Transcript Lesson 16
AOSC 200 Lesson 15 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 Damage from hurricane Andrew, August 1992 Fig. 8-19, p. 224 Fig. 8-23, p. 228 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 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 <119 BUT > 61 - TROPICAL STORM • NAMES GIVEN WHEN STORM REACHES TROPICAL STORM STATUS 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. Schematic of a Hurricane 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. Fig. 8-24, p. 229 Fig. 8.29 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 Fig. 8.27 STORM SURGE Fig. 8.35 TROPICAL CYCLONE DAMAGE • WIND DAMAGE • STORM SURGE • INLAND FLOODING Fig. 8-39, p. 247