A wet and unstable weather pattern was caused by a surface short-wave trough associated with the remnants of a frontal boundary. The Blended Total Precipitable Water (TPW) Percent of Normal indicated moisture levels exceeding 145% of the climatological normal from the Leeward Islands through the local area.
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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.
A wet and unstable weather pattern was caused by a surface short-wave trough associated with the remnants of a frontal boundary. The Blended Total Precipitable Water (TPW) Percent of Normal indicated moisture levels exceeding 145% of the climatological normal from the Leeward Islands through the local area. A Saharan Air Layer also helped promote more frequent lightning. Flooding, Landslides (due to high soil saturation) and even a Funnel Cloud were reported under this unsettled weather. By Tuesday (23rd), USGS river sensors still indicate that most rivers over the eastern half of Puerto Rico exceeded the 75th percentile, with half of them surpassing the 90th percentile or well above normal.
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 22, 4:14 AM AST, 30 minutes earlier.
Area Forecast Discussion National Weather Service San Juan PR 414 AM AST Mon Apr 22 2024 .SYNOPSIS... Numerous showers moved across eastern Puerto Rico and the Caribbean waters during the night hours, triggering some flooding. The wet pattern is expected to stretch into the end of the workweek, with some improvements Saturday onward. The risk for flooding will remain elevated. In the meantime, Saharan dust will arrive on Tuesday, with hazy skies in some areas. && .SHORT TERM...Today through Wednesday... It was a very active night, particularly for the eastern coastal area of Puerto Rico. While heavy showers that affected St. Croix subsided, shower activity shifted to the eastern portions of Puerto Rico. Several rounds of showers resulted in excessive runoff high in the mountains of Naguabo, causing water levels at Rio Blanco to rise quickly. A Flood Warning was issued, and shortly afterward, the USGS river sensor indicated Moderate Flood Stage later in the night. Additionally, a convergence line developed, affecting northeastern municipalities. Flood Advisories were issued for municipalities from Luquillo westward through Bayamon. In these areas, several rivers experienced rapid rises in water levels, with at least four rivers reaching Action stage according to USGS river sensors. The convergence line persisted, exacerbating the situation across Loiza, northern Canovanas, and northwestern Rio Grande. Therefore, a Flash Flood Warning was also issued. Meanwhile, in the Caribbean, a line of strong thunderstorms developed and is now approaching southeastern municipalities. Expect shower and thunderstorm activity across southeastern municipalities during the early morning hours." This wet and unstable weather pattern is caused by a surface short- wave trough associated with the remnants of a frontal boundary. The Blended Total Precipitable Water (TPW) Percent of Normal indicates moisture levels exceeding 145% of the climatological normal from the Leeward Islands through the local area. Therefore, moisture advection will persist today, promoting periods of moderate to heavy showers, particularly over windward sections of Puerto Rico and USVI during the morning hours and across interior and northwestern Puerto Rico as moisture availability combines with diurnal heating. No relief is expected for the rest of the short-term forecast as some troughing aloft will maintain instability at upper levels. The day with the least showers could be anticipated by Tuesday as an area of suspended Saharan dust fills the area, which could somewhat inhibit shower activity. However, in some areas, this won't be enough to suppress showers; in fact, it could even promote frequent lightning activity due to the presence of Saharan dust. This won't last long, as high moisture content and favorable dynamics will persist, maintaining elevated flooding risk across the islands. Soils are saturated, which will promote excessive runoff easily with potential landslides, while river streamflows are elevated with the potential of overflowing with any strong shower activity. Therefore, continue to monitor this forecast and pay attention to any advisories/warnings that we could issue. .LONG TERM...Thursday through Monday... The wet pattern will not give way by the end of the workweek. Moisture associated with an old frontal boundary will reach the islands, triggering another