Heavy rains from thunderstorms developed over much of the interior and southern portions of Puerto Rico on the 12th of August. This activity was associated with a surface trough and TUTT low.
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The episode as NWS SJU wrote it up.
Heavy rains from thunderstorms developed over much of the interior and southern portions of Puerto Rico on the 12th of August. This activity was associated with a surface trough and TUTT low.
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, 11:38 AM AST, 3 hours 8 minutes earlier.
Area Forecast Discussion National Weather Service San Juan PR 1138 AM AST Sat Aug 12 2023 ...New UPDATE... .UPDATE... The brisk northeast trade winds continued to transport a surge of moisture across the region enhanced by a Tutt low and associated trough now moving westward across the region. A tropical wave with axis now crossing the Lesser Antilles and the Tutt low will continue to bring additional moisture and instability respectively, to the region during the rest of the afternoon and evening hours. Suspended Saharan dust particulates although lesser amounts, will also mix in and linger across the region during the rest of the day. Recent TJSJ upper air sounding suggestS increasing moisture in the low levels with precipitable water at 1.97 inches. Low level winds were from the northeast between 15 to 25 mph below 500 millibars, then becoming more easterly while increasing with height. Otherwise no change to the inherited short term grids and reasoning at this time. .AVIATION UPDATE... Prevailing VFR at all terminals but intervals of SHRA/Isold TSRA will continue to move through the region carried by the brisk nE trade winds. This will result in brief MVFR conds at TJSJ/TJBQ and USVI terminals til 12/17Z and another round btw 12/20Z-12/22Z. Winds will be fm NE 15-20 knots with higher gusts btw 25-30 kts psbl. Winds bcmg fm E and less than 10 kts aft 12/22Z. && .MARINE UPDATE... NDBC San Juan bouy 41043 and Previous 41056 Vieques Island Buoy data both suggest seas between 3-4 feet occasionally up to 5 feet and winds between 15 to 18 knots with occasionally higher gusts between 22 to 25 knots. Choppy conditions will therefore persists across the coastal waters. Therefore, small craft operators are urged to exercise caution across the coastal local waters due to hazardous wind driven marine conditions. && .SYNOPSIS... .Previous discussion.../issued at 408 AM AST Sat Aug 12 2023/. Patches of moisture will continue to move across the area today and Sunday increasing the chance for rain. Breezy conditions will keep enhancing choppy seas at times. Saharan Dust remains present, but will reduce in concentration by Monday when a thick layer arrives. && .SHORT TERM...Today through Monday... Today's hazard risks focus on excessive rainfall at limited to elevated and Wind and lightning at limited threat levels. Despite the expected rains, expect excessive heat hazard risks each day. Fair weather conditions, hazy skies, and limited shower activity prevailed in the evening. After midnight, radar and satellite imagery indicated an increase in shower with thunderstorm activity across the waters, with some moving over northern and eastern Puerto Rico and the U.S. Virgin Islands. So far, rainfall totals have peaked around half an inch over northeastern Puerto Rico. Overnight low temperatures fell to around 70 degrees across higher elevations of the interior and lower 80s across lower elevations. Winds were generally light from the east-northeast but calm and variable further inland. Surface high pressure over the North Atlantic will maintain breezy to windy conditions, with peak 15-25 mph winds veering from the east today and east-southeast on Sunday and Monday. Steered by this general wind flow, moderate to high moisture airmass, spreading across the region from the east, will gradually replace a drier airmass and Saharan Air Layer that dominated the area in recent days. Precipitable Water (PWAT) values will likely rise to one standard deviation or into the above climatological thresholds around 2.0 inches later this afternoon, as suggested by satellite- derived Total PWAT and the most recent model guidance, and hold within normal moisture levels at 1.7-1.9 inches throughout the period. As this transition materializes, reduced visibilities are still possible, mainly across rain-free areas today. Adding to the already moist environment, a retrograding TUTT will continue to move westward over the northeastern Caribbean region today, increasing instability and setting the perfect environmental conditions to support scattered to numerous showers with isolated to scattered thunderstorm development. Over the local waters, this activity will decrease but persist throughout the day. In contrast, the focus of the rain activity shifts over land areas, aided by local effects and diurnal heating, with the most vigorous activity, steered by easterly winds, clustering across the interior to western sections of Puerto Rico, where moderate to heavy rains will likely lead to elevated excessive rainfall hazard risks. Elsewhere, showers with isolated thunderstorms are possible, mainly downwind from El Yunque into the San Juan metropolitan area. As a result, weekend outdoor activities could be affected, primarily by potential flooding impacts, including rapid rises along small streams and main rivers, thunderstorm winds, and increased lightning activity. A similar weather pattern is likely on Sunday but with more localized and lesser showers and thunderstorms favoring more northern sections of the local islands steered by east-southeast winds. A more patchy weather scenario is likely on Monday, with more frequent patches of relatively drier air supporting fairer weather conditions, which presents an excellent start to the work and school week. Southeasterly winds and a lower chance of precipitation will lead to higher excessive heat hazard risk levels, with heat index values likely to exceed 108 degrees across most lower elevations and urban areas. && .LONG TERM...Tuesday through Saturday... The inherited forecast remains unchanged. At this time, precipitable water models suggest PW values falling below normal climatological levels through mid-week. Precipitable water