Transcript 140404SanDiego_AMSTropicalConf_DeHart.ppt

QUADRANT DISTRIBUTION OF
TROPICAL CYCLONE INNER-CORE
KINEMATICS IN RELATION TO
ENVIRONMENTAL SHEAR
This research was supported by
NASA grants NNX12AJ82G and
NNX13AG71G and NSF grant ATM0743180
Jennifer C. DeHart, Robert A. Houze, Jr., and Robert F. Rogers
AMS Tropical • April 4th, 2014
Prior Composite Studies
Big Takeaways
• General downshear-upshear convective pattern
• No analysis of vertical dimension

Horizontal Composites
 Rainfall
(Chen et al. 2006)
 Lightning (Corbosiero and Molinari 2002, 2003)
Vertical Structure

Hence and Houze
(2011)
 TRMM
PR
 convective evolution
 BUT: lack velocity

Reasor et al. (2013)
 vertical
motion
consistent with previous
studies
 BUT: only examine mean
Objective

Examine the PDF of vertical velocity to determine
if it is consistent with the eyewall convective
evolution implied by the radar reflectivity
statistics
Dataset



2003-2010
125 eyewall crossings,
39 flights, 12 hurricanes
SHIPS deep-layer shear
(850-200 hPa)
>
2 kts
NOAA WP-3D Tail Radar
 Automated variational
algorithm

 Gamache

1997
Normalize horizontal
dimension by RMW2km
Eyewall Radar-derived Vertical Velocity CFAD
contours: 5%
--------------: 50%
Eyewall Vertical Velocity -- Anomalies
contours: 2%
+%
0
-%
Conclusion #1: Confirmation of
convective evolution hypothesis
What about outlier velocities?

Recent studies have analyzed strong updrafts in
relation to intensity changes
 how

do they behave in relation to shear?
Isolate data points where:
w
>= 5 m s-1
 w <= -4 m s-1

Investigate radial-height structure
Intense Updrafts -- Shear
contours: 5%
--------------: 50%
Intense Downdrafts -- Shear
contours: 5%
--------------: 50%
Conclusion #2
Intense drafts follow same pattern in relation to shear:
• Strong updrafts occur more often downshear.
• Strong downdrafts are highly concentrated in the UL
quadrant.
Frame drafts in context of w, vr




Identify azimuth of strong drafts
Isolate sector +/- 2 degrees from azimuth
Composite cross-sections
Only unique data points used
 sectors
of adjacent drafts used only once
Total Eyewall
Intense Updrafts
Intense Downdrafts
w
w
vr
vr
Radial Flow in left of shear quadrants
Intense Updrafts
Intense Downdrafts
Relationship
between radial and
vertical flow:
• is vertical motion
amplified by
radial flow?
• does vertical
motion induce
radial flow?
• do they arise
from a common
cause
Conclusion #3

Radial flow suggests different dynamical behavior when
intense updrafts and downdrafts present