TC inner-core structure and intensification

TC inner-core structure and intensification

Robert Rogers, Paul Reasor, Hua Chen, GopalNOAA Hurricane Research Division

NASA HS3 Science MeetingMay 8, 2013

Motivation

• Comparisons of composites of airborne Doppler radial passes in multiple hurricanes show statistically significant differences in inner-core structure of hurricanes that are intensifying compared with those that are remaining steady-state (Rogers et al., MWR, 2013, in press)

• Intensifying (IN) – 40 radial passes in 8 different TCs• Steady-state (SS) – 53 radial passes in 6 different TCs

•Composites consist of snapshots – do these structures appear in individual case studies, with observations collected serially?• Can a regional model capture inner-core structures associated with intensification? • Can a regional model distinguish between IN and SS cases based on inner-core structure?

Symmetric vortex structure and TC intensification

IN

SS

Axisymmetric tangential wind (m/s)

• Tangential wind decreases more rapidly with radius outside RMW for IN cases

IN IN

SS SS

Axisymmetric tangential wind (m/s) Axisymmetric vorticity (x 10-4/s)

• Tangential wind decreases more rapidly with radius outside RMW for IN cases • IN cases have a ring-like vorticity structure inside RMW• IN cases have weaker vorticity outside RMW

Symmetric vortex structure and TC intensification

IN SS

Shear-relative tilt (red line) between 2 and 7-km altitude

Asymmetric vortex structure and TC intensification

• negligible difference in tilt magnitude between IN and SS cases

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Convective bursts and TC intensificationNumber and shear-relative location

of convective bursts

• Bursts defined as top 1% of vertical velocity distribution at 8 km altitude (i.e., 5.5 m/s)• IN cases have more bursts, more of them inside RMW compared with SS cases

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Convective bursts and TC intensificationNumber and shear-relative location

of convective burstsRadial distribution of convective bursts (%) and

axisymmetric vorticity (shaded, x 10-4 s-1)

• Bursts defined as top 1% of vertical velocity distribution at 8 km altitude (i.e., 5.5 m/s)• IN cases have more bursts, more of them inside RMW compared with SS cases

Earl 2010: Intensifying

P-3 flights

Do structures associated with IN vs. SS appear in individual cases?

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Hurricane Ophelia6 - 17 September 2005

Hurricane

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Hurricane OpheliaSeptember 6 - 17 2005

BEST TRACKSat (TAFB)Sat (SAB)Sat (AFWA)Obj T-NumAC (sfc)AC (flt>sfc)AC (DVK P>W)SurfaceDrop (sfc)Drop (LLM xtrp)Drop (MBL xtrp)

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Ophelia 2005: Steady-state

P-3 flights

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Earl

Ophelia

• Decrease of tangential wind with radius outside RMW for Earl, not for Ophelia

Do structures associated with IN v. SS appear in individual cases?Doppler-derived axisymmetric structure

Tangential wind (m s-1)

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• Decrease of tangential wind with radius outside RMW for Earl, not for Ophelia• More of a ring-like structure inside RMW for Earl• Weaker vorticity outside RMW for Earl

Do structures associated with IN v. SS appear in individual cases?Doppler-derived axisymmetric structure

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Tangential wind (m s-1) Vertical vorticity (x 10-4 s-1)

Number and radial distribution of convective bursts for Earl and Ophelia

Burst counts:Earl – 193Ophelia – 102

Burst counts:Earl – 193Ophelia – 102

• 80% of convective bursts are at or inside RMW for Earl (IN)

• 30% of convective bursts are at or inside RMW for Ophelia (SS)

Do structures associated with IN v. SS appear in individual cases?

Earl 2010: HWRF 3-km runModel initialized at 18 UTC August 26 (2618 run)

Track Intensity

Does HWRF capture inner-core structures associated with IN?

