{
 "generated_utc": "2026-08-21T05:26:41Z",
 "gfs_cycle_utc": "2026-08-21T00:00:00Z",
 "model": {
  "source": "NCEP GFS 0.50 degree",
  "vertical_coordinate": "constant density (isopycnic)",
  "horizon_hours": 431.5,
  "output_interval_min": 30,
  "integration_step_s": 900,
  "wind_field_interval_h": 3
 },
 "staleness": {
  "fresh_seed_max_h": 24.0,
  "served_until_h": 336.0,
  "track_max_age_h": 72.0,
  "region_spread_deg": 60.0,
  "note": "A trajectory is served for 336 h after the last real fix and then the flight disappears. That matches the archive's own bridging limit: 23% of flights go quiet for over a week and are then heard again, so a shorter window drops balloons that are still flying. Past dead_reckoned flights the balloon has not been heard from since seed_time, so its present position is a prediction too -- the silent period is reconstructed from GFS analyses of weather that has already happened, which is why wind_source distinguishes analysis from forecast. Use display_as, not seed_age_h, to decide how to draw a flight: 'track' means the members still agree and a line is meaningful, 'region' means draw the member envelope instead because the nominal member is no better than any other."
 },
 "members": {
  "offsets_m": [
   -2000,
   -1500,
   -1000,
   -500,
   0,
   500,
   1000,
   1500,
   2000
  ],
  "nominal_offset_m": 0,
  "note": "Each member is seeded at the last observed altitude plus its offset and then conserves the density it started with. The ladder is a sensitivity fan, not a probability distribution: adjacent members diverge by roughly 1,200 km over seven days. levels_spanned reports how many GFS levels the fan actually straddles, usually 2 or 3."
 },
 "files": {
  "trajectories_csv_gz": "PBA_forecast_20260821_00Z.csv.gz",
  "trajectories_geojson_gz": "PBA_forecast_20260821_00Z.geojson.gz"
 },
 "counts": {
  "flights": 22,
  "members": 9,
  "rows": 86976
 },
 "flights": [
  {
   "callsign": "AG6NS-23",
   "flight_id": "AG6NS-23_2026-02-07",
   "payload_type": "WSPR",
   "seed_time": "2026-08-20 13:13:40",
   "seed_lat": -54.16667,
   "seed_lon": -61.99999,
   "seed_alt_m": 12300.0,
   "seed_age_h": 16.11,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-08-27 23:45:00",
    "lat": -82.8594,
    "lon": -129.60949,
    "alt_m": 12532.8
   },
   "member_spread_deg": {
    "lat": 40.15,
    "lon": 302.22
   },
   "member_spread_now_deg": {
    "lat": 1.99,
    "lon": 11.36
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "BSS53",
   "flight_id": "BSS53_2026-03-09",
   "payload_type": "WSPR",
   "seed_time": "2026-08-20 23:54:48",
   "seed_lat": 69.52083,
   "seed_lon": -158.91667,
   "seed_alt_m": 12300.0,
   "seed_age_h": 5.42,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-08-27 23:30:00",
    "lat": 67.86413,
    "lon": 25.7674,
    "alt_m": 12543.7
   },
   "member_spread_deg": {
    "lat": 29.31,
    "lon": 63.27
   },
   "member_spread_now_deg": {
    "lat": 1.52,
    "lon": 3.44
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "BSS54",
   "flight_id": "BSS54_2026-07-09",
   "payload_type": "WSPR",
   "seed_time": "2026-08-19 19:59:18",
   "seed_lat": 51.08333,
   "seed_lon": -140.58333,
   "seed_alt_m": 14060.0,
   "seed_age_h": 33.35,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-08-27 23:30:00",
    "lat": 51.20392,
    "lon": 25.79825,
    "alt_m": 14063.0
   },
   "member_spread_deg": {
    "lat": 23.97,
    "lon": 141.33
   },
