The combination of a frontal boundary and above normal moisture resulted in heavy shower activity across Hatillo during the afternoon of April 6th and across the municipalities of Loiza and Canovanas during the early morning hours of April 7th.
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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.
The combination of a frontal boundary and above normal moisture resulted in heavy shower activity across Hatillo during the afternoon of April 6th and across the municipalities of Loiza and Canovanas during the early morning hours of April 7th.
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 6, 8:04 PM AST, 36 minutes earlier.
Area Forecast Discussion
National Weather Service San Juan PR
804 PM AST Tue Apr 6 2021
.UPDATE...Significant adjustments were made to the weather grids
to incorporate the most recent model guidance and both radar and
satellite observations. The main adjustment was the removal of
thunderstorms and lowering POPs across the local Atlantic waters.
Both GFS and ECMWF model guidance have been too aggressive in
suggesting a high potential for shower and thunderstorms activity
over these waters, but so far only isolated to scattered showers
have been detected. This discrepancy may be associated with a
continuous layer of mid-to-upper clouds that have affected the
region; layer that is expected to hold through at least Wednesday.
In contrast, High Resolution models have suggested less shower
activity across the local Atlantic waters, with highest activity
focused over the coastal areas and adjacent waters of northern
Puerto Rico. Based on recent observations and current shower
weather pattern, the current forecast follows the latter.
Overall, the forecast calls for isolated to scattered shower
activity across the local Atlantic waters, moving into portions of
eastern and northern Puerto Rico through the morning hours.
Thereafter, another active afternoon is anticipated. This will
result from the combination of local effect, diurnal heating and
the presence of normal- to- above normal available moisture
content, with model guidance suggesting a gradual increase of up
to around 1.90 by 08/00Z. Winds will somewhat increase, but the
steering flow is expected to remain at 5-15 knots. This will
support relatively slow-moving showers and possible isolated
thunderstorms that could result in localized urban and small
stream flooding. The afternoon convective activity is expected to
linger through the evening hours, favoring portions of the
interior and western Puerto Rico. Nevertheless, shower development
downwind from El Yunque and the local islands cannot be ruled
out. Overnight lows are expected to drop into the lower to mid
70s, while daytime highs will reach the mid to upper 80s across
coastal areas. Winds will remain light to moderate at 5-15 mph
with higher gusts near the shower activity and sea breeze
variations.
&&
.AVIATION...Mainly VFR conditions expected. However, SHRA in and
around TJSJ, TJPS and TJBQ may cause brief MVFR conditions with
SCT-BKN at FL020-040 and reduced visibility. VCSH expected at
TJSJ between 07/04-19Z; TJPS through 07/02z and after 07/19Z; TJBQ
through 07/14Z and between 07/17-23Z; and for TIST/TISX between
07/13-20Z. Winds will be light and variable through 07/13Z,
turning from the ENE at 10-15 knots with sea breeze variations
thereafter.
&&
.MARINE...Hazardous marine conditions will continue as a decaying
northerly swell invades the Atlantic waters, maintaining seas up
to 7 feet through late tonight. As a result, Small Craft
Advisories will remain in effect for the offshore Atlantic
waters. Thereafter, as well as elsewhere across the local waters,
tranquil to choppy marine conditions are expected, with small
craft exercising caution criteria through Wednesday. Winds will
remain light to moderate at 5-15 knots from the east- northeast.
A High Risk of Rip Currents remains in effect for north-facing
beaches of Puerto Rico and Culebra through Wednesday afternoon.
Surf zone coastal conditions will improve by Wednesday night, with
moderate risk of rip currents for most north-facing beaches of
Puerto Rico, Vieques, Culebra and all the US Virgin Islands.
&&
.PREV DISCUSSION... /issued 509 PM AST Tue Apr 6 2021/
SYNOPSIS...Frontal boundary will continue across the region
through late Friday night. Drier air moves in briefly during the
weekend. Fading northerly swell and moderate to locally fresh
trades over the offshore Atlantic waters will continue to cause
hazardous seas up to 7 feet tonight, and a high risk of rip
currents along the northern beaches of Puerto Rico through
Wednesday.
