# Presentation: 089819

## Some Characteristics of Developing and Non-Developing Vorticity Maxima:

**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**

**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
- further westward, possibly inducing cyclogenesis again (possible Emily-Eugene connection)?

- 3. _Properties whose importance depends on region:_

- UNITS: X 10-6 s-1

- UNITS: X 10-6 s-1

- UNITS: X 10-6 s-1

- UNITS: m/s

- UNITS: m/s

- UNITS: m/s

- UNITS: m/s

- UNITS: m/s

- UNITS: m/s

- UNITS: g/kg

- UNITS: g/kg

- UNITS: g/kg

-     FLIGHTS:
- X = ER-2
- + =  NOAA P3
- *  = ER2+P3
-     = Aerosonde
- LETTERS:
-      named storms

- SHEAR IS **THIS**
- UNIMPORTANT?????

- BIG!

- BIG!

- TCSP

- NAMMA

**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 (< 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.**

- Eugene ***wave***
- crosses Central
- America;
- may be related to
- Emily!

- But Eugene vorticity
- Maximum does not
- Track back across
- Central America

- Of all these VORT MAX tracks for May-October 1998-2006...

- Look at where the EPAC VORT MAX tracks start.

- Look at what happens to the
- VORT MAX tracks leaving Africa.

- 2. _Two vorticity maxima properties that matter for each region:_

- DIMENSIONLESS

- DIMENSIONLESS

- DIMENSIONLESS

**RATIO**

**RATIO**

**RATIO**

**    ****DEF:**
- DGP = VORT925-VORT200
- (Average Over 2-8 degrees).

**     ****DEF:**
-  210 K AREA
- ------------------
-  235 K AREA
- (count all cold cloud area up to
-   3 degrees from VORT center)

**    ****DEF:**
- SH = ||**V**200-**V**850||
- (Vector Average over 0-5 degrees,
- Then vector difference, then norm).

**    ****DEF:**
- SH = ||**V**200-**V**500||
- (Vector Average over 0-5 degrees,
- Then vector difference, then norm).

- The shear statistics
- Do not appear to depend
- On the specific radius
- Or level combination.

- CATL seems to be the winner here.

**    ****DEF:**
- Q_MID = (Q700+Q600 ) / 2
- (Gridpoint nearest VORT max).

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

-                                                       1. Two Views of tracking: Wave Features vs. Vorticity Maxima
-    Wave Feature View: TCSP and NAMMA Hovmollers                         Vorticity Feature View: TS Eugene 2005

- 07/16/0Z

- 07/19/0Z

- 07/18/0Z

- 07/17/0Z

- 07/20/0Z

**Tracks (925-850 hPa  averaged)**

**EPAC**

**CATL**

**EATL**

- Track figure courtesy of Greene (2006; MS thesis, U of Utah); Box regions mine.

- NON-
-   DEVELOPING

- DEVELOPING
- (includes
- mature stage)

**EPAC**

**CATL**

**EATL**

- 1998

- 1999

- 2000

- 2001

- 1998

- 1999

- 2000

- 2001

- + = track start
- X = track end

- UNFILTERED

- UNFILTERED

- BASED ON LANCZOS
- FILTER 2.5-10 DAYS AND
- GAUSSIAN SMOOTHING
- 3 GRIDPOINTS WIDE.