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Geography 1000 – for Quiz #3 Part 2 of 4 parts. Cyclone Effects: Storm Surge. 1. Low atmospheric pressure allows sea water to rise as much as three feet , like drawing soda up a straw.
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Cyclone Effects: Storm Surge 1. Low atmospheric pressure allows sea water to rise as much as three feet, like drawing soda up a straw. 2. High winds can push storm water far upstream and inland, adding perhaps 6-10 feet of flooding above normal sea level. 3. High winds can cause severe damage even without water involved. 4. High winds cause higher and faster wave crests that push inland. 5. Heavy rain can cause downstream flooding even as sea water is pushing upstream. People live in between and sometimes drown. 6. Flooding is even worse if the storm coincides with high tide. Spring tide would be worse yet = Super Storm Sandy had it all – 20 feet of surge in some places. Combined total flooding in a hurricane can even exceed 30 feet.
A classic “extra-tropical” cyclone, moving away from the tropics and into sub-tropical USA. In our hemisphere they are called hurricanes.Notice the tall clouds, well-developed “eye” and the counter-clockwise winds.Low air pressure inside these storms (rising air) allows ocean levels to rise also, allowing ‘taller’ sea level during the storm.High winds and heavy rain then add much more to ‘storm surge.’Flooding. 600+ miles wide
Tropical storms can become stronger when they take their energy (heat) into encounters with cooler/drier air.
Westerlies – cooler/drier Trade winds flow east to west. After collision with westerlies, storm fronts tend to flow SW to NE. Easterly Trade Winds – warmer/wetter
Looking down on a cyclonic storm, notice that the right side probably exhibits higher wind speeds because the forward speed of the storm adds to the wind speed inside the storm. If wind speed inside the storm reaches 100 mph and if the entire storm is moving forward at 20 mph, then the combined speed of wind on the forward-moving side should be 120 mph. Likewise, the “back side” of the storm subtracts forward speed to yield just 80 mph winds. Higher wind means higher storm surge flooding. Storm forward track = 20 mph Lower wind speed Higher wind speed
Can you see why cyclonic storms can “hit” twice? For the same reason a‘dust devil’ hit Mr. Allred’scar twice.Still, it is important that dry dust devils rise only until they lose their heat source, such as a black asphalt parking lot.But wet tornadoes contain their own source of heat – latent heat in invisible water vapor.They rise until they run out of water & heat.
Cyclone Effects: High Winds • A hurricane is spilling over with hidden heat, in the form of humid air. • Even a blizzard is a “heat engine” because the coldest air in the winter is still hundreds of degrees warmer than absolute zero.
Human Interaction with Cyclones • People are moving to coastlines • Destruction of sand dunes • Construction of seawalls and bulkheads • Poor building materials and practices • Global warming
Hurricane Prediction and the Future • Deaths have decreased dramatically because of better forecasting, improved education, and greater public awareness. • However, coastal populations are increasing, causing an increasing risk for damage and personal injury. • Even where death rates are down, property loss is increasing rapidly.
Perception of and Adjustment to Cyclones • Perception of hazard depends on personal experience. • More experienced people may take hazard more precautions. • More experienced people may also take less precautions. • Community adjustments to cyclone hazard: • Warning systems(Hurricane Katrina may have been the most advertised disaster in human history. The whole world watched it develop). • Evacuation plans and shelters • Insurance • Building design
Tornado warnings in the United States used to be only 2-3 minutes before arrival.Tornado warnings now provide as much as 10 minutes of warning. How do tornado warnings compared to hurricane warnings?Hurricanes are known well in advance – tornadoes are often too small and quick-moving for the forecast.
How do Utah cyclonic storms compare to elsewhere? We see the same general pattern of storms that often move from southwest to northeast. Tornadoes are uncommon in Utah because we are a dry region -- there is seldom enough humidity to hold the latent heat needed to produce a tornado or other severe winds.
Perception of and Adjustment to Cyclones, cont. • Personal adjustments to cyclone hazard • Be aware of hurricane season • Prepare homes and property for hazard • Obtain flood insurance • Install heavy shutters that can be latched • Learn evacuation route • Make a family emergency plan • Collect emergency supplies
This imaginary storm expected storm surge up to 21 feet above normal sea level. A recent Geography student found a Web page that claimed “Super-Storm Sandy” created 39 feet of flood on Long Island, NY in 2012.
Are levees reliable? Is the Mississippi River under control?
If you wait too long, will your escape route close behind you?
A picture is worth 1,000 words. Figure 9.8
Figure 9.A This guy spent a month in jail for just riding-out the storm at home. Soldiers thought he was a “looter.” Took a month to figure it out. Storms create confusion.
Most of these areas have been rebuilt or repaired. People are “gamblers” and usually buy or sell their homes more often than severe storms arrive. We tend to believe that someone will get “whacked” instead of us.Usually we are right, but the dead don’t come back to tell us what they learned.
Scenes like this are common in tsunami waves and ocean cyclones. Water levels rise very quickly for a few minutes or hours.
Hurricane Katrina – 2005The city has been slowly sinking below sea level. Levees and dikes were never expected to outlast big storms. Repairs have not yet been completed.
