LECTURE #18: Hurricane Damage, Monitoring & Case Study

Transcription

1 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

2 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 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

3 o most-recent Cat-5 hurricanes: Name Date Max Wind Speed Maria mph Irma mph Matthew mph Felix mph Dean mph Wilma mph Rita mph Katrina mph Emily mph Ivan 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

4 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

5 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

6 8/23/92 o Andrew reaches peak intensity classified as borderline Category 4-5 o passes over Bahamas storm surges 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 inches II. Costs Andrew was the costliest disaster in US history (until Hurricane Katrina) Page 6/7

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