An upper-level trough located north of the an area and abundant moisture combined with local and diurnal effects to generate afternoon showers and thunderstorms across the northwestern quadrant of Puerto Rico. Very heavy rainfall occurred, particularly in the urban areas of Arecibo, where accumulations in excess of 3-4 inches were observed.
Every event with a place to put it. Tap one for its entry below.
Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS SJU wrote it up.
An upper-level trough located north of the an area and abundant moisture combined with local and diurnal effects to generate afternoon showers and thunderstorms across the northwestern quadrant of Puerto Rico. Very heavy rainfall occurred, particularly in the urban areas of Arecibo, where accumulations in excess of 3-4 inches were observed.
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 13, 3:37 PM AST, 2 hours 8 minutes earlier.
Area Forecast Discussion
National Weather Service San Juan PR
337 PM AST Sun Sep 13 2020
.SYNOPSIS...
Upper level low and above normal PWAT will continue to promote
unstable weather through mid-week. Then a drier weather pattern is
expected, as a mid to upper level ridge moves over the region
through the end of the week. A northeasterly swell will continue
to cause hazardous marine and coastal conditions for the Atlantic
waters.
&&
.SHORT TERM...Tonight through Tuesday...
An upper level low moving westward will continue to promote
instability aloft through the short term period. Therefore, expect
passing showers mainly over the local and outer waters now, and
through the overnight hours. Above normal PWAT are expected on
tomorrow, and Monday looks to be the most active weather day of
the period. The conditions above will cause widespread showers
with isolated thunderstorms mainly during the afternoon over most
land areas, regional and local waters. Therefore, there is an
increased potential for urban and stream flooding across the areas
that will experience the heaviest and persistent rains. A
southeasterly wind flow will persist through Tuesday, thus the
highest chance for heavy rain will be over portions of the
northwestern portions of Puerto Rico.
Tuesday will be a transitional day to a somewhat drier weather
pattern. Models are indicating that the upper level low will move
away from the area. The upper-level moving away from the forecast
area will decrease the favorable upper-level instability and
decrease the likelihood of area-wide development of deep
convection for Puerto Rico and the U.S. Virgin Islands.
Nevertheless, lingering moisture coupled with local effects, and
an easterly wind flow will aid in the development of shower and
isolated thunderstorms for portions of interior and western during
the afternoon. Shower activity will also be possible over the San
Juan metro area. Rainfall accumulations are expected to at least
result in localized urban and small stream flooding.
&&
.PREV DISCUSSION... /issued 435 AM AST Sun Sep 13 2020/
.LONG TERM...Wednesday through Monday...
A relatively dry air mass is forecast to be over the region
Wednesday and Thursday. A mid- to upper-level ridge will also
contribute to relatively stable conditions; afternoon shower and
thunderstorm activity is likely to be inhibited. Fragments of
moisture are forecast to push into the region on Friday, what will
be left of what is currently Tropical Depression Rene. Meanwhile,
conditions aloft will be increasingly unstable, under the
influence of the troughing aloft that is expected to be associated
with what is currently Tropical Depression Twenty. By the end of
the week, that system is forecast to intensify into a hurricane,
but its current projected trajectory keeps the system well to the
northeast of the area. That being said, as noted above, indirect
impacts are likely to be felt across the local islands and waters.
Increasing shower and thunderstorm activity is anticipated,
lasting into the weekend. Late Saturday into Sunday, a dry slot
will cross the area ahead of a tropical wave, which is forecast to
reach the area by Monday, bringing another bout of unstable
weather.
All of that being said, however, uncertainty remains quite high for
the long-term period. As alluded to above, impacts are possible from
tropical cyclones passing by the region to the north. Much of the
forecast hinges on the development and trajectory of Tropical
Depression Twenty. Given that the system is still a depression and
is expected to strengthen substantially, and we still have
significant lead time, confidence is generally low in the forecast.
Changes to the forecast - both for this system and its indirect
impacts on the local islands - are likely. Especially with this
being the peak of the hurricane season, it is very strongly
suggested that all those with interests in the area monitor products
from the National Hurricane Center, as well as future forecasts from
this office.
&&
.AVIATION...
Mainly VFR conditions. SHRA/TSRA expected across portions of
northern PR through 13/22z, affecting the vicinity of TJBQ and
possibly TJSJ. MVFR conditions are possible, especially across
TJBQ. Winds will continue from the SE between 8 and 12 kts with
sea breeze variations through 13/22z, becoming light and variable
overnight.
&&
.MARINE...
