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Chuntao Liu, Earle R. Williams, Edward J. Zipser, and Gary Burns

, Argentina, and the southern United States is from thunderstorms. b. Carnegie curve versus rainfall in thunderstorms and electrified shower clouds Figure 4 shows that the diurnal variation of total rainfall in universal time over 35°S–35°N has a consistent phase with the Carnegie curve, but with substantially lower amplitude. This is because nearly 75% of all rainfall is over ocean, which has a weaker diurnal cycle. The diurnal variation of rainfall over ocean has a substantially smaller amplitude (10

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Jonathan Zawislak and Edward J. Zipser

original tracking; Fig. 5 ) appears in the analysis over the ocean in the southern track on 20 August and appears to have developed between 19 and 20 August. Figure 7 provides a closer look at the GDAS analysis wind vectors at 1200 UTC on 19 ( Fig. 7a ) and 20 August ( Fig. 7b ), which clearly depict a tight circulation along 8°N at 925 hPa. In contrast to the dry, low-level northern track vorticity maximum tracked from northern Africa ( Fig. 5 ), the circulation at 925 hPa depicted in Fig. 7b is

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Syed Ismail, Richard A. Ferrare, Edward V. Browell, Gao Chen, Bruce Anderson, Susan A. Kooi, Anthony Notari, Carolyn F. Butler, Sharon Burton, Marta Fenn, Jason P. Dunion, Gerry Heymsfield, T. N. Krishnamurti, and Mrinal K. Biswas

limit (∼30°N and 38°W) of National Oceanic and Atmospheric Administration (NOAA) research aircraft that were conducting coordinated Saharan Air Layer Experiment (SALEX) research missions from Barbados ( Zipser et al. 2009 ). The study of African easterly waves (AEWs; Thorncroft and Hoskins 1994a , b ) and the potential development of AEWs into major Atlantic hurricanes is of great interest because nearly 85% of intense (or major) hurricanes have their origins as AEWs ( Landsea 1993 ). Seven AEWs

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Robert Cifelli, Timothy Lang, Steven A. Rutledge, Nick Guy, Edward J. Zipser, Jon Zawislak, and Robert Holzworth

convection associated with MCSs. In this study, we examine the relationship of convection to an AEW as it moved over West Africa, crossed the coastline, and entered the oceanic environment. In particular, we make use of ground-based radar data from three locations—Niamey, Niger; Dakar, Senegal; and Praia, Cape Verde—during the AMMA–NAMMA campaign, representing three distinct geographical locations—continental, coastal, and maritime—to explore the relationship between the wave and MCS precipitation

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Scott A. Braun, Michael T. Montgomery, Kevin J. Mallen, and Paul D. Reasor

tilting of horizontal vorticity into the vertical, provides a source of concentrated midlevel vorticity ( Gamache and Houze 1982 ; Verlinde and Cotton 1990 ; Brandes and Ziegler 1993 ; Chen and Frank 1993 ; Bister and Emanuel 1997 ; Chong and Bousquet 1999 ; Yu et al. 1999 ) that often becomes the precursor to surface development. Although MCSs occur frequently over the tropical oceans, only a few develop into tropical cyclones and the mechanisms that inhibit or favor development are still

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Chanh Q. Kieu and Da-Lin Zhang

MV2 storm, given all the possibly favorable conditions, and if so, how long it would take for such a breakdown to reach TS intensity under the present eastern Pacific conditions. On the other hand, a comparison between WST_V2 and WSST will allow us to assess the efficiency of the ITCZ rollup versus vortex merger in the development of Eugene from a weak disturbance to a tropical storm over the same tropical ocean surface. c. Diminished frictional convergence in the PBL Craig and Gray (1996

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Stephen R. Guimond, Gerald M. Heymsfield, and F. Joseph Turk

Oceanic and Atmospheric Administration (NOAA) WP-3D (P-3) aircraft have been providing a wealth of details on TCs that has revolutionized the understanding and operational forecasting of these systems (e.g., Jorgensen 1984 ; Marks and Houze 1987 ; Aberson et al. 2006 ; Reasor et al. 2009 ). In addition to the P-3 TA radar, the more advanced Electra Doppler Radar (ELDORA) operated by the National Center for Atmospheric Research (NCAR) has flown recent missions into TCs revealing convective

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Chanh Q. Kieu and Da-Lin Zhang

global models in predicting TC tracks indicate that the large-scale circulation is the key parameter in determining where TCG may occur. It is well known that the large-scale conditions conducive for TCG over different ocean basins include weak vertical wind shear ( Gray 1968 ; McBride and Zehr 1981 ; DeMaria 1996 ), warm sea surface temperature (SST) and deep moist layers ( Emanuel 2000 ), well-organized angular momentum fluxes ( Challa and Pfeffer 1990 ), easterly waves ( Molinari et al. 2000

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Edward K. Vizy and Kerry H. Cook

the National Center for Atmospheric Research–National Oceanic and Atmospheric Administration (NCAR–NOAA) Advanced Research Weather Research and Forecasting model (ARW-WRF) and National Aeronautics and Space Administration observations taken in support of the African Monsoon Multidisciplinary Analyses (AMMA) field campaign. Background on the conditions necessary for tropical cyclogenesis is reviewed in section 2 . Section 3 describes the regional model and the modeling approach. In section 4

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Chanh Q. Kieu and Da-Lin Zhang

. TCG occurs as soon as the WISHE process is initiated. A recent statistical study of TCG over the eastern Pacific during the active seasons of 1999–2003 shows that most of the TCG events in this ocean basin are associated with intertropical convergence zone (ITCZ) breakdowns caused by easterly propagating tropical disturbances ( Wang and Magnusdottir 2006 ). Although the ITCZ breakdowns could be attributed to the internal dynamical instability—that is, the so-called roll-up mechanism discussed by

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