Strong surface high pressure across the central Atlantic produced hazardous seas between 5 to 7 feet and winds up to 20 knots. This created dangerous rip currents along the north coast of Puerto Rico.
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.
Strong surface high pressure across the central Atlantic produced hazardous seas between 5 to 7 feet and winds up to 20 knots. This created dangerous rip currents along the north coast of Puerto Rico.
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 21, 11:29 AM AST, 4 hours 31 minutes earlier.
Area Forecast Discussion National Weather Service San Juan PR 1129 AM AST Sat Apr 21 2018 .UPDATE...No major changes to the inherited short term forecast package at this time which had a good handle on present and expected conditions during the rest of the weekend.Quick surge of low to mid level moisture accompanying a weak easterly perturbation will continue to cross the region and provide sufficient low level convergence and instability to support locally and diurnally induced convection during the rest of the day. Recent TJSJ 21/12z upper air sounding showed a slight increase in layered precipitable water to around 1.70 inches, with low level winds becoming more easterly in response to a high pressure ridge which will build north of the area over the rest of the weekend. In addition, the ridge aloft will slightly erode through Sunday as a short wave trough will become amplified and move across the southwest Atlantic. This feature should provide sufficient instability and ventilation for the development of afternoon showers and thunderstorms mainly across portions of the interior including parts of the San Juan metro and the west and northwest sections of Puerto Rico. Locally heavy rainfall will therefore be possible across these areas. Isolated showers are forecast elsewhere including the U.S. Virgin Islands where partly cloudy skies and brief showers and clouds in the form of streamers will occur. && .AVIATION...Prevailing VFR. Sct-Bkn cld lyrs btw FL025-Fl100... Isold Tops 150-180...except higher with Isold TSRA psbl ovr PR fm 21/17z-21/22z where brief MVFR conds will be likely vcty TJSJ/TJMZ/TJBQ. Isold SHRA ovr coastal waters and en route btw islands durg prd. Sfc winds fm E around 15 kts with ocnly higher gusts along coastal areas and with aftn convection. && .MARINE...Recent data from local buoys suggest gradually subsiding seas over the local waters with seas no longer at or above small craft advisory criteria. The small craft advisory for the offshore Atlantic waters was cancelled. However, the moderate to locally fresh easterly trade winds will continue to create choppy conditions and therefore small craft operators should exercise caution over most of the coastal waters and local passages. && .PREV DISCUSSION... /issued 500 AM AST Sat Apr 21 2018/ SYNOPSIS...At the surface, high pressure system will continue to dominate the local region through the weekend. A patch of low level moisture will move across the region today. A sharp increase in low level moisture is expected early next week. Upper level trough will dominates the western Atlantic Monday through Wednesday next week. SHORT TERM...Short Term...Today through Sunday... A patch of moisture is expected to move in today, the rainfall has already made an impact with numerous showers affecting eastern PR during the overnight hours. This moisture will combine with the local effects this afternoon and help develop scattered to locally numerous showers with isolated thunderstorms over the interior into NW-PR, with showers and thunderstorms possibly streaming off of the Luquillo Mountain range into the San Juan metro area. On Sunday, drier air is expected in and wind flow may shift a bit to the ENE, which may cause afternoon convection across W and SW-PR with isolated showers elsewhere. Both Saturday and Sunday, we may observe isolated to scattered brief showers across the local waters, USVI, and eastern PR in the nighttime and early morning hours. Monday may be a bit more active if the guidance were to verify. We have additional moisture moving in again and the wind flow becomes easterly. There is also an upper trough that may be digging just west of the local islands, increasing instability and also increasing the chances for thunderstorms over the local islands, especially over several sectors in Puerto Rico when the moisture, diurnal heating and instability