   "member_spread_now_deg": {
    "lat": 17.5,
    "lon": 9.2
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-23",
   "flight_id": "DG2GG-23_2026-05-23",
   "payload_type": "WSPR",
   "seed_time": "2026-08-21 03:24:00",
   "seed_lat": 55.64583,
   "seed_lon": -168.45833,
   "seed_alt_m": 12690.0,
   "seed_age_h": 1.93,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-28 03:00:00",
    "lat": 51.58625,
    "lon": -21.8847,
    "alt_m": 12640.2
   },
   "member_spread_deg": {
    "lat": 25.98,
    "lon": 49.01
   },
   "member_spread_now_deg": {
    "lat": 1.1,
    "lon": 0.92
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-27",
   "flight_id": "DG2GG-27_2026-07-04",
   "payload_type": "WSPR",
   "seed_time": "2026-08-10 00:18:00",
   "seed_lat": 17.10417,
   "seed_lon": -113.33333,
   "seed_alt_m": 14010.0,
   "seed_age_h": 269.03,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-08-27 23:45:00",
    "lat": 0.7675,
    "lon": -34.94844,
    "alt_m": 14076.7
   },
   "member_spread_deg": {
    "lat": 50.57,
    "lon": 147.09
   },
   "member_spread_now_deg": {
    "lat": 47.14,
    "lon": 117.98
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "DG2GG-30",
   "flight_id": "DG2GG-30_2026-08-07",
   "payload_type": "WSPR",
   "seed_time": "2026-08-20 16:01:00",
   "seed_lat": 54.91667,
   "seed_lon": 15.08333,
   "seed_alt_m": 12380.0,
   "seed_age_h": 13.32,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-08-27 23:30:00",
    "lat": 51.55511,
    "lon": -131.03785,
    "alt_m": 12595.4
   },
   "member_spread_deg": {
    "lat": 14.07,
    "lon": 62.73
   },
   "member_spread_now_deg": {
    "lat": 3.72,
    "lon": 13.75
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-31",
   "flight_id": "DG2GG-31_2026-08-13",
   "payload_type": "WSPR",
   "seed_time": "2026-08-21 04:17:00",
   "seed_lat": 45.64583,
   "seed_lon": 145.83333,
   "seed_alt_m": 13130.0,
   "seed_age_h": 1.05,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-28 03:45:00",
    "lat": 43.68778,
    "lon": -78.09938,
    "alt_m": 13118.5
   },
   "member_spread_deg": {
    "lat": 11.91,
    "lon": 54.85
   },
   "member_spread_now_deg": {
    "lat": 0.31,
    "lon": 0.32
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DN3LEO-13",
   "flight_id": "DN3LEO-13_2026-04-12",
   "payload_type": "WSPR",
   "seed_time": "2026-08-20 10:08:00",
   "seed_lat": 78.95833,
   "seed_lon": 117.79167,
   "seed_alt_m": 11880.0,
   "seed_age_h": 19.2,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-08-27 23:45:00",
    "lat": 84.58666,
    "lon": 114.07697,
    "alt_m": 11714.4
   },
   "member_spread_deg": {
    "lat": 15.25,
    "lon": 290.26
   },
   "member_spread_now_deg": {
    "lat": 2.65,
    "lon": 10.19
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "EI6BFW-18",
   "flight_id": "EI6BFW-18_2026-07-25",
   "payload_type": "WSPR",
   "seed_time": "2026-08-20 17:48:00",
   "seed_lat": 58.08333,
   "seed_lon": -17.54167,
   "seed_alt_m": 12620.0,
   "seed_age_h": 11.53,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-27 23:45:00",
    "lat": 62.10041,
    "lon": 68.71894,
    "alt_m": 12462.0
   },
   "member_spread_deg": {
    "lat": 23.37,
    "lon": 328.51
   },
   "member_spread_now_deg": {
    "lat": 4.78,
    "lon": 0.51
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "K5NOT-11",
   "flight_id": "K5NOT-11_2026-06-20",
   "payload_type": "WSPR",
   "seed_time": "2026-08-15 20:50:37",
   "seed_lat": 40.97911,
