Hurricane CharleyAug. 2004 Rapid Intensification and Trough Interaction By: Andy Latto
Objectives • What is trough interaction? • EFC Theory (Eddy Flux Convergence) • Potential Vorticity – PV • Model’s incorporating and forecasting trough interaction.
Trough Interaction • Dynamical and thermodynamic interaction between a hurricane vortex and upper level trough. • Trough needs to be close but not too close to storm for positive interaction (< 400 to 1000km) • Trough acts as a catalyst and storm responds positively or negatively.
Trough Interaction Theories • EFC – • PV 2 – Added heating (omega) aloft forces a stronger thermal gradient below. • Enhanced outflow due to increase in upper level flow. • Potential Vorticity: According to QG Theory, added positive vorticity advection increasing with height causes low level ascent.
Hurricane Charley August 2004
Hurricane Charley • Rapid Intensification: -24 hPa in 6 hours
Models Used GFDL AVN Global Model 100KM resolution Good for synoptic scale flows Bad for hurricane intensity • Uses Axi-symmetic vortex • Adds in asymmetric vortex • Triple-nested movable mesh • 1/12 degree resolution • Good for hurricane intensity • Problems with initialization
Results / Conclusion • EFC and PV during trough interaction can either strengthen or weaken a TC • Excess vertical shear caused by either PV of EFC is negative factor for intensification. (Balance is important) • Rapid intensification of TC’s is believed to need trough interaction, in part to occur. • Better data analysis, more offshore vertical data, and incorporation of data/equations into models necessary for accurate forecasting of trough interactions. • Lots theories at work here, and more work needs to be done to confirm these ideas.
ANY • QUESTIONS???????????????????????????????????????????? • References are in typed paper