What is the difference between a tornado and a hurricane?

Tornadoes and hurricanes appear to be similar in their general structure. Both are characterized by extremely strong horizontal winds swirling around the center, strong upward motion dominating the circulation with some downward motion in the center. The tangential winds far exceed the radial inflow or the vertical motion, and can cause much damage. Hurricanes always rotate counterclockwise in the northern hemisphere (clockwise in the southern), the direction of their rotation being determined by the Earth's rotation. This is almost always true of tornadoes too, although on rare occasions "anticyclonic" tornadoes spinning in the opposite direction do occur (tornadic circulation is determined by the local winds). This is where the similarities end.

The most obvious difference between tornadoes and hurricanes is that they have drastically different scales. They form under different circumstances and have different impacts on the environment. Tornadoes are "small-scale circulations", the largest observed horizontal dimensions in the most severe cases being on the order of 1 to 1.5 miles. They most often form in association with severe thunderstorms which develop in the high wind-shear environment of the Central Plains during spring and early summer, when the large-scale wind flow provides favorable conditions for the sometimes violent clash between the moist warm air from the Gulf of Mexico with the cold dry continental air coming from the northwest. However, tornadoes can form in many different circumstances and places around the globe. Hurricane landfalls are often accompanied by multiple tornadoes. While tornadoes can cause much havoc on the ground (tornadic wind speeds have been estimated at 100 to more than 300 mph), they have very short lifetimes (on the order of minutes), and travel short distances. They have very little impact on the evolution of the surrounding storm, and basically do not affect the large-scale environment at all. Hurricanes, on the other hand, are large-scale circulations with horizontal dimensions from 60 to well over 1000 miles in diameter. They form at low latitudes, generally between 5 and 20 degrees, but never right at the equator. They always form over the warm waters of the tropical oceans (sea-surface temperatures must be above 26.5° C, or about 76° F) where they draw their energy. They travel thousands of miles, persist over several days, and, during their lifetime, transport significant amounts of heat from the surface to the high altitudes of the tropical atmosphere. While their sporadic occurrence prevents them from drastically impacting the large-scale circulation, they still affect it in ways which must be accounted for and need to be better understood.

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IMERG rainfall totals from the Nov. 2021 atmospheric river.
The Pacific Northwest coast saw two atmospheric rivers (ARs) bring heavy rains from Nov. 10-16, 2021, resulting in severe flooding, landslides, and damage to infrastructure in the British Columbia province of Canada. ARs are long, narrow corridors of water vapor that travel vast distances above the ocean from warm, tropical regions to higher latitudes, where they often release their moisture as rainfall when they reach land areas. While ARs occur across the globe, this year has been notable for several strong events that have impacted the Pacific Northwest coast. The two atmospheric rivers in
IMERG rainfall totals from recent atmospheric river.
The Pacific Northwest experienced a memorable series of storms in late Oct. 2021 as several low-pressure systems rolled in from the northeast Pacific Ocean. One of the systems was classified by meteorologists as a “bomb cyclone”, meaning that its central pressure (an indication of storm strength) had dropped particularly rapidly in a short time period. At its minimum pressure (highest strength), the system was reported by the National Weather Service to have had the lowest pressure of a system over the northeastern Pacific Ocean since reliable observations began in 1974. The system was notable
IMERG Comparison of Typhoon Mindulle and Hurricane Sam
From late Sept. through early Oct. 2021, two powerful storms churned over the Pacific and Atlantic Oceans: Typhoon Mindulle, which peaked as a Category 5 storm, and Hurricane Sam, a Category 4 hurricane and one of the longest-lived hurricane-strength storms on record over the Atlantic Ocean. While neither storm posed a direct threat to land, Mindulle brushed by eastern Japan, leaving heavy rainfall accumulations in the area near Tokyo. Despite the fact that neither storm made landfall, the storms’ slow-motion tracks across warm ocean waters allows an opportunity to observe how the strong winds
GPM overpass of Hurricane Nicholas
Although it only reached hurricane status for a brief period, Hurricane Nicholas made an impact on the northern Gulf Coast by bringing heavy rains to an area still recovering from the devastating effects of powerful Hurricane Ida, which made landfall in Louisiana just over 2 weeks earlier. Nicholas formed after a tropical wave passed over the Yucatan Peninsula and into the Bay of Campeche, providing a focus for shower and thunderstorm development. On the morning of Sunday September 12th, the National Hurricane Center (NHC) found that this area of storms had developed a closed circulation with
Hurricane Ida IMERG Totals
All eyes were on Hurricane Ida as it made landfall in Louisiana on Aug. 29, 2021, but many people were taken by surprise by the power of Hurricane Ida's remnants when they reached Virginia during the day on Sept.1 and New York City late at night on Sept. 1 into early morning on Sept. 2. The below animation shows the precipitation that fell during the entire lifecycle of Ida from before landfall in Louisiana through the impacts on New York City. Download this video (right-click -> "Save As") This animation uses data from the near real-time version of NASA's IMERG algorithm, a data product that