Severe Storms:

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• Severe Storms
• Tropical Cyclones
• Thunderstorms
• Tornadoes

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Typhoon Lupit, which means "fierce" in Filipino,
is taking dead aim at the already storm battered
Philippines, which will make it the 18th typhoon
to hit the country this seasonOver the last
month two storms, Ketsana and Parma, struck the
country, causing flooding and landslides. Over
800 people were killed ABC World News, Oct. 22,
2009.

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Tropical Cyclones

• Violent, long-lived cyclonic storms with
  sustained winds in excess of 74 mph that
  originate in tropical latitudes, usually in late
  summer and early autumn.
• Hurricane -- W. Hemisphere, named for Mayan sky
  god Hurican (Sp. Huricán, Fr. Ouragan)
• Typhoon -- W. Pacific, named for great wind
  (Cantonese)
• Cyclones -- Indian Ocean and Australia

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Saffir-Simpson Scale

• NAME WINDS (mph) DAMAGE
• Tropical depression 23-39 minor
• Tropical storm 40-74 from rains
• Hurricane CAT I 74-95 trees
• CAT II 96-110 roofs
• CAT III 111-130 light structures
• CAT IV 131-155 extensive
• CAT V gt 155 devastating

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Hurricane Structure
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• Computer model of hurricane wind structure

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Hurricane Origins and Tracks

• Formed by disturbance in trade winds near ITCZ.
• Needs warm ocean water T gt 26 oC
• Needs Coriolis force to support rotation, so
  never found in latitudes less than 5o North or
  South
• Needs conditions with no wind shear aloft to get
  organized.
• Sustained by massive release of latent heat of
  condensation.

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• Please Read
• Hurricane Mechanics
• Nuts and Bolts of Heat Engines
• Hurricane Engine Basic Operating Manual
• http//www.ems.psu.edu/nese/ch11sec3.htm

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Hurricanes Demise

• Over land hurricanes are
• 1) Cut off from warm ocean moisture
• 2) Slowed down by increased surface friction
• 3) Torn apart by increased wind shear aloft in
  the westerlies
• 4) Accelerated northward by mid-latitude winds

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Energy Generated by a Hurricane

• Rain formation An average hurricane produces 1.5
  cm/day of rain inside a circle of radius 665 km.
  Converting this to a volume of rain gives 2.1 x
  1016 cm3/day. A cubic cm of rain weighs 1 gm.
  Using the latent heat of condensation, this
  amount of rain produced gives 5.2 x 1019
  Joules/day or 6.0 x 1014 Watts. This is
  equivalent to 200 times the world-wide electrical
  generating capacity - an incredible amount of
  energy produced! And the storm can last for 10
  days or so! This power would illuminate 6 x 1012
  lightbulbs!
• 2. Wind energy Proportional to the the wind
  speed cubed. Using 40 m/s for an inner radius of
  60 km yields 1.5 x 1012 Watts.
• So a hurricane produces an amazing amount of
  energy. 400 times more by rain formation than by
  wind energy.

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Hazards of Tropical Cyclones

• Torrential rains (10 inches is common),
• Storm surges of as much as 25 feet (from low
  pressure, onshore winds, and high tides),
• Flooding can be widespread.
• Mud Slides in hilly terrain
• Wind gusts of up to twice the average wind speed
• Tornadoes and Thunderstorms embedded in the
  tropical storms
• Storm track is somewhat erratic and is determined
  by the interaction of the storm with its
  environment.

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Hurricane Andrew 1992
Last CAT 5 to hit U.S., 43 deaths, 30B damage.
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Past Dealiest Hurricanes

• 1900 Galveston hurricane, Isaacs Storm (6,000
  dead)
• 1938 New England Hurricane (Miller video 1687)
• The hurricane had no name, it was not tracked,
  and it came with little or no warning. There
  were no emergency services available.
• Killer storm surge caused by extreme low
  pressure, offshore winds, and the timing of the
  high tide. Great loss of life.
• 1969 Hurricane Camille
• 200 mph wind gusts, 25 foot storm surge, 256
  deaths, 4 Billion damage.
• 1970 Bengal cyclone (500,000 dead)
• 2005 Katrina (over 1800 deaths, mainly from
  flooding)

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Hurricane Mitch (22 Oct.-5 Nov. 1998)

• Mitch was responsible for over 9,000 deaths
  predominately from rain-induced flooding in
  portions of Central America, mainly in Honduras
  and Nicaragua. This makes Mitch one of the
  deadliest Atlantic tropical cyclones in history.
• The 905 mb minimum central pressure and estimated
  maximum sustained wind speed of 155 knots
  (Category V) over the western Caribbean make
  Mitch the strongest October hurricane since
  records began in 1886.