   "seed_lon": -75.41666,
   "seed_alt_m": 13300.0,
   "seed_age_h": 128.49,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-27 23:45:00",
    "lat": 20.86804,
    "lon": -80.84715,
    "alt_m": 13416.2
   },
   "member_spread_deg": {
    "lat": 43.52,
    "lon": 202.7
   },
   "member_spread_now_deg": {
    "lat": 31.42,
    "lon": 51.08
   },
   "display_as": "region",
   "display_reason": "seed_age"
  },
  {
   "callsign": "KC3LBR-449",
   "flight_id": "KC3LBR-449_2026-07-06",
   "payload_type": "WSPR",
   "seed_time": "2026-08-21 04:47:18",
   "seed_lat": 69.58333,
   "seed_lon": 106.5,
   "seed_alt_m": 13300.0,
   "seed_age_h": 0.55,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-28 04:45:00",
    "lat": 78.46689,
    "lon": -86.24021,
    "alt_m": 13133.9
   },
   "member_spread_deg": {
    "lat": 24.74,
    "lon": 277.36
   },
   "member_spread_now_deg": {
    "lat": 0.06,
    "lon": 0.19
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KC5TRB-1",
   "flight_id": "KC5TRB-1_2026-06-20",
   "payload_type": "WSPR",
   "seed_time": "2026-08-12 11:40:43",
   "seed_lat": 57.39578,
   "seed_lon": 26.00003,
   "seed_alt_m": 12570.0,
   "seed_age_h": 209.66,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-27 23:45:00",
    "lat": 53.34671,
    "lon": 97.96914,
    "alt_m": 12556.9
   },
   "member_spread_deg": {
    "lat": 25.01,
    "lon": 293.22
   },
   "member_spread_now_deg": {
    "lat": 28.79,
    "lon": 312.06
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "KD7FXO-1",
   "flight_id": "KD7FXO-1_2026-08-02",
   "payload_type": "WSPR",
   "seed_time": "2026-08-20 20:15:00",
   "seed_lat": 48.97917,
   "seed_lon": 171.625,
   "seed_alt_m": 13040.0,
   "seed_age_h": 9.08,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-27 23:45:00",
    "lat": 34.63674,
    "lon": -87.63477,
    "alt_m": 12982.8
   },
   "member_spread_deg": {
    "lat": 18.48,
    "lon": 351.22
   },
   "member_spread_now_deg": {
    "lat": 2.13,
    "lon": 3.17
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KE8RES-8",
   "flight_id": "KE8RES-8_2026-06-20",
   "payload_type": "WSPR",
   "seed_time": "2026-08-20 10:01:00",
   "seed_lat": 85.25,
   "seed_lon": 45.875,
   "seed_alt_m": 11960.0,
   "seed_age_h": 19.32,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-08-27 23:30:00",
    "lat": 70.71824,
    "lon": 159.80532,
    "alt_m": 12037.1
   },
   "member_spread_deg": {
    "lat": 22.6,
    "lon": 346.93
   },
   "member_spread_now_deg": {
    "lat": 8.11,
    "lon": 27.04
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KE9DAB-11",
   "flight_id": "KE9DAB-11_2026-07-29",
   "payload_type": "WSPR",
   "seed_time": "2026-08-13 21:11:00",
   "seed_lat": 63.66667,
   "seed_lon": 161.54167,
   "seed_alt_m": 10970.0,
   "seed_age_h": 176.15,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-08-27 23:45:00",
    "lat": 27.32395,
    "lon": -31.76574,
    "alt_m": 11208.4
   },
   "member_spread_deg": {
    "lat": 37.05,
    "lon": 313.3
   },
   "member_spread_now_deg": {
    "lat": 21.26,
    "lon": 102.1
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "KI6DS-11",
   "flight_id": "KI6DS-11_2026-02-03",
   "payload_type": "WSPR",
   "seed_time": "2026-08-21 04:30:45",
   "seed_lat": 68.79161,
   "seed_lon": 179.37502,
   "seed_alt_m": 12870.0,
   "seed_age_h": 0.82,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-28 04:00:00",
    "lat": 82.39321,
    "lon": 46.50031,
