Meteorology of Windstorms Forces and Wind Field Characteristics

Meteorology of Windstorms Wind loading and structural response Lecture 1 Dr. J.D. Holmes

Meteorology of windstorms ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Meteorology of windstorms ,[object Object],[object Object],[object Object],[object Object],[object Object]

Meteorology of windstorms ,[object Object],Pressure gradient force per unit mass = p  y  z  z (p+  x)  y  z  x  y  x  y  z

Meteorology of windstorms ,[object Object],[object Object],AA  =  U (  t) 2 a = 2 U  = ( ½)a (  t) 2 (S. Pole)

Meteorology of windstorms ,[object Object],[object Object],[object Object],[object Object], = angle of latitude  = angular velocity of the earth f= 2  sin  Coriolis force is zero where  and f are zero i.e. at Equator f U

Meteorology of windstorms ,[object Object],[object Object],[object Object],[object Object]

Meteorology of windstorms ,[object Object],[object Object],[object Object]

Meteorology of windstorms ,[object Object],[object Object],Clockwise rotation in Southern Hemisphere ,[object Object],Near the equator (  < 5° N), hurricanes cannot form

Meteorology of windstorms ,[object Object],Includes centrifugal force : (U 2 /r) per unit mass r = radius of curvature of isobars ,[object Object],[object Object],Quadratic equations for gradient wind speed, U cyclone

Meteorology of windstorms ,[object Object],[object Object],[object Object],U is limited to for an anti-cyclone, but unlimited for a cyclone cyclone

Meteorology of windstorms ,[object Object],[object Object],[object Object],Direction change with height - Ekman spiral <30 o

Meteorology of windstorms ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Meteorology of windstorms ,[object Object],[object Object],(S. Hemisphere)

Meteorology of windstorms ,[object Object],Wind speed Direction (Figure 1.7 in book shows low wind speed in ‘eye’)

Meteorology of windstorms ,[object Object]

Meteorology of windstorms ,[object Object],pressure gradient wind speed pressure gradient  p = p n -p 0 where p 0 is central pressure Holland (1980)

Meteorology of windstorms ,[object Object],pressure profile gradient wind speed profile Cyclone ‘Tracy’ 1974

Meteorology of windstorms ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Meteorology of windstorms ,[object Object],[object Object],[object Object],[object Object],[object Object],warm air cool air cumulus cloud

Meteorology of windstorms ,[object Object],Wind speed Direction Max gust 1 hour

Meteorology of windstorms ,[object Object],15m/s 20 30 40 50 Direction of storm

Meteorology of windstorms ,[object Object],Funnel-shaped vortex created in thunderstorms

Meteorology of windstorms ,[object Object],‘ Supercell’ - intense convective cell

Meteorology of windstorms ,[object Object],[object Object],Tangential velocity Static pressure Radial V r  0.5V  Vertical V v  0.62V 

End of Lecture 1 John Holmes 225-405-3789 JHolmes@lsu.edu

Meteorology of Windstorms Forces and Wind Field Characteristics

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