{
 "generated_utc": "2026-08-18T23:25:45Z",
 "gfs_cycle_utc": "2026-08-18T18:00:00Z",
 "model": {
  "source": "NCEP GFS 0.50 degree",
  "vertical_coordinate": "constant density (isopycnic)",
  "horizon_hours": 377.5,
  "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_20260818_18Z.csv.gz",
  "trajectories_geojson_gz": "PBA_forecast_20260818_18Z.geojson.gz"
 },
 "counts": {
  "flights": 21,
  "members": 9,
  "rows": 77319
 },
 "flights": [
  {
   "callsign": "AG6NS-23",
   "flight_id": "AG6NS-23_2026-02-07",
   "payload_type": "WSPR",
   "seed_time": "2026-08-18 22:38:40",
   "seed_lat": -63.6875,
   "seed_lon": -147.37499,
   "seed_alt_m": 12300.0,
   "seed_age_h": 0.69,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-08-25 22:45:00",
    "lat": -48.27167,
    "lon": 128.27779,
    "alt_m": 12340.1
   },
   "member_spread_deg": {
    "lat": 27.76,
    "lon": 306.34
   },
   "member_spread_now_deg": {
    "lat": 0.12,
    "lon": 0.17
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "BSS53",
   "flight_id": "BSS53_2026-03-09",
   "payload_type": "WSPR",
   "seed_time": "2026-08-18 22:29:49",
   "seed_lat": 66.04167,
   "seed_lon": 159.375,
   "seed_alt_m": 12420.0,
   "seed_age_h": 0.84,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-25 22:00:00",
    "lat": 70.60144,
    "lon": 160.9942,
    "alt_m": 12178.8
   },
   "member_spread_deg": {
    "lat": 28.08,
    "lon": 303.65
   },
   "member_spread_now_deg": {
    "lat": 0.24,
    "lon": 0.6
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "BSS54",
   "flight_id": "BSS54_2026-07-09",
   "payload_type": "WSPR",
   "seed_time": "2026-08-18 03:48:18",
   "seed_lat": 43.79167,
   "seed_lon": -166.58333,
   "seed_alt_m": 14200.0,
   "seed_age_h": 19.53,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-25 17:45:00",
    "lat": 46.77279,
    "lon": -80.08221,
    "alt_m": 13768.2
   },
   "member_spread_deg": {
    "lat": 20.87,
    "lon": 151.87
   },
   "member_spread_now_deg": {
    "lat": 4.99,
    "lon": 12.87
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-23",
   "flight_id": "DG2GG-23_2026-05-23",
   "payload_type": "WSPR",
   "seed_time": "2026-08-18 09:19:00",
   "seed_lat": 47.58333,
   "seed_lon": 106.54167,
   "seed_alt_m": 12620.0,
   "seed_age_h": 14.02,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-25 17:45:00",
    "lat": 54.34237,
    "lon": -122.04268,
    "alt_m": 12671.8
   },
   "member_spread_deg": {
    "lat": 16.05,
    "lon": 8.03
   },
   "member_spread_now_deg": {
    "lat": 2.39,
    "lon": 4.71
   },
   "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": 215.03,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-08-25 17:45:00",
    "lat": 7.13829,
    "lon": -85.51301,
    "alt_m": 14111.0
   },
   "member_spread_deg": {
    "lat": 75.26,
    "lon": 167.57
   },
   "member_spread_now_deg": {
    "lat": 42.69,
    "lon": 88.49
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "DG2GG-30",
   "flight_id": "DG2GG-30_2026-08-07",
   "payload_type": "WSPR",
   "seed_time": "2026-08-18 19:36:00",
   "seed_lat": 54.4375,
   "seed_lon": -45.375,
   "seed_alt_m": 12580.0,
   "seed_age_h": 3.73,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-25 19:00:00",
    "lat": 52.75714,
    "lon": 163.73143,
    "alt_m": 12635.3
   },
   "member_spread_deg": {
    "lat": 6.8,
    "lon": 347.34
   },
   "member_spread_now_deg": {
    "lat": 0.41,
    "lon": 2.93
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-31",
   "flight_id": "DG2GG-31_2026-08-13",
   "payload_type": "WSPR",
