Picture it, you're sitting on a beach along the Gulf of Mexico coast. It's warm and sunny, but there are a few clouds over the ocean. You hear a few beachgoers exclaim "Look!" and you look up. About a mile off the shoreline is a skinny rope-like waterspout. You watch in awe as it twirls over the ocean, harming nothing but a few unfortunate fish in its path. Waterspouts are relatively common along the Gulf Coast. You watch it for around 10 minutes as it dissipates before your eyes.
Now imagine that same scenario, except you are not at the beach, but in downtown Omaha. Someone tells you to look to your south, and you see it. A thin rope tornado churning somewhere southeast of downtown. A few minutes later you hear the tornado sirens being sounded in Council Bluffs. You watch it for a few minutes before it dissipates 10 minutes after it formed. What did you just witness? This scenario occurred on August 4, 2016, when a rare waterspout formed from a thunderstorm over Lake Manawa. So, how did this happen? How rare is it? Find out in this installment of This Week in Weather History.
WHAT IS A WATERSPOUT/LANDSPOUT?
Most of us at least know the basic ingredients for tornado formation. Warm air from the Gulf of Mexico, cold air from Canada, wind shear changing with speed and direction with height, and a trigger for storms. These are how traditional tornadoes form, but waterspouts are somewhat different. There are two types of waterspouts, there are tornadic waterspouts, which are just tornadoes over water. Then there are the more common fair weather waterspouts, which occurred over Lake Manawa that day.
However, the Lake Manawa Waterspout could also be called a "landspout" tornado, which is the same thing just over land. Landspouts are most common in places like eastern Colorado or even western Nebraska. They form not from the cloud down, but from the ground up.
To get a waterspout/landspout, you begin with a clash of wind directions at the surface. These little areas of circulation could be caused by the presence of a front, or other boundary, in the vicinity. Sure enough, the day of August 4 there was a cold front in the vicinity of eastern NE and western IA. Thus, there were plentiful small areas of circulation.
These areas of circulation could strengthen, once a cloud goes over it, it can intensify the ground circulation. Once that ground circulation begins to stretch upward, a landspout/waterspout tornado can form. These types of tornadoes are often weak and do not move much, but sometimes they can do damage. This is why you should take any tornado/waterspout seriously. Even benign waterspouts that come ashore can injure people by throwing beach furniture at you.
THE LAKE MANAWA WATERSPOUT
The conditions described above were all present on August 4. The cold front is nearby, thunderstorms developing, and a small area of circulation over Lake Manawa. At around 5:30 pm, the waterspout formed over Lake Manawa, causing initial panic among onlookers on the lake. These types of tornadoes are nearly impossible to predict before they touch down, so there was no Tornado Warning when it was first sighted.
At 5:25, a Tornado Warning was issued for parts of Mills and Pottawattamie Counties. 10 minutes later, a Tornado Warning was issued for Council Bluffs. Both of these warnings were canceled at 5:38 pm when the tornado lifted.
THE NATIONAL WEATHER SERVICE IN OMAHA HAS ISSUED A * TORNADO WARNING FOR... SOUTHWESTERN POTTAWATTAMIE COUNTY IN SOUTHWESTERN IOWA... * UNTIL 600 PM CDT * AT 535 PM CDT...A CONFIRMED TORNADO WAS LOCATED NEAR COUNCIL BLUFFS... OR 10 MILES EAST OF OMAHA...MOVING SOUTHEAST AT 5 MPH. HAZARD...TORNADO. SOURCE...WEATHER SPOTTERS CONFIRMED TORNADO.
From Council Bluffs to downtown Omaha, onlookers watched as the tornado drifted over the lake. Those in the taller buildings in downtown had a good look. Motorists on the I-480 Missouri River Bridge stopped and took pictures of the tornado over Lake Manawa.
The storm caused a stir on social media as many posted pictures. It was also streamed live from KMTV television cameras as the tornado drifted across the lake. It never came ashore, and no one was injured. However, there were reports of dead fish being found inland as the waterspout sucked them up.
While rare, landspout/waterspout tornadoes are not unheard of in Omaha, as the events of 2016 showed.
