The formation of hurricane Hilda is followed using satellite photographs, surface and 200-mb. streamline nnnlyses, and 500- to 200-mb. thickness and shear wind analyses. The formation of a strong uppcr level anticyclone nearly over the perturbation coincided with marked warming in the 500- to 200-mb. level. Significant dccpening wns delayed until the disturbance was clear of the island of Cuba. Profiles of meteorological parameters arc studied ns thc deepening proceeds and details of the structure from photographs and radar film are prcsented. 1.

Aircraft data from five levels (900 to 180 mb.) are used to depict the structure of a mature hurricane. Horizontal analyses, vertical cross sections, and various budgets, which have been prepared from the research flight data only, are presented. New estimates of the drag coefficient under hurricane conditions are derived from a different formulation-utilizing the momentum budget inthe inflow layer. 1.

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Horizontal and vertical temperature variations along with true gust velocity measurements of atmospheric turbulence were obtained above hurricane Beulah (1967) by an instrumented U-2. The U-2 flight was part of the US. Air Force High Altitude Clear Air Turbulence program. Pertinent findings include: (1) location of the tropopause just above the cloud tops at 54,000 ft (100 mb) with a temperature of-86OC, 12°C lower than the mean; (2) a vertical temperature rise of ll°C in a few hundred feet just above the tropopause; (3) horizontal temperature changes up to 7°C and smooth flight conditions in the stable layer above the cloud tops; and (4) small temperature fluctuations and generally turbulent conditions at cloud top level. Aircraft measured winds, although questionable as'to their exact directions and speeds, indicated that the flow was weak and anticyclonic near Beulah's top, becoming increasingly anticyclonic above. 1.

Doppler winds measured by an instrumented aircraft are of great value in determining the wind field accompanying large-scale atmospheric disturbances. When they are utilized in interpreting and computing the wind fields of so-called mesoscale disturbances with their horizontal dimensions of a few to a few hundred miles, slight errors in the vector quantities forming the navigation triangle result in fictitious winds which differ considerably from the real winds. In the first part of this paper,Jhe wind velocity errors due to the backscattering water particles illuminated by Doppler beams, designated as wet beams, are discussed. The influence of wet beams upon Doppler winds was calculated theoretically under various conditions to allow an estimate of maximum wird velocity error. Following the solution of wet-beam cases, theoretical consideration was given to the fluctuation of the measured winds caused by the constant errors in the true air speed, the aircraft heading, the Doppler ground speed, and the Doppler drift angle. For the purpose of investigating whether this type of error occurs or not, test flights were made over Florida and Oklahoma along a number of loops with varying djameters. Results of the evaluation revealed that the error in airciaft heading is of least importance and that the other errors can be determined and corrected with a high degree of accuracy provided only a few specific loops are flown during each mission. It has become feasible to calculate both divergence and vorticity associated with mesoscale disturbances from the calibrated Doppler winds measured along well-designed flight tracks. It is expected that the basic research presented in this paper will stimulate the use of Doppler wind systems in the determination of the detailed structure of winds accompanying mesoscale meteorological systems. 1.

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