round of showers and isolated thunderstorms. At the same time, a deep layered trough moving east of the United States will cause the winds to shift from the south at the mid and upper levels, while winds will remain from the east steered by a surface high pressure over the central Atlantic. The southerly flow will bring a moist column into the region, while a short wave trough (the type that increase instability aloft) will approach the region. These factors should combine to generate more rainfall activity. Since it has been raining for a couple of days now, rivers will remain high and soils saturated, hence the risk for urban and small stream flooding will be elevated. A change in the pattern will begin on Saturday. A broad surface high pressure exiting the eastern seaboard will push a drier air mass into the region...finally. Winds will become more northerly, so temperatures will cool down a little too. The probability of precipitation decreases Saturday onward, although with some showers due to local effects still possible. This drier pattern should stretch into early next week. && .AVIATION... (06Z TAFs) Although fairly active night, mostly VFR conditions can be expected to prevail across all terminals through the forecast period. Brief MVFR/IFR due to reduced VIS and CIG are possible at TJSJ thru 22/14z due to SHRA, and at TJBQ/TJSJ, aft 22/17z along with mtn obscuration. ENE winds at 10-15 kt mostly aft 22/14z. with higher gusts near showers. && .MARINE... A surface high pressure north of the area will continue to yield a moderate northeasterly wind flow through at least Monday. Winds are expected to become from the east southeast on Tuesday as a surface trough prevails across the northeast Caribbean. Showers and isolated thunderstorms will continue to affect the local waters today. && .BEACH FORECAST... Breaking waves around 4 feet will maintain the risk of rip currents moderate for the north facing beaches of Puerto Rico and for some beaches in Culebra. Elsewhere, the risk of rip currents will remain low. && .SJU WATCHES/WARNINGS/ADVISORIES... PR...None. VI...None. AM...None. && SHORT TERM...CVB LONG TERM....ERG
Hazardous Weather Outlook National Weather Service San Juan PR 428 AM AST Mon Apr 22 2024 AMZ711>745-PRZ001>013-230830- San Juan and Vicinity-Northeast-Southeast-Eastern Interior- North Central-Central Interior-Ponce and Vicinity-Northwest- Western Interior-Mayaguez and Vicinity-Southwest-Culebra-Vieques- The nearshore and off shore Atlantic and Caribbean Coastal Waters- 428 AM AST Mon Apr 22 2024 This Hazardous Weather Outlook is for portions of Puerto Rico. .DAY ONE...Today and Tonight .Lightning...Isolated to scattered thunderstorms possible across the area. Be aware of thunderstorms in your area and be prepared to take shelter. .Excessive Rainfall...Flooding of urban areas, roads, small streams, and washes. Isolated flash floods possible. .Rip Currents...Life-threatening rip currents are possible in the surf zone particularly along northern and eastern Puerto Rico and Culebra. .DAYS TWO THROUGH SEVEN...Tuesday through Sunday The threat of urban and small stream flooding and mudslides will persist through much of the week. Heat indices above 102 degrees expected from Tuesday through Thursday across urban and coastal areas. The risk of rip currents will remain moderate for the most part. .SPOTTER INFORMATION STATEMENT... Spotter activation is encouraged. Please relay any information about flooding, winds, waves, and rip currents to the National Weather Service in San Juan. AMZ716-726-VIZ001-002-230830- St. Thomas St. John adjacent Islands-St Croix- Nearshore Atlantic and adjacent Caribbean Coastal Waters- 428 AM AST Mon Apr 22 2024 This Hazardous Weather Outlook is for portions of USVI. .DAY ONE...Today and Tonight .Lightning...Isolated to scattered thunderstorms possible over the waters, with some moving over the local islands. Be aware of thunderstorms in your area and be prepared to take shelter. .Excessive Rainfall...Ponding of water in roads and poorly drained areas. Urban and small streams flooding is possible. .DAYS TWO THROUGH SEVEN...Tuesday through Sunday The threat of urban and small stream flooding and mudslides will persist through much of the week. Heat indices above 102 degrees expected from Tuesday through Wednesday across urban and coastal areas. The risk of rip currents will remain moderate. .SPOTTER INFORMATION STATEMENT... Spotter activation is encouraged. Please relay any information about flooding, winds, waves, and rip currents to the National Weather Service in San Juan.
