NATIONAL HURRICANE RESEARCH PROJECT •'•'•'• / •ST" jj&ifs v •'•'T' 0 W- L7 REPORT NO. 67 On the Thermal Structure of Developing Tropical Cyclones F=* ^ \ S>1 lv'r*;>k . SPritiJ LABORATORY i U. S. DEPARTMENT OF COMMERCE Luther H. Hodges, Secretary WEATHER BUREAU Robert M. White, Chief NATIONAL HURRICANE RESEARCH PROJECT REPORT NO. 67 On the Thermal Structure of Developing Tropical Cyclones DATE DUE V, Jr. -Project, Miami, Fla. QEMCO 38-297 Washington, D. C. January 1964 UlfiMDl DbDlH4fi I NATIONAL HURRICANE RESEARCH PROJECT REPORTS this seSeTto'f^ the hurricane problem are preprinted in paperthis limitedin the seriesreproductionshouldandideS^Tdistributionasa^XSTrSJo!!?in this fom %?ZTC°nStltUte+T2S V*f0rnalWOrkers•*««««•»* otherpublication,interestedreferenceunits. toAs a Bo. 1. Objectives and basic design of the NHRP. March 1956. So. 2. Numerical weather prediction of hurricane motion. July 1956 Supplement: J™ «£jj ^prognostic 500-mb. maps made for numerical weather prediction of hurricane Ho. 3. Rainfall associated with hurricanes. July 1956 Jo. k. Some problems involved in the study of storm surges. December 1956. «o. 5. ^^-teorological factors pertinent to reduction of loss or life and property in hurricane situations. Mo. 6. Amean atmosphere for the West Indies area. May 1957 foil:, jtriTtsiwa^:^^^^^tr'i^zr1^"^^^^^0-and the atmosphere in relationVi^lSS^Sl^'j^^. "* QXtbB^ °f eBer6y between **«***•8ea «o. 9. Seasonal^variations in the fluency of Horth Atlantic tropical cyclones related to the general circulation. Ho. 10. Estimating central pressure of tropical cyclones from aircraft data. August 1957. Ho. 11. Instrumentation of National Hurricane Research Project al^Sft™Amaurt^s? Ho. 12. Studies of hurricane spiral bands as observed on radar. September^?? Ko. 13. Mean soundings for the hurricane eye. September 1957. Ho. Ik. On the maximum intensity of hurricanes. December 1957. S* 3' ?«.Jr«;diaef^ wind structure around atropical cyclone. January 1958. Ho. 16. Modification of hurricanes through cloud seeding. May 1958 2°* %' f?*1*818 of *«>Pical storm Frieda 1957. A preliminary report. June 1958. S* K' ^Z+?* °f «"» layer "iad* aa ahurricane steering mechanism. June 1958. 2*«T I?*™ ^r!?er2LS.TJ1",0',*1"exanination <* «»emturebalancehurricaneof angularand othermomentumrotatingin theiS^JStX,mature hurricane £58.July 1Q58^ fcho. S"22. STSLon production Sftf°mof kinetic energy^ from tocondensationr1168 heating.«" «« ^^nKOctober 1958. ciiS: September*-««»«^ 1958.j*?o. Ko. 23. Hurricane Audrey storm tide. October 1958. S* S* Sf*^ ^f circulation in the high energy core of hurricane Carrie. November 1958. Ho. 25. Distribution of surface friction in hurricanes. November 1958. £' Vn tZ***? ^J^8*? °f hurricane radar spiral bands and the echoes which form them. February 1959. Ko.S' 20.£ Arr!!!efngL°fmodel hurricane*•*planBoardforofaReviewcoastal•»*community.ConferenceMarchon Research1959. Progress. March•1959. ^^^ ™ Ho. 30.29. MeanExchangesoundingsof heat,formoisture,the Gulf ofandMexicomomentumarea.betweenAprilhurricane1959. Ella (1958) and its environment.ironware, ju>rnApril 195Q1959. Ko. 31. On the dynamics and energy transformations in steady-state hurricanes. August 1959. Ko. 32. An interim hurricane storm surge forecasting guide. August 1959. No. 33. Meteorological considerations pertinent to standard project hurricane, Atlantic and Gulf coasts of the United States. November 1959. —*«««. No. 3h. Fining and intensity changes in hurricanes over land. November 1959. !£* %' n^ ff V™**"*6 neldB la **» stratosphere over the West Indies region in August 1958. December 1959. No. 36. Climatological aspects of intensity of typhoons. February i960. *** No. 37. Unrest In the upper stratosphere over the Caribbean Sea during January i960. April I960. Ho. 38. On quantitative precipitation forecasting. August i960. Ko. 39. Surface winds near the center of hurricanes (and other cyclones). September i960. No. kO. On initiation of tropical depressions and convection in a conditionally unstable atmosphere. October i960 No. kl. On the heat balance of the troposphere and water body of the Caribbean Sea. December i960. No. k2. Climatology of 2l*-hour North Atlantic tropical cyclone movements. January 1961. !£* n ?e^1Ctl0n °f movenents a*1 surface pressures of typhoon centers in the Far East by statistical methods. May 1961 Ho. «W. Marked changes in the characteristics of the eye of intense typhoons between the deepening and filling states May I96I. No. 1*5. The occurrence of anomalous winds and their significance. June 1961. No. kb. Some aspects of hurricane Daisy, 1958. July 1961. •No..!£' LA*kQ. Onn^f^*8the structure!^ "ec^nicsof hurricaneand theniwiynamicsDaisy (1958). ofOctoberthe inflowI961.layer of the mature hurricane.