1 26 april 2013 future workresultsmethodologymotivation chip helmscomposite analyses of tropical...

1

26 April 2013Future WorkResultsMethodologyMotivation

Chip Helms Composite Analyses of Tropical Convective Systems

Composite Analyses of Tropical Convective Systems Prior to

Tropical Cyclogenesis

Chip Helms

Tropical Lunch

26 April 2013

2

26 April 2013Future WorkResultsMethodologyMotivation

Chip Helms Composite Analyses of Tropical Convective Systems

Cyclone Tracy (1974)

Genesis: 12/21

Landfall: 12/24110 kts

(Saffir-Simpson Cat. 3)

Image courtesy Wikipedia

Motivation

3

26 April 2013Future WorkResultsMethodologyMotivation

Chip Helms Composite Analyses of Tropical Convective Systems

Motivation

Methods for Studying TC Genesis

• Case Study– Allow for detailed analysis– May not be representative of population

• Composite Study– Identify prominent features in set of cases– Lose details in compositing process

4

26 April 2013Future WorkResultsMethodologyMotivation

Chip Helms Composite Analyses of Tropical Convective Systems

Motivation

Example: Non-developing system

8/18/2010 ~14 UTC8/17/2010 ~13 UTC

Longitude [°E] Longitude [°E]Mid-levels will appear weaker in composite

Pre

ssur

e [h

Pa]

Pre

ssur

e [h

Pa]

Zonal Cross-sections

5

26 April 2013Future WorkResultsMethodologyMotivation

Chip Helms Composite Analyses of Tropical Convective Systems

Solution: Composite on a Subset• Select a subset of cases with similar structure

– More homogenous subset provides more detail in composites

• Create subsets using phase space– Position in phase space indicates current state of

important, yet highly variable structures

• Composite all cases located in a given volume of the phase space– Retain more detail (like case studies)– Representative results (like composite studies)

Methodology

6

26 April 2013Future WorkResultsMethodologyMotivation

Chip Helms Composite Analyses of Tropical Convective Systems

Data

• CFSRv2, HURDAT2+INVESTs– Convenient for testing methodology– CFSR: Uniform in time– INVEST files contain a selection bias as not

every disturbance triggers an INVEST– INVEST files only available since 2005

• Use best track as first guess position– Find 500 hPa and 850 hPa center by minimizing

difference between tangential and total winds

Methodology

7

26 April 2013Future WorkResultsMethodologyMotivation

Chip Helms Composite Analyses of Tropical Convective Systems

Methodology

Phase Space

N = 5817All HURDAT Systems 2005-2012

ALL INVESTs

Wor

k in

Pro

gres

s

500 hPa center position relative to 850 hPa Center

8

26 April 2013Future WorkResultsMethodologyMotivation

Chip Helms Composite Analyses of Tropical Convective Systems

Results

N=516, Red=15

INVESTs+Pre-Genesis 2010

16<σ<22

No 80% Contour

9

26 April 2013Future WorkResultsMethodologyMotivation

Chip Helms Composite Analyses of Tropical Convective Systems

Results

N=107, Red=6

80% Contour

Was 16<σ<22

8<σ<22

INVESTs+Pre-Genesis 2010

10

26 April 2013Future WorkResultsMethodologyMotivation

Chip Helms Composite Analyses of Tropical Convective Systems

Results

N=25, Red=6

Was 16<σ<22

8<σ<22

INVESTs+Pre-Genesis 2010

11

26 April 2013Future WorkResultsMethodologyMotivation

Chip Helms Composite Analyses of Tropical Convective Systems

Results

N=45, Red=6

Was 16<σ<22

6<σ<22

INVESTs+Pre-Genesis 2010

12

26 April 2013Future WorkResultsMethodologyMotivation

Chip Helms Composite Analyses of Tropical Convective Systems

Results

N=16, Red=4

6<σ<18

Was 16<σ<22

INVESTs+Pre-Genesis 2010

13

26 April 2013Future WorkResultsMethodologyMotivation

Chip Helms Composite Analyses of Tropical Convective Systems

System Evolution: Sandy (2012)Results

850 vs 500 hPa Tangential Velocity

14

26 April 2013Future WorkResultsMethodologyMotivation

Chip Helms Composite Analyses of Tropical Convective Systems

Unwrapping TCs

Results

15

26 April 2013Future WorkResultsMethodologyMotivation

Chip Helms Composite Analyses of Tropical Convective Systems

Primary Future Work

• Create an algorithm to identify pre-genesis systems without relying on best track

• Test and finalize phase space variables• Examine composites

– e.g. Dev vs Non-dev

• System evolution in phase space

Future Work

16

26 April 2013Future WorkResultsMethodologyMotivation

Chip Helms Composite Analyses of Tropical Convective Systems

Side Project Future Work

• Create real-time phase space diagrams– Generate a climatology of phase space

Genesis Productivity (% dev in each volume)– Apply to forecast times to provide a forecast

