Abundant moisture as well as weak steering flow caused the development of showers and isolated thunderstorms across interior and western portions of Puerto Rico during the afternoon hours.
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The episode as NWS SJU wrote it up.
Abundant moisture as well as weak steering flow caused the development of showers and isolated thunderstorms across interior and western portions of Puerto Rico during the afternoon hours.
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 4, 4:45 PM AST, 45 minutes earlier.
Area Forecast Discussion National Weather Service San Juan PR 445 PM AST Mon May 4 2020 .SYNOPSIS... && .SHORT TERM...Today through Wednesday... A wetter pattern will prevail across the local islands under a southeasterly wind flow. A subtropical jet (at 250 mb) will promote the erosion of a mid-level ridge and upper-level divergence, allowing deeper moisture over the islands Monday and Tuesday. Model guidance is also suggesting a weak steering flow, and afternoon convection once it forms, could linger longer, especially over the interior, western and northern sections of Puerto Rico. However, due to this weak steering flow, this activity could spread across the southern plains too. Under this weather pattern, local effects, diurnal heating, and sea breeze variations will likely enhance the potential to observe urban and small stream flooding as well as flash flooding mainly across mainland Puerto Rico Monday and Tuesday. The U.S. Virgin Islands can expect isolated to locally scattered showers, without ruling out urban and small stream flooding. Although TPW between 1.5 and 2.0 inches will continue, a ridge building from the Atlantic Ocean into the eastern-Caribbean will decrease the potential for widespread activity across the islands. However, streamer like showers downwind from the U.S. Virgin Islands into eastern PR and from La Sierra de Luquillo into the San Juan Metro-Area will be possible. Afternoon convection will also be likely over the northwest quadrant. A drier air mass will slowly move into the region from the east, leaving mostly clear skies with drier conditions Wednesday night into the long-term. .LONG TERM...Thursday through Monday... From previous dis.. issued 409 AM AST Mon May 4 2020/ A deep southeasterly wind flow is expected to encompass the forecast area Thursday and Friday as a surface high pressure and a ridge at 700 mb will be located over the Central Atlantic. This southeasterly wind flow is expected to induce very warm temperatures across northern Puerto Rico, where high temperatures in the lower 90s are likely, especially across the urban areas. Winds will then switch more easterly during the weekend as another surface high pressure moves across the western Atlantic. This will result in slightly cooler temperatures. In terms of the overall weather conditions, a mid to upper-ridge is expected to build overhead and prevail through the period. This will result in a strengthening of the trade wind cap at lower- levels, promoting fair weather conditions across the area. Shower activity through the period will be driven by local and diurnal effects. However, given the unfavorable conditions aloft, the shower activity that does materialize is expected to be limited in coverage and not produce significant rainfall accumulations. Another feature noteworthy is that under the deep southeasterly flow expected for both Thursday and Friday, a plume of Saharan Dust particulates will move over the area as indicated by the NASA GEOS-5 Aerosol Model. This will result in hazy skies. && .AVIATION... Aviation...Mainly VFR conditions expected during the morning hrs. SHRA will affect ISX reducing VIS creating brief MVFR btwn 04/10- 13z. SHRA are expected to increase in coverage and intensity across portions of interior, northern, and western PR between 04/15-23z, resulting in SHRA/TSRA especially near/over TJMZ/TJBQ/TJSJ. Winds light and variable through 04/12z, increasing btwn 10-15 kts from the ESE with sea breeze variations after 04/14z. && .MARINE... A surface high pressure across the across the north-central Atlantic will continue to produce a light to moderate east to east- southeast wind flow across the region. As a result, tranquil marine conditions are expected through midweek, when winds increase and will create choppy seas for the region. Tonight, some fragments of low-level moisture can generate some isolated to scattered showers across the local waters. && .PRELIMINARY POINT TEMPS/POPS... SJU 76 88 77 91 / 30 40 20 20 STT 77 87 79 86 / 40 20 30 40 && .SJU WATCHES/WARNINGS/ADVISORIES... PR...None. VI...None. AM...None. && SHORT TERM...ICP LONG TERM....LIS PUBLIC DESK...ERG
