Chapter 14 — AIR MASSES AND FRONTS 



300 150 



150 300 450 Miles 



50W 



40W 



30W 



A|^ Qg'^'P^FW^ 3 



(A) 



SOW 



70W 



60W 



SOW 



70W 



60W 



(B) 



209.373 

 Figure 14- 22. — Basic tropical wave model 

 (A) Vertical; (B) Horizontal. 



INTERTROPICAL CONVERGENCE 

 ZONE (ITCZ) 



As satellites have provided great amounts 

 of pictorial information to today's meteorologists 

 for research, it has become apparent that some 

 changes in previous theories were needed. One 

 of these so affected is the Intertropical Con- 

 vergence Zone (ITCZ), or as it is frequently 

 referred to now, zone of Intertropical Con- 

 fluence (ITC). 



The ITCZ is a nearly continuous line of 

 horizontal convergence along the Equatorial 



209.374 

 Figure 14-23. — Inverted- V tropical wave model. 



Trough. Figure 14-24 shows a typical cloud 

 band associated with the ITCZ. It is within 

 this cloud band that disturbances frequently 

 occur. 



Generally, disturbances along the ITCZ 

 move from east to west and can move poleward 

 and develop into tropical storms. These 

 disturbances are most frequent in the doldrum 

 portions of the equatorial trough. In that area, 

 low-level cyclonic wind shear is present over 

 large areas. This, together with friction, 

 produces the forced convergence necessary for 

 development of the individual cloud systems 

 which form the ITCZ cloud band. 



It has been determined that surges of flow 

 from one hemisphere to the other one of the 

 controlling factors of ITCZ clouds. As air 

 moves across the equator, anticyclogenesis takes 

 place. This results in a reduction or clearing 

 of clouds along one portion of the ITCZ cloud 

 band and an intensification of the cloud band 

 in advance of the burst of cross equatorial 

 field. 



Weather Along the ITCZ 



The degree and severity of the weather 

 along the ITCZ varies considerably with the 



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