1. Objective Dvorak Technique (ODT) AFWA/XOGM
NCEP will be testing their model backup procedures on 2/14/01 between 1730Z and 2000Z.

2. UW-CIMSS Objective Dvorak Technique
Material for this training module largely comes from:
UW-CIMSS Objective Dvorak Technique
Tim Olander and Chris Velden
University of Wisconsin - Madison
Cooperative Institute for Meteorological Satellite Studies
In cooperation with :
Jeff Hawkins
Naval Research Laboratory - Monterey, CA
Office of Naval Research

3. Objective Dvorak Technique (ODT)
Overview
- What is the ODT? - How does it work? - Why use it? - How will we use it here?
NCEP will be testing their model backup procedures on 2/14/01 between 1730Z and 2000Z.

4. Objective Dvorak Technique (ODT)
What is the ODT? ODT is a computerized method for determining the intensity of tropical cyclones. It was originally developed by the University of Wisconsin, and we are able to perform some ODT functions currently. Ok, so how does it work?
NCEP will be testing their model backup procedures on 2/14/01 between 1730Z and 2000Z.

5. ODT Methodology

6. ODT Methodology Identification of two environmental temperatures (BTs)
Uses IR data only
Eye Temperature (0-40 km)
Cloud Temperature ( km)
Scene identification performed
ODT is only performed for four types of features:
Eye, Embedded Center, CDO, and Shear
SIDAS version only handles EYE currently
Based on histogram and Fourier Transform Analysis

7. ODT Methodology
Determination of the cloud pattern is performed objectively (in other words, by the computer) by examining area histograms of cloud top temperatures and corresponding Fourier Analysis for the eye region and surrounding cloud region. Based on this analysis, four scene patterns can be categorized by ODT: Eye, Central Dense Overcast, Embedded Center, and Shear.

8. ODT Methodology Storm Center Location EYE determination
The only user input is the specification of the storm center location
ODT only does intensities
EYE determination
If the storm has an eye, it uses the warmest pixel temperature within a 40 km radius of the chosen storm center
Warm values represent ocean surface or low cloud within the eye
This value is retained as the 'eye temperature'.

9. ODT Methodology

11. Warmest value = 'eye temperature'

12. ODT Methodology EYE determination (con’t)
ODT analyzes temperatures on concentric rings (1 pixel wide) centered on the eye between 24 km and 136 km from the eye location (this range was empirically determined by many observations of coldest ring radii).
For GOES data with 4km pixel resolution, this results in a total of 28 rings that are analyzed to determine the 'surrounding temperature'.
In addition, a continuous ring of cold temperatures surrounding the eye is more indicative of an organized (and more intense) storm than one with breaks in the convection.
Therefore, the warmest temperature found on each ring is identified and stored, with the coldest of these retained as the final surrounding temp value.
ODT does not reposition the storm center, since it has been found that the subsequent analysis of the surrounding temperature field may be improperly influenced by this adjustment in some cases ('false' eyes).

13. ODT Methodology

14. ODT Methodology

15. ODT Methodology
The warmest temperature
is found on each ring...

16. ODT Methodology
This ring has “Light Grey”
as its warmest temp.

17. ODT Methodology Of those temps that are left, the coldest is taken
as the surrounding ring

18. ODT Methodology “No Eye” Condition
ODT can handle Central Dense Overcast (CDO)/Embedded Center
Temperatures near the storm center are dominated by cold cloud tops and a warm eye is not resolvable.
The value of the pixel at the user-defined storm center location is used as the 'eye’ temperature
Shear scenario is also detected in ODT
The SHEAR, CDO/EMBD CTR ARE NOT YET AVAILABLE IN SIDAS VERSION OF SOFTWARE

19. ODT Methodology Initial intensity estimate determined (Raw T#)
Based on original Dvorak Rules for different patterns and cloud top temperatures. Eye temperature serves as adjustment
Use history file with previous storm analysis data
(Final T#)
Provide data for 12-hour time weighted time averaging scheme
This means we have to perform ODT every hour
Data is saved in SIDAS interface
Implementation of Dvorak Rule 9 for weakening storms (CI#)
Corrects underestimate bias in weakening storms
Hold T# constant for 12 hours after initial weakening, add 1.0 T# until dissipation or restrengthening
Not currently implemented in SIDAS

20. ODT Purpose 3. It’s WANTED Ok, but why use it? 1. It’s OBJECTIVE
Doesn’t depend on opinions of human being
Done the same way every time
Can be more accurate (sometimes)
2. It’s FAST
Computer derived
Some storms are harder than others
3. It’s WANTED
JTWC has formally requested that we do this
We are holding off until full capability is here
Test mode only for now

21. Current User Status Operational Use Experimental Use
NOAA/NESDIS Satellite Analysis Branch
NHC/Tropical Analysis Forecast Branch
Experimental Use
Joint Typhoon Warning Center
Air Force Weather Agency
Central Pacific Hurricane Center
Australian Bureau of Meteorology
Japanese Meteorological Agency

22. Developmental Data Sample Independent Data Sample
ODT Past Performance
Units in hPa Bias RMSE Sample
ODT
Op. Center
TAFB
ODT
SAB
ODT
AFWA
ODT
Developmental Data Sample
Units in hPa Bias RMSE Sample
ODT
Op. Center
TAFB
ODT
SAB
ODT
AFWA
ODT
Independent Data Sample
Legend : TAFB - Tropical Analysis Forecast Branch - NOAA/NCEP
SAB Satellite Analysis Branch - NOAA/NESDIS
AFWA - U.S. Air Force Weather Agency

