{
 "generated_utc": "2026-09-04T17:27:41Z",
 "gfs_cycle_utc": "2026-09-04T12:00:00Z",
 "model": {
  "source": "NCEP GFS 0.50 degree",
  "vertical_coordinate": "constant density (isopycnic)",
  "horizon_hours": 429.5,
  "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_20260904_12Z.csv.gz",
  "trajectories_geojson_gz": "PBA_forecast_20260904_12Z.geojson.gz"
 },
 "counts": {
  "flights": 17,
  "members": 9,
  "rows": 74196
 },
 "flights": [
  {
   "callsign": "AG6NS-23",
   "flight_id": "AG6NS-23_2026-02-07",
   "payload_type": "WSPR",
   "seed_time": "2026-08-28 16:13:40",
   "seed_lat": -64.54167,
   "seed_lon": -17.12499,
   "seed_alt_m": 11900.0,
   "seed_age_h": 169.11,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-11 11:45:00",
    "lat": -54.94691,
    "lon": -130.37102,
    "alt_m": 12583.8
   },
   "member_spread_deg": {
    "lat": 28.82,
    "lon": 270.65
   },
   "member_spread_now_deg": {
    "lat": 25.64,
    "lon": 84.11
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "BSS54",
   "flight_id": "BSS54_2026-07-09",
   "payload_type": "WSPR",
   "seed_time": "2026-09-04 15:28:18",
   "seed_lat": 36.89583,
   "seed_lon": -108.95833,
   "seed_alt_m": 14470.0,
   "seed_age_h": 1.86,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-11 15:00:00",
    "lat": 37.93816,
    "lon": -17.95696,
    "alt_m": 14543.7
   },
   "member_spread_deg": {
    "lat": 28.49,
    "lon": 134.04
   },
   "member_spread_now_deg": {
    "lat": 0.35,
    "lon": 0.91
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-23",
   "flight_id": "DG2GG-23_2026-05-23",
   "payload_type": "WSPR",
   "seed_time": "2026-08-25 21:29:00",
   "seed_lat": 33.10417,
   "seed_lon": -84.75,
   "seed_alt_m": 13050.0,
   "seed_age_h": 235.85,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-11 11:30:00",
    "lat": 3.60943,
    "lon": -101.38585,
    "alt_m": 13159.3
   },
   "member_spread_deg": {
    "lat": 21.95,
    "lon": 73.11
   },
   "member_spread_now_deg": {
    "lat": 21.73,
    "lon": 46.69
   },
   "display_as": "region",
   "display_reason": "seed_age"
  },
  {
   "callsign": "DG2GG-30",
   "flight_id": "DG2GG-30_2026-08-07",
   "payload_type": "WSPR",
   "seed_time": "2026-09-04 06:56:00",
   "seed_lat": 84.47917,
   "seed_lon": 75.83333,
   "seed_alt_m": 11790.0,
   "seed_age_h": 10.4,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-11 11:30:00",
    "lat": 83.78339,
    "lon": -138.90192,
    "alt_m": 11591.8
   },
   "member_spread_deg": {
    "lat": 34.28,
    "lon": 338.52
   },
   "member_spread_now_deg": {
    "lat": 3.6,
    "lon": 8.38
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-31",
   "flight_id": "DG2GG-31_2026-08-13",
   "payload_type": "WSPR",
   "seed_time": "2026-09-04 07:27:00",
   "seed_lat": 53.39583,
   "seed_lon": 126.70833,
   "seed_alt_m": 13200.0,
   "seed_age_h": 9.88,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-11 11:30:00",
    "lat": 45.89139,
    "lon": -30.51368,
    "alt_m": 13292.7
   },
   "member_spread_deg": {
    "lat": 33.73,
    "lon": 125.2
   },
   "member_spread_now_deg": {
    "lat": 1.79,
    "lon": 2.68
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DN3LEO-13",
   "flight_id": "DN3LEO-13_2026-04-12",
