Summary of meetings between Jeff Kepert and HRD

Tuesday morning (April 22, 2003) GPS sonde meeting:

Jeff Kepert : started by describing some of his preliminary landfall boundary layer modeling which indicates that friction-induced asymmetries from motion and also from landfall yield wind maxima at different altitudes in boundary layer, an anticyclonic spiral. This shows up as a secondary wind max in the offshore flow. In Hurricane Danny (1997), Jeff Kepert's model reproduces features noted by Keith Blackwell in his study of the WSR-88D data from Mobile, AL. It was suggested that Eric Uhlhorn and Pete Black need to validate (or reject) the use of SFMR winds at landfall.

Pete Black: But large-scale forcing would overwhelm these effects. Much discussion ensued and then we discussed which storms would be best to look at.

Mike Black : suggested Hurricane Isisdore (2002) at the the Merida, MX landfall might be the best case.

Jeff Kepert mentioned that Hurricane Floyd (1999) sonde data also seems to show anticyclonic wind max spiral. But Floyd and Bonnie (1999) were sheared cases.

Mark Powell : asked about significance of boundary layer features, any significance to forecasters. Can we use it to diagnose asymmetry in wind reduction factors?

We decided that the storms to look at would be Bret,Isidore, Floyd and Bonnie.

- Peter Dodge and Shirley Murillo


Thursday afternoon (April 24, 2003) landfall meeting :

Jeff Kepert plans to work on Hurricane Isidore's landfall in Yucatan and Hurricane Humberto (2001), then Hurricane Bret (1999), and Hurricane Bonnie and/or Floyd as sheared landfall cases.

Hurricanes Bret and Isidore effort:
Jeff Kepert will look at sondes while Shirley Murillo will look at H*Wind analyses with attention to reduction factors, maybe compare flight level reduction to sonde values. Peter Dodge will work with John Gamache to generate Planetary Boundary Layer Doppler profiles for Hurricanes Bret and Isidore, Peter Dodge will also verify wind distributions in Hurricane Bret landfall radar analyses.

The idea is to email 1-2 page PDF's, with figures back and forth as we discover/notice features and complete analyses. These can then be cut and pasted for conference preprints and then congeal (we hope) into a series of papers, one per storm.

- Peter Dodge