An upper-level trough combined with moisture lingering from a departing tropical wave to generate showers and strong thunderstorms across interior and western PR during the afternoon hours.
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The episode as NWS SJU wrote it up.
An upper-level trough combined with moisture lingering from a departing tropical wave to generate showers and strong thunderstorms across interior and western PR during the afternoon hours.
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 30, 11:20 AM AST, 1 hour 36 minutes earlier.
Area Forecast Discussion National Weather Service San Juan PR 1120 AM AST Tue May 30 2017 .UPDATE...After the very early morning showers that affected eastern Puerto Rico that caused some urban flooding, moderate to locally heavy showers have moved through eastern and north central Puerto Rico this morning but the accumulations have not been too significant since the showers are moving relatively quickly. The rest of the morning we expect these scattered showers to continue across eastern and central PR with some showers moving into the northern USVI, however Saint Croix is expected to observe mainly fair weather with isolated showers. Satellite imagery shows clouds developing further west which indicates that later today we will observe showers and thunderstorms across western and the western interior sections of PR. No changes were made to the inherited forecast as the latest guidance and observations are in agreement with the inherited forecast. && .AVIATION...No significant changes from previous discussion. VFR conds expected across the local terminals with SHRA/TSRA possibly affecting and causing TEMPO MVFR conds at TJMZ, TJBQ, and TJSJ after 30/16Z. Brief SHRA possible across TIST after 30/15Z as well. Winds from the east with sea breeze variations at around 15kt and gusty. && .MARINE...Seas still 3 to 5 feet and winds of up to 15 knots except for the coastal northern waters of PR where winds could reach 20 knots. Moderate risk of rip currents for several of the local beaches across PR, Vieques, Culebra, and Saint Croix. && .PREV DISCUSSION... /issued 450 AM AST Tue May 30 2017/ SYNOPSIS...A trough aloft will continue to interact with moisture associated with a departing tropical wave to result in periods of showers and thunderstorms today. The proximity of this trough will continue to enhance afternoon showers and thunderstorms Wed-Thu. A more seasonable weather pattern is expected Fri-Sat with the next tropical wave passage on Sunday. SHORT TERM...Today through Thursday... Abundant amounts of moisture trailing the tropical wave and the instability aloft due to the lingering mid to upper level trough/TUTT, continued to favor the development of showers and isolated thunderstorms across the region during the overnight and early morning hours. Expect these unstable conditions to continue today, but with a slight break in cloudiness, shower and thunderstorm activity by mid morning. However, instability aloft and good moisture convergence along with daytime heating will quickly give way to another round of afternoon convection across the islands especially over the interior and west sections of Puerto Rico. Showers and or isolated thunderstorms may also form along the Yunque area then stream across the San Juan metro area during the afternoon. Expect the tropical wave to exit the region later today however recent models guidance continued to suggest a TUTT low will continue to develop and linger just north of the region through Thursday. Although this feature will shift slowly eastward during the period, Upper level divergence/diffluence associated with this feature should persist over the northeastern Caribbean. This will therefore maintain unstable conditions which in combination with ample trade wind moisture transport and local effects, will continue to enhance the development of showers/thunderstorms across the regional waters and parts of the islands each day at least through Thursday. The activity on Wednesday and Thursday should however be less widespread as lesser moisture pooling is expected due to somewhat drier air filtering from the east along with a fine to moderate concentration of Saharan dust. LONG TERM...FRIDAY THROUGH WEDNESDAY... The aforementioned mid to upper level trough/TUTT low...which is now located north of Hispaniola...will move eastward while weakening with its associated axis crossing the local islands on Friday. As this feature weakens Sat-Sun, a weak mid level ridge pattern is expected to slowly build across Caribbean. At lower levels, a tropical wave will reach the eastern Caribbean on Sunday, bringing once again plenty of tropical moisture to the forecast area. After the wave passage, a broad surface high pressure across the central Atlantic will promote east southeast winds Monday through much of the next work week. Therefore, if the long term forecast holds, expect a seasonal weather pattern Friday and Saturday with locally induced showers and thunderstorms, followed by a wetter period on Sunday and early Monday associated with a wave passage. Fair weather conditions with warm to hot temperatures are expected next work week under a mid level ridge pattern and east southeast winds. AVIATION...SHRA/ISOLD TSRA across the local flying til at least 30/12z. This will result brief MVFR en route btw islands with VCSH or SHRA at TJSJ/TJNR/TNCM/TKPK. Aft 30/16z...SHRA/ISOLD TSRA psbl at and vcty TJMZ/TJBQ. Also, psbl MVFR at TJSJ due to isold streamer- like SHRA/TSRA from el Yunque area. Latest TJSJ sounding indicated ESE winds below FL050 at 10-22 kts. Sfc wnds lgt/vrb bcmg E-NE 10-15 kts at most terminals except for local sea breeze variations. MARINE...Moisture associated with a departing tropical wave will continue to result in periods of showers and thunderstorms today. Seas are expected to remain at or below 6 feet and winds at 15-20 knots, particularly across the Caribbean waters. Mariners are advice to exercise caution as winds and seas could be locally higher in the vicinity of thunderstorms. There is a moderate risk of rip currents across most of the local beaches. && .PRELIMINARY POINT TEMPS/POPS... SJU 87 79 86 79 / 40 20 40 40 STT 89 80 87 80 / 40 50 50 40 && .SJU WATCHES/WARNINGS/ADVISORIES... PR...None. VI...None. AM...None. && SHORT TERM...JA LONG TERM....99
