Abundant moisture combined with local and diurnal effects to result in the development of showers and isolated thunderstorms across northwestern Puerto Rico.
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The episode as NWS SJU wrote it up.
Abundant moisture combined with local and diurnal effects to result in the development of showers and isolated thunderstorms across northwestern 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 May 27, 11:58 AM AST, 4 hours 2 minutes earlier.
Area Forecast Discussion National Weather Service San Juan PR 1158 AM AST Wed May 27 2020 .UPDATE...Clouds have increased somewhat north of the Cordillera Central, but the thunderstorms north of the Anegada Passage are fading slowly. The morning sounding came in with only 1.75 inches of precipitable water which is drier than the previous 2 soundings, but especially the one last night, which had over 2 inches. Current GFS is suggesting that a drier band of of air is sandwiched between the weak wave moving in from the southeast and the current moisture over the area. This should give us a slight break in the showers overnight and then expect rain chances to be the best we can expect for the next several days. Winds are fairly light except for sea breezes on the coasts. && .AVIATION...SHRA forming over the COrdillera Central and in wrn PR while TSRA fading over the Atlantic waters north of the Anegada passage. Expect SHRA/TSRA over NWrn PR and interior til arnd 27/22Z with some SHRA contg ovr ern PR afterward.Sfc winds 5-10 kt except alg the coast where sea breezes dominate at 10-15 kt. Max winds WNW 35-45 kt btwn FL440-480. && .MARINE...Showers and thunderstorms will be widely scattered over the area with some increase on Thursday. But, no small craft advisory conditions expected next 10 days. && .PREV DISCUSSION... /issued 457 AM AST Wed May 27 2020/ SYNOPSIS...An upper level trough and a tropical wave will increase shower activity and the potential for flooding through at least Thursday across all islands. A Saharan Air Layer is forecast to move across the region during the weekend. East to southeast winds will prevail through the long term period. Diurnally induced afternoon showers can be expected each afternoon through next week over western Puerto Rico. SHORT TERM...Today through Friday... The digging mid to upper-level trough aided in the development of isolated thunderstorms across the Atlantic and Caribbean waters during the overnight. Showers are forecast to continue to develop through the rest of the morning, producing light rainfall amounts. This afternoon the showers and thunderstorms will move to the northwest and the northern areas of Puerto Rico. A southerly wind flow will keep showers and thunderstorms across the northern, central, and the metro areas of Puerto Rico. However, I can't rule out thunderstorms developing in other areas of Puerto Rico and the adjacent islands, especially with moisture and instability increasing this afternoon across most of the region. A light steering flow will cause showers and thunderstorms to move slowly, leading to urban and small stream flooding. Rainfall amounts of 1 to 2 inches with isolated amounts up to 3 inches fell over the northwestern areas of Puerto Rico yesterday. If Additional rainfall amounts of 2 to 3 inches fall across portions of northwest Puerto Rico this afternoon, flooding will occur. Thursday, the tropical wave talked about in the previous forecast discussions this week, finally moves into the Caribbean waters late tonight into Thursday. Guidance shows precipitable water peaking to the highest total this week at 2.05 inches on Thursday morning. The forcing provided by the mid to upper-level trough coupled with the instability provided by the tropical wave will induce numerous showers and thunderstorms across the region. The moderate to heavy rainfall could cause flooding for many areas across Puerto Rico. Friday, the wave moves west of the area; however, moisture is forecast to linger over Puerto Rico and the adjacent islands. The lingering moisture plus diurnal and local effects will lead to the development of showers and thunderstorms during the afternoon. LONG TERM...Saturday through Thursday... A building 