A followup to Tuesday’s lecture: Reading assignment (on the course outline) for hurricanes: Required reading: Link to all of the hurricane subtopics: Tropical Cyclones Introduction Classification Structure Names Hazards Safety

At least 4 degrees from the equator: Coriolis force can be large enough to produce rotation (deflecting to right in the Northern Hemisphere) Before: After:

For the Northern Hemisphere, the Coriolis force deflects air to the right:

Hurricane Hazards One of the areas most vulnerable to storm surge is Tampa Bay, FL. This is of major concern, because over 3 million people live the region, and it is highly vulnerable to storm surge-- particularly for a storm moving northeast or north-northeast at landfall, The largest damage will be to right of track, as the winds are stronger than to the left. (motion of the storm is added (in the same direction as for the winds of the storm).

Hurricane Hazards Examples of hurricanes with noteworthy storm surge Galveston, Texas (Sept. 8, 1900) 6,000 perished Camille (Aug. 17, 1969) Cat. 5 system with 186 mile per hour winds; 7.3 metre surge Bangladesh (Bay of Bengal); November 13, 197o; 7 metre surge; 500,000 perished

Hurricane Hazards

Coastal effects of Camille (1969)

When Warnings are Ignored

The same apt. building destroyed with 22 lives lost

Flooding-Floyd (1999) The hurricane produced torrential rainfall in eastern North Carolina, adding more rain to an area hit by Hurricane Dennis just weeks earlier. The rains caused widespread flooding over a period of several weeks; nearly every river basin in the eastern part of the state exceeded 500-year flood levels. In total, Floyd was responsible for 57 fatalities and $4.5 billion ($5.7 billion in 2006 U.S. dollars) in damage, mostly in North Carolina

Flooding-Floyd (1999) Floyd dropped nearly 17 inches (430 mm) of rain during the hours of its passage and many residents weren’t aware of the flooding until the water came into their homes. The National Guard and the Coast Guard performed nearly 1700 fresh water rescues of people trapped on the roofs of their homes due to the rapid rise of the water. By contrast, many of the worst affected areas did not reach peak flood levels for several weeks after the storm, as the water accumulated in rivers and moved downstream.

Flooding-Floyd (1999) The extensive flooding resulted in significant crop damage. Around 31,000 jobs were lost from over 60,000 businesses through the storm, causing nearly $4 billion (1999 USD, $4.7 billion 2006 USD) in lost business revenue.

Forecasting There are several elements to tropical cyclone forecasting: track forecasting, intensity forecasting, rainfall forecasting, storm surge, and tornado forecasting. The large-scale synoptic flow determines 70 to 90 percent of a tropical cyclone's motion. The deep-layer mean flow is considered to be the best tool in determining track direction and speed.

Forecasting The rule (mariners' rule or danger area) is a guideline commonly taught to mariners for hurricane and tropical storm tracking and prediction. It refers to the rounded long-term NHC/TPC forecast errors of nautical miles at hours, respectively.

Forecasting Because of the inherit uncertainty in the exact track forecast, the national Hurricane Center issues forecasts that include an ever expanding envelope of threat area.

Forecasting Some forecasts however, have less confidence than others. Consider the spread in the various track forecasts from different models for Hurricane Katrina when Katrina was crossing Florida.

Forecasting However, once the storm moved into the Gulf of Mexico and intensified, forecast models came into better agreement concerning the track of Katrina.

Forecasting Hurricane Hunters are aircraft that fly into tropical cyclones in the North Atlantic Ocean and Northeastern Pacific Ocean for the specific purpose of directly measuring weather data in and around those storms. 1) Need to know how intense the storm is. 2) Need adequate data to determine where the storm will track. 3) Need to know the details of the hurricane to verify computer models of hurricanes.

Forecasting Naming Storms reaching tropical storm strength were initially given names to eliminate confusion when there are multiple systems in any individual basin at the same time, which assists in warning people of the coming storm. Naming of Atlantic tropical storms has occurred since 1953 Lists included only women’s names until 1979 Since 1979, men’s and women’s names have been alternated Six lists are used The 2005 list will be used again in 2011 (minus Dennis, Katrina, Rita, Stan, and Wilma)

Forecasting Naming Storms reaching tropical storm strength were initially given names to eliminate confusion when there are multiple systems in any individual basin at the same time, which assists in warning people of the coming storm. Naming of Atlantic tropical storms has occurred since 1953 Lists included only women’s names until 1979 Since 1979, men’s and women’s names have been alternated Six lists are used The 2005 list will be used again in 2011 (minus Dennis, Katrina, Rita, Stan, and Wilma) There is a large year-to-year variability in hurricane activity: examples being Gilbert (September 16, 1988, from video), Rita (September 16, 2005), Karl (September 16, 2010).

Long Term Trends While the number of storms in the Atlantic has increased since 1995, there is no obvious global trend; the annual number of tropical cyclones worldwide remains about 87 ± 10. In spite of that, there is some evidence that the intensity of hurricanes is increasing.

References Gray, W. M., C. W. Landsea, P. W. Mielke, Jr., and K. J. Berry, 1994: Predicting Atlantic Basin seasonal tropical storm activity by June 1. Weather Forecasting, 9, Larson, E., 2000: Isaac’s storm: A man, a time, and the deadliest hurricane in history. Vintage. Organization of American States: Primer on Natural Hazard Management in Integrated Regional Development Planning. Available at Toomey, D., 2002: Storm chasers: The hurricane hunters and their fateful flight into Hurricane Janet. W. W. Norton and Co. Web Sites