Locally induced afternoon thunderstorms produced heavy rainfall over Aguada, causing minor flooding on May 27th.
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The episode as NWS SJU wrote it up.
Locally induced afternoon thunderstorms produced heavy rainfall over Aguada, causing minor flooding on May 27th.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS San Juan, PR wrote its last area forecast discussion before the first event at May 27, 1:10 PM AST, 3 hours 38 minutes earlier. Its key messages:
Area Forecast Discussion National Weather Service San Juan PR 110 PM AST Wed May 27 2026 ...New SHORT TERM, LONG TERM, AVIATION, MARINE, BEACH FORECAST... .KEY MESSAGES... Updated at 104 PM AST Wed May 27 2026 * This afternoon, showers and thunderstorms over interior and western Puerto Rico will increase flooding potential, resulting in ponding of water and urban and small stream flooding. * A gradual drying trend is expected for the next days, with concentrations of Saharan Dust filtering into the region and resulting in hazy skies and reduced visibility. * Warmer-than-normal conditions this upcoming weekend could will increase heat risk across urban and coastal areas of the islands. Stay hydrated. && .Short Term(This evening through Friday)... Issued at 104 PM AST Wed May 27 2026 A gradual drying trend is expected through the rest of the short- term period as a moist airmass over the region slowly erodes. Precipitable water (PWAT) content is expected to drop from near 2.00 inches today to 1.50 inches (in the 50th percentile) by Friday. High- res NWS/ECMWF guidance reflects this transition, keeping the heaviest and strongest convective activity today, with rainfall totals of 0.50 to 1.00 inches, with localized higher amounts up to 1.50 inches possible over the western and interior sections of Puerto Rico due to diurnal heating and local effects. Breezy conditions will persist through this evening with trade winds between 15 and 20 mph and stronger gusts at times. Winds will decrease to around 10-15 kt for the remainder of the workweek and turn more southeasterly. In response, the 925 mb temperatures are expected to increase to 22C by Friday, which is in the 75th percentile, promoting warmer-than-normal surface temperatures across the lower elevations of the islands. Therefore, Heat Advisory conditions are possible on Friday. In addition, a strong Saharan Air Layer is filtering across the eastern Caribbean, and it is expected to linger through next week over the local area. Therefore, hazy conditions and reduced visibility will prevail across the islands and surrounding waters. On Thursday and Friday, as PWAT gradually decreases, shower activity will become much more scattered and localized. The region will transition to a typical trade wind pattern with passing morning showers across the USVI and eastern Puerto Rico, followed by limited afternoon development over western Puerto Rico. Urban and small stream flooding risks will progressively diminish through the end of the workweek. && .Long Term(Saturday through next Tuesday)... Issued at 104 PM AST Wed May 27 2026 During the long-term forecast period, broad surface high pressure over the central Atlantic will remain the dominant weather feature. This pattern will maintain a southeasterly wind flow of around 10 to 15 mph through the weekend, with winds becoming breezier early next week as speeds increase to 15 to 25 mph from Monday through Wednesday. Through the weekend, PWAT values are expected to remain near normal, generally ranging between 1.5 and 1.75 inches. Although a more stable pattern is anticipated overall, local effects and diurnal heating will continue to promote afternoon convection, mainly across northwestern Puerto Rico. The strongest activity could produce periods of moderate to locally heavy rainfall, isolated lightning strikes, and gusty winds. This may result in a limited flood risk, including ponding of water on roads and in poorly drained areas. In addition, moderate concentrations of Saharan dust will persist across the islands, resulting in hazy skies and reduced air quality. Early next week, global models continue to indicate a significant drying trend across the northeastern Caribbean as another surge of Saharan air spreads across the region. PWAT values are forecast to fall below normal, dropping below 1.50 inches. Based on current guidance, Monday and Tuesday appear to be the driest days of the long-term period. Furthermore, the NASA Goddard Earth Observing System model suggests moderate to high dust concentrations across the area. This pattern will promote drier and more stable conditions, limiting rainfall and thunderstorm development across Puerto Rico. Any shower activity that develops will likely remain brief and mainly confined to western Puerto Rico due to local effects. Another primary hazard during the long-term period will be above- normal temperatures. The 925 mb temperature guidance continues to suggest temperatures in the 75th percentile. Limited cloud cover, persistent hazy skies, and southerly winds will continue to support a warming trend across the region. As a result, elevated heat indices are expected through at least Tuesday, and the issuance of Heat Advisories cannot be ruled out. Residents and visitors should take precautions to avoid heat-related illnesses, including staying hydrated and limiting prolonged sun exposure during the hottest hours of the day. && .AVIATION... (18Z TAFS) Issued at 104 PM AST Wed May 27 2026 Mainly VFR conditions are expected to prevail across all terminals during the next 24 hours. However, tempo MVFR conds are possible thru 27/22z at TJSJ/TJBQ due to locally induced SHRA/-TSRA. The 27/12z TJSJ sounding indicated ESE winds up to 19 kt blo FL060. Lighter winds and land breeze variations are expected overnight. HZ will gradually increase through the fcst period, and VSBY could drop btw 6-8 SM. && .MARINE... Issued at 104 PM AST Wed May 27 2026 Seas will continue to subside to around 5 feet or lower from tonight and through the rest of the week as easterly winds gradually diminish. Regardless, choppy seas are posible in some areas over the offshore Atlantic waters as a high pressure system remains over the central Atlantic maintaining a tight pressure gradient across the northeastern Caribbean. Mariners should also remain alert for afternoon thunderstorms developing near the western coastal waters of Puerto Rico, which may produce locally higher winds, rough seas, and dangerous lightning, particularly today and on Thursday. Low concentrations of saharan dust will result in hazy skies and a slight reduction in visibility through this weekend. && .BEACH FORECAST... Issued at 104 PM AST Wed May 27 2026 A moderate risk of life-threatening rip currents will persist across the north, east, and southeastern beaches of the islands through Friday. Winds and seas will gradually diminish through the weekend, and a low risk of rip currents should prevail across all the islands on Saturday and Sunday. Even if the risk decreases, life-threatening rip currents often occur in the vicinity of groins, jetties, reefs, and piers. && .SJU WATCHES/WARNINGS/ADVISORIES... PR...None. VI...None. AM...None. && MORNING CREW...DS/MNG EVENING CRERW...MMC/YZR
The national radar mosaic for the moment the first event began.
1 flood. Local standard time, as filed.
Emergency managers reported standing water from recent heavy rainfall along PR-115 at km 21.9 near Cielo Mar Bakery.
After NWS Directive 10-1605, the rules offices file Storm Data by.
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