   "payload_type": "WSPR",
   "seed_time": "2026-08-31 09:53:00",
   "seed_lat": 62.54167,
   "seed_lon": 91.41667,
   "seed_alt_m": 11930.0,
   "seed_age_h": 103.45,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-11 11:30:00",
    "lat": 50.41622,
    "lon": -124.77106,
    "alt_m": 12061.5
   },
   "member_spread_deg": {
    "lat": 25.05,
    "lon": 341.61
   },
   "member_spread_now_deg": {
    "lat": 26.69,
    "lon": 326.77
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "DO3GU-47",
   "flight_id": "DO3GU-47_2026-09-03",
   "payload_type": "WSPR",
   "seed_time": "2026-09-04 13:23:25",
   "seed_lat": 40.625,
   "seed_lon": 28.375,
   "seed_alt_m": 13960.0,
   "seed_age_h": 3.94,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-11 13:00:00",
    "lat": 50.23098,
    "lon": -116.41166,
    "alt_m": 13883.4
   },
   "member_spread_deg": {
    "lat": 23.28,
    "lon": 93.93
   },
   "member_spread_now_deg": {
    "lat": 0.62,
    "lon": 0.96
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "EI6BFW-18",
   "flight_id": "EI6BFW-18_2026-07-25",
   "payload_type": "WSPR",
   "seed_time": "2026-08-24 14:13:00",
   "seed_lat": 65.52083,
   "seed_lon": 37.33333,
   "seed_alt_m": 12490.0,
   "seed_age_h": 267.12,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-11 11:45:00",
    "lat": 50.28847,
    "lon": -31.23242,
    "alt_m": 13101.7
   },
   "member_spread_deg": {
    "lat": 23.95,
    "lon": 176.35
   },
   "member_spread_now_deg": {
    "lat": 24.48,
    "lon": 288.13
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "KC3LBR-449",
   "flight_id": "KC3LBR-449_2026-07-06",
   "payload_type": "WSPR",
   "seed_time": "2026-08-25 06:33:48",
   "seed_lat": 61.6875,
   "seed_lon": -165.70833,
   "seed_alt_m": 13200.0,
   "seed_age_h": 250.77,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-11 11:30:00",
    "lat": 55.08382,
    "lon": -113.88093,
    "alt_m": 13387.7
   },
   "member_spread_deg": {
    "lat": 18.86,
    "lon": 246.06
   },
   "member_spread_now_deg": {
    "lat": 36.42,
    "lon": 165.16
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "KC7RW-3",
   "flight_id": "KC7RW-3_2026-08-20",
   "payload_type": "WSPR",
   "seed_time": "2026-09-03 08:04:00",
   "seed_lat": 37.27083,
   "seed_lon": 133.375,
   "seed_alt_m": 12750.0,
   "seed_age_h": 33.27,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-11 11:30:00",
    "lat": 7.48508,
    "lon": 127.32723,
    "alt_m": 12880.0
   },
   "member_spread_deg": {
    "lat": 34.28,
    "lon": 285.21
   },
   "member_spread_now_deg": {
    "lat": 4.81,
    "lon": 350.98
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "KD7FXO-1",
   "flight_id": "KD7FXO-1_2026-08-02",
   "payload_type": "WSPR",
   "seed_time": "2026-09-04 16:20:00",
   "seed_lat": 25.41667,
   "seed_lon": -34.875,
   "seed_alt_m": 13050.0,
   "seed_age_h": 1.0,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-11 15:45:00",
    "lat": 38.45061,
    "lon": 49.49358,
    "alt_m": 12814.6
   },
   "member_spread_deg": {
    "lat": 13.39,
    "lon": 122.66
   },
   "member_spread_now_deg": {
    "lat": 0.13,
    "lon": 0.27
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KE8RES-8",
