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Unit 9: Tropical Weather

It's Weather Academy Wednesday! Join Meteorologist Corey Thompson for some information on tropical storms and hurricanes.

Posted by KCRG-TV9 First Alert Weather on Wednesday, June 3, 2020

These systems are one of the ways the atmosphere tries to achieve balance

Tropical systems normally start somewhere near the equator where the heat builds up and transfer that heat to either the north or south pole

Like thunderstorms in Iowa, it’s not always pretty. Transfer of heat can cause quite a bit of damage

Direct effects can sometimes be felt in Iowa. Normally can see the moisture or remnants of a tropical system in the Midwest

Tropical systems will most likely weaken immediately after making landfall. They lose their source of warmth and moisture as they moves onto dry land.

Types of Storms

  • Tropical Depression: Defined area (disturbance) of low-pressure circulation with maximum sustained winds of 38 mph or less.
  • Tropical Storm: Maximum sustained winds of 39m mph to 73 mph. Can start to see some wind damage.
  • Hurricane: Maximum sustained winds of 74 mph or greater

Saffir-Simpson Scale

  • Category 1: Maximum sustained winds of 74-95 mph
  • Tree damage, power lines, shingles on a roof, structural damage to mobile homes
  • Category 2: Maximum sustained winds of 96-110 mph
  • More power outages, roof damage, signs or canopies destroyed

Major Hurricanes Category 3 or above

  • Category 3: Maximum sustained winds of 111-129 mph
  • Most window blown out, major home damage or destruction
  • Category 4: Maximum sustained winds of 130-156 mph
  • Even well-built homes lose roof or walls, lots of flying debris causing more damage
  • Category 5: Maximum sustained winds of 157+ mph
  • Lives of those in the direct path of the storm are endangered as catastrophic damage occurs

Hurricane Michael

  • Hit the Florida Panhandle in 2018. Category 4 in the beginning and then upgraded to a Category 5 later after the storm moved through.
  • Made landfall near Mexico Beach, Florida on Oct. 10, 2018
  • Category 5, 160 mph maximum sustained winds
  • Approx. $25.1 billion in damages
  • Most intense storm to hit the Florida panhandle

Tropical Storm Ingredients

  1. Warm ocean water of at least 80 degrees
  2. Atmosphere unstable enough for thunderstorms (upward motion)
  3. An area of low pressure near the surface
  4. Low wind shear - the opposite of severe thunderstorms

Tropical System Structure

  1. Rain-bands: Spiral-patterned showers and storms circulating around the outer edge
  2. Eyewall: Ring of most intense storms surrounding the center eye
  3. Eye: Light winds, clear or partially clear skies. 20-40 miles long. Normally fairly calm. Once the center of the eye move along the coast, that’s when the storm itself makes landfall that is recorded
  4. Tropical systems can vary very much in size
  5. Usually somewhere around 300 miles wide, but can vary

What’s in a name?

  • Storms get names to help separate between different storms
  • Names are memorable and make communication easier
  • World Meteorological Organization sets name lists
  • Atlantic tropical storms and hurricanes rotate every 6 years
  • Storms that are partially damaging have their names retired, like Andrew or Katrina
  • “I” has the most retired names with 11
  • “V” has not retirements at this time

Threats from Tropical Systems

  • Storm Surge: cause by high winds pushing the water onshore and is an abnormal rise in seawater
  • Wind
  • Flooding
  • Tornadoes

Can they get to Iowa?

As in the tropical system? Almost never

Impacts can still be felt from the remnants of the system

The most rain in Iowa to come from an old tropical system was Carla in 1961 of 9.03″