   "seed_time": "2026-08-18 11:07:00",
   "seed_lat": 46.0,
   "seed_lon": 78.58333,
   "seed_alt_m": 13100.0,
   "seed_age_h": 12.22,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-25 17:30:00",
    "lat": 50.79981,
    "lon": -154.35084,
    "alt_m": 13192.3
   },
   "member_spread_deg": {
    "lat": 24.46,
    "lon": 321.32
   },
   "member_spread_now_deg": {
    "lat": 0.15,
    "lon": 3.15
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DN3LEO-13",
   "flight_id": "DN3LEO-13_2026-04-12",
   "payload_type": "WSPR",
   "seed_time": "2026-08-18 16:38:00",
   "seed_lat": 81.58333,
   "seed_lon": 14.95833,
   "seed_alt_m": 11970.0,
   "seed_age_h": 6.7,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-08-25 17:45:00",
    "lat": 77.09155,
    "lon": -77.38898,
    "alt_m": 11966.8
   },
   "member_spread_deg": {
    "lat": 20.67,
    "lon": 119.34
   },
   "member_spread_now_deg": {
    "lat": 0.3,
    "lon": 5.5
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "EI6BFW-18",
   "flight_id": "EI6BFW-18_2026-07-25",
   "payload_type": "WSPR",
   "seed_time": "2026-08-18 19:28:00",
   "seed_lat": 64.0,
   "seed_lon": -37.41667,
   "seed_alt_m": 12680.0,
   "seed_age_h": 3.87,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-25 19:00:00",
    "lat": 58.32898,
    "lon": 75.86204,
    "alt_m": 12456.3
   },
   "member_spread_deg": {
    "lat": 10.8,
    "lon": 99.34
   },
   "member_spread_now_deg": {
    "lat": 0.65,
    "lon": 0.56
   },
   "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": 74.49,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-25 17:45:00",
    "lat": 25.46779,
    "lon": -106.72005,
    "alt_m": 13424.9
   },
   "member_spread_deg": {
    "lat": 30.22,
    "lon": 103.24
   },
   "member_spread_now_deg": {
    "lat": 20.94,
    "lon": 36.21
   },
   "display_as": "region",
   "display_reason": "seed_age"
  },
  {
   "callsign": "KC3LBR-449",
   "flight_id": "KC3LBR-449_2026-07-06",
   "payload_type": "WSPR",
   "seed_time": "2026-08-18 18:47:18",
   "seed_lat": 74.04167,
   "seed_lon": 47.16667,
   "seed_alt_m": 13210.0,
   "seed_age_h": 4.55,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-25 18:15:00",
    "lat": 66.71272,
    "lon": 132.42264,
    "alt_m": 13190.7
   },
   "member_spread_deg": {
    "lat": 28.18,
    "lon": 353.66
   },
   "member_spread_now_deg": {
    "lat": 0.56,
    "lon": 2.46
   },
   "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": 155.66,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-25 17:45:00",
    "lat": 74.04689,
    "lon": -114.12218,
    "alt_m": 12372.3
   },
   "member_spread_deg": {
    "lat": 26.87,
    "lon": 312.72
   },
   "member_spread_now_deg": {
    "lat": 25.92,
    "lon": 334.11
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "KD7FXO-1",
   "flight_id": "KD7FXO-1_2026-08-02",
   "payload_type": "WSPR",
   "seed_time": "2026-08-18 22:35:00",
   "seed_lat": 56.66667,
   "seed_lon": 150.91667,
   "seed_alt_m": 12910.0,
   "seed_age_h": 0.75,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-25 22:00:00",
    "lat": 35.20081,
    "lon": -128.78147,
    "alt_m": 13021.1
   },
   "member_spread_deg": {
    "lat": 20.32,
    "lon": 359.47
   },
   "member_spread_now_deg": {
    "lat": 0.07,
    "lon": 0.57
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KE8RES-8",
   "flight_id": "KE8RES-8_2026-06-20",
   "payload_type": "WSPR",
   "seed_time": "2026-08-18 17:46:00",
   "seed_lat": 78.58333,
   "seed_lon": -21.91667,
   "seed_alt_m": 12200.0,
