As Hurricane Harvey approaches the Texas coastline, we have already seen several tornado warnings. This is actually a common occurrence with land-falling hurricanes.
Winds rotate around the center of the hurricane, in a counter-clockwise direction. Winds to the right of the storm’s center, blow across the ocean, and then onto the shoreline.
When the winds are over water, there is relatively little friction. The surface of the ocean is relatively smooth, even with wave action. However, once the surface winds encounter land, there is more friction, compared to the ocean. This causes the winds to slow down at the surface. But the winds above the surface don’t encounter this friction, and do not slow down. This creates wind shear, with slower winds near the ground, and faster winds aloft. This can lead to rotating columns of air, and tornadoes are born.
This phenomenon almost always occurs in the right front quadrant of the hurricane. This is shown using Hurricane Harvey as a current example. The right front quadrant is within the red circle below:
And that’s exactly where the Storm Prediction Center has issued a Tornado Watch for today. This watch is in effect until 2am central time.
The watch actually includes some southwestern counties in Louisiana. Most tornadoes associated with hurricanes are fairly weak, and short lived. However, even EF-zero and EF-1 tornadoes have the capability of doing significant damage in a short amount of time. Tornadoes often take a back seat to the more obvious hurricane dangers, of high winds, storm surge, and torrential rains. But they are a very real concern with powerful storms, like Hurricane Harvey.
For WeatherNation: Meteorologist Matt Monroe