Some Characteristics of Developing and NonDeveloping Vorticity Maxima:

1
Some Characteristics of Developing and
Non-Developing Vorticity Maxima East Pacific
Versus Atlantic. Brandon W. Kerns, Kantave M.
Greene, Chuntao Liu, and Edward J.
Zipser University of Utah, Department of
Meteorology
2. Two vorticity maxima properties that matter
for each region

1. Two Views of tracking Wave Features vs.
Vorticity Maxima Wave Feature View TCSP and
NAMMA Hovmollers
Vorticity Feature View TS Eugene 2005
DEF DGP VORT925-VORT200 (Average Over 2-8
degrees).
UNFILTERED
FLIGHTS X ER-2 NOAA P3 ER2P3
Aerosonde LETTERS named storms
07/20/0Z
UNITS X 10-6 s-1
UNITS X 10-6 s-1
UNITS X 10-6 s-1
07/19/0Z
07/17/0Z
07/18/0Z
RATIO
RATIO
RATIO
07/16/0Z
TCSP
DEF 210 K AREA ------------------ 235 K
AREA (count all cold cloud area up to 3
degrees from VORT center)
But Eugene vorticity Maximum does not Track back
across Central America
Eugene wave crosses Central America may be
related to Emily!
BASED ON LANCZOS FILTER 2.5-10 DAYS AND GAUSSIAN
SMOOTHING 3 GRIDPOINTS WIDE.
DIMENSIONLESS
DIMENSIONLESS
DIMENSIONLESS
CATL seems to be the winner here.
Of all these VORT MAX tracks for May-October
1998-2006
Tracks (925-850 hPa averaged)
3. Properties whose importance depends on region
NON- DEVELOPING
DEF SH V200-V850 (Vector Average over
0-5 degrees, Then vector difference, then norm).
EPAC
CATL
EATL
UNFILTERED
DEVELOPING (includes mature stage)
The shear statistics Do not appear to depend On
the specific radius Or level combination.
NAMMA
SHEAR IS THIS UNIMPORTANT?????
UNITS m/s
UNITS m/s
UNITS m/s
EPAC
CATL
EATL
Track figure courtesy of Greene (2006 MS thesis,
U of Utah) Box regions mine.
DEF SH V200-V500 (Vector Average over
0-5 degrees, Then vector difference, then norm).
Look at where the EPAC VORT MAX tracks start.
Look at what happens to the VORT MAX tracks
leaving Africa.
track start X track end
UNITS m/s
UNITS m/s
UNITS m/s
1998
1999
1998
1999
DEF Q_MID (Q700Q600 ) / 2 (Gridpoint
nearest VORT max).
BIG!
BIG!
2000
2001
2000
2001
UNITS g/kg
UNITS g/kg
UNITS g/kg

• Conclusions on waves versus vorticity maxima
  (caveat based on NCEP/ERA40 Reanalysis V
  wind)
• When Hovmoller plots are used, we are tracking
  the Wave Features. Vorticity maxima must be
• tracked by hand or with automated algorithms.
• Vorticity maxima come and go every few days while
  the parent wave continues westward.
• Wavelike features are much more likely than
  vorticity maxima to track coherently across the
  Atlantic.
• Wavelike features are more likely to cross
  Central America, but still it is difficult to
  find clear-cut cases
• of waves crossing Central America using
  Hovmollers of V component wind.
• The vorticity features in the EPAC are probably
  linked to those in the Atlantic through tropical
  waves.
• However, it is rare to see a wave plowing over
  Central America from the Caribbean!
• There are ways for wave energy to cross Central
  America without showing up in a Hovmoller of V
• Terrain effects (Zehnder )
• Wave accumulation mechanism
• QUESTION TO PONDER When a tropical cyclone
  forms, does the wave disappear, or does it move

• Conclusions on properties of Vorticity Maxima
  (caveat Based on ERA-40)
• DGP discriminated well in all regions, consistent
  with numerour previous studies.
• The fraction of the cloud shield (lt 235K) with
  clouds colder than 210 K, and with
• rain rates above 5 mm/hr, seems to matter in all
  regions.
• Vertical shear is most significantly different in
  the EATL region from 500-200 hPa.
• In contrast, SHEAR DOES NOT SEEM IMPORTANT AT ALL
  IN THE EPAC!!!!
• These conclusions do not seem to depend on the
  specific radius or levels
• used to calculate shear.
• Mid-level moisture is a significant inhibitor of
  cyclogenesis in the CATL and EATL.
• In the EPAC, mid-level moisture is generally
  elevated and is not such a good
• discriminator.
• A theory of cyclogenesis should allow for these
  regional variations
• and not depend Critically on the specific
  characteristics of any given region.

This research funded under the NASA Earth
and Space Science Fellowship, Grant NNX06AF94H.