The combination of an upper-level trough and moisture associated with a tropical wave produced moderate to heavy rains across portions of northeast, interior, and northwest PR.
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The episode as NWS SJU wrote it up.
The combination of an upper-level trough and moisture associated with a tropical wave produced moderate to heavy rains across portions of northeast, interior, and northwest PR.
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 Sep 7, 11:59 AM AST, 21 minutes earlier.
Area Forecast Discussion National Weather Service San Juan PR 1159 AM AST Mon Sep 7 2020 .UPDATE...The morning sounding came out drier, but this was mainly due to the mid levels. Showers, however, continued to roll across Puerto Rico leaving amounts generally less than one tenth inch. The sounding was rather unstable with a CAPE of 3800, and therefore will leave a mention of isolated thunderstorms in the forecast despite the mid level drying. Another band of moisture is approaching the island behind a tropical wave now moving through western Puerto Rico and out of the area, this will enhance the shower activity in eastern Puerto Rico again tonight. Still amounts of less than one half inch are expected. Latest GFS and NHC guidance shows Tropical Storm Paulette and a developing tropical Depression 18 still passing well northeast of the local area. && .AVIATION...SHRA have formed over PR and downstream from TIST/TISX. Isold TSRA expected aft 07/17Z. Hir trrn obscured and MVFR conds in lcly hvy SHRA. Sfc winds 12 kt or less with hir gusts nr SHRA. Max winds NNE 25-30 kt btwn FL420-470 diminishing drg the period. && .MARINE...Sea are relatively tranquil with 4 feet or less. Seas will begin to build on Wednesday. Under the influence of migrating tropical cyclones seas may reach 7 feet by late Friday night in the outer Atlantic waters and the Anegada passage. Mariners expecting to transit the area should monitor conditions as the track of Tropical Storm Paulette is still somewhat uncertain and these seas may not materialize. && .PREV DISCUSSION... /issued 457 AM AST Mon Sep 7 2020/ SYNOPSIS...Mid and upper level ridge over the local area is gradually weakening and is losing the dominance over the local area today and tomorrow, slight increase in moisture will move in today. Locally induced showers and possible thunderstorms are expected in the afternoons across portions of central and western Puerto Rico, isolated to scattered showers expected elsewhere in the forecast area. SHORT TERM...Today through Wednesday... A mid to upper level ridge will shift westward and loosen its hold across the region today through Wednesday, as an upper trough(TUTT) will cross into the northeastern Caribbean and linger across the region during the period. This will destabilize the upper levels and therefore support more favorable conditions for shower development over the region today and on Tuesday. At the surface, a weak tropical wave will continue to move across the eastern Caribbean today through Tuesday, while bringing an increase in low level moisture. Recent model guidance, as well as satellite imagery and doppler weather radar all suggest an increase in moisture and layered precipitable water values between 1.8 to 2.0 inches today through Tuesday. Winds are forecast to become more east to southeast, hence afternoon convection should be focused across the west interior, and northwestern Puerto Rico, with some streamers possible from El Yunque toward the San Juan metro area. Some brief afternoon showers will also be possible around Vieques and the west end of the U.S. Virgin Islands. For today and on Tuesday, isolated thunderstorms will be possible during the afternoon hours but mainly over the central interior and west sections of Puerto Rico. On Wednesday the upper trough and associated induced low level trough will gradually weaken favoring improving conditions and an erosion of low level moisture. Winds are forecast to become more east to northeast as a ridge is to build north of the region. Therefore, the typical passing early morning trade wind showers can be expected carried by the northeast wind flow, followed by some locally and diurnally induced afternoon convection mainly over parts of the west interior sections of Puerto Rico. LONG TERM...Thursday through Monday... The long term forecast has a bit more confidence today, compared to the discussion yesterday, as the global models are today once again in better agreement compared to a few days ago. We saw a bit more consistency between the model runs for the long term forecast, and therefore only small changes were necessary, mainly due to slightly deeper moisture over the local area. Once again today, we used the GFS model for the wind forecast, and the rainfall pattern due to local effects were derived from the general wind flow. The GFS was a bit more aggressive than the ECMWF with the amount of rain in the long term. That said, the latest forecast favors lingering moisture across the local area for Thursday, which will help cause locally induced showers and isolated thunderstorms across western PR. Also, for Friday and the coming weekend, an upper low could retrogress and move into the local area starting on Friday, positioning itself over Hispaniola by Sunday. This upper low would cause an increase