No abstract

Observational evidence is provided for t,he occurrence of anomalons winds which represent it11 anticyclonic rotation in space, and a mechanism for their development is suggested. Thc unstable natnre of these winds and the role they play in the development of certain types of atmospheric disturhmces is then discussed, and it is suggested that anomalous winds provide the dynamic mechanism for triggering hurricane formation and for the observed deepening of troughs downstream from intense pressure ridges. Finally it is noted that although the Observational evidence presented is for the occurrence of anomalons winds over small regions of the atmosphcrc, their development is dependent on large-scale processes and their effect cxtcnds beyond the area where they occur.

No abstract

Observations made by the specially inst,rurnonted aircraft, opcbratcd by thc National Hurricane Research Project, establish the occurrence of dynamic instability, notably in the form of anomalous winds in the upper troposphere above hurricane Daisy, shortly after its inception. It is infcrred that the dynamic instability released by these anomalous winds, which represent anticyclonic rotation in space, triggered Daisy's development. Since the observed dynamic instability occurred on a mcsoscalc, the above inference is not amenable to direct verification from synoptic maps. Howrvcr, synoptic cotlditions favorable for the development of anomalous winds are discussed and it is found that thcse conditions prevailed in the upper troposphere directly above Ilaisy and Gracie a short time before they reached hurricane intensity. The role of negative absolute vorticity is shown to vary. 111 the presencc of anomalous winds it is a stabilizing factor which is nonetheless important in channeling outflow at the top of the hurricane. With normal winds, negative absolute vorticity is a destabilizing agent and some rvidcncc is presented that it may also be responsible for. " initiating the development of certttitl hurricanes.

No abstract