Heavy showers and thunderstorms affected the San Juan metro area during the early afternoon hours due to local and diurnal effects.
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.
Heavy showers and thunderstorms affected the San Juan metro area during the early afternoon hours due to local and diurnal effects.
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 23, 12:01 PM AST, 1 hour 33 minutes earlier.
Area Forecast Discussion
National Weather Service San Juan PR
1201 PM AST Sun Sep 23 2018
.UPDATE...No change to the inherited forecast grids and reasoning
at this time. Available moisture combined with local and diurnal
effects will support continued afternoon showers and isolated
thunderstorm development, mainly over parts of the interior and
northern half of Puerto rico and over portions of northwest sections
and just offshore of the U.S. Virgin Islands. Activity and cloudiness
should diminish and dissipate just after sunset. Easterly trades will
continue to bring periods of passing low level clouds and showers across
the coastal waters and some may reach parts of the islands during the
early morning hours.
&&
.AVIATION UPDATE...VFR conds durg entire prd at all terminals and
en routed btw islands. Few passing -SHRA/SHRA with SCT-BKN cld
lyr nr FL025...FL050. Wnds fm E-SE BLO FL100...then backing and
incr w/ht abv. Sfc wnds fm E 10-15 kt with ocnl hir gusts with
sea breeze variation bcmg mostly LGT/VRB aft 23/23z.
&&
.MARINE UPDATE...No change to previous marine discussion. Moderate
to locally fresh easterly wind flow continued across the local waters,
and will persist through the upcoming week. A northerly swell will
continue to spread across the local Atlantic waters today through Monday.
The next tropical wave, remnants of Tropical Depression Eleven is forecast
to approach the regional waters by late Monday through Tuesday. This
will therefore increase the potential for thunderstorm development
with areas of heavy rainfall across the coastal waters.
&&
.PREV DISCUSSION... /issued 432 AM AST Sun Sep 23 2018/
SYNOPSIS...
A TUTT low/trough as well as low level moisture will increase
showers and thunderstorms over Puerto Rico, and the U.S. Virgin
Islands though the end of next week. Moisture is forecast to move
from the Caribbean across the U.S. Virgin Islands and Puerto Rico
on Tuesday and remain through late Wednesday. Friday another
surge of moisture is forecast to move into the local area and
remain through the weekend. Showers and thunderstorms that
develop each day could cause urban and small stream flooding over
portions of Puerto Rico.
SHORT TERM...Today through Tuesday...
For today, diurnally induced afternoon showers and thunderstorms
are expected to develop over the interior and west/northwest
sections of Puerto Rico. Urban and small stream flooding is
possible with this activity. Also, the streamer from el Yunque
could develop and affect San Juan and vicinity during the early
afternoon hours. Across the USVI, showers are expected to develop
around noon, downwind from the islands and move mainly across the
western sections and surrounding waters. Upper level low over the
Leeward Islands will continue to approach the region and induce
passing showers across the regional waters. These showers will
move at times across the USVI and the eastern coastal areas of
Puerto Rico. Shower and thunderstorm activity is forecast to
advect from the east on Monday night into Tuesday, in association
with Tropical Depression Eleven, which is forecast to dissipate
today east of the Windward Islands and move over the local area as
an open trough. The upper level low is forecast to move over and
just west of the area on Tuesday, providing good divergence aloft
while interacting with the remnants of TD#11.
LONG TERM...Wednesday through Monday...
An unsettled pattern will persist most of the long-term period as
a result of TUTTS, and upper level troughs that are forecast to
remain over or near the area. Moisture from TD#11 which is
forecast to dissipate east of the area will bring a surge of
moisture over the region on Tuesday. The bulk of the moisture
will arrive on Wednesday, this moisture combined with the TUTT
low will increase instability over the entire area. Therefore, an
increase in showers and thunderstorms is forecast each day, with
the possibility of urban and small stream flooding. A pocket of
drier air is forecast to move in behind the moisture on Friday,
but early Saturday another round of moisture is forecast to lift
out of the Caribbean waters and move across the region, therefore
another round of showers and thunderstorms will develop over
Puerto Rico, and the U.S. Virgin Islands. Model guidance shows
moisture remaining across most of the Caribbean and local waters
through early next week.
AVIATION...Mainly VFR conditions are expected to prevail across all
terminals during the next 24 hours. However, SHRA/TSRA is expected
to develop over west/northwest PR btw 16z-22z. This can result in
tempo MVFR conds at TJMZ/TJBQ. VCTS/SHRA possible at TJSJ btw 16z-
20z. Also, trade wind showers will continue across the regional
waters, moving briefly across some of the terminals. Low level
winds E-ESE at 10-15 kt with higher gusts and sea breeze variations
after 14z.
MARINE...Seas will range from 3 to 6 feet with seas occasionally
reaching 8 feet across the local and outer waters. East winds
will prevail between 10 to 15 knots. A northerly swell is forecast
to increase the North Atlantic and Caribbean waters on Tuesday. A
high risk of rip currents exist for the northern beaches of
Puerto Rico today.
&&
.PRELIMINARY POINT TEMPS/POPS...
