CH10b: tornadoes and microbursts

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CH10b: tornadoes and microbursts

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Tornado. 1- a turbulent to convective scale vortex, 100 to 1000 m in diameter ... tornadoes: 1- last for a few minutes and usually are 100. m in diameter ... – PowerPoint PPT presentation

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Title: CH10b: tornadoes and microbursts

1
CH10b tornadoes and microbursts
2

Fig. 10-38, p. 291
3

Fig. 10-27, p. 284
4

Tornado
1- a turbulent to convective scale vortex, 100 to
1000 m in diameter
2- life time 2- 20 min, far less than parent Cb
3- wind speeds have reached over 300 mph
4- pressure gradient must be extreme
5- can spin cyclonically or anticyclonically,
Coriolis
is not important
6- a tornado is declared when the circulation
reaches the ground

5

Fig. 10-42, p. 294
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Fig. 10-32, p. 288
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Figure 3, p. 295
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Fig. 10-39, p. 292
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Table 10-2, p. 288
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Stepped Art
Fig. 10-37, p. 291
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Fig. 10-31, p. 287
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Fig. 10-28, p. 285
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Fig. 10-29, p. 285
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Table 10-1, p. 287
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What is the critical ingredient that
differentiates a supercell from a ordinary
cell? A robust rotating updraft
How is this achieved? Key mechanism is the
tilting of a vortex tube, caused by the vertical
shear of the horizontal wind being lifted by
an updraft

18

Stepped Art
Fig. 10-34, p. 289
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Fig. 10-5, p. 268
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Fig. 10-33, p. 289
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Microburst a downdraft with a diameter of a
few km that produces very strong outflows
Why should you care?
BOAC 252 at Kano Nigeria, 1956 32 dead
Eastern 66 at JFK, 1975 112 d.
Continental 426 at Denver,1975 15 injured
Pan Am 759 at New Orleans, 1982 152 d.
Pan Am 806 at Pago-Pago, 1974 86 d.
Jack Bonham Scholarship for top UH athlete

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Fig. 10-14, p. 273
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Fig. 10-15, p. 273
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Summary, CH10b
tornadoes
1- last for a few minutes and usually are 100
m in diameter
2- supercells produce the strongest
3- can exceed 300 mph
4- motion and suction vortices may cause highly
unusual damage patterns

Microburst
1- a downdraft that causes strong divergence
(wind flow in opposite directions)
2- often comes from benign looking clouds
that evaporate rain into very dry air
3- major threat to aircraft at landing and
take-off

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Fig. 10-13, p. 272
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Fig. 10-16, p. 273
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Fig. 10-8, p. 270
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Fig. 10-30, p. 286
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Overshooting top
Anvil
Mammatus
Wind
Mesocyclone
Rear flank downdraft
Rainfree base
Inflow
Inflow
Wall cloud
Light rain
Hail
Tornado
Heavy rain
Editable Text
Fig. 10-35, p. 290

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