1 22 July 2013 Future WorkResultsMethodologyMotivation Chip HelmsComposite Analyses of Tropical Convective Systems Composite Analyses of Tropical Convective Systems Prior to Tropical Cyclogenesis Chip Helms Cyclone Research Group 22 July 2013

2 Future WorkResultsMethodologyMotivation Chip HelmsComposite Analyses of Tropical Convective Systems Questions What makes a tropical convective system (TCS) fail to develop? –Especially for TCS expected to develop How often/easily do TCSs change from being unfavorable for development to being favorable? Is TCS structure a function of basin? Season? Mesoscale/Synoptic Scale Environments? Future development? Development pathway? –If so, what processes generate the relationship? What causes a TCS to become vertically aligned with time? Do all TCS do so? What about this vertical alignment makes the low levels rapidly spin-up? What causes this spin-up to fail in non-developing systems?

3 22 July 2013 Future WorkResultsMethodologyMotivation Chip HelmsComposite Analyses of Tropical Convective Systems Genesis Process Hypothesis Tropopause 500 hPa Surface Convergence and ascent along wave Cooling (Melting, Evaporation, Radiation?) Concentration of background vorticity produces low-level vortex Deep convection forms along convergence line Deep convection fuels formation of stratiform sheild downshear +PV Mid-Level Vortex Low- Level Vortex Latent Heat Release Shear Hydrostatic response to heating profile results in PV convergence and a non-linear feedback due to thermal wind balance

4 22 July 2013 Future WorkResultsMethodologyMotivation Chip HelmsComposite Analyses of Tropical Convective Systems Vertical Alignment Process ?

5 22 July 2013 Future WorkResultsMethodologyMotivation Chip HelmsComposite Analyses of Tropical Convective Systems Method Motivation Two general approaches to studying genesis –Case Studies Detailed analyses, may not be representative –Composite Studies Represenative features, loss of detail Solution: Composite on homogeneous subset –Select based on important, highly-variable structures Make subset selections using phase space

6 22 July 2013 Future WorkResultsMethodologyMotivation Chip HelmsComposite Analyses of Tropical Convective Systems Old Phase Space N = 5817 All HURDAT Systems ALL INVESTs 15 Variables, 10 Plots

7 22 July 2013 Future WorkResultsMethodologyMotivation Chip HelmsComposite Analyses of Tropical Convective Systems New Phase Space 12 Variables, 6 Plots

8 22 July 2013 Future WorkResultsMethodologyMotivation Chip HelmsComposite Analyses of Tropical Convective Systems Current Variables

9 22 July 2013 Future WorkResultsMethodologyMotivation Chip HelmsComposite Analyses of Tropical Convective Systems Planned Variable Changes

10 22 July 2013 Future WorkResultsMethodologyMotivation Chip HelmsComposite Analyses of Tropical Convective Systems Moving Beyond NHC INVESTs Using INVEST files introduces a selection bias and reduces potential data ranges –Only NHC basins from 2005 onwards Vortex detection and tracking algorithm –Uses 850 hPa ‘Percent Idealized’ variable for vortex identification Positions found using overlapping 5°x 5° boxes –Tracking based on Hart (2003) Cyclone Phase Space vortex tracker

11 22 July 2013 Future WorkResultsMethodologyMotivation Chip HelmsComposite Analyses of Tropical Convective Systems Example Vortex Identification

12 22 July 2013 Future WorkResultsMethodologyMotivation Chip HelmsComposite Analyses of Tropical Convective Systems Idealized Example Percent Idealized Mean V λ +

13 22 July 2013 Future WorkResultsMethodologyMotivation Chip HelmsComposite Analyses of Tropical Convective Systems Tracking Algorithm (Hart 2003)

14 22 July 2013 Future WorkResultsMethodologyMotivation Chip HelmsComposite Analyses of Tropical Convective Systems Example Tracking First Pass Tracks Adjoint Tracks Extensions Deletion

15 22 July 2013 Future WorkResultsMethodologyMotivation Chip HelmsComposite Analyses of Tropical Convective Systems Future Work Run tracking algorithm –Extend to multiple data sets Test and finalize phase space variables Examine composites –e.g. Dev vs Non-dev System evolution in phase space

16 22 July 2013 Future WorkResultsMethodologyMotivation Chip HelmsComposite Analyses of Tropical Convective Systems END

17 22 July 2013 Future WorkResultsMethodologyMotivation Chip HelmsComposite Analyses of Tropical Convective Systems EXTRA SLIDES

18 22 July 2013 Future WorkResultsMethodologyMotivation Chip HelmsComposite Analyses of Tropical Convective Systems N=516, Red=15 Year: 2010

19 22 July 2013 Future WorkResultsMethodologyMotivation Chip HelmsComposite Analyses of Tropical Convective Systems N=107, Red=6 Year: 2010

20 22 July 2013 Future WorkResultsMethodologyMotivation Chip HelmsComposite Analyses of Tropical Convective Systems N=25, Red=6 Year: 2010

