What made Laura so strong?
Hurricane Laura slammed into the Louisiana coast during the early morning hours, about 40 miles from the Texas border—a Category 4 storm with sustained winds of 150 miles per hour (mph). She topped Katrina’s wind-strength record and joined a select list of hurricanes making landfall with such devastatingly strong winds.
1935, Labor Day Hurricane in Florida, 185 mph wind speed
1969, Hurricane Camille in Mississippi, 175 mph wind speed
1992, Hurricane Andrew in Florida, 165 mph wind speed
2018, Hurricane Michael in Florida, 160 mph wind speed
2020, Hurricane Laura in Louisiana, 150 mph wind speed
Twenty-four hours before landfall Laura was a Category 2 storm gliding over the Gulf of Mexico’s warm waters, winds reaching as high as 110 mph. But, how did she transform into a monster storm in just 24 hours?
Heat
Hurricanes start as tropical storms, but not all tropical storms become hurricanes. The basic recipe for a hurricane is warm water, moist air, and a low-pressure center (converging winds). Heat is a critical enabler for hurricane development, because as winds sweep across the ocean’s surface, they suck up heat energy from the warm waters. Physics dictates that warm air holds more moisture, so the winds become saturated with water. But warm air also rises, and this moist, water-saturated air ascends due to buoyancy, creating an area of low pressure. Winds then converge on the low-pressure area, and a tropical storm is born.
Tropical storms sometimes grow up to become hurricanes, and the more heat a storm draws from the ocean, then the stronger it becomes. Remember, the atmosphere is not the only recipient of heat from global warming; ocean temperatures also rose over the past 40 years. These warmer seas translate to more potential storm energy, explaining the increase in Category 3 storms over the past four decades.
Space above
Wind speed in a hurricane is related to the pressure drop in the eye of the storm. Remember, warm moist air, rising due to buoyancy, initially drives the process, but the storm also needs vertical space to develop into a powerful low-pressure cell. Calm upper-level atmospheric conditions facilitate storm development by not disrupting the upper portion of a hurricane’s internal circulation cell. In contrast, when strong upper-level winds are present, they can shear off the top of a storm and keep it from strengthening.
Warm seas and a calm upper atmosphere provide the right conditions for a process called “rapid intensification.” Typically a Category 4 storm develops slowly over days or even weeks, but conditions were right for Laura, and she blasted from Category 2 to Category 4 in just 24 hours. The risk of damaging storm surges and high winds dramatically increases when rapid intensification occurs immediately before landfall. Unfortunately, climate change is making storms like Hurricane Laura more common, and she will not be the last Category 4 storm to lash the Gulf of Mexico coastline.
ArcheanWeb:
Hurricanes more dangerous than in the past (Source: ArcheanWeb) – https://archeanweb.com/2020/06/01/hurricanes-more-dangerous-than-in-the-past/ Also:
Sources:
Laura ‘rapidly intensified’ overnight. Here’s what that term means (By Brandon Miller and Judson Jones; CNN) – https://www.cnn.com/2020/08/25/weather/hurricane-laura-rapid-intensification/index.html Also:
Feature Image: Hurricane Laura (Modified by ArcheanWeb) – Original Credit: By EOSDIS – Public Domain, https://commons.wikimedia.org/w/index.php?curid=93571213
