Atmospheric River Bringing Heavy Rain to Southern California and Heavy Snow to the Sierra Nevadas

A strong atmospheric river will continue heavy rain over southern California through Friday. The heaviest rainfall is ongoing today in the Los Angeles Basin. Flash and urban flooding is possible. A prolonged heavy snowfall has begun over the Sierra Nevada Mountains and will continue through Friday. Travel will become increasingly difficult over the passes due to snow and strong winds. Read More >

Overview

On July 14, 2010 favorable atmospheric conditions led to severe thunderstorms that produced hail, strong winds, and tornadoes in Minnesota and Wisconsin. There were two tornadoes reported near Northfield, Minnesota that caused damage to trees, crops, farm sheds, a camper, and a few houses. Low pressure, high dewpoints, and high wind shear values allowed the formation of these storms and tornadoes.

EF-1 tornado near County Road 47 northeast of Northfield

Tornado
Photos
Radar
Storm Reports
Environment

Tornadoes:

Tornado #1- I-35/N of Hwy 19
Dakota and Rice Counties

Date	14 July 2010
Report Time (Local)	2:20 PM CDT
EF Rating	EF-0
Est. Peak Winds	85 mph
Path Length	3.4 miles
Max Width	75 yards
Injuries/Deaths	None
Summary: This tornado touched down about ¾ of a mile north of Highway 19 on Interstate 35. A two ton truck was overturned on Interstate 35, causing damage to the median. The tornado then lifted one mile east-northeast, and touched down again around the intersection of Jamaica Avenue and 320th St SW. The tornado then tracked east-northeast for about 2 ½ miles across farm fields (around 4.2 miles northwest of Northfield). A farm shed was damaged ¼ mile east of the Jamaica Avenue and 320th St SW intersection. Overall, the tornado caused mainly tree and corn field damage.

Track Map

Tornado #2- NE of Northfield
Dakota County

Date	14 July 2010
Report Time (Local)	2:30 PM CDT
EF Rating	EF-1
Est. Peak Winds	95 mph
Path Length	1.6 miles
Max Width	100 yards
Injuries/Deaths	None
Summary: This tornado touched down at a farm house 3.9 miles northeast of Northfield, near the junction of 313th St and County Road 47. There, a metal shed was blown over a home for a distance of about 100 yards. There was some damage to the home, but most of the damage was associated with uprooted trees and debris from the metal shed. The tornado lifted ¼ mile east of the home and caused a semi-truck to be overturned on County Road 47. The tornado then touched down ¾ mile east of County Road 47 in a corn field. From there, it tracked ½ mile east before lifting at the intersection of County Road 59 and Cannon River Road. The tornado caused damage to a farm house along this path, and blew a storage shed 200 yards into their corn field. The tornado also destroyed a camper at the farm house.

Track Map

The Enhanced Fujita (EF) Scale classifies tornadoes into the following categories:

EF0 Weak 65-85 mph	EF1 Moderate 86-110 mph	EF2 Significant 111-135 mph	EF3 Severe 136-165 mph	EF4 Extreme 166-200 mph	EF5 Catastrophic 200+ mph

Photos:


Damage to camper in Dakota County	Tree damage at Heritage Links Golf Course in Scott County	Funnel south of intersection of Hwy 3 and 300th St W near Northfield	Tree damage in Dakota County

Radar:


	Reflectivity (left) and storm relative velocity (right) at 2:32 PM	Afternoon reflectivity loop of storms

Storm Reports

Environment

A deep low pressure system developed east-northeast across Minnesota in the afternoon and evening of July 14, 2010. This transported incredibly moist low-level air northward, with dewpoints as high as 79°F at the MSP International Airport, and the low 80s at other southern Minnesota airports. This warm and moist air created high values of instability, as well as low cloud bases to allow thunderstorm rotation closer to the ground. Strong southerly winds also created convergence for thunderstorm development. There were high values of wind shear as atmospheric winds increased rapidly in speed with height by the afternoon.


Surface dewpoint and mean sea-level pressure loop	Water vapor imagery showing favored area for thunderstorms	Surface analysis showing unstable air behind warm front


12Z 850 mb analysis showing southerly flow into MN	12Z 500 mb analysis	12Z 250 mb analysis

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Atmospheric River Bringing Heavy Rain to Southern California and Heavy Snow to the Sierra Nevadas

Summary of July 14, 2010 Northfield Tornadoes