23. Super Typhoon Bilis (18W)
Good agreement with operational center and Best Track estimates
Slight overestimate during intensification and at peak
CI#s compare better with Best Track during weakening than Final T#s
Rapid weakening indicated by Final T#s supported by AMSU data (landfall)
SAB ODT estimates differ from JTWC ODT during intensification

24. Super Typhoon Saomai (22W)
Good agreement with operational center and Best Track estimates
Underestimate during weakening with Final T#s (should use CI#s)
Initial estimates off due to very cold cloud top temperatures (~-80ºC)
SAB ODT analysis very similar to JTWC ODT analysis

25. Super Typhoon Shanshan (26W)
Slight disagreement with operational center and Best Track estimates
Over/Underestimate during strengthening/weakening processes
CI#s compare better with Best Track during weakening than Final T#s
Rapid intensification cycles noted but led to ODT overestimates
SAB ODT analysis very similar to JTWC ODT analysis

26. Summary and Conclusions
6 storm sample for 2000 West Pacific season
Overall, good comparison between JTWC and SAB ODT estimates
JTWC and SAB ODT Final T# estimates were typically within 0.5 T# of JTWC Best Track estimates
Very cold cloud temperatures led to high bias in Final T# relative to JTWC Best Track estimates (cloud temperatures < upper -70°C)
Rapid intensification flag correctly identified events but led to large Final T# high bias when coupled with very cold cloud top temperatures (tuning to West Pacific needed)
Slight differences between JTWC and SAB ODT estimates
Possible errors with ocean basin identification (basin flag is manually adjusted; could be automated)
Implementation of 48 Hour Rule is slightly different between JTWC and SAB due to different ODT versions (fixed vs. time-weighted value)
Overall, CI#s provided better fit to JTWC Best Track estimate than Final T#s during weakening

27. Future Directions Operational ODT Usage
Full operational test at JTWC during 2001 with devoted analyst (patterned after SAB and TAFB evaluation)
Experimental use only here at AFWA
Research Focus
Further tune ODT for West Pacific based on JTWC and SAB 2000 results
Expand analysis range for tropical storms and weaker systems (will remove need for 48 Hour Rule)
Investigate application of rapid intensification flag based on user analysis and feedback
Begin development of Multispectral Dvorak Technique (MDT), incorporating multiple satellite and channel information (AMSU, SSM/I, visible, water vapor, etc.)

28. ODT Implementation JTWC uses it on NSDS-E SAB uses it in MCIDAS
How will we use it here?
SIDAS
New Eye Intensity Calculation
ODT IS ALWAYS TO BE PERFORMED AFTER YOU COMPLETE YOUR OWN INDEPENDENT ANALYSIS!
NCEP will be testing their model backup procedures on 2/14/01 between 1730Z and 2000Z.

29. ODT Implementation
NCEP will be testing their model backup procedures on 2/14/01 between 1730Z and 2000Z.

30. ODT Implementation
NCEP will be testing their model backup procedures on 2/14/01 between 1730Z and 2000Z.

31. ODT Implementation
NCEP will be testing their model backup procedures on 2/14/01 between 1730Z and 2000Z.

32. ODT Implementation
NCEP will be testing their model backup procedures on 2/14/01 between 1730Z and 2000Z.

33. ODT Implementation
NCEP will be testing their model backup procedures on 2/14/01 between 1730Z and 2000Z.

34. ODT Implementation
NCEP will be testing their model backup procedures on 2/14/01 between 1730Z and 2000Z.

35. ODT Implementation
NCEP will be testing their model backup procedures on 2/14/01 between 1730Z and 2000Z.

36. ODT Implementation Previous SIDAS Method ODT Method
NCEP will be testing their model backup procedures on 2/14/01 between 1730Z and 2000Z.

37. ODT Methodology
ODT uses rings….

38. Previous SIDAS Method The SIDAS method uses radial measurements of
temperature. ODT and
SIDAS are different!
Neither include
any banding features!

39. ODT Implementation The SIDAS method is only for a “point
in time”. The ODT
is time averaged. ~
So…..we need to
save this ODT
calculation……..
NCEP will be testing their model backup procedures on 2/14/01 between 1730Z and 2000Z.
Hit the button

40. ODT Implementation Once you hit the button, the names of all available
ODT storm
archives will
appear
NCEP will be testing their model backup procedures on 2/14/01 between 1730Z and 2000Z.
Hit the button:

41. ODT Implementation Highlight the ODT storm archive file that you need
NCEP will be testing their model backup procedures on 2/14/01 between 1730Z and 2000Z.

42. ODT Implementation Highlight the ODT storm archive file that you need
Then Hit
the button:
NCEP will be testing their model backup procedures on 2/14/01 between 1730Z and 2000Z.

43. ODT Implementation Remember that you will need to do this every hour
NCEP will be testing their model backup procedures on 2/14/01 between 1730Z and 2000Z.
Remember that
you will need to
do this every hour
(while the storm
has an EYE!)

44. Questions? Objective Dvorak Technique (ODT) AFWA/XOGM
NCEP will be testing their model backup procedures on 2/14/01 between 1730Z and 2000Z.