content is expected to remain around 1.30 to 1.60 inches. Nonetheless, patches of moisture will still filter across the area from time to time, allowing some occasional passing showers from the waters to move into the windward sections of Puerto Rico and the U.S. Virgin Islands. This activity will be followed by afternoon showers and thunderstorm development, mainly across the western- southwestern quadrant of Puerto Rico, even during the driest day. During the first half of the workweek, excessive heat threat is anticipated, with heat index values of 108 degrees or higher. Therefore, heat- related illnesses with prolonged exposure are foreseen. The latest model guidance suggests wetter conditions across the islands by the latter part of the workweek. This increase in tropical moisture and precipitable water content will be due to a robust tropical wave spreading across the forecast area. Therefore, the potential for excessive rainfall threats increases. As mentioned in previous discussions, the confidence levels on this wet scenario are low, particularly with potential impacts, due to its timing in the forecast. However, increased tropical wave activity is likely during this time of the year. && .AVIATION...TSRA/SHRA could result in brief MVFR conditions across TJSJ and USVI terminals through 12/13Z and after 12/22Z. Between 12/13-22Z, TSRA/SHRA could also bring similar conditions across most terminals, with the highest impact on operations at TJSJ and TJBQ between 12/16-22Z. Winds will remain light from the east with land breeze variations, gradually increasing to 15-20 knots with higher gusts and sea breeze variations by 12/14-20Z. Winds will become lighter after 12/22Z. && .MARINE...Latest CariCOOS coastal buoys indicated seas around 3 feet. Today, expect an increase in moisture, as well as, seas and winds increasing slightly. There is a low risk of rip currents for all the coastal beaches of PR and moderate over Ct. Croix. && .SJU WATCHES/WARNINGS/ADVISORIES... PR...Heat Advisory until 5 PM AST this afternoon for PRZ012-013. VI...Heat Advisory until 5 PM AST this afternoon for VIZ001-002. AM...None. && SHORT TERM...RAM LONG TERM....LIS AVIATION...RAM
Perspectivas sobre las Condiciones Peligrosas del Tiempo Nacional de Meteorologia en San Juan PR 400 AM AST sabado 12 de agosto de 2023 AMZ711>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 del Caribe- 400 AM AST sabado 12 de agosto de 2023 Esta perspectiva sobre las condiciones peligrosas del tiempo es para Puerto Rico. .DIA UNO...Hoy y esta noche .Rayos...Es posible el desarrollo de tormentas electricas de aisladas a dispersas, con el mayor impacto en sectores del interior y oeste de Puerto Rico. Planee detener todas las actividades al aire libre y trasladarse a un refugio seguro. .Lluvia Excesiva...Inundaciones de areas urbanas, carreteras y riachuelos. Las inundaciones repentinas aisladas son posibles .Calor Excesivo...Indices de calor de 108-111 grados en Vieques y Culebra, donde es probable el agotamiento por calor con una exposicion prolongada. El golpe de calor es posible. En otros lugares, particularmente en elevaciones bajas y areas urbanas, indices de calor de 102-107 grados, donde el agotamiento por calor es posible con una exposicion prolongada. .Vientos...Condiciones de brisa fuerte en las areas costeras. Los articulos no asegurados podrian salir volando. .Condiciones Maritimas...Las embarcaciones pequenas deben ejercer precaucion a traves de las aguas lejanas a la costa del Caribe, la mayoria de las aguas costeras y los pasajes locales. .Corrientes Marinas...Las corrientes marinas amenazantes a la vida son posibles en la zona de olas rompientes, particularmente en las playas del norte y este de Puerto Rico, Vieques y Culebra. .DIAS DOS A SIETE...domingo a viernes Las condiciones de calidas a calurosas persistiran durante la mayor parte del periodo de pronostico. Las condiciones de brisa fuerte, oleaje picado y un riesgo moderado de corriente marinas prevaleceran hasta principios de la proxima semana. Es probable que las condiciones maritimas y de la zona de olas rompientes se deterioren para mediados de semana. Se puede esperar un desarrollo convectivo por la tarde todos los dias, incluso durante los periodos mas secos. .Comunicado sobre informacion reportada por observadores... Se recomienda la activacion de los observadores. Transmita cualquier informacion sobre inundaciones, vientos, oleaje y corrientes marinas al Servicio Nacional de Meteorologia en San Juan. AMZ716-726-VIZ001-002-131000- San Tomas, San John y las Islas Adyacentes-Santa Cruz-Aguas cercanas a la Costa del Atlantico y aguas costeras adyacentes del Caribe- 400 AM AST sabado 12 de agosto de 2023 Esta perspectiva sobre las condiciones peligrosas del tiempo es para las Islas Virgenes Estadounidenses. .DIA UNO...Hoy y esta noche .Rayos...Es posible el desarrollo de tormentas electricas aisladas. Este atento a las tormentas electricas en su area y este preparado para refugiarse. .Lluvia Excesiva...Acumulacion de agua en carreteras y areas mal drenadas. Las inundaciones urbanas y de riachuelos son posibles. .Calor Excesivo...Indices de calor de 108-111 grados en todas las islas, donde es probable el agotamiento por calor con una exposicion prolongada. El golpe de calor es posible. .Condiciones Maritimas...Las embarcaciones pequenas deben ejercer precaucion a traves de las aguas lejanas a la costa del Caribe, la mayoria de las aguas costeras y los pasajes locales. .Corrientes Marinas...Las corrientes marinas amenazantes a la vida son posibles en la zona de olas rompientes, particularmente en las playas del noroeste de San Thomas y las playas del este de Santa Cruz. .DIAS DOS A SIETE...domingo a viernes Las condiciones de calidas a calurosas persistiran durante la mayor parte del periodo de pronostico. Oleaje picado y un riesgo moderado de corriente marinas prevaleceran hasta principios de la proxima semana. Es probable que las condiciones maritimas y de la zona de olas rompientes se deterioren para mediados de semana. .Comunicado sobre informacion reportada por observadores... Se recomienda la activacion de los observadores. Transmita cualquier informacion sobre inundaciones, vientos, oleaje y corrientes marinas al Servicio Nacional de Meteorologia en San Juan.
