Quadrant distribution of tropical cyclone inner-core kinematics in relation to environmental shear

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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
ATM-0743180

• Jennifer C. DeHart, Robert A. Houze, Jr., and
  Robert F. Rogers
• AMS Tropical April 4th, 2014

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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)

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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

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Objective

• Examine the PDF of vertical velocity to determine
  if it is consistent with the eyewall convective
  evolution implied by the radar reflectivity
  statistics

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Dataset

• 2003-2010
• 125 eyewall crossings, 39 flights, 12 hurricanes
• SHIPS deep-layer shear (850-200 hPa)
• gt 2 kts

• NOAA WP-3D Tail Radar
• Automated variational algorithm
• Gamache 1997
• Normalize horizontal dimension by RMW2km

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Eyewall Radar-derived Vertical Velocity CFAD
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Eyewall Vertical Velocity -- Anomalies

contours 2
0
-
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Conclusion 1 Confirmation of convective
evolution hypothesis
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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 gt 5 m s-1
• w lt -4 m s-1
• Investigate radial-height structure

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Intense Updrafts -- Shear
contours 5 -------------- 50
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Intense Downdrafts -- Shear
contours 5 -------------- 50
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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.

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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

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Total Eyewall
Intense Updrafts
Intense Downdrafts
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Radial Flow in left of shear quadrants

• 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

Intense Updrafts
Intense Downdrafts
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Conclusion 3

• Radial flow suggests different dynamical behavior
  when intense updrafts and downdrafts present