A northeasterly swell associated with Hurricane Paulette will
continue to cause hazardous marine and coastal conditions for the
Atlantic waters for the rest of the day. Hence, a Small Craft
Advisory continues for these waters. Seas are expected to
gradually improve by Monday and Tuesday, but still choppy. A High
Rip Current risk is expected for the northern coast of Puerto Rico
and St. Croix.
&&
.PRELIMINARY POINT TEMPS/POPS...
SJU 79 90 78 91 / 20 70 40 40
STT 80 88 80 90 / 20 20 40 40
&&
.SJU WATCHES/WARNINGS/ADVISORIES...
PR...High Rip Current Risk through late tonight for Northeast-
Southeast.
High Rip Current Risk through Monday afternoon for North Central-
Northwest-San Juan and Vicinity.
VI...High Rip Current Risk through late tonight for St Croix.
AM...Small Craft Advisory until 8 PM AST this evening for Atlantic
Waters of Puerto Rico and USVI from 10 NM to 19.5N-Coastal
Waters of Northern Puerto Rico out 10 NM.
&&
SHORT TERM...GL
LONG TERM....ERG
PUBLIC DESK...FRGPerspectivas sobre Condiciones Peligrosas del Tiempo Servicio Nacional de Meteorologia San Juan PR 338 AM domingo 13 de septiembre de 2020 AMZ710>745-PRZ001>013-140745- 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- 338 AM domingo 13 de septiembre 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 una probabilidad de tronadas con fuertes lluvias y vientos en rafaga a traves de sectores del oeste y interior de Puerto Rico durante la tarde. .Inundaciones...Se espera inundaciones urbanas y de pequenos riachuelos en areas con lluvia fuerte. .Oleaje...Oleaje vigoroso de hasta 7 pies a traves de las aguas del Atlantico. .Corrientes Marinas... Existe un riesgo alto de corrientes marinas a traves de las playas del norte de Puerto Rico. .Calor...Vientos alisios de sureste resultaran en indices de calor en encima de lo normal en algunas areas. .Dias dos hasta el siete...domingo a viernes El riesgo de inundaciones urbanas y de los riachuelos continuara por la mayoria de la semana en los sectores oeste y centro de Puerto Rico. Se espera oleaje de 7 a 8 pies en las aguas del Atlantico jueves hasta el sabado. Habra un riesgo alto de corrientes marinas a lo largo de a costa del norte el lunes y tambien el jueves en la noche hasta el sabado. Se esperan areas de calor en las elevaciones bajas donde el indice de calor sera hasta 105 grados Fahrenheit lunes hasta miercoles. .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-VIZ001-002-140745- San Tomas, San John e Islas Adyacentes-Santa Cruz-Aguas cercanas del Atlantico y aguas costeras adyacentes del Caribe- 338 AM domingo 13 de septiembre 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 .Oleaje...Oleaje vigoroso de hasta 7 pies a traves de las aguas del Atlantico. .Corrientes Marinas... Existe un riesgo alto de corrientes marinas para las playas del este de Santa Cruz. .Dias dos hasta el siete...domingo a viernes. Se espera oleaje de 7 a 8 pies en las aguas del Atlantico el jueves hasta el sabado. El riesgo alto de corrientes marinas continuara para el este de Santa Cruz el domingo. Estaran areas de calor en las elevaciones bajas donde el indice de calor sera de hasta 105 grados Fahrenheit hasta el jueves. .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 San Juan radar (TJUA), 80 km away, was scanning. The volume nearest the first event began at 21:46 UTC.
10 flash flood. Local standard time, as filed.
Residence flooded in Calle Aragon in the Urbanization of Victor Rojas 1. 2 people were trapped.
Residences flooded along Calle Q in Urbanization Jardines de Arecibo.
Exit 77B in PR-129 towards Lares was flooded.
Residence flooded in Calle 6. 3 people trapped inside residence.
Calle 10, house and street flooded. One person trapped inside the house.
Water surge in the intersection of PR-10 with PR-652 trapped 2 people.
Two people were trapped inside vehicle in Ave Consititucion.
Residence flooded in Calle O near a community center.
Residence was flooded in Road PR-653 in Barrio Barranca. 3 people and 3 dogs were trapped inside.
A man died due to flash flooding in an unnamed small creek in Sector Las Canelas between Arecibo y Hatillo.
As the offices recorded each death: direct deaths were caused by the weather itself, indirect ones by something it set in motion.
| Event | Date | Age | Sex | Where | Kind |
|---|---|---|---|---|---|
| Flash Flood, Arecibo | 2020-09-13 | Male | Vehicle/Towed Trailer | Direct |
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: 920692, 920693, 920694, 920695, 920696, 920697, 920698, 920699, 920700, 921014.