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A Mul*-‐Scale Analysis of the Genesis of Typhoon Nuri

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A Mul*-‐Scale Analysis of the Genesis of Typhoon Nuri 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 VorKcity – ConvecKve Organizaon • Typhoon Nuri’s tropical cyclogenesis sequence – IdenKficaon & tracking of easterly wave – Wave weakened as it transgressed through a hosKle environment – ConvecKon was reinvigorated & transiKon to a tropical cyclone IniKaon of Genesis Propagaon through HosKle 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 interacKon provides a dynamical pathway to “bottom-up” development of the proto vortex CriKcal Layer or Wave Pouch H2. The Kelvin’s cat’s eye located within the wave’s criKcal layer: Wave Trough •Provides a set of quasi-closed material v=0 contours •Air is repeatedly moistened by convecKon, •Protected from lateral intrusion of dry air • Protected from impinging vercal wind shear CriKcal 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) ResKng Co-Moving Circulaon Dynamics dΓ a = − v η dl + η v dl + Fdl dt !∫ n z !∫ n z !∫ t Convergence “Tilng-like” FricKon & other sub- of vorKcity term grid scale forces Fixed domain analysis Nuri 1 Nuri 2 Raymond and López Carrillo (2011) Dropwindsonde derived tangenKal 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 resoluKon/0.5 km verKcal −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 tangenKal wind and angular momentum calculaons are consistent with the dropwindsonde only data, indicang low-level spin-up on the system scale VorKcity Organizaon Nuri 2 Nuri 1 VorKcity organizaon near sweet spot and improved verKcal 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 VorKcity consolidang near 8 0.7 0.6 6 0.5 sweet spot & verKcal growth Height (km) 4 0.4 0.3 of cyclonic vorKcity 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 reflecKvity 00-14UTC 16 Aug Growth and decay of mulKple MCSs within the wave pouch ConvecKon 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 – VorKcity organizaon and verKcal growth around the sweet spot – VorKcity concentraon near the sweet spot owed in part to low-level vortex tube stretching associated with deep convecon – MulKple MCSs within the wave pouch Ques&ons? Photo courtesy of Jeff Hawkins .
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