1. STATISTICAL ANALYSIS OF ORGANIZED CLOUD CLUSTERS ON WESTERN NORTH PACIFIC AND THEIR WARM CORE STRUCTURE KOTARO BESSHO* 1 Tetsuo Nakazawa 1 Shuji Nishimura 2 Koji Kato 2 and Shunsuke Hoshino 1 1 Meteorological Research Institute 2 JMA / Meteorological Satellite Center

2. 1.Using Early stage Dvorak Analysis data and reanalysis data of JRA-25, statistical analyses were done for Organized Cloud Clusters on western North Pacific in 2002-2005. - There are big differences of physical parameters between clusters developing and not developing to TS. - Vertical wind shear showed small difference between clusters. 2. Warm core structure of the clusters estimated from Advanced Microwave Sounding Unit (AMSU) in 2004 - Almost clusters developing to TS have warm core structure. - Almost clusters staying at L have no warm core structure. - Lead time from detection of warm core to TS is 28 hours. - Large possibility to detect and forecast the genesis of TS by AMSU retrieved air temperature anomalies Conclusions

3. Motivation and Goal Dvorak technique - Excellent and reasonable work, but subjective Motivation - To supplement the Dvorak technique by objective method especially in the genesis stage of TS - To investigate the difference between clusters developing and not developing to TS - Inspired by Zehr (1992) and so many preceding papers - To use data from microwave sensors, especially of AMSU Goal - Development of objective method to predict the tropical cyclone genesis by satellite microwave observation

4. Data and Methodology Data - Early stage Dvorak Analysis (EDA) log files - Reanalysis data of JRA-25 with the spatial resolution of 1.25 o - Air temperature retrieved from AMSU data by DDK algorithm Methodology - Statistical analysis of Organized Cloud Clusters from 2002 to 2005 by JRA-25 - Analysis of warm core structure of the clusters in 2004 by AMSU data

5. Definition of OCC - OCC (Organized Cloud Cluster) Cloud Clusters with CSC (Cloud System Center) OCCs staying with the stage of L or TD, or developing to TS - OCCs are classified by T# and Maximum Wind Speed (MWS) Low pressure area ( L ; Tropical Disturbance)T#<1 Tropical Depression ( TD ) T#>=1 and MWS < 34kt Tropical Storm ( TS ; Named Tropical Cyclone) T#>=1 and MWS >=34kt

6. Early stage Dvorak Analysis (EDA) - Including the position and T# of OCCs - Subjective analysis for warning the genesis of Tropical Cyclones - After Dvorak (1975), Dvorak (1984) and Tsuchiya et al. (2001) - Edited by Japan Meteorological Agency / Meteorological Satellite Center (JMA/MSC) from 2002 - 2 steps procedure 1. Detecting the CSC to find OCC itself 2. T-number 1 (T1) diagnosis to find the stage of OCC

7. Statistical Analysis of OCCs by JRA-25 - Following Zehr (1992) - Seasonal variation and Geophysical distribution - Investigated the structure of OCCs Air temperature anomaly on 250 hPa Wind convergence on 850 hPa Wind divergence on 250 hPa Relative vorticity on 850 hPa Wind shear between 250 hPa and 850 hPa - Averaged the parameters within 5 o x5 o grid

8. Statistical Analysis of OCCs Total numbers and percentages of OCCs in 2002 - 2005 L TD TS

9. Seasonal variations of occurrence of each stage OCCs in 2002 - 2005

10. Geographical distribution of genesis of each stage OCCs LTD TS ALL 18. 1 9.7 44. 0 4.2 24. 1 32. 7 11. 5 46. 2 3.8 5.812. 5 8.3 58. 3 6.314. 6 18. 7 9.6 48. 1 4.719. 0

11. OCC L EDA 0413 00Z18Apr OCC TS EDA 0453 00z14Aug GMS IR 250 TMP ANOM 850 VOR 850 COV 250 DIV Wind Shear Surf Pressure Examples of OCC L and OCC TS

