A Mul-Scale Analysis of the Genesis of Typhoon Nuri as Observed during the Tropical Cyclone Structure 2008 Field Campaign

ICMCS-X Lou Lussier Michael T. Montgomery Michael M. Bell 16 Sep 2014

Photo courtesy of Jeff Hawkins Overview • Quick Synopc Overview • Mesoscale Organizaon – Test “Thermodynamic Control” Mechanism • e.g., Raymond et al. (2011) – Aggregaon of Vorcity – Convecve Organizaon • Typhoon Nuri’s tropical cyclogenesis sequence – Idenficaon & tracking of easterly wave – Wave weakened as it transgressed through a hosle environment – Convecon was reinvigorated & transion to a tropical cyclone

Iniaon of Genesis Propagaon through Hosle Origin of Easterly Sequence Environment Wave Precursor 12Z 15 Aug - 12Z 10 Aug - 12Z 7 Aug - 12Z 17 Aug 00Z 15 Aug 00Z 10 Aug Overview The three hypotheses presented by DMW09 are… H1. The critical layer and Kelvin cat’s eye within, contain a region of cyclonic rotation and weak straining/ shearing deformation • Within this critical layer, synoptic and mesoscale anomalies move together and amplify • This multi-scale interacon provides a dynamical pathway to “bottom-up” development of the proto vortex

Crical Layer or Wave Pouch H2. The Kelvin’s cat’s eye located within the wave’s crical layer: Wave Trough •Provides a set of quasi-closed material v=0 contours •Air is repeatedly moistened by convecon, •Protected from lateral intrusion of dry air • Protected from impinging vercal wind shear Crical Latude u=Cp Sweet Spot

H3. The parent wave is maintained and possibly enhanced by diabacally amplified eddies within the wave

Adapted from Wang et al (2009) Resng Co-Moving Circulaon Dynamics dΓ a = − v η dl + η v dl + Fdl dt !∫ n z !∫ n z !∫ t Convergence “Tilng-like” Fricon & other sub- of vorcity term grid scale forces

Fixed domain analysis

Nuri 1 Nuri 2

Raymond and López Carrillo (2011) Dropwindsonde derived tangenal wind profiles

Radius < 1 Degree 1 < Radius < 2 Degrees 300 300 Nuri1 Nuri1 Nuri2 Nuri2 400 400

500 500

600 600

700 700 Pressure (hPa) Pressure (hPa)

800 800

900 900

1000 1000 −5 0 5 10 15 −5 0 5 10 15 Average Tangential Wind (m s−1) Average Tangential Wind (m s−1)

2 < Radius < 3 Degrees Radius > 3 Degrees 300 300 Nuri1 Nuri1 Nuri2 Nuri2 400 400 500 SAMURAI Analysis (Bell at all 2012) 500 600 - 3D-Var analysis scheme 600 700 700 Pressure (hPa) Pressure (hPa)

800 - Using ELRDORA Radar & Drops 800

900 - No background 900

1000 1000 −5 0 5 10 15 −5 0 5 10 15 - 10 km horizontal resoluon/0.5 km vercal −1 −1 Average Tangential Wind (m s ) Average Tangential Wind (m s )

No compelling evidence of a “thermodynamic control” Profile at 2 degrees similar to Raymond and López Carrillo (2011) SAMURAI tangenal wind and angular momentum calculaons are consistent with the dropwindsonde only data, indicang low-level spin-up on the system scale Vorcity Organizaon

Nuri 2

Nuri 1

Vorcity organizaon near sweet spot and improved vercal alignment

Radius < 0.5 Degrees Radius < 1 Degree 0.4 0.4 Nuri 1 Nuri 1 0.35 Nuri 2 0.35 Nuri 2 Nuri 3 Nuri 3 0.3 0.3

0.25 0.25

0.2 0.2

0.15 0.15 Relative Frequncy Relative Frequncy 0.1 0.1

0.05 0.05

0 0 −0.4 −0.2 0 0.2 0.4 0.6 0.8 1 1.2 1.4 −0.4 −0.2 0 0.2 0.4 0.6 0.8 1 1.2 1.4 Absolute Vorticity (ks −1) Absolute Vorticity (ks −1)

Radius < 1.5 Degrees Radius < 2 DegreesNuri 1 Relative Frequency of Positive Okubo−Weiss 0.4 0.4 12 1 Nuri 1 Nuri 1 0.9 0.35 Nuri 2 0.35 Nuri 2 Nuri 3 10 Nuri 3 0.8 0.3 0.3 0.7 0.25 0.25 8 0.6 0.2 0.2 6 0.5 0.15 0.15 0.4 Relative Frequncy Relative Frequncy Height (km) 0.1 0.1 4 0.3 0.05 0.05 0.2 2 0 0 −0.4 −0.2 0 0.2 0.4 0.6 0.8 1 1.2 1.4 −0.4 −0.2 0 0.2 0.4 0.6 0.8 1 1.2 1.4 0.1 Absolute Vorticity (ks −1) Absolute Vorticity (ks −1) 0 0 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 Radius (Degrees)

Nuri 2 Relative Frequency of Positive Okubo−Weiss 12 1

0.9 10 0.8 Vorcity consolidang near 8 0.7 0.6 6 0.5

sweet spot & vercal growth Height (km) 4 0.4

0.3 of cyclonic vorcity monolith 2 0.2

0 0.1 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 Radius (Degrees) Convecve Organizaon

Low-level stretching tendency Guam Doppler radar composite reflecvity 00-14UTC 16 Aug Growth and decay of mulple MCSs within the wave pouch Convecon organizes around the sweet spot Summary • Typhoon Nuri is an excellent example of the applicability of the ‘marsupial paradigm’ in the western North Pacific basin • On the mesoscale, within the wave pouch, we saw: – No indicaon that a ‘thermodynamic control’ was necessary for low-level spin-up – Vorcity organizaon and vercal growth around the sweet spot – Vorcity concentraon near the sweet spot owed in part to low-level vortex tube stretching associated with deep convecon – Mulple MCSs within the wave pouch Quesons?

Photo courtesy of Jeff Hawkins