Downdrafts and the Evolution of Boundary Layer Thermodynamics in Hurricane Earl (2010) before and during Rapid Intensification

AbstractUsing a combination of NOAA P-3 aircraft tail Doppler radar, NOAA and NASA dropsondes, and buoy and drifter based sea surface temperature data, different types of downdrafts and their influence on boundary layer (BL) thermodynamics are examined in Hurricane Earl (2010) during periods prior to rapid intensification (RI; a 30 knot increase in intensity over 24 hours) and during RI. Before RI, the BL was generally warm and moist. The largest hindrances for intensification are convectively driven downdrafts inside the radius of maximum winds (RMW) and upshear-right quadrant, and vortex-tilt induced downdrafts outside the RMW in the upshear-left quadrant. Possible mechanisms for overcoming the low entropy (θe) air induced by these downdrafts are BL recovery through air-sea enthalpy fluxes and turbulent mixing by atmospheric eddies.During RI, convective downdrafts of varying strengths in the upshear-left quadrant had differing effects on the low-level entropy and surface heat fluxes. Interestingly, the ...