JTWC/SATOPS/TN-97/002, Intensity Estimation of Tropical Cyclones During Extratropical Transition, April 1997, has been reviewed and is approved for public release.  There is no objection to unlimited distribution of this document to the public at large, or by the Defense Technical Information Center (DTIC) to the National Technical Information Service (NTIS).

 
RICHARD A. ANSTETT, Capt, USAF
JTWC Meteorological Satellite Coordinator

2 April 1997

3.  Report Type:  Technical Note

4.  Title:  Intensity Estimation of Tropical Cyclones During Extratropical Transition

6.  Author:  TSgt Dennis W. Miller and Dr. Mark A. Lander

7.  Performing Organization Name and Address:  JTWC/SATOPS, Nimitz Hill, Guam,               PSC 489 Box 20, FPO AP 96536

8.  Performing Organization Report Number:  JTWC/SATOPS/TN-97/002

12. Distribution/Availability Statement:  Approved for public Release;  distribution unlimited

13. Abstract: This report provides satellite analysts with a technique to estimate the intensity of tropical cyclones as they transition into extratropical cyclones.  The primary satellite-based intensity estimate technique underpredicts the intensity of tropical cyclones as they lose persistant deep central convection.  This report describes the extratropical transition (XT) technique, and provides examples and a flow chart for it’s application.

14. Subject Terms:  meteorology, weather, tropical cyclone, typhoon, hurricane,  extratropical cyclone, Dvorak, satellite analysis

15: Number of Pages:  9

17. Security Classification of Report:  Unclassified

18. Security Classification of this Page:  Unclassified

19. Security Classification of Abstract:  Unclassified

20. Limitation of Abstract:  UL

PREFACE

A significant number of cyclones that recurve and move out of the tropics are underestimated by satellite analysts using the Dvorak (1984) method to determine intensity. This report was initiated to determine the intensity of transitioning systems to insure that the best tropical satellite reconnaissance data are provided.

Table of Contents

Introduction                                                                                                                       1

Procedures                                                                                                                        2

Technique Application                                                                                                        3

Acknowledgments                                                                                                              9

References                                                                                                                         9
 

List of Figures

Figure 1:  Cyclonic vortex that has completed extratropical transition process                      2

Figure 2:  Northern hemisphere extratropical transition cloud pattern schematic with            4
                log 10 spiral overlay

Figure 3:  Southern hemisphere extratropical transition cloud pattern schematic with            5
                log 10 spiral overlay

Figure 4a and b: Low level circulation organization                                                             6

Figure 5: Convection between primary outer cloud band and circulation center                   7

Figure 6:  Extratropical technique flowchart                                                                       8