Thermodynamic Structure of Tropical Cyclones From Aircraft Reconnaissance Kay Shelton University at Albany/SUNY, Albany, New York

US Air Force reconnaissance flights. –Archive maintained by John Knaff (CIRA) , 77 storms  619 flights. Equivalent potential temperature  e. –Bolton (1980). Case-study: Bret, –Comparison of  e and windspeed through storm evolution from tropical depression through to category 4 hurricane. Composite of all storms. –Data every 30s, averaged into 20km radial bins –(>5 points per bin to be included) –Categorised average  e profiles by level and intensity. DATA AND METHODOLOGY

Instrument wetting errors (IWE). –Eastin et al. (2002).LIMITATION Adapted from Eastin et al. 2002b IWE minimised away from eyewall. In eyewall, maximum mean error < 3K. Removal of IWE acts to move maximum radial gradient towards outer edge of eyewall. Errors may be larger for individual cases.

Hurricane Bret, –Organised to TD at 18Z on 18 th August, in Bay of Campeche. –Bret strengthened to category 4, then decreased to category 3 prior to landfall on Padre Island, TX at 00Z on 23 rd August. –Scatter plots of  e and windspeed in six flights will be shown. CASE STUDY

<500m TD-TS TS <500m ee Windspeed

TS H1-H2 ~850hPa 37.5km ee Windspeed

H4 H4-H3 ~700hPa 17.8km 32.5km ee Windspeed

COMPOSITE Flight level must increase as storms intensify. Weaker systems have fewer flights above PBL, stronger systems have fewer flights below 700hPa. Comparison between levels at a given intensity is limited to TS and H1.

COMPOSITE INWARD RADIAL GRADIENT OF  e -  e /  r ( K/100km) <500m ~850hPa ~700hPa

 e DIFFERENCE BETWEEN 2 LEVELS TS:  e (BL) –  e (850hPa)H1:  e (850hPa) –  e (700hPa)  e (K)   Arrows indicate relevant tropical environment  e /  p (Jordan, 1958)

SUMMARY RADIAL TD: |  e /  r| ~ 0 at all radii TS:  e increases first in the core (r<90km) H1-H4: |  e /  r| increases with intensity, within r=100km VERTICAL TS and H1: In lower troposphere convective instability increases outward. –Both profiles are close to convective neutrality near storm centre and convective instability increases outwards to their respective tropical environmental values.