Radar Image Showing "Hook Echo"
Courtesy: GRLevelX
On Sunday, May 22, there were 56 reports of tornadoes extending from northeastern Oklahoma, up the Mississippi Valley to northern Wisconsin. The strongest hit was Joplin, Missouri where 158 people lost their lives and thousands are displaced from their homes. In Minnesota, there were reports in Fillmore, Hennepin, Anoka, and Washington Counties of tornadoes and property damage. Here is a radar image, taken at 2:19 CST on May 22 that shows the pronounced hook echo southwest of Columbia Heights moving to the northwest at 35 miles per hour.
The National Weather Service ranked the strength of the tornado in Minneapolis as an EF1 tornado with winds between 86 to 110 miles per hour. The majority of the damage came from mature trees being uprooted and falling on houses and vehicles. Tragically, one man lost his life when a tree fell on his vehicle in North Minneapolis.
The fuel for these storms came from a strong low pressure system that developed on the lee side of the Rocky Mountains. The counter clockwise rotation associated with low pressure systems allowed the mixing of warm, moist air from the Gulf of Mexico and cool, dry air from the north. As the cold air surged eastward, it lifted the warmer air causing convection and multiple super-cells to develop, spawning the tornadoes
The storms in the Twin Cities took on a familiar path for residents. On May 10, 2011 an EF1 tornado moved through St. Michael, Minnesota tearing the roof off a house and a severe thunderstorm-- close to developing a tornado-- moved northeast through the downtown area causing golf ball sized hail falling on players and fans at the Twins vs. Tigers game. This severe weather event was also caused by a low pressure system that developed on the lee side of the Rocky Mountains and took a similar track across Minnesota, thus leading to the similar storm paths.
Besides the tornado in Minneapolis, there were severe weather reports in other Minnesota locales. Tornadoes were reported in Anoka, Washington, Chisago, Fillmore and Houston counties.
-climatology intern Anna Louks assisted with this report
Public Information Statements from the National Weather Service
PUBLIC INFORMATION STATEMENT NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN 752 PM CDT MON MAY 23 2011 ...SURVEY TEAM ASSESSMENT ON THE NORTHERN TWIN CITIES METRO TORNADO OF SUNDAY AFTERNOON MAY 22ND... THE TORNADO THAT HIT NORTH MINNEAPOLIS AND OTHER AREAS WILL BE RATED EITHER AS A STRONG EF1 OR AN EF2. THERE REMAIN SOME UNCERTAINTIES IN RATING THE TORNADO THAT HIT NORTH MINNEAPOLIS...ST. LOUIS PARK...GOLDEN VALLEY...FRIDLEY AND MOUNDS VIEW AND BLAINE SINCE SOME OF THE FIELD INFORMATION GATHERED STILL NEEDS TO BE PROCESSED. HOWEVER...IT IS SAFE TO SAY THAT IT WILL BE RATED AS EITHER A STRONG EF1 OR POSSIBLY AN EF2. THE TORNADO WAS ABOUT 1/2 MILE WIDE AT ITS WIDEST POINT. IT WAS ON THE GROUND FOR 6 AND ONE QUARTER MILES IN HENNEPIN COUNTY...PLUS AN ADDITIONAL 8 MILES ACROSS ANOKA AND RAMSEY COUNTIES AS THE TORNADO WENT THROUGH PARTS OF FRIDLEY...MOUNDS VIEW...AND BLAINE. THE INITIAL TOUCHDOWN IN ST. LOUIS PARK WAS 3/4 OF A MILE SOUTH-SOUTHWEST OF THE INTERSECTION OF INTERSTATE 394 AND HIGHWAY 100 WHERE TWO BUSINESSES SUSTAINED ROOF DAMAGE. THE TORNADO MOVED NORTHEAST...CROSSING HIGHWAY 100 WHERE IT HIT THE FIRST RESIDENCES ALONG CEDAR LAKE ROAD. IT THEN