   "flight_id": "KE8RES-8_2026-06-20",
   "payload_type": "WSPR",
   "seed_time": "2026-09-04 05:21:00",
   "seed_lat": 52.1875,
   "seed_lon": 166.16667,
   "seed_alt_m": 12060.0,
   "seed_age_h": 11.98,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-11 11:45:00",
    "lat": 78.68255,
    "lon": -13.79779,
    "alt_m": 12104.1
   },
   "member_spread_deg": {
    "lat": 25.45,
    "lon": 212.35
   },
   "member_spread_now_deg": {
    "lat": 0.69,
    "lon": 3.17
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KI6DS-11",
   "flight_id": "KI6DS-11_2026-02-03",
   "payload_type": "WSPR",
   "seed_time": "2026-09-04 16:55:45",
   "seed_lat": 60.52078,
   "seed_lon": -5.29165,
   "seed_alt_m": 12960.0,
   "seed_age_h": 0.41,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-11 17:00:00",
    "lat": 57.71316,
    "lon": -177.29633,
    "alt_m": 13098.6
   },
   "member_spread_deg": {
    "lat": 24.86,
    "lon": 329.9
   },
   "member_spread_now_deg": {
    "lat": 0.04,
    "lon": 0.03
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KJ4AWK-1",
   "flight_id": "KJ4AWK-1_2026-08-22",
   "payload_type": "APRS",
   "seed_time": "2026-08-26 15:51:36",
   "seed_lat": 41.62025,
   "seed_lon": 25.112,
   "seed_alt_m": 13223.0,
   "seed_age_h": 217.47,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-11 11:45:00",
    "lat": 25.77435,
    "lon": -31.37452,
    "alt_m": 13357.2
   },
   "member_spread_deg": {
    "lat": 21.39,
    "lon": 159.53
   },
   "member_spread_now_deg": {
    "lat": 17.04,
    "lon": 71.97
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "SP2ROC-41",
   "flight_id": "SP2ROC-41_2026-01-25",
   "payload_type": "WSPR",
   "seed_time": "2026-09-04 03:51:00",
   "seed_lat": 39.39583,
   "seed_lon": -175.08333,
   "seed_alt_m": 16100.0,
   "seed_age_h": 13.48,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-11 11:45:00",
    "lat": 30.1372,
    "lon": -153.34658,
    "alt_m": 16416.2
   },
   "member_spread_deg": {
    "lat": 19.51,
    "lon": 354.01
   },
   "member_spread_now_deg": {
    "lat": 4.3,
    "lon": 4.08
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "VE3VRO-36",
   "flight_id": "VE3VRO-36_2026-07-30",
   "payload_type": "WSPR",
   "seed_time": "2026-09-04 16:16:00",
   "seed_lat": 37.14583,
   "seed_lon": -128.08333,
   "seed_alt_m": 13210.0,
   "seed_age_h": 1.07,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-11 15:45:00",
    "lat": 42.78395,
    "lon": 55.05848,
    "alt_m": 13325.1
   },
   "member_spread_deg": {
    "lat": 20.36,
    "lon": 61.9
   },
   "member_spread_now_deg": {
    "lat": 0.1,
    "lon": 0.49
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "ZS6WBT-1",
   "flight_id": "ZS6WBT-1_2026-08-19",
   "payload_type": "WSPR",
   "seed_time": "2026-09-04 14:41:00",
   "seed_lat": -33.35417,
   "seed_lon": -2.91667,
   "seed_alt_m": 15420.0,
   "seed_age_h": 2.65,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-11 14:15:00",
    "lat": -27.25827,
    "lon": 68.75018,
    "alt_m": 15356.7
   },
   "member_spread_deg": {
    "lat": 16.39,
    "lon": 337.58
   },
   "member_spread_now_deg": {
    "lat": 0.86,
    "lon": 0.19
   },
   "display_as": "track",
   "display_reason": "fresh"
  }
 ]
}