Hurricane Information

Very good information on Hurricanes...if your a weather geek. excerpt from Jeff Masters weather underground blog.

"Why hurricanes recurve
The prevailing winds over the U.S. are from west to east, but in the tropics, they blow east to west. This pattern arises because we live on the surface of a spinning sphere that is heated unequally at the poles and equator. When a hurricane forms in the tropics, it moves east to west with the prevailing winds. However, if the storm gets far enough north, it will suddenly encounter a flow of air moving the opposite direction. This will force the hurricane to move northwards and then eastwards, as the storm gets caught up in the west to east flow of air. The boundary between these two air flow regimes fluctuates, depending upon the position of the jet stream. When a low pressure system moves across the U.S., the jet stream dips to the south, bringing the prevailing west to east winds over the U.S. closer to the tropics. Thus, hurricanes are more prone to recurve to the north when there is an approaching low pressure system passing to their north.

When hurricanes collide
Many readers have asked if Hanna and Ike could collide and make a super hurricane. Well, hurricanes cannot collide to make a bigger hurricane. When hurricanes get within about 900 miles of each, they begin to interact. There are three possible outcomes:

1) The larger storm will destroy the smaller one. The larger storm's upper-level outflow will bring hostile wind shear over the smaller storm, and the larger storm may steal the smaller storm's moisture. This occurred in 2005, when Hurricane Wilma destroyed Tropical Storm Alpha over Hispaniola.

2) Both hurricanes will compete for the same energy, resulting in weakening of both storms.

3) The storms will rotate around a common center of rotation (the Fujiwhara Effect), before going on their separate ways. Hurricane Humberto and Hurricane Iris took part in a brief Fujiwhara interaction in 1995. Iris then began interacting with a third storm, Tropical Storm Karen, which orbited and later merged with the more intense Iris. In
cases, the two storms will merge, such as occurred in 1997 in the Pacific with Typhoon
Yule and TD 16W.

Sometimes, a recurving hurricane will leave behind an enhanced trough of low pressure that will act to help recurve the storm behind it along the same path. This is possible this week with Ike and Hanna."



Jeff Masters