Tropical Cyclone Formation, Structure, and Longevity during HS3

Tropical CycloneFormation, Structure, and Longevity during HS3

Mike Montgomery and Mark BootheNaval Postgraduate School

Tim Dunkerton and Blake RutherfordNorthWest Research Associates

Sponsored by NSF

20102012-2014

Overarching NASA-HS3 Science Questions:How do hurricanes form?

What causes rapid intensity change?

What is the role of deep convection in intensification?

What is the role of Saharan Air Layer (SAL) on intensity change?

What determines storm resilience and longevity, such as Nadine (2012)?

Understanding NadineScientific Questions

FormationHow did it form? (Is there a pouch?)

StructureHow does the wind field evolve?

LongevityWhy so resilient? (Was Nadine always in a favorable environment OR was it able to protect itself from an occasionally hostile environment?)

Understanding NadineApproach

Conduct Lagrangian analyses within the marsupial frameworkReview genesis sequenceExamine dropsonde data to study change in circulationExamine dividing streamlines to document structure change with the ECMWF model analysesExamine ECMWF theta-e tracer field for possible interaction with environmental dry air

Animations of Nadine

Animations of Nadine

Formation of Nadine

ComovingPhase speed: -7.3 m/sEarth-relativePhase speed: 0 m/s0000 UTC 4 SeptemberInitial time of pouch designation~ 13N, 4W700 hPa ECMWF Streamlines and Okubo-Weiss

Formation of Nadine700 hPa ECMWF Streamlines and Okubo-WeissP25L frame of reference

P25LP23LP24L

P23LP24LP25L

P23LP24LP25L

P23LP24LP25L

0000 UTC 4 September 2012 0000 UTC 5 September 2012 0000 UTC 6 September 2012 1200 UTC 6 September 2012 P25L initially arrests P24L/pre-Nadine westward motion,but growing P24L/pre-Nadine then absorbs P25L on 7 September

Formation of NadineP23LP24LP23LP24L

0000 UTC 8 September 2012 1200 UTC 8 September 2012 1200 UTC 8 September 2012 0000 UTC 10 September 2012 700 hPa ECMWF Streamlines and Okubo-Weiss (P24L/pre-Nadine frame of reference)700 hPa ECMWF Ozone Tracer (P24L/pre-Nadine frame of reference)Stretched P23L is then absorbed into the outer portion of P24L/pre-NadineP23L tracks along blue manifold around P24L

RF3RF4RF2RF5RF6

Track of Nadine65-70 kt50 kt50 kt50 kt~30-35 kt

-10.3RF2RF3RF4

50 kt30-35 kt

65-70 ktNHCHURDAT2Intensities

CirculationAverage tangential cyclonic windC / perimeter

NINE DAYS11

RF4

RF5

50 kt

50 kt50 ktRF6

50 ktONE WEEK TIME FRAME12

ECMWF Dividing Streamline Analysis 2012091500 Drops: 1701Z Sept 14 0808Z Sept 15 (-6:59+8:08) 194718331824174318482003175617281715170119212058220008081901193520182032204521262146222822412256231323282339000000150031005001040117013102131809211322110228024102560316033203460403041604480502051805380557061106230633064606570708072107190725072901450745075604300159170100000808072207240728Small, vertically aligned (925-700 hPa) pouchHigh TPWSaddle point to the southwestUnderstanding Nadine: Dividing StreamlinesRF03Courtesy Michael Riemer, NRC postdoc13

ECMWF Dividing Streamline Analysis 2012092012Drops: 0107Z 1235Z Sept 20 (-10:53+00:35)

Larger, with a saddle point to the northeastTPW decreasedVertically aligned07391101105009561023094709380931052907580732053705180633064206590304031303450357042610410445045405050107011601260556054704070255024302050155014601360604021404160107120004350606060906110614061606190623065007480807081608210827083208370842084808520901091009191005101410321108112811351144115212011210121812261235Understanding Nadine: Dividing StreamlinesRF0414

ECMWF Dividing Streamline Analysis 2012092700Drops: 1638Z Sept 26 0428Z Sept 27 (-7:22+4:28) Has shrunkTPW had continued to decrease, now increasing againStill vertically aligned16381648165817081718172817381748175818101822183518451855190519151927193616380000042819461956201220222034204220522101211121142117212021232127213021402149220122092220222822382248230423082313231823282338235100000012002100310040005100582258010501120122}0132-03300344040104180428Understanding Nadine: Dividing StreamlinesRF0615

Simple Kinematic Model of Point Vortex in Uniform Flow with Mass Sink

For nondivergent model without mass sink/source,

Rsp = \Gamma / U

Rnd (closet approach) = \alpha * Rsp (occurs at angle = 0 [due south] in above sketch)

where \alpha = approx. = 0.27 (roughly of Rsp).

(see Riemer and Montgomery 2011, pages 9406 9408)

For weak mass sink of normalized strength D, (i.e., D