1. Convective Contribution to the Genesis of Hurricane Ophelia (2005)
Robert A. Houze, Jr.
University of Washington
Wen-Chau Lee and Michael M. Bell National Center for Atmospheric Research
Seminar at National Hurricane Center, Miami, 25 August 2008

2. Mesoscale convective system lifecycle
~200 km
~100 km

3. Convection in an intensifying tropical depression--idealized
Ritchie & Holland 97
Bister & Emanuel 97
Zipser & Gautier 78
Hendricks et al. 03
Montgomery et al. 06

4. Hurricane Ophelia (2005)
Ophelia formed from a non-tropical weather system. A cold front moved off the eastern coast of the United States on 1 September. The front moved southeastward and became part of an elongated trough of low pressure that extended from Tropical Depression Lee east of Bermuda to near the Florida Peninsula. Two areas of low pressure formed in the trough on 4 September. The eastern low, south of Bermuda, eventually became Hurricane Nate. The western low, near the Bahamas, became Ophelia.

6. Ophelia formed from a non-tropical weather system
Ophelia formed from a non-tropical weather system. A cold front moved off the eastern coast of the United States on 1 September. The front moved southeastward and became part of an elongated trough of low pressure that extended from Tropical Depression Lee east of Bermuda to near the Florida Peninsula. Two areas of low pressure formed in the trough on 4 September. The eastern low, south of Bermuda, eventually became Hurricane Nate. The western low, near the Bahamas, became Ophelia.
500 mb

8. NOAA Hurricane Field Program Flight Plan for “Convective Burst”

16. dBZ, vorticity, pv

18. For whole volume. Outliers in cell
For whole volume. Outliers in cell. Bulk of mass transport is by moderate updrafts. These are probably the remnants of previously strong cells. --> stratiform

19. Stratiform region
Strat refl. Probably remnants.

20. Stratiform region

21. Stratiform region
No downdraft

22. Stratiform region sounding (“onion sounding”)

23. Stratiform region 30 20 10

25. Convection in an intensifying tropical depression--idealized
Ritchie & Holland 97
Bister & Emanuel 97
Zipser & Gautier 78
Hendricks et al. 03
Montgomery et al. 06

26. Conclusions Convective cells extremely deep & intense
Downdraft outflow convergence absent--buoyancy probably due to wind-induced mixing
PV generated in convective cells at low-mid levels
Stratiform region accumulates vorticity generated in cells
Vorticity in both convective and stratiform regions is axisymmetrized into the parent vortex
Stratiform region downdrafts not significant
Bullet 1--Zipser
Bullet 2--Crook & Moncrieff
Bullet 3--Zipser/Gautier, Montgomery
Bullet 4--Montgomery
Bullet 5--Bister & Emanuel

27. Extra slides