ENTERED THE SOUTHEAST PORTION OF GOLDEN VALLEY...CROSSED INTERSTATE 394 AND HEADED FOR THEODORE WIRTH PARK. DURING THIS TIME IT TOOK A BIT OF A NORTHWARD TURN AND BEGAN MOVING TO THE NORTH-NORTHEAST. THE TORNADO MOVED ACROSS WIRTH LAKE AND ENTERED THE CITY OF MINNEAPOLIS BETWEEN GLENWOOD AVENUE AND 16TH AVENUE. UP TO THIS POINT...DAMAGE WAS EF0 WITH THE VAST MAJORITY OF THE DAMGE BEING DOWNED TREES ATOP OF BUILDING AND VEHICLES. AS THE TORNADO ENTERED MINNEAPOLIS, IT STRENGTHENED TO EF1. THE TORNADO HEADED FOR THE HARD-HIT AREA AROUND LOWRY AVENUE AND LOGAN AVENUE...THEN TO 42ND AVENUE AND LYNDALE AVENUE. IT CROSSED THE MISSISSIPPI RIVER JUST NORTH OF THE CAMDEN BRIDGE...AND BEGAN CAUSING DAMAGE IN ANOKA COUNTY. IT MOVED ACROSS THE MINNEAPOLIS WATER INTAKE FACILITY. AT THE WATER TREATMENT FACILITY...A FREE STANDING STORAGE GARAGE WAS COMPLETELY DESTROYED...WITH NUMEROUS COTTONWOOD TREES ON THE GROUNDS UPROOTED OR HAVING LARGE LIMBS SNAPPED OFF. FROM THE WATER FACILITY...THE TORNADO TRACKED NORTHEAST TO A LARGE INDUSTRIAL FACILITY...WHERE A LARGE METAL BUILDING ON THE GROUNDS HAD PARTS OF TWO WALLS RIPPED OFF AND A LARGE SECTION OF THE ROOF BLOWN OFF. IT THEN MOVED INTO THE TRAIN YARD WHERE SEVERAL TRAIN CARS WERE TIPPED OVER. ON THE OTHERSIDE OF THE TRAIN YARD...MORE INDUSTRIAL FACILITIES AND WAREHOUSES SUSTAINED DAMAGE ALONG MIAMI STREET...THE WORST BEING A WAREHOUSE THAT LOST PART OF ITS ROOFING. THE STRONGER EF1 OR EF2 DAMAGE OCCURRED IN THE AREA BETWEEN PENN AND BROADWAY AND THE AREA NORTHEAST OF THE CAMDEN BRIDGE...IN THE VICINITY OF THE WATER PLANT AND TRAIN YARD FACILITY. THIS IS WHERE ADDITIONAL INFORMATION NEEDS TO BE PROCESSED BEFORE A FINAL RATING CAN BE ASSIGNED. THE TORNADO THEN MOVED ACROSS RESIDENTIAL SECTIONS OF FRIDLEY...WHERE EXTENSIVE TREE DAMAGE WAS DONE NORTHEAST TO THE AREA OF THE MIDDLE SCHOOL. THE TORNADO THEN WEAKENED AS IT CONTINUED NORTHEAST ACROSS THE EAST SIDE OF OF FRIDLEY TO SPRING LAKE...WHERE IT MOVED INTO THE NORTHWEST SIDE OF MOUNDS VIEW. SPORADIC TREE DAMAGE OCCCURRED DURING THIS TIME FRAME. THE LAST SIGNS OF DAMAGE WERE SEEN ON THE SOUTH SIDE OF THE BLAINE-ANOKA COUNTY AIRPORT...WHER A FEW HANGARS RECIEVED SOME MINOR EXTERIOR DAMAGE. THE TORNADO WAS ON THE GROUND FOR ABOUT 8 MILES FROM FRIDLEY TO BLAINE. PUBLIC INFORMATION STATEMENT NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN 828 PM CDT MON MAY 23 2011 ...SURVEY TEAM ASSESSMENT OF THE FOREST LAKE TORNADO OF SUNDAY AFTERNOON MAY 22ND... THE TORNADO THAT OCCURRED IN FOREST LAKE WAS A HIGH END EF-0 WITH MAXIMUM SUSTAINED WINDS BETWEEN 80 AND 85 MPH. THERE WAS INTERMITTENT DAMAGE ALONG A PATH LENGTH OF APPROXIMATELY TWO AND SIX TENTHS OF A MILE. THE MAXIMUM PATH WIDTH OF 75 YARDS. THE FIRST SIGN OF TREE DAMAGE OCCURRED ALONG 200TH STREET NEAR IMPERIAL AVENUE. THE TORNADO CONTINUED NORTH TO JUST WEST OF THE INTERSECTION OF 210TH STREET AND INGERSOLL AVENUE. THE WORST DAMAGE OCCURRED IN THIS AREA...WHERE A METAL POLE BARN HAD ITS ROOF LIFTED OFF AND DOOR BLOWN OUT. IN ADDITION...A NEIGHBORING PROPERTY HAD SEVERAL TREES UPROOTED OR SNAPPED OFF. THE TORNADO CONTINUED NORTH-NORTHEAST TO 215TH STREET...WHERE A LARGE OAK TREE FELL ON A HOUSE. AT THIS POINT...THE TORNADO CROSSED THE EAST SIDE OF THE BODY OF WATER KNOWN AS FOREST LAKE. AFTER CROSSING THE LAKE...THE TORNADO LIFTED UP NEAR SHADYLAND POINT...WHERE A FEW TREES WERE DOWN ALONG JASON AVENUE.