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AMS Hurricane and Tropical Meteorology Conference Tucson May 9, 2010 Vertical distribution of radar reflectivity in eyewalls observed by TRMM Deanna A.

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Presentation on theme: "AMS Hurricane and Tropical Meteorology Conference Tucson May 9, 2010 Vertical distribution of radar reflectivity in eyewalls observed by TRMM Deanna A."— Presentation transcript:

1 AMS Hurricane and Tropical Meteorology Conference Tucson May 9, 2010 Vertical distribution of radar reflectivity in eyewalls observed by TRMM Deanna A. Hence and Robert A. Houze, Jr. University of Washington

2 Idealized vertical structures suggested by past studies Inner rainband Outer rainband Inner rainband Deep Restricted From Houze et al. (2007) How does the eyewall structure change with storm evolution and environmental conditions?

3 Primary Analysis Tools TRMM Precipitation Radar (PR) NCAR Zebra software Contoured Frequency by Altitude Diagrams (CFADs) Yuter and Houze 1995, Houze et al Relative frequency of occurrence From NASA TRMM website (http://trmm.gsfc.nasa.gov/)

4 Annuli and Quadrant Analysis Reflectivity (dBZ) TRMM PR Maximum Reflectivity at 03:26 on 28 August 2005 Shear Vector DL UL UR DR From the National Hurricane Center (NHC) best track data Center location Eye diameter Storm motion

5 Raw Number CFADs, Not Normalized, All Overpasses UR UL DL DR peak of low-level distribution Track Shear

6 How shear affects the eyewall shear From Black et al. (2002)From Braun et al. (2006) Updrafts initiating just upwind of the downshear-left quadrant shear ULDL URDR UL DL DR UR

7 Vertical structure in weaker and stronger storms Greater reflectivity overall More extreme outliers  intermittent intense cells CAT4,5 CAT1,2 Total Eyewall Annulus, Normalized

8 Majority of distribution similar High SST (>28 °C) Vertical structure over cooler and warmer water Outliers much stronger and higher in high SST cases Marginal SST (26-28 °C) Total Eyewall Annulus, Normalized

9 Vertical structure by quadrant relative to shear

10 Brightband appears Weaker overall, no distinct peak No brightband, broad upper levels Normalized CFADs, All Overpasses Track Shear Brightband intensifies DL UL UR DR

11 Normalized CFADs, High SST Tighter Distribution DL Weakening UL Strengthening UR Track Shear Weakening DR More distinct brightband

12 Vertical wind shear Determines echo placement around the eyewall Cat. 4 and 5 storms More intense More intermittent intense cells Lower SST values Suppress intense outliers Doesn’t change the mean reflectivity distribution Track motion ≥ shear, opposite in direction echo formation region shifts upshear right Conclusions

13 Ongoing Work Expand analyses to rainband and outer regions Expand analyses to intense cyclones in worldwide basins

14 Normalized CFADs, High SST Tighter Distribution DL Weakening UL Strengthening UR Track Shear Weakening DR More distinct brightband

15 Normalized CFADs, Low Shear Track Narrowing of upper levels Shear Tighter Distribution DL Weakening UL Strengthening UR DR More distinct brightband

16 This research was supported by NSF Grant ATM and NASA Grants NNX07AD59G and NNX10AH70G


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