all combine on Monday afternoon. Isolated to scattered showers can be expected for the USVI during the day with showers possibly streaming off the islands. LONG TERM...Monday through Saturday... For Monday into Tuesday, a sharp increase in low level moisture is forecast to occur, with best moisture and favorable upper level atmospheric conditions expected on Tuesday. As a result, an increase in showers and thunderstorms are expected by early next week. By late in the forecast period, drier air mass is expected to encompass the region from the east. AVIATION...VFR conds in the morning hours across the local terminals. SHRA/SHRA expected this afternoon may cause moments of MVFR across TJSJ, TJMZ, and TJBQ after 21/16Z. TEMPO groups were left out due to exact location uncertainty since guidance suggests that the activity will be mostly in the vicinity. Winds will be from the east at around 15kt and gusty. MARINE....Seas will slowly diminish and most areas will come below 7 feet this morning. However, seas at 7 feet are expected to continue across the offshore Atlantic waters through this evening. Elsewhere, small craft should exercise caution. && .PRELIMINARY POINT TEMPS/POPS... SJU 87 75 85 75 / 40 20 20 40 STT 86 75 87 75 / 20 20 20 40 && .SJU WATCHES/WARNINGS/ADVISORIES... PR...None. VI...High Rip Current Risk through late tonight for St Croix. AM...None. && SHORT TERM...RAM LONG TERM....RAM
Perspectivas sobre Condiciones Peligrosas del Tiempo Servicio Nacional de Meteorologia San Juan PR 430 AM AST sabado 21 de abril de 2018 AMZ710>745-PRZ001>013-221000- 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- 430 AM AST sabado 21 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 la posibilidad de tronadas con lluvia fuerte y rafagas de vientos esta tarde a traves del oeste interior, oeste y noroeste de Puerto Rico. Existe ademas, probabilidad de tronadas a traves de sectores del area metro de San Juan. .Inundaciones...Lluvias fuertes pudieran resultar en inundaciones urbanas y de riachuelos. .Viento...Se esperan vientos en exceso de 20 mph a traves de las aguas locales. .Olas...Se espera oleaje peligroso y picado hasta 7 pies a traves de las aguas mar afuera del Atlantico. .Corrientes marinas...Existe un riesgo moderado de corrientes marinas para todas las playas de Puerto Rico, excepto para algunas playas a traves del oeste de Puerto Rico. .Dias dos a siete...domingo a viernes Se esperan aguaceros y tronadas en las tardes durante los proximos dias. Estas tronadas pudieran producir inundaciones urbanas y de riachuelos. Habra riesgo moderado de corrientes marinas a traves de algunas de las playas locales durante los proximos dias. .Comunicado sobre informacion reportada por observadores... No se anticipa activacion amplia de observadores. Sin embargo, se les exhorta a los observadores a reportar vientos fuertes, inundaciones, trombas marinas y corrientes marinas al Servicio Nacional de Meteorologia en San Juan. AMZ715-725-VIZ001-002-221000- San Tomas, San John e Islas Adyacentes- Santa Cruz-Aguas cercanas del Atlantico y aguas costeras adyacentes del Caribe- 430 AM AST sabado 21 de abril de 2018 Esta perspectiva sobre las condiciones del tiempo peligrosas es para las Islas Virgenes Americanas y las aguas costeras adyacentes. .Dia Uno...Hoy y esta noche .Viento...Se esperan vientos sostenidos en exceso de 20 mph a traves de las aguas locales. .Olas...Se espera oleaje picado y peligroso de hasta 7 pies a traves de las aguas mar afuera del Atlantico. .Corrientes marinas...Existe riesgo moderado de corrientes marinas para las playas del oeste de Santa Cruz y de San Thomas, mientras el riesgo de corrientes marinas es alto para las playas del este de Santa Cruz. .Dias dos a siete...domingo a viernes Se espera riesgo moderado a alto de corrientes marinas a lo largo de las Islas Virgenes estadounidenses durante los proximos dias. .Comunicado sobre informacion reportada por observadores... No se anticipa activacion amplia de observadores. Sin embargo, se les exhorta a los observadores a reportar vientos fuertes, inundaciones, trombas marinas, y corrientes marinas al Servicio Nacional de Meteorologia en San Juan.
1 rip current. Local standard time, as filed.
A person was trapped by rip currents in the vicinity of Ocean Park in Condado sector in San Juan. The person was rescued successfully without no major issues.
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: 747739.