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Lance F. Bosart

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Lance F. Bosart

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Lance F. Bosart

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Average kinematic vertical motion and relative vorticity profiles are presented for a long-lived midlatitude convective complex. A breakdown into active convective and stratiform precipitation regions shows very good agreement in the vertical motion profiles with published results for tropical convective systems.

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Lance F. Bosart

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An analysis of skill in predicting daily temperature and precipitation is presented for six years (1969–1975) of forecasts made for the Albany County Airport by students and faculty in the Department of Atmospheric Science of the State University of New York at Albany. The daily consensus forecast (made up by averaging the forecasts of all forecasters) shows no significant secular increase in skill for temperature. An apparent increase in the consensus skill in precipitation forecasting is noted with most of the increase occurring in the spring 1972 semester. Possible reasons for this increase are discussed. The skill (defined as the percentage improvement over a persistence climatological forecast) of the ensemble of forecasters over a persistence climatological control is near 50% for the first day decaying to 10% and near zero by the 3rd and 4th day for precipitation and to just under 10% for temperature by the 4th day. These results are consistent with the results presented by Sanders (1973).

Some relationship is found for skill to be a function of the variability of the daily temperature about the climatological mean. Skill, however, appears to be insensitive to the frequency of days with radiational cooling, a major local forecast problem. likewise skill appears to be independent of daily rainfall amount or frequency. These findings are consistent with those found for Boston by Sanders (1973).

Finally, the trend towards a plateau in skill noted by Sanders (1973) is confirmed for a different location.

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Lance F. Bosart

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Correction to Volume 5, Issue 3, pages 527-528.

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Lance F. Bosart

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Lance F. Bosart

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A case study is made of a period of exceptional warmth in the mid and upper troposphere over the Carib-bean from 19–21 February 1964. The case is a good example of intense winter interaction of mid-latitude and tropical circulations during which lateral forcing from higher latitudes appears to play a prominent role. For example, at 500 mb, temperatures of −1 to −2C which exhibited spacial and temporal continuity on the synoptic scale were noted. These values were more than three standard deviations warmer than monthly mean values and occurred in association with a strong low-latitude polar jet along the Gull Coast of the United States.

Isentropic trajectories document average 12-hr descent rates of up to 2 cm sec−1 in the vicinity of 15N in association with the warmth area. Criteria for inertial instability is satisfied over a portion of the anti-cyclonic flank of the strong jet stream leading to a speculative case for a transverse thermally indirect circulation such that a persistent anticyclone north of Puerto Rico is strengthened. Reed and Vleck's hypothesis on the annual temperature cycle of the tropical lower stratosphere is examined on a limited basis with daily data both directly and indirectly with rather inconclusive results.

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Lance F. Bosart

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During the period 26–29 May 1968 a shallow cyclonic circulation, known 1ocally as a Catalina eddy, developed in the offshore waters of southern California. A synoptic and mesoscale analysis of the event establishes the following: 1) the incipient circulation forms on the coast near Santa Barbara downwind of the coastal mountains, 2) cyclonic shear vorticity appears offshore in response to lee troughing downstream of the coastal mountains between Vandenberg and Pt. Mugu, California, 3) mountain wave activity may be aiding incipient eddy formation in association with synoptic-scale subsidence and the generation of a stable layer new the crest of the coastal mountains, 4) a southeastward displacement and offshore expansion of the circulation occurs following the passage of the synoptic-scale ridge line, and 5) dissipation of the eddy occurs with the onset of a broad onshore flow.

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Lance F. Bosart

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Lance F. Bosart
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