SJU 90 80 89 80 / 30 20 30 60
STT 89 82 90 82 / 40 40 40 70
&&
.SJU WATCHES/WARNINGS/ADVISORIES...
PR...High Rip Current Risk through late tonight for North Central-
Northeast-Northwest-San Juan and Vicinity-Southeast-Western
Interior.
VI...None.
AM...None.
&&
SHORT TERM...RAM
LONG TERM....RAMPerspectivas sobre Condiciones Peligrosas del Tiempo Servicio Nacional de Meteorologia San Juan PR 510 AM AST domingo 23 de septiembre de 2018 AMZ710>745-PRZ001>013-240915- 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 lejanas a la costa del Atlantico y Caribe- 510 AM AST domingo 23 de septiembre de 2018 Esta perspectiva sobre las condiciones peligrosas del tiempo es para Puerto Rico y las aguas costeras adyacentes del Atlantico. .Dia Uno...Esta noche .Tronadas...Existe la probabilidad de tronadas con lluvia fuerte y periodos breves de vientos en rafaga esta tarde a traves de partes del oeste de Puerto Rico. .Inundaciones...Lluvia fuerte pudiera resultar en inundaciones urbanas y de riachuelos. .Olas...Se espera oleaje picado de hasta 6 pies a traves de las aguas del Atlantico. .Corrientes marinas...Existe riesgo alto de corrientes marinas para las playas del norte de Puerto Rico. .Calor...Se esperan indices de calor de hasta 104 grados mayormente a traves de las areas costeras del norte y sur de Puerto Rico. .Dias dos a siete...lunes a sabado Se esperan tronadas el lunes en la tarde sobre el oeste de Puerto Rico. Esto pudiera resultar en lluvia fuerte e inundaciones urbanas y de riachuelos. Se espera que la actividad de aguaceros y tronadas aumente desde el este para tarde el lunes en la noche al martes en asociacion con los remanentes de la Depresion Tropical Once. Un riesgo de moderado a alto de corrientes marians prevalecera, particularmente a traves de las playas hacia el norte de las islas locales por los proximos dias. .Comunicado sobre informacion reportada por observadores... No se anticipa activacion amplia de observadores, sin embargo, se les exhorta a los observadores individuales a reportar corrientes marinas al Servicio Nacional de Meteorologia en San Juan. AMZ715-725-VIZ001-002-240915- San Tomas, San John e Islas Adyacentes-Santa Cruz- Aguas cercanas del Atlantico y aguas costeras adyacentes del Caribe- 510 AM AST domingo 23 de septiembre de 2018 Esta perspectiva sobre las condiciones del tiempo peligrosas es para las Islas Virgenes Americanas y las aguas costeras adyacentes. .Dia Uno..Esta noche .Olas...Se espera oleaje picado de hasta 6 pies a traves de las aguas del Atlantico. .Corrientes marinas...Existe un riesgo moderado de corrientes marinas para las playas del norte de San Thomas. .Dias dos a siete...lunes a sabado Se espera que la actividad de aguaceros y tronadas aumente desde el este para tarde el lunes en la noche al martes en asociacion con los remanentes de la Depresion Tropical Once. Se espera un riesgo moderado de corrientes marinas para mediados de semana para Santa Cruz. .Comunicado sobre informacion reportada por observadores... No se anticipa activacion amplia de observadores, sin embargo, se les exhorta a los observadores individuales a reportar corrientes marinas al Servicio Nacional de Meteorologia en San Juan.
The San Juan radar (TJUA), 30 km away, was scanning. The volume nearest the first event began at 17:34 UTC.
9 flood, 7 flash flood. Local standard time, as filed.
Flooding reported in the intersection of Calle Pauda with Calle Budapest in the Urbanization of College Park.
Urbanization Mallorca, Calle Nebraska, House R16 flooded.
Urbanization San Francisco, Avenida de Diego-House 174 flooded.
Cupey, Sector El Cinco Road PR-1 flooded.
Urbanization Reparto Metropolitano, flooding reported at Calle 15 and house 990.
Rio Piedras, Avenida Marginal, flooded.
Car stranded on flooded road San Roberto, Urb. Monacillos.
House 1602 at Urb. El cerezal, Loira street, was reported flooded.
Flash flooding was reported at Urb. Villa Nevarez, street 5. House 1044 was flooded.
A tributary of Rio Piedras at Reparto Metropolitano, street 42 reported as out of its banks.
Quebrada Margarita near Highway 20 out of its banks.
Car stranded due to flooding along 65 Infanteria road towards Caguas before Lobby sports bar.
Road PR-1 in Cupey under bridge of Road PR-177 near Urbanization Santa Maria was reported as flooded.
Urbanization San Ignacio, Calle San Alejandro, was reported as flooded.
Flooding was reported at Urbanization Villa Nevares Calle 16.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Puerto Rico in 2018Every state in 2018This day in weather historyWarnings in Puerto Rico, September 2018
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: 783504, 783505, 783506, 783669, 783671, 783673, 783757, 783758, 783761, 784409, 784420, 783676, 783675, 783678, 783680, 783953.