Hazardous Weather Outlook...CORRECTED National Weather Service San Juan PR 540 AM AST Tue May 30 2017 AMZ710>745-PRZ001>013-310915- San Juan and Vicinity-Northeast-Southeast-Eastern Interior- North Central-Central Interior-Ponce and Vicinity-Nortwest- Western Interior-Mayaguez and Vicinity-Southwest-Culebra-Vieques- The nearshore and off shore Atlantic and Caribbean Coastal Waters- 540 AM AST Tue May 30 2017 This Hazardous Weather Outlook is for Puerto Rico and the adjacent Atlantic Coastal Waters. .Day One...Today and Tonight .Thunderstorms...There is a chance of thunderstorms with heavy rainfall and brief gusty winds today across portions east interior, San Juan Metro and west sections of Puerto Rico. .Flooding...Heavy rains may again lead to urban and small stream flooding and quick rises along major rivers. .Wind...Sustained winds up to 20 MPH with higher gusts are expected mainly across the Caribbean waters and the Atlantic Coastal waters. .Rip Currents...There is a a moderate risk of rip currents along the north facing beaches as well as some beaches across Culebra, Vieques and the south coast of Puerto Rico. .Days Two through Seven...Wednesday through Monday The chance of showers and thunderstorms and therefore urban and small stream flooding will continue through at least Wednesday as plenty of available moisture will interact with a lingering mid to upper level trough. A moderate risk of rip currents is expected during the next several days. .Spotter information statement... Widespread spotter activation is not anticipated, however individual spotter are encouraged to report High winds, Flooding and Rip Currents to the National Weather Service in San Juan. AMZ715-725-VIZ001-002-310915- St. Thomas St. John adjacent Islands-St Croix- Nearshore Atlantic and adjacent Caribbean Coastal Waters- 540 AM AST Tue May 30 2017 This Hazardous Weather Outlook is for the U.S. Virgin Islands and the ADJACENT Coastal Waters. .Day One...Today and Tonight .Thunderstorms...There is a chance of thunderstorms with periods of heavy rainfall and brief gusty winds today due to a lingering upper level trough and moisture trailing a tropical wave. .Flooding...Heavy rains could lead to minor flooding of urban areas as well as ponding of water on roadways and in poor drainage areas. .Wind...Sustained winds of up to 20 MPH are expected mainly across the offshore Caribbean waters. .Rip Currents...There is a moderate risk of rip currents across the west and south coast of Saint Croix. .Days Two through Seven...Wednesday through Monday A moderate risk of rip currents is expected during the next few days particularly Saint Croix. The chance of showers and thunderstorms and therefore minor flooding in urban areas will continue through at least Wednesday as plenty of available moisture will interact with a lingering mid to upper level trough. .Spotter information statement... Widespread spotter activation is not anticipated, however individual spotter are encouraged to report High winds, Flooding and Rip Currents to the National Weather Service in San Juan.
Special Weather Statement
National Weather Service San Juan PR
1239 PM AST TUE MAY 30 2017
PRZ007-009-301730-
Western Interior-Ponce and Vicinity-
1239 PM AST TUE MAY 30 2017
...A STRONG THUNDERSTORM WILL AFFECT LARES...GUAYANILLA...MARICAO...
PONCE...UTUADO...ADJUNTAS...NORTHEASTERN YAUCO AND PENUELAS
MUNICIPALITIES...
At 1238 PM AST, a strong thunderstorm was located over Adjuntas. the
storm is moving west at 5 mph.
Winds in excess of 30 mph, frequent lightning and pea size hail are
possible with this storm.
Torrential rainfall is also occurring with this storm, and may cause
localized flooding. Do not drive your vehicle through flooded
roadways.
Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.
LAT...LON 1808 6669 1809 6688 1823 6687 1823 6677
1822 6664
TIME...MOT...LOC 1638Z 240DEG 0KT 1817 6675
JJAComunicado Especial sobre las Condiciones del Tiempo Servicio Nacional de Meteorologia San Juan PR 1239 PM AST martes 30 de mayo de 2017 PRZ007-009-301730- Oeste interior-Ponce y vecindad- 1239 PM AST martes 30 de mayo de 2017 ...Una tronada fuerte afectara Lares, Guayanilla, Maricao, Ponce, Utuado, Adjuntas, noreste de Yauco y Penuelas... A las 12:38 PM AST,una tronada fuerte estaba localizada sobreAdjuntas. La tormenta se mueve hacia el oeste a 5 mph. Vientos en exceso de 30 mph, rayos frecuentes y granizo pequeno son posibles con esta actividad. Lluvias torrenciales tambien ocurren con esta tormenta, y podrian causar inundaciones localizadas. Nunca maneje su vehiculo por carreteras inundadas. Rayos frecuentes de nube a suelo estan ocurriendo con esta tormenta. Impactos de rayos pueden ocurrir a 10 millas de la tronada. Busque refugio seguro dentro de un edificio o vehiculo. JJA/RVT
The San Juan radar (TJUA), 97 km away, was scanning. The volume nearest the first event began at 16:56 UTC.
1 hail. Local standard time, as filed.
Social media picture indicated small hail...estimated to be penny size across Alto Sano...Anones and the town of Las Marias.
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, May 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: 699787.