Special Weather Statement
National Weather Service San Juan PR
1218 PM AST Sat Aug 12 2023
PRZ010-011-121745-
Mayaguez and Vicinity PR-Southwest PR-
1218 PM AST Sat Aug 12 2023
...A strong thunderstorm will impact portions of Lajas, Cabo Rojo,
southwestern San German and Hormigueros Municipalities through 145 PM
AST...
At 1217 PM AST, a strong thunderstorm was over Puerto Real, or near
Cabo Rojo, moving west around 20 mph.
HAZARD...Frequent lightning and heavy rain.
SOURCE...Radar indicated.
IMPACT...Lightning is one of nature's leading killers. If you can
hear thunder, you are close enough to be struck by
lightning. Heavy rain may cause temporary street flooding
especially in poor drainage areas.
Locations impacted include...
Hormigueros, Cabo Rojo, Lajas, Puerto Real, Monte Grande, Pole Ojea,
Boqueron, Sabana Eneas and Betances.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
People outdoors should seek shelter immediately. Electrical
appliances should not be used unless in an emergency. Motorists
should slow down and be prepared for possible loss of control due to
hydroplaning.
&&
LAT...LON 1795 6722 1799 6722 1801 6716 1804 6721
1807 6718 1807 6720 1809 6720 1815 6717
1815 6709 1805 6703 1795 6716 1796 6718
1795 6720 1793 6719
TIME...MOT...LOC 1617Z 067DEG 22KT 1805 6720
MAX HAIL SIZE...0.00 IN
MAX WIND GUST...<30 MPH
RAMComunicado Especial sobre las Condiciones del Tiempo Servicio Nacional de Meteorologa San Juan PR 1218 PM AST sbado 12 de agosto de 2023 Mayagez y Vecindad PR-Suroeste PR- 1218 PM AST sbado 12 de agosto de 2023 ...Una tronada fuerte impactar sectores de Lajas, Cabo Rojo, suroeste de San German y Hormigueros hasta las 145 PM AST... A las 1217 PM AST, una troanda fuerte estaba sobre Puerto Real, o cerca de Cabo Rojo, movindose hacia el oeste alrededor de 20 mph. PELIGRO...Rayos frecuentes y lluvia fuerte. FUENTE...Indicado por radar. IMPACTO...Los rayos son uno de los principales asesinos de la naturaleza. Si puedes or un trueno, ests lo suficientemente cerca como para ser alcanzado por un rayo. La lluvia fuerte puede causar inundaciones temporales de las calles, especialmente en reas de drenaje pobre. Las localidades afectadas incluyen... Hormigueros, Cabo Rojo, Lajas, Puerto Real, Monte Grande, Pole Ojea, Boquern, Sabana Eneas y Betances. MEDIDAS DE PRECAUCIN/PREPARACIN... Las personas en el exterior deben buscar refugio inmediatamente. Los aparatos elctricos no deben usarse a menos que en una emergencia. Los automovilistas deben reducir la velocidad y estar preparados para una posible prdida de control debido al hidroplaneo. && LAT...LON 1795 6722 1799 6722 1801 6716 1804 6721 1807 6718 1807 6720 1809 6720 1815 6717 1815 6709 1805 6703 1795 6716 1796 1795 6720 1793 6719 HORA...MOT..LOC 1617Z 067 22KT 1805 6720 TAMAO DE GRANIZO MXIMO...0.00 EN RFAGA DE VIENTO MXIMA...<30 MPH RAM/LIS/RC
The national radar mosaic for the moment the first event began.
1 debris flow. Local standard time, as filed.
A 911 Call Center report indicated a landslide affecting PR-1 W, towards Aibonito.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Puerto Rico in 2023Every state in 2023This day in weather historyWarnings in Puerto Rico, August 2023
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: 1122498.