Low level moisture combined with daytime heating and orographic effects to produce scattered to locally numerous showers across the western interior and northwest sections of Puerto Rico. Heavy rainfall led to rapid rises in small stream and rivers across the area.
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.
Low level moisture combined with daytime heating and orographic effects to produce scattered to locally numerous showers across the western interior and northwest sections of Puerto Rico. Heavy rainfall led to rapid rises in small stream and rivers across the area.
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 Apr 12, 11:32 AM AST, 4 hours 58 minutes earlier.
Area Forecast Discussion
National Weather Service San Juan PR
1132 AM AST Thu Apr 12 2018
.UPDATE...Available moisture is increasing slightly as the day
progresses. The latest high resolution model guidance is
suggesting that showers and thunderstorms are possible across many
portions of western PR and some areas near the San Juan metro. The
latest satellite imagery is also indicating that cloudiness is
developing downwind after orographic lifting. Since there is a
slight ESE component in the overall wind flow, clouds can stream
off the Luquillo Mountain Range and pass over the San Juan metro.
There is also a small area of showers across the Caribbean waters
moving west, which could briefly affect the southeastern portions
of PR in the early afternoon hours.
Because of all this, some minor changes were made to the inherited
forecast. We added the chance of scattered showers and a slight
possibility of thunderstorms across portions of the San Juan
metro, and also increased the coverage area of showers across the
western interior and southern slopes of PR for this afternoon.
Isolated showers are still expected for the USVI, so no major
change there.
&&
.AVIATION...VFR conds expected across the local terminals with
SHRA/TSRA possibly affecting the vicinity of the terminals. TJMZ
has a higher chance of TSRA so a TEMPO group was written, but the
rest of the terminals in PR may observe VCSH or VCTS this
afternoon. The USVI terminals should have VFR conds with VCSH
overnight. Winds will be from the East to ESE at 10-15kt and gusty
with sea breeze variations through 12/22Z.
&&
.MARINE...Small Craft Advisory continues in effect for the
offshore Atlantic waters and the Anegada passage due to seas up to
7 feet. The rest of the local waters will be generally between 3-6
feet. Seas will improve slightly today but are expected to gradually
become more hazardous for this weekend as winds increase.
&&
.PREV DISCUSSION... /issued 534 AM AST Thu Apr 12 2018/
SYNOPSIS...
A band of moisture will bring passing showers across the local
waters, the U.S. Virgin Islands and the eastern half portion of
Puerto Rico through the morning hours. Locally and diurnally
induced showers and possibly an isolated thunderstorm are expected
to form across the western interior of Puerto Rico during the
afternoon hours. A high pressure ridge aloft will weakens
throughout the end of the work-week. An easterly wave
perturbation will enhance the potential for shower and
thunderstorm development on Friday.
Short Term...Thursday through Saturday...
Occasional patches of low level moisture will continue to move
over the islands today under the influence of an east to southeast
wind flow. This will result in showers moving over portions of
eastern PR, including Vieques and Culebra, as well as the U.S.
Virgin Islands in the morning, followed by locally and diurnally
induced showers and possibly isolated thunderstorms across the
interior and western sections of Puerto Rico in the afternoon.
This activity could lead to ponding of waters in roads and poorly
drained areas across these sections.
As the mid level ridge weakens and an easterly wave approaches the
local area, an increase in available tropical moisture will result
in a higher frequency of passing showers over eastern Puerto Rico
and the U.S. Virgin Islands during the morning hours, and enhanced
intensity and coverage of showers and isolated thunderstorm during
the afternoon hours on Friday.
Once the easterly wave moves away, shower intensity and coverage is
expected to decrease. However, a few passing showers remain possible
over eastern Puerto Rico and U.S. Virgin Islands during the morning
hours, while limited shower activity is expected over the interior
and western Puerto Rico on Saturday afternoon.
LONG TERM...Sunday through Friday...
A migratory high pressure over the Atlantic ocean will maintain a
tight pressure gradient across the local islands through at least
Tuesday. When, a surface low pressure and associated cold front
is forecast to enters the western Atlantic on Tuesday. At upper
levels, a polar trough is forecast to move north of the islands
around midweek.
Moisture levels across the region is forecast to remain around
the normal values for April through at least Tuesday. Under an
easterly trade wind flow patches of moisture will move across the
region at times inducing the typical passing showers during the
overnight and morning hours, followed by diurnal and locally
induced showers across the western interior of PR each afternoon.
A frontal system, forecast to move north of the islands, could
induce prefrontal troughs over the region after mid-week. Model
guidance suggested moisture to increase above normal levels after
mid week, and winds are forecast to shift from the south to
southeast. At this time, the islands seems to be moving into a
more wet and unstable weather pattern by the second part of the
upcoming week. Confidence is moderate at this time.
AVIATION...
