Extratropical transition technique

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Typhoon Kong-rey undergoing extratropical transition

The extratropical transition (XT) technique is a system used to subjectively estimate the intensity of tropical cyclones undergoing transition into extratropical cyclones based on visible and infrared satellite imagery. The system is used by the Joint Typhoon Warning Center (JTWC) in place of the Dvorak technique, as the loss of central convection in transitioning tropical cyclones can cause the Dvorak technique to fail;[1] the loss of convection results in unrealistically low estimates using the Dvorak technique.[2]

Technique details

The system combines aspects of the Dvorak technique, used for estimating tropical cyclone intensity, and the Hebert-Poteat technique, used for estimating subtropical cyclone intensity.[3] The technique is applied when a tropical cyclone interacts with a frontal boundary or loses its central convection while maintaining its forward speed or accelerating.[4] The XT scale corresponds to the Dvorak scale and is applied in the same way, except that "XT" is used instead of "T" to indicate that the system is undergoing extratropical transition.[5] Also, the XT technique is only used once extratropical transition begins; the Dvorak technique is still used if the system begins dissipating without transition.[4] Once the cyclone has completed transition and become cold-core, the technique is no longer used.[5]

See also

References

  1. ↑ Velden, C. et al. (Aug 2006). "The Dvorak Tropical Cyclone Intensity Estimation Technique: A Satellite-Based Method that Has Endured for over 30 Years". BAMS (AMS) 87 (9): 1195–1210. Bibcode:2006BAMS...87.1195V. doi:10.1175/BAMS-87-9-1195. Retrieved 2008-11-07. 
  2. ↑ Lander, Mark A. (2004). "Monsoon depressions, monsoon gyres, midget tropical cyclones, TUTT cells, and high intensity after recurvature: Lessons learned from the use of Dvorak's techniques in the world's most prolific tropical-cyclone basin". 26th Conference on Hurricanes and Tropical Meteorology. Retrieved 2008-11-08. 
  3. ↑ JTWC TN 97/002 Page 1
  4. ↑ 4.0 4.1 JTWC TN 97/002 Page 8
  5. ↑ 5.0 5.1 JTWC TN 97/002 Page 2

External links


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