Lingering moisture from a departing tropical wave combined with diurnal heating and local effects to produce showers and thunderstorms across northwest PR.
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The episode as NWS SJU wrote it up.
Lingering moisture from a departing tropical wave combined with diurnal heating and local effects to produce showers and thunderstorms across northwest PR.
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 12, 4:06 PM AST, 3 hours 36 minutes earlier.
Area Forecast Discussion National Weather Service San Juan PR 406 PM AST Sat Aug 12 2017 .SYNOPSIS... A low pressure off to the northwest of Puerto Rico, and near the Turks islands will continue moving northwestward across the west Atlantic Ocean. A Subtropical Ridge will continue to build over the islands from the Atlantic Ocean. An induce surface perturbation with a surge of moisture is forecast to move near the islands by Sunday. Another tropical waves is expected by late Monday or Tuesday. && .SHORT TERM... Under a southeasterly wind flow above normal temperatures were observed across the coastal areas today. Then, thunderstorms and showers developed mainly across the Northwest quadrant of Puerto Rico during the afternoon and elsewhere the weather conditions were mostly sunny with warm to hot temperatures. Satellite imagery detected streamers development downwind from the U.S. Virgin Islands and Culebra but without significant rainfall activity. Tranquil weather conditions are expected to prevailed, as a dry air mass with Saharan dust particles filters across the region late this afternoon into the evening hours. In addition, easterly winds are expected to return alleviating the warm temperatures. For Sunday, an induce surface trough with a patch of low level moisture will move by the region Sunday afternoon. The increase in low level moisture combined with the local and diurnal effect will again give way to afternoon convection mainly over parts of the interior and west Puerto Rico with some streamer like showers possible in and around the San Juan metro area and east Puerto Rico. In general, the U.S. Virgin Islands can expect mostly sunny to partly cloudy skies with showers embedded on the trade winds. .LONG TERM...Tuesday through Saturday...(PREVIOUS DISCUSSION) A tropical wave along 46 West is expected to reach the region Monday night into early Tuesday. This wave in combination with a developing upper trough north and northeast of the forecast areas will produce an increase in showers and thunderstorms across the local islands. However, the wave and the upper trough are expected to move rapidly westward and away from the region. Accordingly to latest model guidance, after the passage of the wave, an area relative drier air accompanied with Saharan dust will encompass the region late Tuesday through at least Wednesday. By late Wednesday, a large area of moisture oriented southwest to northeast is expected to move across the northeast Caribbean increasing again the chances of showers and thunderstorms across the region until at least Thursday. The typical diurnal induced shower and thunderstorm activity will return to the forecast area on Friday. Looking well ahead, the GFS model guidance suggest that a strong tropical accompanied by an upper level low will move over the northeast Caribbean by the upcoming weekend inducing widespread shower and thunderstorm activity with possible gusty winds across the local islands and surrounding waters. Stay tuned, because there is a lot of uncertainty about the development of this system. && .AVIATION... Mostly VFR conds durg prd. SHRA/ isold TSRA expected to affect northern half and parts of western PR til 12/22z. This will lead to brief MVFR/psbl IFR conds in SHRA/TSRA impacting mainly TJBQ/TJMZ...and VCTY of TJSJ. S-SE winds 5-15 blo FL200. Sfc wnds mainly fm E-SE 5-10 knots, except for sea breeze variations and occasionally higher gusts. && .MARINE... Tranquil marine conditions with seas at less than 5 feet and winds around 15 knots. Marine conditions will deteriorate by the upcoming week as a tropical wave move across the Caribbean waters by Monday. && .PRELIMINARY POINT TEMPS/POPS... SJU 80 92 80 90 / 30 30 40 20 STT 80 91 81 91 / 40 40 50 20 && .SJU WATCHES/WARNINGS/ADVISORIES... PR...None. VI...None. AM...None. && SHORT TERM...CAM LONG TERM....PREVIOUS DISCUSSION AVIATION...RAM
Perspectivas sobre condiciones peligrosas del tiempo Servicio Nacional de Meteorologia San Juan PR 548 AM AST sabado 12 de agosto de 2017 AMZ710>745-PRZ001>013-131000- 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- 548 AM AST sabado 12 de agosto de 2017 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 probabilidad de tronadas con lluvias fuertes y vientos en rafaga breves esta tarde a traves de porciones del noroeste de Puerto Rico. .Inundaciones...Fuertes lluvias podran resultar en inundaciones urbanas y de riachuelos. .Vientos...Se esperan vientos sostenido en exceso de 20 mph a traves de las aguas costeras del norte de Puerto Rico. .Calor...Vientos alisios del sureste resultaran en indices de calor sobre lo normal a lo largo de la costa sur y norte de Puerto Rico. .Corrientes marinas...Existe un riesgo moderado de corrientes marinas para la costa norte de Puerto Rico. .Dias dos a siete...Domingo a viernes Se pronostica que una onda tropical se mueva a traves del area local temprano la proxima semana. Eso podra aumentar la probabilidad de tronadas e inunadciones sobre porciones de las islas. Se espera un riesgo moderado de corrientes marinas a traves de gran parte de las playas del norte y sur de las islas durante la semana laboral. .Comunicado sobre informacion reportada por observadores... No se anticipa activacion generalizada de observadores, sin embargo, se exhorta a los observadores a reportar inundaciones y corrientes marinas a la oficina del Servicio Nacional de Meteorologia en San Juan. AMZ715-725-VIZ001-002-131000- San Tomas, San John e Islas Adyacentes-Santa Cruz- Aguas cercanas del Atlantico y aguas costeras adyacentes del Caribe- 548 AM AST sabado 12 de agosto de 2017 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 .Corrientes marinas...Existe un riesgo moderado de corrientes marinas para la costa este de Santa Cruz. .Calor...Vientos alisios del sureste resultaran en indices de calor sobre lo normal a traves de las islas hoy. .Dias dos a siete...Domingo a viernes Se pronostica que una onda tropical se mueva a traves del area local temprano la proxima semana. Eso podra aumentar la probabilidad de tronadas e inunadciones sobre porciones de las islas. Se espera un riesgo moderado de corrientes marinas a traves de gran parte de las playas del norte y sur de las islas durante la semana laboral. .Comunicado sobre informacion reportada por observadores... No se anticipa activacion generalizada de observadores, sin embargo, se exhorta a los observadores a reportar corrientes marinas a la oficina del 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.
PR-2 from Hatillo to Arecibo inundated after Plaza del Norte.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Puerto Rico in 2017Every state in 2017This day in weather historyWarnings in Puerto Rico, August 2017
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: 718935.