   "seed_age_h": 5.57,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-08-25 17:45:00",
    "lat": 72.34231,
    "lon": -63.32232,
    "alt_m": 12053.8
   },
   "member_spread_deg": {
    "lat": 18.63,
    "lon": 303.33
   },
   "member_spread_now_deg": {
    "lat": 0.66,
    "lon": 5.89
   },
   "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": 122.15,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-08-25 17:45:00",
    "lat": 31.15691,
    "lon": -58.71722,
    "alt_m": 11227.9
   },
   "member_spread_deg": {
    "lat": 27.14,
    "lon": 221.61
   },
   "member_spread_now_deg": {
    "lat": 22.52,
    "lon": 74.56
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "KI6DS-11",
   "flight_id": "KI6DS-11_2026-02-03",
   "payload_type": "WSPR",
   "seed_time": "2026-08-18 22:45:45",
   "seed_lat": 61.41661,
   "seed_lon": 125.70835,
   "seed_alt_m": 13000.0,
   "seed_age_h": 0.57,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-25 22:45:00",
    "lat": 62.00688,
    "lon": -69.59599,
    "alt_m": 13156.3
   },
   "member_spread_deg": {
    "lat": 17.43,
    "lon": 126.33
   },
   "member_spread_now_deg": {
    "lat": 0.02,
    "lon": 0.22
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "SP2ROC-41",
   "flight_id": "SP2ROC-41_2026-01-25",
   "payload_type": "WSPR",
   "seed_time": "2026-08-18 08:51:00",
   "seed_lat": 9.625,
   "seed_lon": 112.125,
   "seed_alt_m": 16560.0,
   "seed_age_h": 14.48,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-25 17:45:00",
    "lat": 12.93514,
    "lon": -7.52749,
    "alt_m": 16543.2
   },
   "member_spread_deg": {
    "lat": 35.14,
    "lon": 166.67
   },
   "member_spread_now_deg": {
    "lat": 5.97,
    "lon": 3.62
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "VE3VRO-36",
   "flight_id": "VE3VRO-36_2026-07-30",
   "payload_type": "WSPR",
   "seed_time": "2026-08-18 22:41:00",
   "seed_lat": 45.5,
   "seed_lon": -148.20833,
   "seed_alt_m": 13520.0,
   "seed_age_h": 0.65,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-25 22:45:00",
    "lat": 29.3859,
    "lon": -38.49302,
    "alt_m": 13725.2
   },
   "member_spread_deg": {
    "lat": 32.24,
    "lon": 114.61
   },
   "member_spread_now_deg": {
    "lat": 0.03,
    "lon": 0.22
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "W0RBO-12",
   "flight_id": "W0RBO-12_2026-05-02",
   "payload_type": "WSPR",
   "seed_time": "2026-08-18 21:30:23",
   "seed_lat": 66.85411,
   "seed_lon": -135.04164,
   "seed_alt_m": 12840.0,
   "seed_age_h": 1.83,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-25 21:00:00",
    "lat": 67.29682,
    "lon": -52.79429,
    "alt_m": 12731.4
   },
   "member_spread_deg": {
    "lat": 12.78,
    "lon": 33.98
   },
   "member_spread_now_deg": {
    "lat": 0.27,
    "lon": 0.17
   },
   "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": 26.35,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-08-25 17:30:00",
    "lat": -23.31473,
    "lon": -176.80623,
    "alt_m": 12072.1
   },
   "member_spread_deg": {
    "lat": 31.84,
    "lon": 300.32
   },
   "member_spread_now_deg": {
    "lat": 19.05,
    "lon": 28.14
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "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": 160.98,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-08-25 17:45:00",
    "lat": -12.62873,
    "lon": -33.82197,
    "alt_m": 15950.2
   },
   "member_spread_deg": {
    "lat": 25.46,
    "lon": 264.04
   },
   "member_spread_now_deg": {
    "lat": 15.04,
    "lon": 144.52
   },
   "display_as": "region",
   "display_reason": "member_spread"
  }
 ]
}