Tornadoes have been confirmed with winds as low as 60 mph. Below that it is debatable as to whether a funnel is a tornado, as winds under 58 mph are not considered severe.
by their windspeed
The wind speed for Waco Tornado was over 250 mph winds.
The lowest rating a tornado can receive is EF0.
The lowest known pressure recorded in a tornado was 688 millibars in a tornado in Tulia, Texas on April 21, 2007.
Yes the pressure drops as the tornado forms and progresses. The tornado's lowest pressure is in the center.
There is no tornado that can definitively be said to be the weakest. The lowest rating a tornado can get is EF0. When you get into the lower ranges of EF0 it becomes debatable as to whether an event should even be considered a tornado.
IN the Enhanced Fujita Scale The Lowest Wind speed to be a tornado is 65 mph
Windspeed
Air in a tornado is rapidly drawn upward. This creates low pressure as more air rushes in to replace it. However this can ever completely fill the pressure deficit until the upward movement stops.
Pressure decreases sharply, reaching its lowest at the center of the tornado. This pulls air toward the center of the tornado and then drawn into the tornado's updraft. The tornado spins as it originates from a larger circulation called a mesocyclone.
In most cases an F5 tornado will be larger than an F1. However, tornado ratings are a measure of the strength of a tornado, not its size. F5 is the strongest category, and such tornadoes are usually very large, but a few have been fairly small. Conversely, F1 is the second lowest rating (F0 is the lowest) and such tornadoes are generally small, but some have been huge.
WindSpeed