diagnosis of genesis probability

• Create real-time unwrapped figures

Future Work

17

26 April 2013Future WorkResultsMethodologyMotivation

Chip Helms Composite Analyses of Tropical Convective Systems

END

18

26 April 2013Future WorkResultsMethodologyMotivation

Chip Helms Composite Analyses of Tropical Convective Systems

EXTRA SLIDES

19

26 April 2013Future WorkResultsMethodologyMotivation

Chip Helms Composite Analyses of Tropical Convective Systems

Results

N=516, Red=15

Year: 2010

20

26 April 2013Future WorkResultsMethodologyMotivation

Chip Helms Composite Analyses of Tropical Convective Systems

Results

N=107, Red=6

Year: 2010

21

26 April 2013Future WorkResultsMethodologyMotivation

Chip Helms Composite Analyses of Tropical Convective Systems

Results

N=25, Red=6

Year: 2010

22

26 April 2013Future WorkResultsMethodologyMotivation

Chip Helms Composite Analyses of Tropical Convective Systems

Results

N=45, Red=6

Year: 2010

23

26 April 2013Future WorkResultsMethodologyMotivation

Chip Helms Composite Analyses of Tropical Convective Systems

Results

N=16, Red=4

Year: 2010

24

26 April 2013Future WorkResultsMethodologyMotivation

Chip Helms Composite Analyses of Tropical Convective Systems

All HURDAT 2005-2012Results

25

26 April 2013Future WorkResultsMethodologyMotivation

Chip Helms Composite Analyses of Tropical Convective Systems

INVEST/Pre-Genesis SystemsResults

Max Freq: 41 ~ 2.5%

26

26 April 2013Future WorkResultsMethodologyMotivation

Chip Helms Composite Analyses of Tropical Convective Systems

Tropical DepressionsResults

27

26 April 2013Future WorkResultsMethodologyMotivation

Chip Helms Composite Analyses of Tropical Convective Systems

Tropical StormsResults

28

26 April 2013Future WorkResultsMethodologyMotivation

Chip Helms Composite Analyses of Tropical Convective Systems

HurricanesResults

29

26 April 2013Future WorkResultsMethodologyMotivation

Chip Helms Composite Analyses of Tropical Convective Systems

Post Extra-Tropical TransitionResults

30

26 April 2013Future WorkResultsMethodologyMotivation

Chip Helms Composite Analyses of Tropical Convective Systems

Sandy (2012)Results

31

26 April 2013Future WorkResultsMethodologyMotivation

Chip Helms Composite Analyses of Tropical Convective Systems

Sandy (2012): 10/18 – 10/21Results

32

26 April 2013Future WorkResultsMethodologyMotivation

Chip Helms Composite Analyses of Tropical Convective Systems

Sandy (2012): 10/22 – 10/25Results

33

26 April 2013Future WorkResultsMethodologyMotivation

Chip Helms Composite Analyses of Tropical Convective Systems

Sandy (2012): 10/26 – 10/29Results

34

26 April 2013Future WorkResultsMethodologyMotivation

Chip Helms Composite Analyses of Tropical Convective Systems

Sandy (2012): 10/30 – 10/31Results

35

26 April 2013Future WorkResultsMethodologyMotivation

Chip Helms Composite Analyses of Tropical Convective Systems

REMOVED SLIDES

36

26 April 2013Future WorkResultsMethodologyMotivation

Chip Helms Composite Analyses of Tropical Convective Systems

TheorySimpson et al. (1997) and Ritchie and Holland (1997)

Prior Work

Evaporative Cooling

StratiformLatent

Heating

p

gfP )(

+ PV Anomaly

Mergers of PV anomalies add PV while averaging

thermal properties

New PV AnomalyOut of balance with thermal structure

Forced Ascent andEvaporative Cooling

Act to cool sub-cloud layer

Warm anomaly growth not detailed by theory, but would be accomplished by forced subsidence or increased LHR

Forced Convergence

+

pf

t

VkV)(

p-f)(V

Concentration term

Stretching termMCS

37

26 April 2013Future WorkResultsMethodologyMotivation

Chip Helms Composite Analyses of Tropical Convective Systems

Pre-Genesis Phase Space

N = 5817All HURDAT Systems 2005-2012

Displacement of 500 hPa center

Displacementvs

Tilt Direction

Displacement vs Shear

500-850 hPa Shearvs

500-850 hPa Vorticity Difference

Vorticity vs Divergence ~Bulk Lapse Ratevs

Upper Level Moisture

Upper-level T’ vs Spec. Hum.500 hPa Vλ vs 850 hPa Vλ

Stronger Mid Vortex

Stronger Low Vortex

850 hPa 500 hPa

500-850 hPa 200-850 hPa

38

26 April 2013Future WorkResultsMethodologyMotivation

Chip Helms Composite Analyses of Tropical Convective Systems

Motivation

Example: Non-developing system

39

26 April 2013Future WorkResultsMethodologyMotivation

Chip Helms Composite Analyses of Tropical Convective Systems

Cyclone Tracy (1974)

Genesis: 12/21

Landfall: 12/24110 kts

(Saffir-Simpson Cat. 3)

Image courtesy Wikipedia

Image courtesy Clark Evans

Genesis: 6/23

Motivation

40

26 April 2013Future WorkResultsMethodologyMotivation

Chip Helms Composite Analyses of Tropical Convective Systems

Motivation

Issues with Traditional Composites

• Mid-level features will appear weaker– High variability in system tilt

• Vertically-aligned systems tend to be stronger– Composites will favor upright systems

41

26 April 2013Future WorkResultsMethodologyMotivation

Chip Helms Composite Analyses of Tropical Convective Systems

Methodology/Data• Locate center at 850 and 500 hPa

1) Maximum Vλ (0.5° search grid)

2) Minimum Difference of Vλ and V (0.25°)

3) Minimum Difference of Vλ and V (0.10°)

• Datasets: CFSRv2, HURDAT2+INVESTs– Convenient for testing methodology– CFSR: Uniform in time– Complete with all the selection bias caveats of

the INVEST files

Methodology