700-500 mb ridge over the Tropical Atlantic will gradually move west into the eastern Caribbean and is expected to move over the region by Thursday. A Saharan Air Layer is expected to filter during the weekend and possibly into early next week, creating hazy skies and limiting widespread shower activity across the islands. A deep layered low over the central Atlantic, just to our northeast will merge with a polar trough over the northwestern Atlantic by early next week. This will keep 500 mb temperatures between minus 8-10 degrees Celsius through the long term period. At lower levels, shallow patches of moisture will move at times and this will result in seasonal rain shower activity across the islands, with passing showers across the USVI and eastern PR during the overnight/early morning hours...followed by diurnally induced afternoon convection over western Puerto Rico each day. AVIATION...Mostly VFR conditions expected until 27/16Z. Then TSRA/RA is forecast across terminals TJBQ,TJMZ AND TJSJ through 27/22Z. The TSRA/SHRA could cause brief MVRF conds over the above terminal sites. Elsewhere, Iso/sct SHRA are possible across other areas of the island through 27/18Z. Sfc winds from the east to south to southeast at 10 to 15 kts with seas breeze variations after 27/15Z. MARINE...Seas will continue at less than 5 feet for the next several days. East to southeast winds will prevail between 5-15 knots. A low to moderate risk of rip currents is expected each day across the islands. Shower and thunderstorm activity will continue to increase today and tomorrow across the regional waters. && .PRELIMINARY POINT TEMPS/POPS... SJU 90 77 88 75 / 60 40 50 50 STT 88 77 87 75 / 50 50 50 50 && .SJU WATCHES/WARNINGS/ADVISORIES... PR...None. VI...None. AM...None. && SHORT TERM...WS LONG TERM....WS PUBLIC DESK...FRG
Perspectivas sobre Condiciones Peligrosas del Tiempo Servicio Nacional de Meteorologia San Juan PR 425 AM AST miercoles 27 de mayo de 2020 AMZ710>745-PRZ001>013-280830- 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 mar afuera del Atlantico y Caribe- 425 AM AST miercoles 27 de mayo de 2020 Esta perspectiva sobre las condiciones peligrosas del tiempo es para Puerto Rico y las aguas costeras del Atlantico. .Dia Uno...Hoy y esta noche .Tronadas...Existe el potencial de tronadas con lluvia fuerte y vientos en rafagas breves esta tarde a traves de sectores del norte, este, interior y oeste de Puerto Rico. .Inundaciones...Lluvias fuertes pudieran resultar en inundaciones urbanas y de riachuelos. .Dias dos hasta el siete...jueves a martes... La actividad de aguaceros y tronadas aumentara el jueves. Esto se debe a que la humedad aumentara, y al paso de una onda tropical a traves de las aguas del Caribe hasta tarde el jueves. .Comunicado sobre informacion reportada por observadores... No se anticipa activacion de observadores, sin embargo, se recomienda a los observadores individuales que reporten inundaciones y corrientes marinas al Servicio Nacional de Meteorologia en San Juan mientras siguen las indicaciones de las autoridades locales y estatales. AMZ715-725-VIZ001-002-280830- San Tomas, San John y Islas Adyacentes-Santa Cruz-Aguas cercanas del Atlantico y aguas costeras adyacentes del Caribe- 425 AM AST miercoles 27 de mayo de 2020 Esta perspectiva sobre las condiciones peligrosas del tiempo es para Islas Virgenes Estadounidenses y las aguas costeras adyacentes. .Dia uno...Hoy y esta noche .No se anticipan condiciones peligrosas en este momento. .Dias dos hasta el siete...jueves a martes... La actividad de aguaceros y tronadas aumentara el jueves. Esto se debe a que la humedad aumentara, y al paso de una onda tropical a traves de las aguas del Caribe hasta tarde el jueves. .Comunicado sobre informacion reportada por observadores... No se anticipa activacion de observadores.
The national radar mosaic for the moment the first event began.
1 flood. Local standard time, as filed.
Flooding was reported along Road PR-125 near Residencial Andres Mendez Liciaga.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Puerto Rico in 2020Every state in 2020This day in weather historyWarnings in Puerto Rico, May 2020
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: 888978.