The dynamic high is a combination of a sur-face cold high and an upper-level warm high or well-developed ridge, or a combination of a surface cold high with a dynamic mechanism aloft for producing high-level anticyclogenesis. Dynamic highs have axes that slope toward the warmest tropospheric air. (See fig. 3-2-9.) In the final stages of warming the cold surface high, the dynamic high becomes a warm high with its axis practically vertical.

A warm core high is accompanied by a high cold tropopause. Since the pressure surfaces are spaced far apart, the tropopause is reached only

at great heights. The temperature continues to decrease with elevation and is cold by the time the tropopause is reached. The subtropical highs are good examples of this type of high. Therefore, anticyclones found in tropical air are always warm cored. Anticyclones found in Arctic air are always cold cored, while anticyclones in polar air may be warm or cold cored.

A cold cored low is accompanied by a low warm tropopause. Since the pressure surfaces are close together, the tropopause is reached at low altitudes where the temperature is relatively warm. Good examples of cold core lows are the Aleu-tian and Icelandic lows. Occluded cyclones are generally cold cored in their later stages because of the polar or Arctic air that has closed in on them.

Warm core lows decrease in intensity with height or completely disappear and are for the most part replaced by anticyclones aloft. The heat lows of the southwestern United States, Asia, and Africa are good examples of warm core lows. Newly formed waves are generally warm cored because of the wide-open warm sector.

Systems which retain their closed circulations to appreciable altitudes and are migratory, are called dynamic lows or highs.

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