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Katrina, Aug. 29, 2005
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For more information

• National Hurricane Center
• http//www.nhc.noaa.gov
• Tropical Meteorology Project
• at Colorado State University
• http//typhoon.atmos.colostate.edu/

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Thunderstorms, Lightning,Tornadoes
Anthes Ch. 5, pp. 124-32
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Thunderstormshttp//www.nssl.noaa.gov

• A thunderstorm is a deep convective cloud (Cb)
  reaching as high as 10 to 18 km, that produces
  lightning, thunder, heavy rain, downbursts,
  possibly hail, flash floods, and on rare
  occasions, tornadoes.
• It is a thermodynamic heat engine driven by the
  latent heat of condensation (vapor to liquid) and
  fusion (liquid to ice).
• Can be caused by solar heating, nighttime
  cooling, sea breeze convergence, mountains, cold
  fronts.
• An average of 1800 thunderstorms are active
  globally at this moment.
• Mesoscale convective complex contains dozens of
  Cbs and is 1000 times larger than a thunderstorm.

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Lifecycle of a Thunderstorm
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Supercell
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Thunderstorm Climatology

• Hail Climatology

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Lightning

• Lightning is an electrical discharge.
• Most flashes originate in clouds.
• Clouds are most commonly in a negative state of
  electricity, but sometimes in a positive state.
• Grounded metallic rods will protect most
  structures from damage.
• Source
• Benjamin Franklin (1750s)

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Lightning

• Lightning is a giant transient high-current
  electrical discharge (or spark) of static
  electricity with a path length of kilometers.
• A typical strike is 100 million volts, 100,000
  amps, and generates temperatures of 30,000 K
  (five times hotter than the suns surface).
• Around the world, there are 1800 thunder storms
  going on at any given time with 100 lightning
  strikes to Earth each second.
• That means 9 million lightning bolts per day!
• Most lighting is within a cloud or between
  clouds.
• Only about 20 is cloud to ground.

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Lightning strike details

• Lightning strike is very fast and very complex
• 1. Cloud to ground stepped leader moves along a
  branching path in 20 to 100 meter steps at 10 to
  20 km/sec.
• 2. Ground to cloud return stroke covers the final
  100 meter spark gap to a high spot (tree, tower,
  golf club).
• 3. Subsequent (3-40) strokes called dart leaders
  give lightning its forked appearance, completing
  the strike.

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Lightning formation

• Necessary condition Separation of charge.
• Cb is a static electricity generator.
• Charge separation caused by collisions of water
  and ice.
• Electrons (-) and ions ( -) transported to
  different levels via updrafts and downdrafts.
• Air is a good insulator.
• Cloud can reach 100 million volts, 100,000 amps.
• Car battery is 12 volts, 8 amps.
• House current is 120 volts, 20 amps.
• Sufficient condition Voltage difference gt
  insulating ability of the air.

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Thunder

• Thunder sound wave
• Long tube of air, 6 km x 15 cm diameter heated
  almost instantaneously to 12-30,000 K expands air
  violently.
• Shock wave thunder (both audible and
  inaudible).
• Speed of light 300,000 km / sec
• Speed of sound 0.33 km / sec
• 3 second delay 3 km 5 second delay 1 mile

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Lightning fatalities
About 60 fatalities per year in the US, 360
severe injuries
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Benefits of lightning

• May have played a role in the pre-biotic
  formation of amino acids.
• Fixes nitrogen, creates natural fertilizer.
• Ignites forest fires -- forest ecology.
• May have been the source of fire for early
  humans.
• E-M fields of lightning used to study the
  atmosphere.
• Global lightning strikes represent a global
  thermometer.
• Lighting strikes on other planets (Jupiter) allow
  remote study.