{
 "generated_utc": "2026-08-21T23:26:54Z",
 "gfs_cycle_utc": "2026-08-21T18:00:00Z",
 "model": {
  "source": "NCEP GFS 0.50 degree",
  "vertical_coordinate": "constant density (isopycnic)",
  "horizon_hours": 449.5,
  "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_18Z.csv.gz",
  "trajectories_geojson_gz": "PBA_forecast_20260821_18Z.geojson.gz"
 },
 "counts": {
  "flights": 21,
  "members": 9,
  "rows": 85662
 },
 "flights": [
  {
   "callsign": "AG6NS-23",
   "flight_id": "AG6NS-23_2026-02-07",
   "payload_type": "WSPR",
   "seed_time": "2026-08-21 16:33:40",
   "seed_lat": -54.3125,
   "seed_lon": -4.04165,
   "seed_alt_m": 12300.0,
   "seed_age_h": 6.77,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-08-28 17:30:00",
    "lat": -66.40209,
    "lon": -117.91075,
    "alt_m": 12591.3
   },
   "member_spread_deg": {
    "lat": 30.47,
    "lon": 193.85
   },
   "member_spread_now_deg": {
    "lat": 0.23,
    "lon": 7.11
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "BSS53",
   "flight_id": "BSS53_2026-03-09",
   "payload_type": "WSPR",
   "seed_time": "2026-08-21 22:04:48",
   "seed_lat": 75.89583,
   "seed_lon": -139.08333,
   "seed_alt_m": 12340.0,
   "seed_age_h": 1.25,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-08-28 21:30:00",
    "lat": 67.53349,
    "lon": -42.91266,
    "alt_m": 12255.7
   },
   "member_spread_deg": {
    "lat": 12.39,
    "lon": 29.02
   },
   "member_spread_now_deg": {
    "lat": 0.14,
    "lon": 0.64
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "BSS54",
   "flight_id": "BSS54_2026-07-09",
   "payload_type": "WSPR",
   "seed_time": "2026-08-21 22:27:49",
   "seed_lat": 55.29167,
   "seed_lon": -113.70833,
   "seed_alt_m": 14030.0,
   "seed_age_h": 0.87,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-08-28 22:00:00",
    "lat": 56.74602,
    "lon": 22.61105,
    "alt_m": 13891.9
   },
   "member_spread_deg": {
    "lat": 32.21,
    "lon": 168.46
   },
   "member_spread_now_deg": {
    "lat": 0.13,
    "lon": 0.8
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-23",
   "flight_id": "DG2GG-23_2026-05-23",
   "payload_type": "WSPR",
   "seed_time": "2026-08-21 22:49:00",
   "seed_lat": 41.02083,
   "seed_lon": -165.66667,
   "seed_alt_m": 12920.0,
   "seed_age_h": 0.52,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-28 22:15:00",
    "lat": 46.5975,
    "lon": 15.59783,
    "alt_m": 12673.0
   },
   "member_spread_deg": {
    "lat": 18.55,
    "lon": 85.91
   },
   "member_spread_now_deg": {
    "lat": 0.06,
    "lon": 0.04
   },
   "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": 287.03,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-08-28 17:45:00",
    "lat": 5.15109,
    "lon": -42.39921,
    "alt_m": 14031.1
   },
   "member_spread_deg": {
    "lat": 46.71,
    "lon": 191.17
   },
   "member_spread_now_deg": {
    "lat": 48.87,
    "lon": 115.13
   },
   "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": 31.32,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-08-28 17:30:00",
    "lat": 48.70586,
    "lon": -128.75847,
    "alt_m": 12361.2
   },
   "member_spread_deg": {
    "lat": 18.68,
    "lon": 52.82
   },
   "member_spread_now_deg": {
    "lat": 8.27,
    "lon": 8.46
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-31",
   "flight_id": "DG2GG-31_2026-08-13",
   "payload_type": "WSPR",
   "seed_time": "2026-08-21 22:07:00",
   "seed_lat": 50.47917,
   "seed_lon": 153.08333,
   "seed_alt_m": 13100.0,
   "seed_age_h": 1.22,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-28 21:30:00",
    "lat": 42.68555,
    "lon": -45.55699,
    "alt_m": 13233.4
   },
   "member_spread_deg": {
    "lat": 17.74,
    "lon": 56.71
   },
   "member_spread_now_deg": {
    "lat": 0.22,
    "lon": 0.25
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DN3LEO-13",
   "flight_id": "DN3LEO-13_2026-04-12",
   "payload_type": "WSPR",
   "seed_time": "2026-08-21 21:53:00",
   "seed_lat": 68.45833,
   "seed_lon": 144.08333,
   "seed_alt_m": 11860.0,
   "seed_age_h": 1.45,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-08-28 21:30:00",
    "lat": 52.73636,
    "lon": 50.73359,
    "alt_m": 11873.9
   },
   "member_spread_deg": {
    "lat": 30.49,
    "lon": 222.31
   },
   "member_spread_now_deg": {
    "lat": 0.12,
    "lon": 0.27
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "EI6BFW-18",
   "flight_id": "EI6BFW-18_2026-07-25",
   "payload_type": "WSPR",
   "seed_time": "2026-08-21 16:58:00",
   "seed_lat": 50.52083,
   "seed_lon": -6.45833,
   "seed_alt_m": 12630.0,
   "seed_age_h": 6.37,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-28 17:30:00",
    "lat": 73.28399,
    "lon": 86.94865,
    "alt_m": 12402.4
   },
   "member_spread_deg": {
    "lat": 13.77,
    "lon": 90.58
   },
   "member_spread_now_deg": {
    "lat": 1.49,
    "lon": 5.48
   },
   "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": 146.49,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-28 17:45:00",