Streamlines and wind speed (shaded, m/s) at 2 km (black) and 8 km (white)Convective burst locations (top 1% of w distribution) denoted by red contour

Doppler analysis centered at 23:28 UTC 28 Aug

Vortex structure and convective burst distribution


850-200 hPa env shear (m/s)

km

• Direction of 2-8 km vortex displacement similar between Doppler and HWRF• Burst area located inside RMW southeast of low-level center, downshear left

2618 HWRF output valid 20 UTC 28 Aug


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Axisymmetric structure

Doppler

HWRF


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Normalized radius

12Z Aug 30RMW=42 km

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Normalized radius

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Tangential wind (m s-1)

• tangential wind at eyewall similar between HWRF and Doppler, decay outside eyewall generally similar but more decay in HWRF

Axisymmetric structure

Doppler

HWRF


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Normalized radius

12Z Aug 30RMW=42 km

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RMW=35 km 12:25Z Aug 30

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RMW=35 km

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12Z Aug 30RMW=42 km

Tangential wind (m s-1) Vertical vorticity (x 10-4 s-1)

• tangential wind at eyewall similar between HWRF and Doppler, decay outside eyewall generally similar but more decay in HWRF

• Indication of ring-like structure in HWRF, but much less pronounced -- resolution limitations?

• Outer core vorticty decay comparable between HWRF and Doppler.

Exp. 2612

Exp. 2618

Storm tracks

Intensity

Can HWRF distinguish between IN and SS cases based on inner-core structure?

Two HWRF runs: initialized at 12 UTC (Exp. 2612) and 18 UTC August 26 (Exp. 2618)

• tracks similar between two runs

• bifurcation period in intensity trace – between 00 UTC Aug 30 and 00 UTC Aug 31

bifurcationperiod

Streamlines at 2 km (black) and 8 km (white); vorticity (shaded, x 10-4 s-1) at 2 km

Asymmetric vortex structure during bifurcation period

Exp. 2618 HWRF output valid 05-08 UTC 30 Aug


Exp. 2612 HWRF output valid 05-08 UTC 30 Aug

• Both runs show 2-8 km vortex displacement < 20 km during bifurcation period, little difference• Vortex tilts downshear, between left and right of shear vector• Exp. 2618 has slightly higher eyewall vorticity; Exp. 2612 has band of higher vorticity at end outside core

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Exp 2618 Exp 2612



Exp. 2618 HWRF output valid 05-08 UTC 30 Aug Exp. 2612 HWRF output valid 05-08 UTC 30 Aug


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850-200 hPa shear (m/s) and 2-8 km tilt magnitude (km)

Asymmetric vortex structure

• shear marginally (2 m/s) higher in 2612 run• both runs show large vortex displacement prior and at RI onset, becomes nearly aligned several hours after RI onset• vortex displacement small during bifurcation period for both runs, slightly smaller for 2618 run

RI onset

bifurcationperiod

Wind speed (shaded, m s-1) at 2 km and convective burst locations (top 1% of w distribution)

• Both runs show convective bursts near, within eyewall at various times during bifurcation period• Bursts located between downshear right and downshear left• Exp. 2618 shows persistent burst in downshear region inside RMW, Exp. 2612 has transient activity• RI occurrence tied to distribution of moist convection – limited predictability? (Zhang and Tao 2013)


Vortex structure and convective burst distribution during bifurcation period


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• Both runs show periods of inner eyewall burst activity prior to bifurcation period• After bifurcation period, coverage of bursts for Exp. 2618 increases markedly• Enhanced coverage occurs prior to significant increase in symmetric wind speed• Transient, limited coverage of bursts for Exp. 2612

Exp. 2618 HWRF Exp. 2612 HWRF

2-km axisymmetric wind maximum and coverage of convective bursts (CB) between r* = 0.5 and 1

Vortex structure and convective burst distribution

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Ongoing/future work

• continue analysis of Earl aircraft observations, HWRF simulations• symmetric and asymmetric structure• convective statistics • thermodynamic properties

• can we explain reason for transience of convective bursts for Exp. 2612 vs. Exp. 2618?

• environmental, vortex structure?• predictability limit due to stochastic nature of moist convection?