SHORT TERM...Today through Thursday...
Afternoon showers will continue to affect portions of the interior
and western Puerto Rico through the early evening hours. There is
a Flood Advisory in effect until 6 PM for Lares and San Sebastian.
Elsewhere, variably cloudy skies will prevail as the local area
remains under the influence of an upper level trough over the
northwestern Atlantic and an upper level ridge southeast of the
Windward Islands, this is promoting a westerly flow aloft and high
cirrus clouds to stream from the Caribbean Sea. At lower levels, a
surface front continues to sink down over the local Atlantic
waters, and a northeast steering wind flow will bring passing
showers through the night across the northern sections of Puerto
Rico.
For Wednesday and Thursday, cloudy skies and scattered showers
are expected to prevail across the islands as the frontal
boundary moves from the Atlantic waters into the southern waters
of the islands by the end of the short term period into Friday.
Rainfall accumulations should be mostly light to moderate in
general across all the islands, however, higher amounts up to 2
inches are possible each afternoon over the western interior and
southwestern sections of Puerto Rico.
LONG TERM...Friday through Wednesday...
From prev discussion.../issued 509 AM AST Tue Apr 6 2021/
The frontal boundary will linger over the area on Friday.
Therefore, another round of afternoon convection is expected,
mainly across the interior and southern portions of Puerto Rico as
the low-level flow will remain from the northeast. Once again,
given the light steering flow expected, convection that develops
will be slow-moving leading to the potential for urban and small
stream flooding.
Model guidance has come into better agreement on the weather
pattern for the upcoming weekend. The GFS model, which in
previous runs lingered the frontal boundary over the area during
the weekend, has now corrected towards the ECMWF model solution
and now pushes the boundary south of the area with a drier air
mass now expected. Therefore, improving weather conditions are
now expected during the upcoming weekend with more limited shower
activity.
Even though model guidance has come into better agreement on the
overall pattern for the upcoming weekend, they disagree once
again on the pattern during the early portion of next week. The
GFS model wants to bring the remnants of the frontal boundary back
towards the area Monday and Tuesday of next week, which would
increase the moisture and thus shower activity. The ECMWF model,
on the other hand, maintains the boundary well south of the area
with a relatively drier than normal air mass prevailing and thus
fair weather conditions. Therefore, there is high uncertainty of
the weather conditions for early next week.
AVIATION...Mainly VFR conditions are expected across all
terminals. However, SHRA over central/western PR may cause tempo
MVFR cigs at TJBQ thru 23z. Low level winds ENE at 10-15 kts.
MARINE...Northerly swell will continue to gradually subside
tonight. Choppy seas up to 7 feet are expected across the offshore
Atlantic waters, where winds are between 15-20 knots. Elsewhere,
seas will continue at less than 6 feet and northeast trades up to
15 knots will prevail through the end of the workweek. There is a
high risk of rip currents along the Atlantic beaches of PR,
Culebra and St. Thomas.
&&
.PRELIMINARY POINT TEMPS/POPS...
SJU 73 83 74 83 / 30 30 50 30
STT 73 85 72 85 / 20 30 30 40
&&
.SJU WATCHES/WARNINGS/ADVISORIES...
PR...High Rip Current Risk until 6 AM AST Wednesday for Culebra-
Northeast-San Juan and Vicinity-Southeast.
High Rip Current Risk through Wednesday afternoon for North
Central-Northwest.
VI...None.
AM...Small Craft Advisory until 2 AM AST Wednesday for Atlantic
Waters of Puerto Rico and USVI from 10 NM to 19.5N.
