Hurricanes Study Notes

Hurricanes: Overview and Formation

  • Source Information: Maureen Padden [2024].

  • Date and Time: 27 Oct 2025 12:40Z - NOAA/NESDIS/STAR GOES-19 - GEOCOLOR Composite - Hurricane Melissa.

Hurricane Formation

  • Essential Conditions for Hurricane Development:

    1. Surface Water Temperature: Must be greater than 27˚C.

    2. Warm Moist Air: Provides energy required for storms.

    3. Weak Upper-Level Winds: Facilitate the vertical development of storms.

    4. Location: Must be approximately 500 km from the equator to enable the Coriolis effect, which influences cyclone rotation.

  • Positive Feedback Mechanisms:

    • First Mechanism: Sea spray from wind increases evaporation rates (by 100–1,000 times).

    • Second Mechanism: Updrafts carry vapor molecules into the upper troposphere, leading to further evaporation and latent heat release, enhancing energy in the storm.

Energy Dynamics in Hurricanes

  • Energy Calculations:

    • The energy released during condensation of moisture is 200 times greater than the worldwide capacity to generate electricity.

    • The kinetic energy of hurricane winds is approximately half of the global electrical capacity.

    • Total energy released by cloud and rain formation is 400 times greater than that of hurricane winds.

Geographic Distribution of Hurricanes

  • Hurricane Geography:

    • Hurricanes in the Atlantic Ocean are simply called hurricanes.

    • In the Pacific Ocean, they are referred to as typhoons; in the Indian Ocean, they are called cyclones.

    • The absence of hurricanes at the equator and polar regions is noted due to the necessary conditions not being met.

Tracking and Frequency of Hurricanes

  • Annual Probability of North Atlantic Hurricanes:

    • Understanding paths and factors affecting hurricane occurrence in North America and the Caribbean region.

  • Hurricane Return Frequency:

    • Return period (in years) for hurricane impacts on the U.S. coast varies. It is essential to know the frequency for emergency preparations and understanding risk zones.

The Saffir-Simpson Scale for Hurricane Intensity

  • Categories:

    • Category 1:

    • Wind Speed: 119–153 km/h (74–95 mph)

    • Damage: Roof shingles, tree branches snap, power outages.

    • Category 2:

    • Wind Speed: 154–177 km/h (96–110 mph)

    • Damage: Major roof damage, blocked roads, near-total power outages.

    • Category 3:

    • Wind Speed: 178–208 km/h (111–129 mph)

    • Damage: Significant damage to homes, blocked roads, loss of electricity and water.

    • Category 4:

    • Wind Speed: 209–251 km/h (130–156 mph)

    • Damage: Severe damage to buildings, power outages lasting weeks/months.

    • Category 5:

    • Wind Speed: 252 km/h or higher (157 mph or higher)

    • Damage: Total destruction of homes, extensive area rendered uninhabitable.

Public Safety During Hurricanes

  • If Trapped in a Hurricane:

    • Stay away from glassed areas.

    • Listen to emergency information on a battery-powered radio.

    • Evacuate to designated shelters following official routes, abandoning mobile homes.

    • If outdoors, take cover, avoiding bridges and overpasses; abandon vehicles for stronger shelter.

Building Resilience Against Hurricanes

  • Construction Recommendations for Coastal Homes:

    • Use pilings driven deep into the ground to avoid total loss if water washes away some surrounding soil.

Survey Insights on Hurricane Preparedness

  • Survey during Hurricane Sandy Warnings:

    • 90% of surveyed individuals made some preparations (extra water, filling gas in cars).

    • 50% of individuals with storm shutters installed them.

    • 20% of individuals under evacuation orders intended to evacuate.

    • Misconceptions noted: Many believed winds would cause the most damage rather than flooding.