12. Some parameters in OCCs in 2002-2005

13. 0413 OCC L vs. 0453 OCC TS in AMSU Weak Warm Core EDA0413 EDA0453 AMSU 250hPa TMI PCT TMI 10GHz GOES-9 IR 10:27z19Aug 06:35z25Aug 09:30z19Aug 08:30z25Aug GMS TPW CLW TMP ANOM Strong Warm Core

14. Time series of Temp Anom of OCC L vs. OCC TS Temp Anom = Temp - Average Temp on grid of 10 o x10 o And Temp Anom is averaged in grid of 4 o x4 o Warm Core : Temp Anom is greater than 0.9 K TSTDL OCC TS EDA0453 13 Aug141516 Warm Core L OCC L EDA0413 17 Apr18 Dissipation No Warm Core 0.9K

15. Warm core structure statistics Total number of time series analysis by AMSU retrieved temp. Total: 97 casesL: 56TD: 13 TS: 28 Including WC structureL: 3TD: 7 TS: 25 Not Including WC structureL: 53TD: 6 TS: 3 Average period from genesis of OCC to TS in 25 OCC TS cases including WC51.1 hours Average period from genesis of OCC to first recognition of T1 in 25 OCC TS cases including WC19.4 hours Average period from genesis of OCC to the recognition of WC in 25 OCC TS cases including WC23.4 hours Average period from detection of CSC to the dissipation of L in 53 OCC L cases not including WC13.6 hours

16. Duration of each stage of OCCs Dissipation OCC L not including WC CSC 13.6 hr TS OCC TS including WC CSCWC 23.4 hr 51.1 hr 27.7 hr (Lead Time) Large possibility to detect and forecast the genesis of TS by Warm Core structure retrieved from AMSU 19.4 hr T1

17. 1.Using Early stage Dvorak Analysis data and reanalysis data of JRA-25, statistical analyses were done for Organized Cloud Clusters on western North Pacific in 2002-2005. - There are big differences of physical parameters between clusters developing and not developing to TC. - Vertical wind shear showed small difference between clusters. 2. Warm core structure of OCC estimated from Advanced Microwave Sounding Unit (AMSU) in 2004 - Almost clusters developing to TS have warm core structure. - Almost clusters staying at L have no warm core structure. - Lead time from detection of warm core to TS is 28 hours. - Large possibility to detect and forecast the genesis of TS by AMSU retrieved air temperature anomalies Conclusions

18. Detecting CSC - OCC is defined as the cloud cluster with CSC. - CSC has one of the features as below. 1. Dense and cold overcast bands that show some curvature around a relatively warm area. 2. Curved cirrus lines indicating a center of curvature within or near a dense, cold overcast. 3. Curved low cloud lines showing a center of curvature within two degrees of a cold cloud mass. 4. Cumulonimbus (Cb) clusters rotating cyclonically on animated images.

19. T1 Diagnosis - When OCC has ALL five conditions as below, T# is 1 1. The cloud clusters have persisted for 12 hours or more. 2. The accuracy of estimation of CSC in the clusters is 2.5 o latitude or less. 3. The CSC has persisted for 6 hours. 4. The clusters have dense, cold overcasts that appear less than 2 o latitude from CSC. 5. The extent of the overcasts is more than 1.5 o latitude.

20. Warm Core and Low Level Circulation OCC L EDA0413OCC TS EDA0453 AMSU 250hPa TMI PCT TMI 10GHz GOES-9 IR 09:19z19Aug10:27z19Aug 08:37z25Aug 09:30z19Aug 08:30z25Aug Average distance between the grids of maximum temp. anom. on 250 hPa and the grids of maximum vorticity on 850 hPa 675 km 135 km

21. Future Work 1. To investigate the relation between warm core structure of OCCs retrieved from AMSU and their environmental condition - Using other reanalysis data such as ERA-40 and NCEP - Using other satellite microwave observational data such as QuikSCAT, AMSR-E and SSM/I 2. To expand the analysis period, especially for warm core analysis by AMSU data from 2002 3. To establish the objective method to detect and forecast the genesis of TS - Need of validation by independent data set