The remnants of Hurricane Rosa brought heavy rain and flooding to parts of Mexico and Arizona USA from 01 October 2018.
Hurricane Rosa formed in the East Pacific and reached Category 4 status at its peak. Rosa then weakened and was downgraded to a tropical storm and later a tropical depression.
Mexico
In Mexico, heavy rainfall was reported in the northern states of Sonora and Baja California, where authorities declared an emergency in the municipalities of Ensenada and Mexicali.
Severe flooding was reported in San Felipe in Baja California after around 100 mm of rain fell on 01 October. Some areas of Sonora recorded between 70 and 100 mm of rain in 2 days to 01 October. One person reportedly died in flood waters from an overflowing river in Caborca, Sonora state.

USA
In the USA, Phoenix, Arizona, saw its wettest October day ever, with 2.36 inches / 59.94 mm of rain falling on 02 October, 2018. According to NWS Phoenix, Storm Rosa brought more rain in 3 days (3.38 inches / 85.85 mm, 30 September to 02 October) than Phoenix saw for the monsoon this year (2.56 inches / 65 mm, 15 June to 29 September).
NWS Phoenix said the heavy rain quickly overwhelmed urban drainage systems, causing numerous road closures. Flooded roads and accidents caused severe traffic problems, and several people had to be rescued from trapped vehicles. Many creeks and washes in the area were flowing at high levels.
Flooding was reported in around 40 locations in Pinal and Maricopa counties, which includes areas of Phoenix, Mesa, Scottsdale and Glendale. Some schools were closed on Tuesday, 02 October, due to the heavy rain and flooding.
Meanwhile further south, evacuations were advised out for communities near Menegers Lake on the Tohono O’odham Nation Reservation after NWS Tucson warned that a dam failure was imminent. Affected families were advised to move to the village of Ali Chuk for safety.
Flooded roads were reported in Tucson and also the city of Yuma on the U.S.-Mexico border.
California, Nevada and Utah
Flash flood watches were also in effect in for parts of California, Nevada and Utah. Utah Governor Gary Herbert declared a state of emergency due to potential flooding in the state.

Social Media
USA
Vekol Wash at I-8 about 10 miles west of Stanfield. Lots of waves. pic.twitter.com/zywtSOFWDe
— FCDMC Flood Info (@FCDFloodInfo) October 2, 2018
https://twitter.com/SchwartzTV/status/1047185382792515585
FLASH FLOOD down creek on west side of Gila Bend with some occasional small debris at 7:00 am! @FCDFloodInfo @ChandraLMiller @NWSPhoenix @breakingweather @accuweather #Rosa pic.twitter.com/e4UIxmsnL7
— Reed Timmer (@ReedTimmerAccu) October 2, 2018
Alright…did some official updating to this chart. Suffice to say it has been raining today! #azwx pic.twitter.com/FFHEr7dVGy
— NWS Phoenix (@NWSPhoenix) October 3, 2018
Here is a look at the 72 hour estimated precipitation in the Menegers Lake area of the T.O. nation where dam overtopping and/or failure is imminent. Widespread 3-5" in the area with isolated 5 to 7" upstream to the NW. #azwx pic.twitter.com/4gnUGhz90W
— NWS Tucson (@NWSTucson) October 3, 2018
Here’s a picture from 11:20am of Guadalupe FRS which is part of the golf course at the Arizona Grand Resort. This is an example of a flood control structure doing its job! #azwx pic.twitter.com/E8qDLQ0bW3
— FCDMC Flood Info (@FCDFloodInfo) October 2, 2018
Vekol Wash at I-8 about 10 miles west of Stanfield. Lots of waves. pic.twitter.com/zywtSOFWDe
— FCDMC Flood Info (@FCDFloodInfo) October 2, 2018
Mexico
AVISO DE PRECAUCIÓN-EVITA TRANSITAR por la CARRETERA COSTERA en su tramo HMO-SLRC, por efectos de la #TormentaTropicalRosa los arroyos están corriendo con fuerza por los vados, generando un situación de PELIGRO INMINENTE, como se observa en el VADO SAN IGNACIO de PUERTO LIBERTAD pic.twitter.com/ZavuN3Z9WT
— Protección Civil Sonora (@uepcsonora) October 1, 2018
MAPA DE PRECIPITACIONES POR TORMENTA TROPICAL ROSA
últimas 24 horas
(Acumulado días 30 de septiembre y 1 de octubre de 2018)@savilac1 @HILDEBRANDORAM8 @CHAVA1964 @sesasm @CEASonora @CLIMAS_UA @uepcsonora pic.twitter.com/unjOCKqyW1— Hidrologia_CEA (@HidrologiaC) October 1, 2018
MAPA DE PRECIPITACIONES POR ROSA (DEPRESIÓN TROPICAL)
últimas 24 horas
(Acumulado días 1 y 2 de octubre de 2018)@savilac1 @HILDEBRANDORAM8 @CHAVA1964 @sesasm @CEASonora @CLIMAS_UA @uepcsonora @NWSTucson pic.twitter.com/pGe7b2ffHi— Hidrologia_CEA (@HidrologiaC) October 2, 2018
DE ÚLTIMO MOMENTO: Cierran tramo carretero Caborca-Puerto Peñasco, debido a la crecida de arroyos a la altura de los ejidos San Pedro y El Coyote. Reportan suspensión de labores en minas y campo fotovoltaico. pic.twitter.com/tapLSnbaJp
— Noticieros Televisa Sonora (@NTelevisaSON) October 1, 2018
Flood Summary
Locations
B - San Felipe (Mexico)
C - Ensenada (Mexico)
D - Mexicali (Mexico)
E - Phoenix (United States)
F - Tucson (United States)
G - Tohono O'odham (United States)
H - Yuma (United States)
Magnitude
Phoenix, AZ, USA - October 2 to October 2, 2018
According to NWS
San Felipe, Baja California, Meixco - October 1 to October 1, 2018
According to local observers
Damages
Caborca, Sonora, Mexico - October 1 to October 1, 2018