in the instability and help with the development of thunderstorms over the area. This time, since the models indicated deeper moisture for this weekend, the rainfall forecast covers a larger area and has higher amounts than previously forecast, though the changes were modest to account for uncertainty. But with the upper trough approaching and higher than normal moisture, showers and thunderstorms are to be expected over a larger portions of the forecast area. However, the day with higher chance of rain is still expected to be Saturday. Mostly fair weather is expected on Sunday and Monday. Also, it is worth pointing out that the local weather and overall pattern could be be highly influenced on the development and trajectory of the new Tropical Depression Seventeen, especially when it comes to wind speeds and direction. As of now, the latest guidance suggests that the local winds will be come very light and highly variable this weekend and the local pressure gradient relaxes significantly with the current Tropical Depression Seventeen hundreds of miles to our northeast. The NHC is now also monitoring Tropical Depression Eighteen, just off the west coast of Africa, this system is also expected to remain far from the local area. AVIATION...VFR cond will persist durg prd. SHRA will continue to move across the flying area with SHRA and SCT-BKN lyrs nr FL025... FL050... FL080 and VCSH at most terminals except for TJPS/TJBQ/TJMZ til 07/14Z. MTN top obscr psbl ovr E PR til 07/12Z due to SHRA/Low cld lyrs. Fm 07/16-07/23Z...SHRA/TSRA will develop ovr the interior and west sections in Puerto Rico, with TSRA psbl mainly at TJBQ and TJMZ. Sfc winds will be calm to light/Vrb bcmg fm E at 10-15 knots aft 07/14z with sea breeze variations in some areas. MARINE...tranquil marine conditions expected for the next several days. Seas of 4 feet or less and winds less than 18 knots are forecast through Tuesday, increasing seas to 5 feet by midweek. There is a low risk of rip currents for all of the local beaches. && .PRELIMINARY POINT TEMPS/POPS... SJU 88 79 90 79 / 50 50 50 50 STT 89 81 89 80 / 40 50 30 50 && .SJU WATCHES/WARNINGS/ADVISORIES... PR...None. VI...None. AM...None. && SHORT TERM...WS LONG TERM....MB PUBLIC DESK...LIS
Perspectivas sobre Condiciones Peligrosas del Tiempo Servicio Nacional de Meteorologia San Juan PR 434 AM AST lunes 7 de septiembre de 2020 AMZ710>745-PRZ001>013-080845- 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- 434 AM AST lunes 7 de septiembre de 2020 Esta perspectiva sobre las condiciones peligrosas del tiempo es para Puerto Rico y las aguas costeras del Atlantico. .Dia Uno...Esta tarde y esta noche .Tronadas... Existe una probabilidad de tronadas con fuertes lluvias y vientos en rafaga esta tarde a traves de sectores del oeste y noroeste de Puerto Rico, y una probabilidad pequena sobre Vieques. .Inundaciones... Fuertes lluvias podrian generar inundaciones urbanas y de pequenos riachuelos, y tambien acumulaciones de lluvia sobre carrateras y en areas de pobre drenaje. .Calor...Se esperan indices de calor por encima de lo normal entre 102 y 107 grados en algunos areas. .Dias dos hasta el siete...viernes a miercoles Humedad aumentando por lo menos hasta martes, y otra vez tarde el jueves hasta el fin de semana. Esto aumentara el riesgo de inundaciones urbanas y de pequenos riachuelos. Se espera un riesgo moderado de corrientes marinas para el jueves y mas adelante. .Comunicado sobre informacion reportada por observadores... No se anticipa activacion de observadores. Favor de reportar cualquier informacion sobre inundaciones y corrientes marinas al Servicio Nacional de Meteorologia en San Juan mientras siguen las indicaciones de las autoridades locales y estatales. AMZ715-725-VIZ001-002-080845- San Tomas, San John e Islas Adyacentes-Santa Cruz-Aguas cercanas del Atlantico y aguas costeras adyacentes del Caribe- 434 AM AST lunes 7 de septiembre de 2020 Esta perspectiva sobre las condiciones peligrosas del tiempo es para Islas Virgenes Estadounidenses y las aguas costeras adyacentes. .Dia Uno...Esta tarde y esta noche .Tronadas... Existe una probabilidad pequena de tronadas aisladas con fuertes lluvias esta tarde principalmente al parte oeste de Santa Cruz. .Inundaciones... Fuertes lluvias podrian resultar en acumulaciones de lluvia sobre carrateras y en areas de pobre drenaje. .Calor...Se esperan indices de calor por encima de lo normal entre 102 y 107 grados en algunos areas. .Dias dos hasta el siete...viernes a miercoles Humedad aumentando por lo menos hasta martes, y otra vez tarde el jueves hasta el fin de semana. Esto aumentara el riesgo de inundaciones urbanas y de pequenos riachuelos. Se espera un riesgo moderado de corrientes marinas para el jueves y mas adelante. .Comunicado sobre informacion reportada por observadores... No se anticipa activacion de observadores. Favor de reportar cualquier informacion sobre 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 heavy rain, 1 flood. Local standard time, as filed.
A woman was trapped due to water surge along El Hippie Waterfall in Naguabo. The woman was successfully rescued.
Flooding was reported along Sector Seburuquillo due to a small stream overflowing its banks.
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, September 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: 920629, 920630.