Special Weather Statement
National Weather Service San Juan PR
431 AM AST Mon Apr 22 2024
PRZ002>004-006-220930-
Central Interior PR-Northeast PR-Eastern Interior PR-Southeast PR-
431 AM AST Mon Apr 22 2024
...STRONG THUNDERSTORMS WILL IMPACT THE MUNICIPALITIES OF
SOUTHEASTERN PUERTO RICO FROM HUMACAO TO SALINAS THROUGH 530 AM
AST...
At 430 AM AST, Doppler radar was tracking strong thunderstorms along
a line extending from Humacao to Salinas. Movement was north at 10
to 15 mph.
HAZARD...Wind gusts up to 40 mph.
SOURCE...Radar indicated.
IMPACT...Gusty winds could knock down tree limbs and blow around
unsecured objects.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
Torrential rainfall is also occurring with these storms and may lead
to localized flooding. Do not drive your vehicle through flooded
roadways.
&&
LAT...LON 1810 6637 1822 6611 1822 6594 1825 6580
1816 6573 1815 6577 1801 6584 1797 6591
1798 6602 1795 6605 1796 6609 1794 6617
1796 6621 1794 6624 1794 6629
TIME...MOT...LOC 0830Z 170DEG 14KT 1815 6568 1803 6590 1798 6612
MAX HAIL SIZE...0.00 IN
MAX WIND GUST...40 MPH
ERGThe San Juan radar (TJUA), 41 km away, was scanning. The volume nearest the first event began at 08:40 UTC.
13 flood, 3 debris flow, 1 funnel cloud. Local standard time, as filed.
A flooded street was reported in Urb Santiago, Loiza, near Rio Grande de Loiza. It seemed that flood waters did not enter residencies in the area.
Flooding was reported at the intersection between roads PR-3 and PR-54. One Lane was impassable.
Minor Flooding was reported at Esteban B. Cruz St. in Guayama. The road was still passable.
Flooding was reported on Geranio St. in Comunidad Miramar.
Street 5 and 9 in Villa Real were affected by Flooding.
Observer reported a Flooded Street in Blvd. Buenos Aires near YMCA San Juan.
Public in Social Media and Emergency Managers reported a Funnel Cloud between Santa Rosa and Paseo Lineal in Bayamon.
Emergency Management reported an impassable road, Venecia, St., near GFR Media.
An impassable road in PR-5 under the bridge was reported, near the Goya building.
Road 871, near the Bayamon Military Academy was reported as flooded. This is near the Bayamon and Toa Baja border.
Magnolia Gardens St. 2, near Hondo River, was reported impassable.
A 911 reporter informed us that there was a landslide near PR-2 just behind the Taco Bell in the municipality of Toa Baja.
An emergency manager from Moca called to inform us that there was a landslide in PR-495, km 3.5 (Cerro Gordo community). They informed that the landslide got close to a residence but did not reach it.
Emergency management from San Sebastian called to inform us that PR-125 intersection |PR-446 is flooded because the river Guatemala is out of its bank.
The emergency manager from San Sebastian called to inform us that PR-111 intersection |with PR-446, near the Walgreens is flooded.
A 911 reporter informed us that a residency in 123 St. in the municipality of Utuado near the McDonalds restaurant, was flooded.
An emergency manager from A asco called to inform us that there was a landslide in Anasco in carretera 09 km 1.9.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Puerto Rico in 2024Every state in 2024This day in weather historyWarnings in Puerto Rico, April 2024
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: 1176396, 1176397, 1176398, 1176399, 1176400, 1176401, 1176381, 1176391, 1176392, 1176394, 1176395, 1176374, 1176375, 1176388, 1176390, 1176389, 1176376.