21 22 July 2013 Future WorkResultsMethodologyMotivation Chip HelmsComposite Analyses of Tropical Convective Systems N=45, Red=6 Year: 2010

22 22 July 2013 Future WorkResultsMethodologyMotivation Chip HelmsComposite Analyses of Tropical Convective Systems N=16, Red=4 Year: 2010

23 22 July 2013 Future WorkResultsMethodologyMotivation Chip HelmsComposite Analyses of Tropical Convective Systems All HURDAT

24 22 July 2013 Future WorkResultsMethodologyMotivation Chip HelmsComposite Analyses of Tropical Convective Systems INVEST/Pre-Genesis Systems Max Freq: 41 ~ 2.5%

25 22 July 2013 Future WorkResultsMethodologyMotivation Chip HelmsComposite Analyses of Tropical Convective Systems Tropical Depressions

26 22 July 2013 Future WorkResultsMethodologyMotivation Chip HelmsComposite Analyses of Tropical Convective Systems Tropical Storms

27 22 July 2013 Future WorkResultsMethodologyMotivation Chip HelmsComposite Analyses of Tropical Convective Systems Hurricanes

28 22 July 2013 Future WorkResultsMethodologyMotivation Chip HelmsComposite Analyses of Tropical Convective Systems Post Extra-Tropical Transition

29 22 July 2013 Future WorkResultsMethodologyMotivation Chip HelmsComposite Analyses of Tropical Convective Systems Sandy (2012)

30 22 July 2013 Future WorkResultsMethodologyMotivation Chip HelmsComposite Analyses of Tropical Convective Systems Sandy (2012): 10/18 – 10/21

31 22 July 2013 Future WorkResultsMethodologyMotivation Chip HelmsComposite Analyses of Tropical Convective Systems Sandy (2012): 10/22 – 10/25

32 22 July 2013 Future WorkResultsMethodologyMotivation Chip HelmsComposite Analyses of Tropical Convective Systems Sandy (2012): 10/26 – 10/29

33 22 July 2013 Future WorkResultsMethodologyMotivation Chip HelmsComposite Analyses of Tropical Convective Systems Sandy (2012): 10/30 – 10/31

34 22 July 2013 Future WorkResultsMethodologyMotivation Chip HelmsComposite Analyses of Tropical Convective Systems REMOVED SLIDES

35 22 July 2013 Future WorkResultsMethodologyMotivation Chip HelmsComposite Analyses of Tropical Convective Systems Theory Simpson et al. (1997) and Ritchie and Holland (1997) Evaporative Cooling Stratiform Latent Heating + PV Anomaly Mergers of PV anomalies add PV while averaging thermal properties New PV Anomaly Out of balance with thermal structure Forced Ascent and Evaporative 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 ++ Concentration term Stretching term MCS

36 22 July 2013 Future WorkResultsMethodologyMotivation Chip HelmsComposite Analyses of Tropical Convective Systems Pre-Genesis Phase Space N = 5817 All HURDAT Systems Displacement of 500 hPa center Displacement vs Tilt Direction Displacement vs Shear hPa Shear vs hPa Vorticity Difference Vorticity vs Divergence ~Bulk Lapse Rate vs Upper Level Moisture Upper-level T’ vs Spec. Hum. 500 hPa V λ vs 850 hPa V λ Stronger Mid Vortex Stronger Low Vortex 850 hPa 500 hPa hPa hPa

37 22 July 2013 Future WorkResultsMethodologyMotivation Chip HelmsComposite Analyses of Tropical Convective Systems Example: Non-developing system

38 22 July 2013 Future WorkResultsMethodologyMotivation Chip HelmsComposite Analyses of Tropical Convective Systems Cyclone Tracy (1974) Genesis: 12/21 Landfall: 12/ kts (Saffir-Simpson Cat. 3) Image courtesy Wikipedia Image courtesy Clark Evans Genesis: 6/23

39 22 July 2013 Future WorkResultsMethodologyMotivation Chip HelmsComposite Analyses of Tropical Convective Systems 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

40 22 July 2013 Future WorkResultsMethodologyMotivation Chip HelmsComposite Analyses of Tropical Convective Systems Methodology/Data Locate center at 850 and 500 hPa 1) Maximum V λ (0.5° search grid) 2) Minimum Difference of V λ and V (0.25°) 3) Minimum Difference of V λ 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

41 22 July 2013 Future WorkResultsMethodologyMotivation Chip HelmsComposite Analyses of Tropical Convective Systems Genesis Process Hypothesis Tropopause 500 hPa Surface

42 22 July 2013 Future WorkResultsMethodologyMotivation Chip HelmsComposite Analyses of Tropical Convective Systems Genesis Process Hypothesis Tropopause 500 hPa Surface Vort. Max

43 22 July 2013 Future WorkResultsMethodologyMotivation Chip HelmsComposite Analyses of Tropical Convective Systems Genesis Process Hypothesis Tropopause 500 hPa Surface