&&
SHORT TERM...ICP
LONG TERM....DS
PUBLIC DESK...ERGPerspectivas sobre Condiciones Peligrosas del Tiempo Servicio Nacional de Meteorologia en San Juan PR 404 AM AST martes 6 de abril de 2021 AMZ710>745-PRZ001>013-070815- San Juan y Vecindad-Noreste-Sureste-Este Interior-Norte Central- Interior Central-Ponce y Vecindad-Noroeste-Oeste Interior-Mayaguez y Vecindad-Suroeste-Culebra-Vieques-Las aguas costeras cercanas y lejanas a la costa del Atlantico y Caribe- 404 AM AST martes 6 de abril de 2021 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 una probabilidad de tronadas con lluvia fuerte y vientos en rafagas breves sobre el interior central y algunas de las pendientes del sur de Puerto Rico durante la tarde y temprano esta noche. .Inundaciones...Lluvia fuerte pudiera resultar en inundaciones urbanas y de riachuelos al igual que acumulacion de agua en carreteras y en areas de pobre drenaje. .Oleaje...Se espera oleaje picado a peligroso entre 6 y 8 pies a traves de las aguas del Atlantico y el pasaje de Mona. .Corrientes Marinas...Existe un riesgo alto de corrientes marinas para las playas del noroeste a noreste de Puerto Rico y Culebra. Existe un riesgo moderado de corrientes marinas para el resto de las playas de Culebra, algunas playas del oeste y este de Puerto Rico al igual que las playas en Vieques. Una Advertencia de Resacas Fuertes esta en efecto para las playas del Atlantico de Puerto Rico. .Dias dos hasta el siete...miercoles a lunes Aguaceros y tronadas aisladas por la tarde son posible sobre sectores de Puerto Rico durante los proximos dias. Esto pudiera resultar en inundaciones urbanas y de riachuelos y acumulacion de agua en carreteras. .Comunicado sobre informacion reportada por observadores... No se espera activacion amplia de observadores. Favor de reportar cualquier informacion sobre inundaciones, vientos, oleaje, y corrientes marinas al Servicio Nacional de Meteorologia en San Juan mientras siguen las indicaciones de las autoridades locales y estatales. AMZ715-725-VIZ001-002-070815- San Tomas, San John e Islas Adyacentes- Santa Cruz-Aguas cercanas del Atlantico y aguas costeras adyacentes del Caribe- 404 AM AST martes 6 de abril de 2021 Esta perspectiva sobre las condiciones peligrosas del tiempo es para Islas Virgenes Estadounidenses y las aguas costeras adyacentes. .Dia Uno...Hoy y esta noche .Oleaje...Se espera oleaje picado a peligroso entre 6 y 8 pies a traves de las aguas del Atlantico y el Pasaje de Anegada. .Corrientes Marinas...Existe un riesgo alto de corrientes marinas para las playas del noroeste de San Thomas. Existe un riesgo moderado de corrientes marinas para el resto de las playas de las Islas Virgenes Americanes. .Dias dos hasta el siete...miercoles a lunes Aguaceros en la tarde seran posibles mayormente en el lado oeste y justo al oeste de las islas sobre las aguas costeras durante los proximos dias. Algunos aguaceros breves de moderados a localmente fuertes pudieran resultar en acumulacion menor de agua en carreteras y en areas de pobre drenaje .Comunicado sobre informacion reportada por observadores... No se espera activacion amplia de observadores. Sin embargo, favor de reportar cualquier informacion sobre vientos, oleaje y corrientes marinas al Servicio Nacional de Meteorologia en San Juan mientras siguen las indicaciones de las autoridades locales y estatales.
The San Juan radar (TJUA), 89 km away, was scanning. The volume nearest the first event began at 00:40 UTC.
2 flash flood, 1 flood, 1 heavy rain. Local standard time, as filed.
Emergency managers reported various sections of Road PR-130 impassable due to flooding.
Emergency managers reported several houses flooded along Road 45, Road 30 and Road 29 in Villa Loiza.
Filtration problem reported in a house located along Street 17 in Barrio San Isidro.
Emergency managers reported various houses affected by flooding along Barrio La Central and Sector Villa Hugo.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Puerto Rico in 2021Every state in 2021This day in weather historyWarnings in Puerto Rico, April 2021
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: 956007, 956004, 956006, 956169.