A tropical wave increased moisture and instability, giving an extra boost to the typical weather pattern. On Saturday (17th), this promoted unsettled conditions with the formation of strong afternoon thunderstorms.
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.
A tropical wave increased moisture and instability, giving an extra boost to the typical weather pattern. On Saturday (17th), this promoted unsettled conditions with the formation of strong afternoon thunderstorms.
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 Aug 17, 7:10 AM AST, 5 hours 20 minutes earlier.
Area Forecast Discussion...CORRECTED
National Weather Service San Juan PR
710 AM AST Sat Aug 17 2024
.SYNOPSIS...
Hot conditions will linger across the islands for the next several
days. A tropical wave will also approach, increasing the chances
of showers and thunderstorms. Saharan dust will follow this wave,
resulting in hazy skies.
&&
.SHORT TERM...Today through Monday...
Current Satellite derived precipitable water (PWAT) indicate a mass
of above normal values (above 2.0 inches) now over
easternmost/southeasternmost Puerto Rico, the USVI, Vieques and
Culebra. This contrasts the normal PWAT values (around 1.80
inches) across the rest of the region. Passing showers slowly
gained more frequency overnight, affecting the eastern region of
the area. One particular isolated thunderstorm moved over St.
Croix overnight with radar rain estimates up to one quarter inch.
Lows ranged from the upper 70s to the low 80s across lower
elevations of the islands to upper 60s and low 70s across interior
Puerto Rico.
We'll start the weekend with increasing moisture and instability as
a weak tropical wave affects the region today and tomorrow. Above
normal PWAT levels (above 2.0 inches) will persist through late
Sunday. These conditions will give an extra boost to the typical
weather pattern. This pattern includes periods of passing
overnight and early morning showers across windward sectors of the
islands, followed by afternoon showers and thunderstorms mainly
over interior to western/northwestern Puerto Rico each day. Lines
of convection can also develop northwest of the local islands and
El Yunque under southeasterly winds. Winds will gradually back
through the period, becoming easterly on Monday. PWAT values will
decrease to more normal values to start the workweek, coinciding
with a pulse of Saharan dust that will also promote hazy skies.
Elevated to significant heat risks will persist through the short
term period. For today (10 AM to 5 PM AST), an Excessive Heat
Warning will be in effect for all coastal and lower elevation areas
of the island, and a Heat Advisory will be in effect for lower
elevations (mostly the valleys of Caguas and Gurabo) of eastern
interior Puerto Rico. Drink plenty of fluids, stay in an air-
conditioned room (if possible and if power is available), stay out
of the sun, check up on relatives and neighbors, and take extra
precautions when outside. Conditions during the coming days present
significant health risks and may require the issuance of additional
Excessive Heat Advisories and Warnings.
.LONG TERM...Tuesday through Saturday
Hazy skies are anticipated on Tuesday as Saharan dust lingers. By
Wednesday, patches of moisture associated with a tropical wave
will approach. However, this system looks weak and rather
fragmented, so the shower activity should not be too widespread.
Additionally, the air mass will remain dry at the mid and upper
levels, so these showers should not have enough vertical
development to drop heavy rainfall accumulations. By the latter
part of the week, moisture will increase, and an upper level
trough will approach from the Lesser Antilles. In fact,
precipitable water value will be well above normal Thursday and
Friday. On these days, showers will become more frequent over the
Virgin Islands and eastern Puerto Rico. The activity will be
stronger in the afternoon for the interior and western Puerto
Rico, where the risk of lightning and flooding will be elevated.
Hot temperatures will continue too. Temperatures at 925 mb will
not be as high as the past couple of days, but still above normal.
This heat will impact sensitive groups, especially those without
effective cooling or adequate hydration.
&&
.AVIATION...
(06Z TAFS)
Mainly VFR conditions across the terminals. S-SE winds up to 12 kts
with sea breeze variations and higher gusts, decreasing after
17/22Z, when land breezes start to influence. Brief MVFR conditions
can result from morning VCSH/VCTS that can affect eastern sites &
VCSH/VCTS starting over the interior that can affect the PR sites,
especially TJBQ around 17/17Z-22Z.
&&
.MARINE...
Light to moderate east-to-southeast winds will continue through the
weekend, providing favorable conditions for small craft. However,
moderate to locally fresh winds from a tropical wave will lead to
choppy seas for small craft early next week.
&&
.BEACH FORECAST...
The risk of rip currents is moderate today across the northern
coast of Puerto Rico. A swell from Hurricane Ernesto will reach
the islands by Monday, and the risk might increase to high.
&&
.SJU WATCHES/WARNINGS/ADVISORIES...
PR...Excessive Heat Warning from 10 AM this morning to 5 PM AST this
afternoon for PRZ001>003-005-007-008-010>013.
Heat Advisory from 10 AM this morning to 5 PM AST this afternoon
for PRZ004.
VI...Excessive Heat Warning from 10 AM this morning to 5 PM AST this
afternoon for VIZ001-002.
AM...None.
