AOSC 200 Lesson 15

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AOSC 200Lesson 15
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Computer generated image of Hurricane Mitch
October 26, 1998. Near Honduras
Note the distinct eye and the large extent of
the hurricane
Fig. 8-18, p. 223
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Damage from hurricane Andrew, August 1992
Fig. 8-19, p. 224
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Fig. 8-23, p. 228
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TROPICAL CYLONES

• THESE INTENSE TROPICAL STORMS ARE KNOWN BY
  DIFFERENT NAMES IN VARIOUS PARTS OF THE GLOBE
• HURRICANES - ATLANTIC
• TYPHOONS - WESTERN PACIFIC
• CYCLONES - INDIAN OCEAN
• MOST FORM BETWEEN THE LATITUDES OF 5 TO 20
  DEGREES.
• LESS THAN 5 DEGREES, THE CORIOLIS FORCE IS TOO
  SMALL
• MORE THAN 20 DEGREES, THE TEMPERATURE OF THE
  OCEAN IS TOO COLD
• MUST HAVE WIND SPEEDS OF MORE THAN 119 KM PER
  HOUR AND HAVE A ROTARY CIRCULATION TO BE A
  HURRICANE/TYPHOON

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TROPICAL CYCLONE FORMATION

• HURRICANES DEVELOP MOST OFTEN WHEN OCEAN WATERS
  HAVE REACHED MAXIMUM TEMPERATURES - 25 C OR
  HIGHER.
• INITIAL STAGE IS SOME FORM OF DISTURBANCE - NAMED
  BY THE WEATHER SERVICE AS TROPICAL DISTURBANCES.
• ONLY A FEW TROPICAL DISTURBANCES DEVELOP 119 KM
  PER HOUR WINDS
• IF WINDS lt119 BUT gt 61 - TROPICAL STORM
• NAMES GIVEN WHEN STORM REACHES TROPICAL STORM
  STATUS

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TROPICAL CYCLONES

• MATURE TROPICAL CYCLONES AVERAGE ABOUT 600 KM
  ACROSS
• BAROMETRIC PRESSURE CAN DROP ACROSS CYCLONE FROM
  1010 TO 950 MILLIBARS
• THIS GENERATES RAPID, INWARD SPIRALING WINDS.
• AS AIR MOVES CLOSER TO CENTER ITS VELOCITY
  INCREASES
• CONSERVATION OF ANGULAR MOMENTUM.
• IN THE CENTER OF THE EYE THE AIR IS DESCENDING
  HENCE IT IS FREE OF CLOUDS.

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Schematic of a Hurricane
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TROPICAL CYCLONES

• MOIST SURFACE AIR IS TURNED UPWARD AND ASCENDS.
• AS MOIST AIR MOVES UP IT COOLS AND WATER VAPOR
  CONDENSES.
• THIS PROVIDES LATENT HEAT TO INCREASE BUOYANCY OF
  THE RISING AIR.
• NEAR THE TOP OF THE HURRICANE THE AIRFLOW IS
  OUTWARD.
• THE CENTRAL DOUGHNUT AREA OF INTENSE CONVECTIVE
  ACTIVITY IS CALLED THE EYE OF THE STORM
• EYE WALL CONTAINS STRONGEST WINDS.

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Fig. 8-24, p. 229
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Fig. 8.29
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TROPICAL CYCLONES

• TROPICAL CYCLONES DIMINISH WHEN
• THEY MOVE OVER COLDER OCEAN WATERS
• MOVE ONTO LAND
• REACH A LOCATION WHEN LARGE-SCALE FLOW ALOFT IS
  UNFAVORABLE

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Fig. 8.27
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STORM SURGE
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Fig. 8.35
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TROPICAL CYCLONE DAMAGE

• WIND DAMAGE
• STORM SURGE
• INLAND FLOODING

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Fig. 8-39, p. 247