Saturday, August 22, 2009

Can human

Can human intervention diminish the force of a hurricane? From the mid-1960s through the early 1980s NOAA actively pursued Project STORMFURY, a program of experimental hurricane modification. The general strategy was to reduce the intensity of the storm by cloud seeding. The seeding, it was argued, would stimulate the formation of a new eyewall that would surround the existing eyewall. The new eyewall would contract, strangling the old eyewall and reducing the intensity of the hurricane. However, research carried out at AOML showed clearly that these "concentric eyewalls" happened often in unmodified hurricanes, thus casting doubt on the seemingly positive results of seeding in earlier experimentation. Hurricane Luis provides an example of this behavior. Moreover, observations showed that hurricanes contain little of the supercooled water necessary for cloud seeding to work.The American Meteorological Society policy statement on planned and inadvertent weather modification, dated October 2, 1998, indicates, "There is no sound physical hypothesis for the modification of hurricanes, tornadoes, or damaging winds in general, and no related scientific experimentation has been conducted in the past 20 years." In the absence of a sound hypothesis, no Federal agencies are presently doing, or planning, research on hurricane modification.

The simplest

A house in Miami is torn apart by Hurricane Andrew.
The simplest characterization of hurricane intensity is embodied in the Saffir-Simpson scale: from Category 1 - barely a hurricane - to Category 5 - the worst imaginable. "Major Hurricanes" are those in Categories 3, 4, and 5 with winds stronger than 110 miles per hour equivalent to 100 kt or 50 m s-1. Category 5 hurricanes are the most extreme and also the most rare. Only two, the 1935 Labor Day Storm and Camille in 1969 are recorded to have struck the United States. Andrew, at the very top of Category 4 was the third strongest U.S. landfall, and the second strongest on the mainland, given that the 1935 storm hit the Florida Keys.In the 20th century, U.S. hurricanes destroyed > $73 billion in property, not corrected for inflation. During the 70-year period from 1925 through 1995, the toll was $61 billion. If the damage from historical hurricanes is normalized for inflation, increased population, and greater individual wealth (Pielke and C. Landsea 1998), the estimate of total damage for the shorter period is $340 billion, equivalent to an average annual loss of $5 billion. During these 70 years, 244 landfalls occurred. The average landfall would have resulted in $1.5 billion in damage with today's prices and costal development. But the average doesn't tell the story. Major hurricanes accounted for 80% of the normalized damage, although they represented only 20% of occurrence.

The Fury of Hurricanes

When Hurricane Andrew of 1992 came booming ashore in South Florida, it caused the United States' most expensive natural disaster $27 billion worth of property destroyed. Loss of life was another matter. In Miami-Dade County, Andrew killed only 15 people by direct force of wind and water. Human casualties were so light because the storm caused little flooding in populated areas and the National Hurricane Center forecast the storm track accurately. Although hurricanes are inevitable on the East Coast of North America, correct characterization of the phenomenon on all scales enables men and women to prepare effectively. Accurate forecasts of individual events give people time and motivate them to act. The climatology of the threat's occurrence and severity is the key to wise policies implemented long before the event. Intelligent responses in the years, months, days, hours and even minutes before hurricane landfall can limit human and material losses.