GEOL 0820 Ramsey Natural Disasters Spring, 2018 LECTURE #18: Hurricane Damage, Monitoring & Case Study Date: 27 March 2018 I. Exam II grades now posted online o high: 98, low: 46, average: 80 (~3 points better than the first exam!) o will have a brief review at the start of the lecture II. Hurricane Damage: wind types o hurricane wind velocity (HWV) speed of the CCW winds number quoted when assessing the category of the storm 79 to >155 mph o storm center velocity (SCV) speed of the storm movement over ocean/land commonly 5 to 60 mph influenced by the upper level winds, regional temps, other weather patterns example: Andrew in 1992 changed direction twice due to a high pressure system over the southeastern US and upper level winds over the Gulf of Mexico (more on this later in the lecture) o both of these can combine to cause more damage o for a hurricane moving N in the NE quadrant (upper right side) of a hurricane the HWV combines with the SCV and produces the most damaging winds in the NW quadrant (upper left side) of a hurricane the SCV is subtracted from the HWV and therefore least damaging winds III. Landfall coast-parallel track: o storm moves along the coast o weaker winds over the land & stronger winds over the ocean Page 1/7
o land is affected by two storm surges flood surge ahead of the storm and an ebb surge behind it results in moderate-heavy damage along the coast coast-normal track: o storm moves perpendicular to coast, moving over land o strongest winds on the right side of the storm produces a band of extreme damage off center to the right of the storm track o caused a large flood surge along the entire coast line coast-parallel coast-normal IV. Hurricane Statistics: yearly averages o number of named Atlantic storms since 1995: 13 compared to 8.6 since 1970 o 7.7 hurricanes and 3.6 major hurricanes since 1995 compared to 5 hurricanes since 1970 1.5 major hurricanes since 1970 o Costliest US Hurricanes: Name Season Cost (unadjusted) Katrina 2005 $160 billion Harvey 2017 $125 billion Maria 2017 $90 billion Sandy 2012 $75 billion Irma 2017 $65 billion Ike 2008 $38 billion Wilma 2005 $28 billion Andrew 1992 $27 billion Page 2/7
o most-recent Cat-5 hurricanes: Name Date Max Wind Speed Maria 2017 175 mph Irma 2017 180 mph Matthew 2016 160 mph Felix 2007 175 mph Dean 2007 175 mph Wilma 2005 185 mph Rita 2005 180 mph Katrina 2005 175 mph Emily 2005 160 mph Ivan 2004 165 mph V. Monitoring & Prediction can monitor a storm much better because of satellites o watch it spawn and develop days weeks o examine the final movements prior to landfall hours days satellite images every 30 minutes over the equatorial regions o visible and infrared coast-normal track of Floyd (colorized visible satellite image) planes flying though the storm center o measure vertical structure, wind speeds, pressure and temperatures o use drop-sondes to relay information regarding the change with height doppler radar o useful only when storm is within ~100 miles of a coastal radar station Page 3/7
VI. Hurricane Maria Case Study this will be an open class discussion, so please come prepared to talk about relevant information for this hurricane Possible Topics: o chronology o impacts human economic o response o costs o others? Page 4/7
Old Case Study: Hurricane Andrew (1992) will not go over in class, but please review for the final exam! I. Chronology: 8/16/92 o convection focuses o spiral clouds develop o transition to tropical depression 8/17/92 o wind shear diminishes o Tropical Storm Andrew 8/18/92-8/20/92 o sporadic convection o low surface winds 8/21/92 o wind shear decreases o high pressure area develops over U.S. o steering winds turn Andrew westward 8/22/92 o Andrew reaches hurricane strength o high pressure region drives Andrew due west o hurricane warning issued for Bahamas Page 5/7
8/23/92 o Andrew reaches peak intensity classified as borderline Category 4-5 o passes over Bahamas storm surges 16-23 ft o hurricane warning issued for Eastern Florida 8/24/92 o Andrew regains strength over Straits of Florida o eye-wall convection strengthens o landfall at Homestead, Florida o sustained winds 145 mph o gusts up to 175 mph o max. storm surge of 16.9 ft o category 4 (later reclassified a Cat 5) resurgence o Andrew passes over Southern Florida in about 4 hours o maximum storm tide in SW Florida 7 ft o storm weakens slightly, but intensifies again over the Gulf of Mexico Louisiana landfall (8/26/92) o steering currents turn Andrew back to the northwest o storm hits the Louisiana coast with Category 3 intensity o tides reach 8 ft o rainfall in Hammond, Louisiana totals 11.92 inches II. Costs Andrew was the costliest disaster in US history (until Hurricane Katrina) Page 6/7
o development along the Florida coast in the 70 s and 80 s put lives and dollars at risk o total damage = $27 billion (8 th costliest in US history) o 26 deaths directly attributable to Andrew structural damage o 25,524 homes destroyed o 101,241 damaged o most devastated regions corresponded to the track of the eye-wall surge damage o most deaths associated with the storm surge and strong waves o storm surges are responsible for erosion and damage caused by floating debris o Andrew severely damaged Florida s artificial reef system moving nearly 1000 tons of concrete 700 ft across the seafloor losses to boats estimated at $½ billion airborne debris o debris propelled at high speeds by the hurricane s winds are a major cause of damage o numerous examples post Andrew o III. Post-Assessment although the damage was extensive, it could have been much worse if Andrew landed a little north, it would have struck downtown Miami and Ft. Lauderdale Andrew also passed far enough from New Orleans to cause little damage there Page 7/7