    "lat": 14.29759,
    "lon": -70.85569,
    "alt_m": 13385.2
   },
   "member_spread_deg": {
    "lat": 30.99,
    "lon": 243.32
   },
   "member_spread_now_deg": {
    "lat": 30.67,
    "lon": 51.81
   },
   "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 22:54:49",
   "seed_lat": 64.83333,
   "seed_lon": 110.20833,
   "seed_alt_m": 13270.0,
   "seed_age_h": 0.42,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-28 23:00:00",
    "lat": 75.79336,
    "lon": 57.9302,
    "alt_m": 13114.5
   },
   "member_spread_deg": {
    "lat": 28.7,
    "lon": 187.11
   },
   "member_spread_now_deg": {
    "lat": 0.02,
    "lon": 0.17
   },
   "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": 227.66,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-28 17:45:00",
    "lat": 48.1352,
    "lon": 145.47766,
    "alt_m": 12618.8
   },
   "member_spread_deg": {
    "lat": 32.84,
    "lon": 335.81
   },
   "member_spread_now_deg": {
    "lat": 25.59,
    "lon": 292.3
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "KD7FXO-1",
   "flight_id": "KD7FXO-1_2026-08-02",
   "payload_type": "WSPR",
   "seed_time": "2026-08-21 22:40:00",
   "seed_lat": 43.5,
   "seed_lon": -176.08333,
   "seed_alt_m": 13070.0,
   "seed_age_h": 0.67,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-28 22:15:00",
    "lat": 26.10067,
    "lon": -170.43017,
    "alt_m": 13113.5
   },
   "member_spread_deg": {
    "lat": 15.55,
    "lon": 87.48
   },
   "member_spread_now_deg": {
    "lat": 0.05,
    "lon": 0.1
   },
   "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": 37.32,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-08-28 17:30:00",
    "lat": 80.30625,
    "lon": 135.3706,
    "alt_m": 11525.5
   },
   "member_spread_deg": {
    "lat": 30.95,
    "lon": 330.31
   },
   "member_spread_now_deg": {
    "lat": 8.29,
    "lon": 29.56
   },
   "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": 194.15,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-08-28 17:45:00",
    "lat": 23.49977,
    "lon": -31.41359,
    "alt_m": 11114.4
   },
   "member_spread_deg": {
    "lat": 42.97,
    "lon": 349.38
   },
   "member_spread_now_deg": {
    "lat": 19.19,
    "lon": 101.92
   },
   "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 21:20:45",
   "seed_lat": 71.58328,
   "seed_lon": -163.95831,
   "seed_alt_m": 12780.0,
   "seed_age_h": 1.99,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-28 20:45:00",
    "lat": 74.72369,
    "lon": -146.79498,
    "alt_m": 12723.5
   },
   "member_spread_deg": {
    "lat": 11.87,
    "lon": 295.89
   },
   "member_spread_now_deg": {
    "lat": 0.39,
    "lon": 0.43
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "SP2ROC-41",
   "flight_id": "SP2ROC-41_2026-01-25",
   "payload_type": "WSPR",
   "seed_time": "2026-08-21 12:21:00",
   "seed_lat": 12.97917,
   "seed_lon": 50.95833,
   "seed_alt_m": 16600.0,
   "seed_age_h": 10.98,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-28 17:45:00",
    "lat": 12.40588,
    "lon": -24.65252,
    "alt_m": 16411.4
   },
   "member_spread_deg": {
    "lat": 18.5,
    "lon": 15.93
   },
   "member_spread_now_deg": {
    "lat": 0.58,
    "lon": 1.8
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "VE3VRO-36",
   "flight_id": "VE3VRO-36_2026-07-30",
   "payload_type": "WSPR",
   "seed_time": "2026-08-21 22:21:00",
   "seed_lat": 53.39583,
   "seed_lon": -120.875,
   "seed_alt_m": 13360.0,
   "seed_age_h": 0.98,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-28 21:45:00",
    "lat": 47.80851,
    "lon": 96.13661,
    "alt_m": 13082.6
   },
   "member_spread_deg": {
    "lat": 28.63,
    "lon": 239.17
   },
   "member_spread_now_deg": {
    "lat": 0.22,
    "lon": 0.54
   },
   "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": 98.35,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-08-28 17:30:00",
    "lat": -27.71131,
    "lon": -72.23934,
    "alt_m": 12356.1
   },
   "member_spread_deg": {
    "lat": 17.64,
    "lon": 137.01
   },
   "member_spread_now_deg": {
    "lat": 30.82,
    "lon": 128.27
   },
   "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": 232.98,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-08-28 17:45:00",
    "lat": -28.22627,
    "lon": 119.16797,
    "alt_m": 15655.6
   },
   "member_spread_deg": {
    "lat": 27.21,
    "lon": 249.29
   },
   "member_spread_now_deg": {
    "lat": 19.47,
    "lon": 179.6
   },
   "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 10:16:00",
   "seed_lat": -20.72917,
   "seed_lon": 71.95833,
   "seed_alt_m": 15680.0,
   "seed_age_h": 13.07,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-08-28 17:45:00",
    "lat": -29.8313,
    "lon": -69.73849,
    "alt_m": 14965.7
   },
   "member_spread_deg": {
    "lat": 16.5,
    "lon": 95.93
   },
   "member_spread_now_deg": {
    "lat": 2.03,
    "lon": 8.75
   },
   "display_as": "track",
   "display_reason": "fresh"
  }
 ]
}