A Multiscale Analysis of the Inland Reintensification of Tropical Cyclone Danny (1997) within an Equatorward

Jet-Entrance Region

Matthew Potter, Lance Bosart, and Daniel KeyserDepartment of Atmospheric and Environmental Sciences

The University at Albany, State University of New York, Albany, NY

6 May 2011Spring 2011 CSTAR Meeting

UCAR/NCEP Grant# S1071092

Motivation

• Document a rare event of a tropical cyclone (TC) that reintensified unexpectedly overland in a low-level baroclinic zone beneath an equatorward jet-entrance region

Purpose

• Document synoptic and mesoscale processes which lead to the inland reintensification of TC Danny (1997)

• Document an interaction between TC Danny with a baroclinic zone beneath an equatorward jet-entrance region

• Establish a climatology of these relatively rare events to put TC Danny into perspective

Outline

• Brief Literature Review

• Data Sources and Methodology

• Preliminary Results

• Technology Transfer

Brief Literature Review• Bosart and Lackmann (1995)– Documented the overland reintensification of TC

David (1979) in a weakly baroclinic environment– Found that David intensified in response to

downstream ridge building and jet development• Bassil and Morgan (2006)– Documented the overland reintensification of TC

Danny (1997)– Used Eta model forecasts to determine that TC Danny

reintensified through cyclonic vorticity advection, trough/jet interactions, and vortex tube stretching

• Evans et al. (2010)– Provided a physical basis for the reintensification

of TC Erin (2007)• Modulation of a moist, unstable thermodynamic

environment by moist soil conditions• Interaction of the remnant vortex with the cyclone-

influenced nocturnal lower tropospheric jet

Data Sources and Methodology

• Datasets/Sources– Preliminary Climatology• NCEP/NCAR Reanalysis datasets (2.5° x 2.5°)• Archived NCDC North American surface charts

– Multiscale Analysis of TC Danny• NCEP/NCAR Reanalysis datasets (2.5° x 2.5°)• 0.5° NCEP Climate Forecast System Reanalysis (CFSR)

datasets• WSR-88D radar datasets

• Outline of Thesis Work– Preliminary Climatology• The NCEP/NCAR Reanalysis datasets and NCDC surface

charts were used to produce a 61-year (1950-2010) climatology of inland reintensification TCs

–Multiscale Analysis of TC Danny• Synoptic Overview– The NCEP/NCAR Reanalysis datasets will be used for

a first hand look at the event– A potential vorticity thinking perspective will be

employed to help elucidate storm-jet interactions.• Mesoscale Overview– CFSR datasets will be used to identify important

mesoscale circulation features –WSR-88 radar will be used to facilitate the

mesoscale analyses and indentify structural changes in convection and stratiform precipitation around Danny

Preliminary Results

• Climatology– Numerous probable inland TC reintensification events:

• Cleo (1964), Agnes (1972), David (1979), Diana (1984), Chris (1988), Danny (1997), Helene (2000), Gaston (2004), Erin (2007)

– Several other TCs will need to dissected in greater detail to determine whether they should be included

– Most TCs reintensify around eastern North Carolina• Multiscale Analyses of TC Danny– Most of the analyses will be conducted this summer

Reintensifying TC Locations

David (‘79)

Gaston (‘04)

Chris (‘88)

Cleo (‘64)

Helene (‘00)

Diana (‘84)Agnes (‘72)

Danny (‘97)Erin (‘07)

100° 90° 80° 70°

30°

40°

50°

1800 UTC 24 July1000 hPa 40 knots

0000 UTC 19 July984 hPa 70 knots

1800 UTC 25 July994 hPa 50 knots

0000 UTC 24 July1012 hPa 20 knots

0000 UTC Locations

1800 UTC 24 July Composite Map and TC Danny Track

KAKQ Radar 1500 UTC - 1800 UTC 24 June 1997

• Possible hypotheses attributed to the inland reintensification of TC Danny: – Frontogenesis along the low-level baroclinic zone

and associated tropospheric-deep ascent beneath the equatorward jet-entrance region

– Deep convection around TC Danny that provided a source of diabatic heating, which reinforced the ascent near the storm center

– Low-level vorticity growth around Danny through vortex-tube stretching in an environment that favored enhanced ascent near the storm center

Technology Transfer

• Establish a basis for synoptic and mesoscale signatures for inland reintensifying TCs

• Provide additional guidance for issuing high wind warnings/advisories

• Allow for identification of possible enhanced precipitation and flooding

Contact Information

Preliminary results are located at:– http://www.atmos.albany.edu/student/mpotter/

research.html– mpotter@atmos.albany.edu

Questions or comments?