Tropical Depression 18W

Passive Microwave (PMW) Intensity Information
Advanced Dvorak Technique
Version 9.1


       --Overpass--              --ARCHER--   Ring  Ring            Eye              BT   -Forecast-  
       Date    Time      Sat     Lat    Lon   Diam   Pct  TbDiff   Score  Meaning   Vmax  Lat    Lon                 
     20231217 220730  SSMISF17    6.6  127.1   112   22%    2.41   -2.41      N/A   30.0   7.1  126.3 Analysis Plot     
     20231218 052702     AMSR2    6.7  124.8   N/A   N/A     N/A     N/A      N/A   30.0   7.3  125.3 Analysis Plot     
     20231218 180659       GMI    7.9  123.1   N/A   N/A     N/A     N/A      N/A   25.0   7.4  123.7 Analysis Plot     
     20231218 210544  SSMISF16    7.2  121.8   N/A   N/A     N/A     N/A      N/A   20.0   7.6  122.5 Analysis Plot     
     20231218 215420  SSMISF17    7.6  122.2   N/A   N/A     N/A     N/A      N/A   20.0   7.6  122.2 Analysis Plot     
     20231219 054216       GMI    8.4  121.5   N/A   N/A     N/A     N/A      N/A   20.0   7.8  120.8 Analysis Plot     
     20231219 075913  SSMISF18    7.9  120.3   290    4%    1.44   -1.44      N/A   20.0   7.9  120.2 Analysis Plot     
     20231219 092009  SSMISF16    8.2  119.8   257   N/A    0.76   -0.76      N/A   20.0   8.0  119.8 Analysis Plot

Legend

  - Overpass Date/Time are determined from satellite overpass of targeted TC (position determined from Best Track Lat/Lon position). Date is YYYYMMDD and time in HHMMSS (UTC).

  - Forecast (Best Track) and ARCHER positions (deg) of the TC center at overpass day/time. Positive/Negative: Latitude = North/South Hemisphere; Longitude = Eastern/Western Hemisphere.

  - BT Vmax is the concurrent ATCF Best Track (BT) wind speed intensity estimate (Vmax) value from either NOAA/National Hurricane Center (NHC) (North Atlantic and Northeast Pacific), NOAA/Central Pacific Hurricane Center (CPHC) (North-central Pacific) or Joint Typhoon Warning Center (JTWC) (Northwest Pacific, Indian Ocean, or Southwest Pacific).

  - Sat is the satellite descriptor providing the overpass. Currently the satellites used are the DMSP/SSMIS-16/17/18, GPM/GMI, and GCOM/AMSR2.

  - Ring Diam (km) indicates the estimated surface eyewall diameter if one is analyzed in the PMW imagery. The value listed is the average PMW-estimated inner eyewall edge diameter minus 10 km for eyewall slope. N/A indicates no appreciable eyewall is analyzed.

  - Ring Pct is the percentage of the analyzed "ring" (eyewall inner boundary) that is 1) colder than the eye Tb (the "hot spot" -- warmest eye pixel) by at least 20K, or 2) that is colder than 232K and colder than the eye Tb by 10K, whichever is greater. Values are red if Ring % ≤65,yellow/brown if Ring % ≤85 and green if Ring % >85. N/A indicates no appreciable eyewall is analyzed. A value over 85% is used in the intensity score by adding 15 points to it.

  - TbDiff is the difference between the warmest eye pixel and the warmest pixel on the eyewall. This value is used in the Intensity Score. N/A indicates no appreciable eyewall is analyzed.

  - Eye Score values are based on the strength and organization of the convective/eyewall signatures in the PMW imagery, and based on the ARCHER center location. They normally range from 0 to 100 with empirically-determined thresholds related to intensity (Vmax) in the "Meaning" column (≥20 suggests ≥65kts; ≥60 suggests ≥85kts). Scores are listed as negative, and not used by the ADT, when the NHC, CPHC, or JTWC Best Track Vmax is <55 kts in order to filter out occasional "false eye" cases. A value of -920 is used when the warmest eye pixel is <200K to prevent false positives; -930 means edge of overpass and <85% of eyewall is captured and therefore can't fully be analyzed.