&&
SHORT TERM...MRR
LONG TERM....ERGPerspectiva sobre las Condiciones Peligrosas del Tiempo Servicio Nacional de Meteorología San Juan PR 449 AM AST sábado 17 de agosto de 2024 AMZ711>745-PRZ001>013-180900- San Juan y Vecindad-Noreste-Sureste-Este Interior- Norte Central-Central Interior-Ponce y Vecindad-Noroeste- Oeste Interior-Mayagüez y Vecindad-Suroeste-Culebra-Vieques- Las aguas cercanas y fuera de la costa del Atlántico y del Caribe- 449 AM AST sábado 17 de agosto de 2024 Esta perspectiva sobre las condiciones peligrosas del tiempo es para sectores de Puerto Rico. .DÍA UNO...Hoy y esta noche .Rayos...Tormentas eléctricas aisladas a dispersas posibles. Esté atento a tormentas eléctricas en su área y esté preparado para buscar refugio. .Lluvia Excesiva...Acumulación de agua en carreteras y áreas de mal drenaje, principalmente a través de municipios del noroeste. Las inundaciones urbanas y de riachuelos son posibles. .Calor Excesivo...Este nivel de calor afecta a cualquier persona sin enfriamiento efectivo y/o hidratación adecuada. Impactos probables en algunos sistemas de salud, industrias sensibles al calor e infraestructura. .Corrientes Marinas...Corrientes marinas amenazantes a la vida son posibles en la zona de resaca particularmente en la costa norte de PR y Culebra. .DÍAS DOS A SIETE...domingo a viernes Habrá mayormente un riesgo limitado de lluvia excesiva y rayos hasta el resto del fin de semana, especialmente durante las horas de la tarde sobre el oeste de Puerto Rico. Se espera calor excesivo en algunas elevaciones más bajas y áreas urbanas cada día. Hay un riesgo de bajo a moderado de corrientes marinas en algunas playas. Peligros maritimos limitados regresan el domingo hasta la próxima semana. Una marejada causada por el Huracán Ernesto alcanzará las islas el lunes, y el riesgo de corrientes marinas podría aumentar a alto. .COMUNICADO SOBRE INFORMACIÓN DE OBSERVADORES... No será necesaria la activación de observadores. AMZ716-726-VIZ001-002-180900- San Thomas San John e islas adyacentes-Santa Cruz- Aguas cercanas a la costa del Atlántico y aguas costeras adyacentes del Caribe- 449 AM AST sábado 17 de agosto de 2024 Esta Perspectiva sobre las Condiciones Peligrosas del Tiempo es para sectores de las Islas Vírgenes Americanas. .DÍA UNO...Hoy y esta noche .Rayos...Tormentas eléctricas aisladas a dispersas posibles. Esté atento a las tormentas eléctricas en su área y esté preparado para buscar refugio. .Lluvia Excesiva...Acumulación de agua en carreteras y áreas de mal drenaje. Las inundaciones urbanas y de riachuelos son posibles. .Calor Excesivo...Este nivel de calor afecta a cualquier persona sin enfriamiento efectivo y/o hidratación adecuada. Impactos probables en algunos sistemas de salud, industrias sensibles al calor e infraestructura. .Corrientes Marinas...Corrientes marinas amenazantes a la vida son posibles en la zona de resaca particularmente a través del noroeste de St. Thomas. .DÍAS DOS A SIETE...domingo a viernes Se espera calor excesivo en algunas elevaciones más bajas y áreas urbanas cada día. Hay un riesgo de bajo a moderado de corrientes marinas en algunas playas. Los peligros maritimos limitados regresan el domingo hasta la próxima semana. Una marejada causada por el Huracán Ernesto alcanzará las islas el lunes, y el riesgo de corrientes marinas podría aumentar a alto. .COMUNICADO SOBRE INFORMACIÓN DE OBSERVADORES... No será necesaria la activación de observadores.
The San Juan radar (TJUA), 34 km away, was scanning. The volume nearest the first event began at 16:28 UTC.
9 flash flood, 6 flood, 1 hail. Local standard time, as filed.
The 911 call center reported flooded roads at calle Italia with calle Julia at area de Los Mitas in San Juan.
The 911 call center reported flooding at Ave Roosevelt before the train station entrance near Rubens Cafe.
The 911 call center reported flooding at calle Antartica near the Ecomax gas station in San Juan.
Flooding rains affected Expreso Las Americas near Hospital Cardiovascular, from San Juan to Caguas. Emergency managers closed some road lanes, leaving just one operational. The rainfall estimates were around 4 inches.
An NWS employee reported that Avenida Jesus T. Pinero, near Farmacia Caridad and the Total Energy gas station in the direction of Carolina, was affected by flooding. Around three inches of rain had fallen in the past two hours.
The 911 call center reported flash flooding at Ave Barbosa in front of Ferreteria National.
The 911 call center reported flash flooding at calle 23 and Calle Alcaiz in Cantera. There were people trapped in one car.
The 911 call center reported flash flooding at Ave Ponce de Leon just in front of the San Juan park apartments. A car with people inside was trapped and getting flooded.
A 911 report stated that Avenida el Comandante in Carolina was affected by flooding and that a small sedan with people inside was trapped.
A tropical wave increased local moisture and instability, boosting local effects and enhancing the formation of an intense thunderstorm, which resulted in the pea-sized hail event. The social media post was validated with the weather data and residents of Barrio Voladora in Moca.
A 911 report indicated that Avenida 65 de Infanteria, right in front of Costco Wholesale, was affected by flooding. Between 1 and 2 inches of rain were recorded near the area.
A 911 report indicated that the Expreso Luis Munoz Rivera near the San Juan natatorium was affected by flooding.
A 911 report indicated that calle Samoa, Jaba, and Guadalupe near the public housing el Flamboyan was affected by flooding.
A 911 report indicated that in Avenida Barbosa intersection to calle Palestina in Bo. Israel near the Kentucky Fried Chicken was affected by flooding.
A 911 report indicated that calle Marte in Isla Verde was affected by flooding.
A 911 report indicated that calle Irlanda in sector Quintana was affected by flooding, as around 2 inches were estimated around that area.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Puerto Rico in 2024Every state in 2024This day in weather historyWarnings in Puerto Rico, August 2024
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: 1214573, 1214574, 1214575, 1207970, 1214576, 1214577, 1214578, 1214583, 1214584, 1207969, 1214586, 1214588, 1214590, 1214595, 1214596, 1214597.