Hurricanes: The Evil Wind

1. Hurricanes: The Evil Wind Anthony R. Lupo Department of Soil, Environmental, and Atmospheric Science 302 E ABNR Building University of Missouri – Columbia Columbia, MO 65211

2. Hurricanes: The Evil Wind • Hurricanes are a tropical system, which have a unique structure, and, sometimes, unique behavior. • “Hurricane” is a Spanish/French/Indian word literally meaning “evil wind” • In the Atlantic, there are typically 6 hurricanes and 10 named storms. They typically last for 5 -10 days.

3. Hurricanes: The Evil Wind • Hurricanes have a special structure, one that is quite different from mid-latitude storms. • There is no frontal structure in tropical systems and they are “warm core”. That is, they are warmer in the center than in the surroundings.

4. Hurricanes: The Evil Wind

5. Hurricanes: The Evil Wind • They also need an atmosphere with very little wind shear (in the vertical) to exist. Otherwise, the circulation can be disrupted. • Hurricanes are sustained by the release on heat due to condensation. They are a convective engine. • They are “spun down” over land by frictional forces.

6. Hurricanes: The Evil Wind • In summary, they need: • A pre-existing area of low pressure. • An atmosphere with little shear • Waters of 80o F (26o C) or more.

7. Hurricanes: The Evil Wind • Hurricane movement is generally east to west in the tropics, but in the vicinity of North America are influenced heavily by mid-latitude circulations. • Winds in a deep layer (850 hPa – 200 hPa), 1 mile – 6 miles up, influence their movement. • Models now doing a good job with their movement.

8. Hurricanes: The Evil Wind • Terminology: • Tropical “wave” – is an area of low pressure and thunderstorms with strong gusty winds, and no “closed” center. • Tropical depression – has sustained winds of up to 35 kts (39 mph), and a closed “cold” center of low pressure.

9. Hurricanes: The Evil Wind • Tropical storm – storm acquires a name, and winds are sustained from 35 – 65 kts (39 – 74 mph). At this point, they are warm core storms. • Hurricane – acquires an eye and sustained winds over 65 kts (74 mph).

10. Hurricanes: The Evil Wind • Tropical Entities passing within 250 miles of Norfolk, VA since 1938.

11. Hurricanes: The Evil Wind • Tropical Entities passing within 250 miles of Birmingham, AL since 1938.

12. Hurricanes: The Evil Wind • Since 1938, 1961-1969 was the longest “threat free” period, and the 1960’s the quietest decade with 2 storms. The 1980s were not far behind with only 3 events. • The year of 2005 was the worst, 5 storms pass within 250 miles of Birmingham. (August 2004, 2 storms!)

13. Hurricanes: The Evil Wind • During the 1960s through 1990s, there were only 15 events (mean 4 storms per decade). During the “oughts” (2000s), there were 15 storms. • Tropical storm threat is greatest in September. Season gears up in June and winds down by mid-October.

14. Hurricanes: The Evil Wind • Ivan (2003) – In AL, none dead and $2.0 B in damage.

15. Hurricanes: The Evil Wind • Frederic (1979) – costliest hurricane in US history up to 1989.

16. Hurricanes: The Evil Wind • Eloise (Sept 1975) remained a Category 3 well inland, brought torrential rains and much flooding along the east coast.

17. Hurricanes: The Evil Wind • "Preparation through education is less costly than learning through tragedy.“ - MAX MAYFIELD, DIRECTOR NATIONAL HURRICANE CENTER • Hurricane Watch – hurricane conditions could happen at your location in 36 hours. • Hurricane Warning – hurricane conditions are expected within 24 hours. • Source: (http://www.nhc.noaa.gov/) National Hurricane Center

18. Hurricanes: The Evil Wind • Storm surge and heavy rains are the biggest killers in a hurricane, not winds, lightning, or tornadoes. • People should be aware that they should take any tropical system seriously. Some of the biggest killers have not been hurricane intensity.

19. Hurricanes: The Evil Wind • Hurricane numbers during a season are impacted by El Nino. El Nino can influence the atmospheric ingredients mentioned earlier. • There tend to be fewer / less intense hurricanes in an El Nino year. This is mainly because of the inactive Gulf and Caribbean.

20. Hurricanes: The Evil Wind • Upper tropospheric trough!

21. Hurricanes: The Evil Wind • Hurricane numbers also fluctuate on the decadal time-scale, especially since the El Nino in influenced in this manner. • There is little long term trend in Atlantic or Pacific hurricane numbers.

22. Hurricanes: The Evil Wind • Are there more severe hurricanes? • Long term, the ratio of Cat 3 – 5 storms to all storms is 42% • In 2000 – 2009, this ratio was 49%, a bit higher.

23. Hurricanes: The Evil Wind • All things being equal, warmer waters will cause more and stronger hurricanes, but remember, these storms need a cooperative ocean and atmosphere. • There is no evidence climate change is leading to more hurricanes.

24. Hurricanes: The Evil Wind • Check this out……… • 2005 (27) versus 1933 (21)

25. Hurricanes: The Evil Wind • Questions? • Comments? • Criticisms? • LupoA@missouri.edu

26. Hurricanes: The Evil Wind