^^ °cpwaroerSeptember 196l.xyox. 2°* !£* ^° P^^rties of hurricane wind fields as deduced from trajectories. November 1961. No. 50. Proceedings of the Second Technical Conference on Hurricanes, June 27-30, 1961, Miami Beach, Fla. March 1962. No. 51. Concerning the general vertically averaged hydrodynamic equations with respect to basic storm ^^ surge equations. April 1962. Ho. 52. Inventory, use, and availability of NHRP meteorological data gathered by aircraft. April 1962. mo. 53. on the momentum and energy balance of hurricane Belene (1958). April 1962. Ko. 5*. On the balance of forces and radial accelerations in hurricanes. June 1962. Ho. 55. Vertical wind profiles in hurricanes. June 1962. Ho. 56. Atheoretical analysis of the field of motion in the hurricane boundary layer. June 1962. 2°' 11' 2? the dynamics of disturbed circulation in the lower mesosphere. August 1962. No. 50.. Mean sounding data over the western tropical Pacific Ocean during the typhoon season, and » «« D Distribution of turbulence and icing in the tropical cyclone. October 1962. Ko. 59. Reconstruction of the surface pressure and wind fields of hurricane Helene. October 1962. Jo' *?* L^"* SeedlDg exPeriment in hurricane Esther, I961. November I962. So* %' SUdJ?%°?fc8I?tletlcal P»«e*ion of typhoons. April 1963. !„' S" 5LdlB*ri,?ufcloB of ***** water in hurricanes. June I963. Ko.No* g.6b' ^J^Instability aspectsbe!Veenof Wind:urricaneaQd theraalgenesis.structureJune I963.of steady state hurricanes. June I963.* * ko.Z' 00.£ "jjJJJ^J^rSf.£ T ^fi0n,°ftropical^ WindcyclonesfiCld dUringover land,the lif«withcycleparticularof tropicalreferencecyclones.to hurricaneNovemberDonna1963.of i960. .A/37 A#' M? / CONTENTS 1. INTRODUCTION * 1 2. CASES SELECTED FOR ANALYSIS 2 3. CHARTS ANALYZED AND ANALYSIS METHODS 3 Thickness values vs. shear winds 3 Parameters measured from thickness charts '. 5 k. RESULTS AND DISCUSSION 5 Description of the developing cases 7 Developing vs. nondeveloping cases 9 large vs. small storms 10 Comparison of different thickness charts 11 Shears of mean layer winds vs. shears of conventional winds ... 1^ 5. COMMENTS ON THE OPERATIONAL USEFULNESS OF THE 500-200-MB. THICKNESS CHART Ik 6. SUMMARIZING STATEMENTS l8 ACKNOWLEDGMENTS 20 REFERENCES 20 APPENDIX A - Characteristics of storms studied 21 APPENDIX B- Parameters measured from thickness charts 22 USCOMM-WB-DC pOLORAWr rTXTl >-fVEMSTT E£r£ Pollingi^^^ »«-C^., ON THE THERMAL STRUCTURE OF DEVELOPING TROPICAL CYCLONES Edward J. Zipser National Hurricane Research Project, U. S. Weather Bureau ABSTRACT In an effort to determine the nature of the thermal field in the vicinity of developing tropical cyclones as distinguishable by use of data from the existing operational network, thickness charts were constructed for the West Indies area. The development of thirteen Atlantic storms was investigated, these being chosen from the population of 1958-1962 Atlantic storms by including only those favorably situated relative to the data network. To serve as a control group, nine disturbances which failed to develop were . treated in the same manner. The method of analysis of the thickness charts is discussed. The thickness and shear patterns in the vicinity of the storms are described, and comparison made between developing and non-developing cases. Changes in the thickness pattern as development proceeds are discussed briefly. Several different thickness layers are compared and rated for their usefulness in delineating the above patterns. Finally, the operational utility of thickness charts as an aid in predicting cyclogenesis is evaluated. 1. INTRODUCTION It is widely known that the ultimate product of the hurricane develop ment process is a warm-core cyclone. The temperature excess over mean tropical conditions is greatest inside the eye wall in the upper troposphere, and the warm anomalies spread farthest from the eye in the upper troposphere. The cross-section presented by LaSeur [5] for hurricane Cleo, 1958, shows these features, and there is every reason to believe that this is a typical dis tribution. To be consistent with this thermal field, actual wind shears should have anticyclonic components, more marked in the upper than in the lower troposphere. That this is indeed observed is amply documented in the literature. Our recent increased understanding of the structure of the mature hurricane is largely attributable to abundant data from research and re connaissance aircraft. The incipient stages of the hurricane are less well observed, however. The same can be said for the more common disturbances of the Tropics. In both cases, models of thermal structure are far from defini tive, and the nature of the evolutionary process by which the warm core of the hurricane develops is not clear. Since the expansion