Perspectivas sobre Condiciones Peligrosas del Tiempo Servicio Nacional de Meteorologia San Juan PR 403 AM AST lunes 4 de mayo de 2020 AMZ710>745-PRZ001>013-050815- San Juan y Vecindad-Noreste-Sureste-Este Interior- Norte Central-Interior Central-Ponce y Vecindad-Noroeste- Oeste Interior-Mayaguez y Vecindad-Suroeste-Culebra-Vieques- Aguas cercanas y mar afuera del Atlantico y Caribe- 403 AM AST lunes 4 de mayo de 2020 Esta perspectiva sobre las condiciones peligrosas del tiempo es para Puerto Rico y las aguas costeras del Atlantico. .Dia Uno...Hoy y esta noche .Tronadas...Existe la probabilidad de tronadas con lluvias fuertes y rafagas de viento esta tarde a traves de porciones del interior, norte y oeste de Puerto Rico. .Inundaciones...Lluvias fuertes daran paso a inundaciones urbanas y de pequenos riachuelos. Lluvias fuertes persistentes podrian ocasionar inundaciones repentinas sobre areas del interior. .Corrientes marinas...Existe un riesgo moderado de corrientes marinas a traves de la mayoria de las playas del norte de Puerto Rico, Vieques y Culebra. .Dias dos hasta el siete...martes a domingo El riesgo de inundaciones urbanas y de riachuelos continuara hasta el martes a medida que se espera el desarrollo de aguaceros inducidos localmente en las tardes sobre el interior y norte de Puerto Rico. Se espera un riesgo moderado de corrientes marinas para varias de las playas locales durante los proximos dias. .Comunicado sobre informacion reportada por observadores... No se anticipa activacion de observadores, sin embargo, se recomienda a los observadores individuales que reporten inundaciones, oleaje y corrientes marinas al Servicio Nacional de Meteorologia en San Juan mientras siguen las indicaciones de las autoridades locales y estatales. AMZ715-725-VIZ001-002-050815- San Tomas, San John y Islas Adyacentes-Santa Cruz- Aguas cercanas del Atlantico y aguas costeras adyacentes del Caribe- 355 AM AST domingo 3 de mayo de 2020 Esta perspectiva sobre las condiciones peligrosas del tiempo es para Islas Virgenes Estadounidenses y las aguas costeras adyacentes. .Dia uno...Hoy y esta noche .Tronadas...Existe la probabilidad de tronadas con lluvias fuertes y rafagas de viento esta tarde a traves de porciones de las aguas locales asi como en porciones de las islas. .Inundaciones...Lluvias moderadas daran paso acumulaciones de agua en carreteras y areas de pobre drenaje. .Corrientes marinas...Existe un riesgo moderado de corrientes marinas para algunas de las playas al norte y este de St Thomas y St Croix. .Dias dos hasta el siete...martes a domingo El riesgo de lluvias fuertes continuara hasta el martes. Se espera un riesgo moderado de corrientes marinas a traves de varias de las playas locales durante los proximos dias. .Comunicado sobre informacion reportada por observadores... No se anticipa activacion de observadores, sin embargo, se recomienda a los observadores individuales que reporten oleaje y corrientes marinas al Servicio Nacional de Meteorologia en San Juan mientras siguen las indicaciones de las autoridades locales y estatales.
The national radar mosaic for the moment the first event began.
1 debris flow. Local standard time, as filed.
Accumulations due to heavy rain caused a protective wall to budge, causing a mudslide/landslide in Carretera 607 Sector Veguita of Barrio Caonilla in Utuado. No injuries reported.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Puerto Rico in 2020Every state in 2020This day in weather historyWarnings in Puerto Rico, May 2020
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 888976.