    "alt_m": 12863.7
   },
   "member_spread_deg": {
    "lat": 22.68,
    "lon": 324.8
   },
   "member_spread_now_deg": {
    "lat": 0.11,
    "lon": 0.22
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "SP2ROC-41",
   "flight_id": "SP2ROC-41_2026-01-25",
   "payload_type": "WSPR",
   "seed_time": "2026-08-21 04:33:00",
   "seed_lat": 12.0,
   "seed_lon": 57.95833,
   "seed_alt_m": 16500.0,
   "seed_age_h": 0.78,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-28 04:00:00",
    "lat": 21.0762,
    "lon": -26.42532,
    "alt_m": 16379.8
   },
   "member_spread_deg": {
    "lat": 27.7,
    "lon": 23.11
   },
   "member_spread_now_deg": {
    "lat": 0.18,
    "lon": 0.18
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "VE3VRO-36",
   "flight_id": "VE3VRO-36_2026-07-30",
   "payload_type": "WSPR",
   "seed_time": "2026-08-21 01:31:00",
   "seed_lat": 37.04167,
   "seed_lon": -128.45833,
   "seed_alt_m": 13200.0,
   "seed_age_h": 3.82,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-28 01:00:00",
    "lat": 47.53012,
    "lon": 51.99915,
    "alt_m": 13054.3
   },
   "member_spread_deg": {
    "lat": 25.37,
    "lon": 121.26
   },
   "member_spread_now_deg": {
    "lat": 3.97,
    "lon": 0.5
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "W0RBO-12",
   "flight_id": "W0RBO-12_2026-05-02",
   "payload_type": "WSPR",
   "seed_time": "2026-08-20 22:05:23",
   "seed_lat": 63.66661,
   "seed_lon": -102.70831,
   "seed_alt_m": 12930.0,
   "seed_age_h": 7.24,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-27 23:30:00",
    "lat": 62.60829,
    "lon": -12.47614,
    "alt_m": 13128.9
   },
   "member_spread_deg": {
    "lat": 21.32,
    "lon": 72.0
   },
   "member_spread_now_deg": {
    "lat": 0.76,
    "lon": 2.24
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "ZS6SRC-37",
   "flight_id": "ZS6SRC-37_2026-07-31",
   "payload_type": "WSPR",
   "seed_time": "2026-08-17 20:59:00",
   "seed_lat": -20.58333,
   "seed_lon": -72.33333,
   "seed_alt_m": 12210.0,
   "seed_age_h": 80.35,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-08-27 23:30:00",
    "lat": -14.34054,
    "lon": 146.01002,
    "alt_m": 12606.9
   },
   "member_spread_deg": {
    "lat": 23.25,
    "lon": 288.53
   },
   "member_spread_now_deg": {
    "lat": 22.93,
    "lon": 117.54
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "ZS6SRC-39",
   "flight_id": "ZS6SRC-39_2026-08-05",
   "payload_type": "WSPR",
   "seed_time": "2026-08-12 06:21:00",
   "seed_lat": -22.16667,
   "seed_lon": 146.45833,
   "seed_alt_m": 15900.0,
   "seed_age_h": 214.98,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-08-27 23:45:00",
    "lat": -32.47958,
    "lon": 109.4553,
    "alt_m": 15620.0
   },
   "member_spread_deg": {
    "lat": 26.45,
    "lon": 254.39
   },
   "member_spread_now_deg": {
    "lat": 20.0,
    "lon": 174.35
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "ZS6WBT-1",
   "flight_id": "ZS6WBT-1_2026-08-19",
   "payload_type": "WSPR",
   "seed_time": "2026-08-21 04:36:00",
   "seed_lat": -20.41667,
   "seed_lon": 69.79166,
   "seed_alt_m": 15680.0,
   "seed_age_h": 0.73,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-08-28 04:00:00",
    "lat": -31.75959,
    "lon": -93.59052,
    "alt_m": 14932.7
   },
   "member_spread_deg": {
    "lat": 20.45,
    "lon": 302.81
   },
   "member_spread_now_deg": {
    "lat": 0.09,
    "lon": 0.36
   },
   "display_as": "track",
   "display_reason": "fresh"
  }
 ]
}