Warm Seclusion Extratropical Cyclones

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Warm Seclusion Extratropical Cyclones

• Ryan N. Maue
• Florida State University
• Cyclone Workshop
• September 22, 2008

Jan 4 1989 1751 NOAA 11
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Introduction

• Shapiro and Keyser (1990) Cyclone Paradigm 4
  distinct phases
• Incipient frontal wave along broad baroclinic
  zone
• Frontal Fracture III. T-Bone cold frontal
  structure weakens near cyclone center bent-back
  warm front development
• IV. Warm Seclusion or mature phase as bbwf
  encircles previously post-cold frontal air

Shapiro and Keyser (1990)
Often a result of Rapid intensification or
bomb-like deepening (Sanders and Gyakum 1980) and
may be associated with Tropical Cyclone
transition or downstream development
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Explosive Cyclone Climatology Track Density
1979-2007
24 hPa / 24 hrs at 45 deg
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GFS Sep 2007- May 2008 Bombs
Average frequency Total 46 Atlantic 16 Pacific
30 Aug 1, Sept 1, Oct 2, Nov 6, Dec 9, Jan 14,
Feb 9, Mar 3, April 1 May 1
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Downstream Development of Tropical Cyclones
September 16-21, 2007 Downstream Development of
Super Typhoon Wipha and Typhoon Nari ETC Minimum
SLP 957 mb GFS analysis
Hart (2003) Cyclone Phase Space
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Explosive Warm Seclusion Feb 10 2008
August 2008 Mariners Weather Log - OPC Analysis
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Explosive Warm Seclusion Feb 10 2008
Hart (2003) Cyclone Phase Space
Deep cold-core structure at cyclogenesis Rapid
intensification 2 bergerons (41 hPa at
37N) Upper-level (600-300 hPa) warm-core
structure at maximum intensity (943 hPa)
Mariners Weather Log
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Predictability of Maximum Intensity
Maue and Langland
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Maximum Intensity 925 hPa Wind Speed
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Example of Poor Predictability
Maue and Langland
Yikes!
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MM5 Simulation of February 2008 Storm
18 km 500x1000x29 KF cupa, Blackadar PBL,
Reisner II 0-84 hrs Initialized at 12Z10FEB2008
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72 hour Initialization Experiments w/o Latent
Heating and Surface Fluxes
Full Physics
? No Latent Heating Weak Warm core develops
(adiabatic)

• No Surface Fluxes
• Seclusion structure weaker,
• Japanese storm considerably weaker

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Explicit Simulation of Warm Core Development
24 hour period of most-rapid intensification
ISCCP GIBBS MTSAT1 Feb 11, 2008 12Z
4 km
925 hPa Wind Speed
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Explicit Simulation of Warm Core Development
24 hour period of most-rapid intensification
ISCCP GIBBS MTSAT1 Feb 12, 2008 12Z
4 km
925 hPa Wind Speed
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Rapid Inner-Core Wind Speed Evolution
0hr
6hr
Sting jet
12hr
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Summary
Warm seclusion cyclones range from
run-of-the-mill to extreme. Those resulting from
rapid-intensification develop HF winds and strong
900-600 hPa warm thermal structure in a period of
6-12 hours.
In this framework, what determines the strength
of the warm-core and the magnitude scale of
Chevron-shaped HF winds? Upper-levels
Convection (LH Release) Surface Fluxes
timing Sensitivity Experiments
Acknowledgements Bob Hart, Mark Bourassa
(COAPS), Rolf Langland NASA ESS Fellowship
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4km 925 hPa Wind Speed