drier air mass into the islands, with precipitable water values falling to near normal values on Saturday, and below normal all the way into Tuesday. Winds will be from the northeast all this period, with a more northerly component at times. It will be brisk too, with speeds at 15 to 20 mph, and stronger gusts. In reality, is not going to be completely dry, since some showers will still develop over the Atlantic, reaching the USVI and northeastern PR at times, and some showers will still develop in the afternoon over southwestern Puerto Rico. However, they will not be as widespread or strong as the one being experienced lately. && .AVIATION... (06Z TAFs) Mainly VFR conditions will prevail during the morning. SHRA ovr the waters could promote MVFR conds thru 23/14z across USVI terminals. Afternoon TSRA/SHRA could result in brief MVFR/IFR conditions, mainly across PR terminals btwn 23/17-23z. After that, SHRA may affect USVI terminals and TJSJ. HZ due to Saharan dust, but VSBY should remain P6SM. Surface winds will remain from the east- southeast at 5 to 10 kt but will then range between 10- 15 knots with higher gusts after 23/13z. && .MARINE... A surface trough crossing the islands will yield winds from the southeast today. Showers and thunderstorms will continue to affect the local waters today. A small northwesterly swell will arrive late Wednesday and Thursday. Another surface trough will shift the winds from the east by Wednesday, before switching from the northeast on Saturday under the influence of a surface high pressure over the western Atlantic. && .BEACH FORECAST... Breaking waves of around 3 feet will maintain the risk of rip currents generally low. The risk will become moderate again on Wednesday night. && .SJU WATCHES/WARNINGS/ADVISORIES... PR...None. VI...None. AM...None. && $$ SHORT TERM...CVB LONG TERM....ERG