Mostly VFR conditions expected across all terminals. Passing
showers will approach the vicinity of TIST/TISX between 12/12-15Z,
but conditions should remain VFR. Showers and possible VCTS could
bring brief MVFR conditions to TJMZ/TJBQ between 12/15-23z. East
to southeast winds between 10 and 15 knots with gusts around 22
knots will continue.
MARINE...
Hazardous seas are expected to continue across the outer Atlantic
waters through the weekend. Although marine conditions will
improve somewhat across the regional waters, choppy seas around 7
feet are expected to return by Saturday as model guidance
suggested. Therefore, small craft operators should exercise
caution across the expose local waters due to seas up to 6 feet.
For the beach goers, there is a high risk of rip currents for the
beaches along the eastern half portion of St Croix and a moderate
for most of the local beaches.
&&
.PRELIMINARY POINT TEMPS/POPS...
SJU 87 75 86 75 / 30 30 30 40
STT 85 75 84 74 / 30 40 40 40
&&
.SJU WATCHES/WARNINGS/ADVISORIES...
PR...None.
VI...High Rip Current Risk through late Friday night for St Croix.
AM...Small Craft Advisory until 8 PM AST this evening for Anegada
Passage Southward to 17N.
Small Craft Advisory until 6 PM AST Sunday for Atlantic Waters
of Puerto Rico and USVI from 10 NM to 19.5N.
&&
SHORT TERM...JA
LONG TERM....ACPerspectivas sobre Condiciones Peligrosas del Tiempo Servicio Nacional de Meteorologia San Juan PR 458 AM AST jueves 12 de abril de abril de 2018 AMZ710>745-PRZ001>013-130900- 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- 458 AM AST jueves 12 de abril de 2018 Esta perspectiva sobre las condiciones peligrosas del tiempo es para Puerto Rico y las aguas costeras adyacentes del Atlantico. .Dia Uno...Hoy y esta noche .Tronadas...Existe posibilidad de tronadas aisladas con lluvia fuerte y rafagas de vientos esta tarde a traves del noroeste de Puerto Rico. .Inundaciones...Lluvias fuertes pudieran resultar en inundaciones urbanas y de riachuelos. .Vientos...Vientos sostenidos de 20 a 24 mph (17-21 mph) a traves de las areas costeras del norte y sur de Puerto Rico. .Oleaje...Se espera oleaje picado y peligroso de hasta 7 pies a traves de las aguas mar afuera, al igual que sobre los pasajes. .Corrientes marinas...Existe riesgo moderado de corrientes marinas para la mayor parte de las playas. .Fuego...Se espera Peligro Elevado de Fuegos a traves de las laderas del sur de Puerto Rico. Refierase al Comunicados sobre Peligro de Fuegos para mas detalles. .Dias dos a siete...viernes hasta miercoles A medida que una onda del este y humedad asociada se acerque al area local, se espera probabilidad mas alta de aguaceros y posibles tronadas aisladas el viernes. Cuando este disturbio se aleje, se puede esperar actividad limitada de aguaceros hasta por lo menos el miercoles en las tardes. El riesgo de corrientes marinas continuara moderado hasta por lo menos la semana proxima. .Comunicado sobre informacion reportada por observadores... No se anticipa activacion amplia de observadores. Sin embargo, se les exhorta a los observadores a reportar inundaciones amplias o corrientes marinas al Servicio Nacional de Meteorologia en San Juan. AMZ715-725-VIZ001-002-130900- San Tomas, San John e Islas Adyacentes- Santa Cruz-Aguas cercanas del Atlantico y aguas costeras adyacentes del Caribe- 458 AM AST jueves 12 de abril de 2018 Esta perspectiva sobre las condiciones del tiempo peligrosas es para Puerto Rico y las aguas costeras adyacentes del Atlantico. .Dia Uno...Hoy y esta noche .Oleaje...Se espera oleaje de hasta 7 pies a traves de las aguas mar afuera y los pasajes locales. .Corrientes Marinas...Existe un riesgo alto de corrientes marinas para algunas el este de Santa Cruz. En el resto del area, existe riesgo moderado de corrientes marinas. .Dias dos a siete...viernes hasta miercoles A medida que una onda del este y humedad asociada se acerque al area local, se espera probabilidad mas alta de aguaceros y posibles tronadas aisladas el viernes. Cuando este disturbio se aleje, se puede esperar actividad limitada de aguaceros hasta por lo menos el miercoles en las tardes. El riesgo de corrientes marinas continuara moderado hasta por lo menos la semana proxima. .Comunicado sobre informacion reportada por observadores... No se anticipa activacion amplia de observadores. Sin embargo, se les exhorta a los observadores a reportar inundaciones amplias o corrientes marinas al Servicio Nacional de Meteorologia en San Juan.
The national radar mosaic for the moment the first event began.
1 flood. Local standard time, as filed.
A 56 year old man was dragged by a surge of water on the Guatemala river. PREMA search and rescue team found the body down river.
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 |
|---|---|---|---|---|---|
| Flood, San Sebastian | 2018-04-12 | 56 | Male | In Water | Direct |
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, April 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: 747736.