The degree of organization and the size of the cloud patterns in TIROS pictures of tropical disturbances are good indicators of the maximum wind speed as observed by airplanes. The organization varies from unorganized bright cloud patterns, to highly Organized spiral arrays of clouds with additional characteristic features, such as the sharp edge of cirrus clouds. Poorly organized clouds are associated with weak disturbances, the most highly organized ones with intense storms. I n addition, within each category a relationship exists between the size of the cloud pattern and the maximum wind speed. Both the organization category and the size of the overcast cloud pattern are related statistically to the maximum wind speed, so that the maximum wind speed can be estimated from the picture of the storm alone. Tests with independent data show that a useful relationship has been obtained. Theoretical justification for the results obtained is necessary but is not yet available.
TIROS I satellite pictures for a 3-day period about, :t developing "Low vysterrl" over the central United States are shown. Cloud distribut,ion about surface fronts and upper-air troughs was examincd and compared to the "ideal" (classical) distribution. The pictures and analyses reveal t,hat cloud patterns w e r e significantly changed by strong subsidence and advection of dry air along a lo~v-levc~l wiud maxirrlum. The cloud patterns whcn compared to the 600-mb. vertical motions computed routinely hy the Joint Xnmerical Wvathcr Prediction Vnit showed only partial agreement. A strong relationship hetween low cloud cover and surface rc1:ttivr humidity \$as found; thjs relationship may be useful under certain conditions in determining the stability of the air over areas where upper-air data are sparse.
The empirical relationship between the maximum wind speed (MWS) of tropical storms and their characteristics pictured from satellites has been employed routinely since 1964. A large number of cases accumulated since then now enables these relationships to be put on a more firm statistical basis and revised MWS curves are presented.
The purpose of this study is t o evaluate the reliability of locating jet streams by means of certain cloud patterns in TIROS pictures, and to determine the most definitive characteristics of those patterns. It would be very useful omrationally, especially in data-sparse regions, if the jet stream could be accurately located from satellite pictures. Jet stream positions over the United States estimated from TIROS pictures are compared with positions from operational analyses during a 3-month period. The cases are reexamined to determine under which conditions agreement did or did not occur. Jet streams can be accurately located in about 80 percent of the cases whenever clearly defined cloud characteristics occur under favorable viewing conditions. The most definitive cloud characteristics are (1) a n extensive cirrus shield having a sharply defined poleward edge, often outlined by a shadow cast on lower cloud surfaces or on the earth, and (2) transverse banding in the cloud shield. Further, cirrus streaks alone prove to be undependable detectors. The greatest danger exists in confusing frontal cloudiness with jet stream cloudiness. There is the suggestion that operational jet analysis can benefit from satellite pictures even in data-rich areas. Initially agreement is achieved in about half the cases. The jet axis is located on the poleward cloud edge. 127 128 MONTHLY WEATHER REVIEW Vol. 94, No. ' He too has noted the streaked nature of cirrus, which he ological Research Committee, Sept. 1955, 7 pp. 9. P. W. Kadlec, "A Study of Flight Conditions Associated with Jet Stream Cirrus, Atmospheric Temperature Change, and Wind Shear Turbulence," Final Report, Contract NO.
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