• expand HWRF analysis to multiple cases for compositing• use HS3 data to test hypotheses

• combination of inner-core and environmental sampling over an extended period provides dataset with high temporal resolution• excellent opportunity to measure structure and evolution of convection, vortex, and environment (and their interactions across scales)

2013 HRD Field Program Plans2013 HRD Field Program Plans Continuation of IFEX objectives

• Shear experiment new

• G-IV TDR• DWL module new

Crews available for twice daily P-3 and G-IV missions• 2 P-3s available (N43RF 1 June; N42RF early Aug)

− WSRA (N42RF) and IWRAP (N43RF) − W-band radar new− Doppler wind lidar (N42RF) new

Fly operationally tasked missions• 2 pm and 2 am ET take-offs new• Based on EMC’s and/or NHC’s operational need• Selected modules may be attempted

Continuation of IFEX objectives• Shear experiment new

• G-IV TDR• DWL module new

Crews available for twice daily P-3 and G-IV missions• 2 P-3s available (N43RF 1 June; N42RF early Aug)

− WSRA (N42RF) and IWRAP (N43RF) − W-band radar new− Doppler wind lidar (N42RF) new

Fly operationally tasked missions• 2 pm and 2 am ET take-offs new• Based on EMC’s and/or NHC’s operational need• Selected modules may be attempted

2013 HRD Field Program Logistics2013 HRD Field Program Logistics

Daily Schedule (all times Eastern):

9 am NOAA conf. call/meeting w. IFEX participants (if needed) 10 am NOAA and NASA HS3 PIs telecon (Aug - Sept) 12 pm weather discussion (29 July – 18 Oct)

− Goto meeting info available Daily blog/email update (during field operations)

HFP Visitors:

[email protected] is coordinating HFP visitors this season. Please contact him if you wish to be put on the list.

Daily Schedule (all times Eastern):

9 am NOAA conf. call/meeting w. IFEX participants (if needed) 10 am NOAA and NASA HS3 PIs telecon (Aug - Sept) 12 pm weather discussion (29 July – 18 Oct)

− Goto meeting info available Daily blog/email update (during field operations)

HFP Visitors:

[email protected] is coordinating HFP visitors this season. Please contact him if you wish to be put on the list.

Extra slides

Background

• Comparisons of composites of airborne Doppler radial passes in multiple hurricanes show statistically significant differences in inner-core structure of hurricanes that are intensifying compared with those that are remaining steady-state (Rogers et al., MWR, 2013, in press)

• Intensifying (IN) – 40 radial passes in 8 different TCs• Steady-state (SS) – 53 radial passes in 6 different TCs

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Best track intensity trace relative to IOP

IN SS

inflow depth

X - burst locations

inflow depth

X - burst locations

TC inner-core structure and intensificationSummary schematic

Rogers et al., MWR, 2013

23:28 UTC 28 Aug

Vortex structure and convective burst distribution for Earl

11:25 UTC 29 Aug 22:47 UTC 29 Aug 12:25 UTC 30 Aug

Streamlines and wind speed (shaded, m/s) at 2 km (black) and 8 km (white)Convective burst locations (top 1% of w distribution at 8 km) denoted by black dots

SHIPS 850-200 hPa shear (m/s)




• Significant displacement of vortex during first flight• Vortex nearly aligned by second flight (~12 h later), after RI onset• Many bursts located inside RMW for most flights, generally downshear and downshear left

Do structures associated with IN v. SS appear in individual cases?


850-200 hPa shear (m/s) and 2-8 km tilt magnitude (km)

Asymmetric vortex structure

• shear marginally (2 m/s) higher in 2612 run• both runs show large vortex displacement prior and at RI onset, becomes nearly aligned several hours after RI onset• vortex tilt small during bifurcation period for both runs, slightly smaller for 2618 run• vortex tilts 45-90 degrees left of shear vector prior to RI, oscillates between 45 degrees right and left of shear after RI, during bifurcation period

2-8 km tilt phase (degrees, relative to shear vector)

RI onset RI onset

bifurcationperiod

bifurcationperiod

Documents

TC inner-core structure and intensification