Category Archives: Tropical
A tropical cyclone is a rotating low-pressure system that has organized thunderstorms but no fronts. When a tropical cyclone’s maximum sustained winds reach 74 mph, it is called a hurricane. Hurricanes have never directly impacted the Upper Midwest region of the U.S.; however, the remnants of a hurricane or tropical storm have impacted the weather in the Midwest, including Wisconsin.
If a hurricane is particularly strong at landfall, it can move far enough northward to cause a significant rain event for areas in the Midwest. For the most part, such storms originally make landfall in Texas, Louisiana or Mississippi. These storms can be tracked by satellites or surface weather observations because they maintain an identifiable circulation pattern along their entire path. Continue reading
On the morning of August 3, 1492, Christopher Columbus set sail on his first voyage to the Americas. He sailed south along the west coast of Africa, searching for the easterly “trade winds,” discovered earlier by the Portuguese, that would propel his fleet westward toward what he thought was India.
The trade winds are a component of a global-scale tropical circulation feature known as the Hadley cell. This cell is driven by the fact that the equator is heated more intensely than latitudes to its north and south, resulting in the production of collections of thunderstorms girdling the globe roughly along the equator. Continue reading
Hurricanes form over warm waters. The evaporation of the warm ocean waters condenses to form clouds and precipitation releasing latent heat energy that helps to maintain the storm.
A general rule of thumb is that hurricanes will not form unless the water temperature is at least 80 degrees. Photographs of hurricanes over the ocean clearly show that hurricanes churn water at the surface, mixing it with cooler waters below. Continue reading
Scientists record global ocean temperatures using satellite observations. Since mid-March, the global average sea surface temperature has been more than 70 degrees, a record high temperature. This indicates rapid warming, which is associated with global warming and ocean circulations.
El Niño and La Niña are climate patterns in the Pacific Ocean. Normally, the trade winds blow west along the equator, moving warm water from South America toward Asia. To replace that warm water, cold water rises from the ocean depths — a process called upwelling. That means cold water rises to the surface near South America. Continue reading
The hurricane season is a distinct time of year when tropical cyclones — tropical depressions, tropical storms and hurricanes — usually develop.
Here in the U.S., we usually refer to the Atlantic hurricane season, as it’s those storms that most commonly affect the U.S., which extends from June 1 to Nov. 30. Continue reading