{
 "generated_utc": "2026-09-04T11:26:09Z",
 "gfs_cycle_utc": "2026-09-04T06:00:00Z",
 "model": {
  "source": "NCEP GFS 0.50 degree",
  "vertical_coordinate": "constant density (isopycnic)",
  "horizon_hours": 423.5,
  "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_06Z.csv.gz",
  "trajectories_geojson_gz": "PBA_forecast_20260904_06Z.geojson.gz"
 },
 "counts": {
  "flights": 17,
  "members": 9,
  "rows": 73404
 },
 "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": 163.11,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-11 05:45:00",
    "lat": -56.32631,
    "lon": -127.39858,
    "alt_m": 12529.9
   },
   "member_spread_deg": {
    "lat": 33.36,
    "lon": 275.12
   },
   "member_spread_now_deg": {
    "lat": 22.97,
    "lon": 106.15
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "BSS54",
   "flight_id": "BSS54_2026-07-09",
   "payload_type": "WSPR",
   "seed_time": "2026-09-04 01:01:18",
   "seed_lat": 31.04167,
   "seed_lon": -119.5,
   "seed_alt_m": 14530.0,
   "seed_age_h": 10.31,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-11 05:30:00",
    "lat": 41.04014,
    "lon": -8.75362,
    "alt_m": 14665.9
   },
   "member_spread_deg": {
    "lat": 27.85,
    "lon": 100.06
   },
   "member_spread_now_deg": {
    "lat": 2.04,
    "lon": 3.4
   },
   "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": 229.85,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-11 05:30:00",
    "lat": 9.46781,
    "lon": -93.0647,
    "alt_m": 13174.2
   },
   "member_spread_deg": {
    "lat": 15.22,
    "lon": 50.08
   },
   "member_spread_now_deg": {
    "lat": 22.38,
    "lon": 46.16
   },
   "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": 4.4,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-11 06:30:00",
    "lat": 85.73651,
    "lon": -172.35594,
    "alt_m": 11641.1
   },
   "member_spread_deg": {
    "lat": 29.16,
    "lon": 334.42
   },
   "member_spread_now_deg": {
    "lat": 1.32,
    "lon": 3.91
   },
   "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": 3.88,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-11 07:00:00",
    "lat": 41.14432,
    "lon": -68.84487,
    "alt_m": 12949.8
   },
   "member_spread_deg": {
    "lat": 23.46,
    "lon": 30.68
   },
   "member_spread_now_deg": {
    "lat": 0.7,
    "lon": 1.35
   },
   "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": 97.45,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-11 05:30:00",
    "lat": 61.52581,
    "lon": 158.05395,
    "alt_m": 11682.3
   },
   "member_spread_deg": {
    "lat": 23.93,
    "lon": 290.77
   },
   "member_spread_now_deg": {
    "lat": 26.81,
    "lon": 335.83
   },
   "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 10:48:39",
   "seed_lat": 39.85417,
   "seed_lon": 26.58333,
   "seed_alt_m": 13960.0,
   "seed_age_h": 0.52,
   "float_reliable": false,
   "dead_reckoned": false,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-11 10:15:00",
    "lat": 36.2063,
    "lon": -176.15372,
    "alt_m": 14264.0
   },
   "member_spread_deg": {
    "lat": 34.03,
    "lon": 353.31
   },
   "member_spread_now_deg": {
    "lat": 0.04,
    "lon": 0.1
   },
   "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": 261.12,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-11 05:45:00",
    "lat": 51.55013,
    "lon": -68.06139,
    "alt_m": 12524.0
   },
   "member_spread_deg": {
    "lat": 35.3,
    "lon": 222.52
   },
   "member_spread_now_deg": {
    "lat": 23.56,
    "lon": 298.02
   },
   "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": 244.77,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-11 05:30:00",
    "lat": 53.85326,
    "lon": -137.65634,
    "alt_m": 13600.9
   },
   "member_spread_deg": {
    "lat": 18.43,
    "lon": 267.21
   },
   "member_spread_now_deg": {
    "lat": 35.08,
    "lon": 164.92
   },
   "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": 27.27,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-11 05:30:00",
    "lat": 10.94979,
    "lon": 130.95524,
    "alt_m": 12863.9
   },
   "member_spread_deg": {
    "lat": 39.0,
    "lon": 303.55
   },
   "member_spread_now_deg": {
    "lat": 4.2,
    "lon": 353.12
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "KD7FXO-1",
   "flight_id": "KD7FXO-1_2026-08-02",
   "payload_type": "WSPR",
   "seed_time": "2026-09-03 20:25:00",
   "seed_lat": 27.25,
   "seed_lon": -50.5,
   "seed_alt_m": 13080.0,
   "seed_age_h": 14.92,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-11 05:30:00",
    "lat": 47.21427,
    "lon": 82.40036,
    "alt_m": 12668.1
   },
   "member_spread_deg": {
    "lat": 34.91,
    "lon": 128.72
   },
   "member_spread_now_deg": {
    "lat": 1.18,
    "lon": 6.03
   },
   "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": 5.98,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-11 05:45:00",
    "lat": 50.96632,
    "lon": -31.08729,
    "alt_m": 12636.0
   },
   "member_spread_deg": {
    "lat": 24.05,
    "lon": 176.91
   },
   "member_spread_now_deg": {
    "lat": 0.54,
    "lon": 1.13
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KI6DS-11",
   "flight_id": "KI6DS-11_2026-02-03",
   "payload_type": "WSPR",
   "seed_time": "2026-09-04 10:55:45",
   "seed_lat": 60.43745,
   "seed_lon": -11.12498,
   "seed_alt_m": 12960.0,
   "seed_age_h": 0.4,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-11 11:00:00",
    "lat": 51.81838,
    "lon": 161.14262,
    "alt_m": 13159.4
   },
   "member_spread_deg": {
    "lat": 18.13,
    "lon": 352.07
   },
   "member_spread_now_deg": {
    "lat": 0.05,
    "lon": 0.09
   },
   "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": 211.47,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-11 05:45:00",
    "lat": 47.38173,
    "lon": -17.82411,
    "alt_m": 13421.3
   },
   "member_spread_deg": {
    "lat": 28.6,
    "lon": 130.84
   },
   "member_spread_now_deg": {
    "lat": 14.19,
    "lon": 70.41
   },
   "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": 7.48,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-11 05:45:00",
    "lat": 42.1529,
    "lon": -138.2616,
    "alt_m": 16086.9
   },
   "member_spread_deg": {
    "lat": 26.23,
    "lon": 343.5
   },
   "member_spread_now_deg": {
    "lat": 2.36,
    "lon": 2.95
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "VE3VRO-36",
   "flight_id": "VE3VRO-36_2026-07-30",
   "payload_type": "WSPR",
   "seed_time": "2026-09-04 01:01:00",
   "seed_lat": 44.22917,
   "seed_lon": -139.91667,
   "seed_alt_m": 13400.0,
   "seed_age_h": 10.32,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-11 05:30:00",
    "lat": 44.66508,
    "lon": 47.06699,
    "alt_m": 13353.0
   },
   "member_spread_deg": {
    "lat": 25.37,
    "lon": 117.76
   },
   "member_spread_now_deg": {
    "lat": 1.66,
    "lon": 2.98
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "ZS6WBT-1",
   "flight_id": "ZS6WBT-1_2026-08-19",
   "payload_type": "WSPR",
   "seed_time": "2026-09-04 10:11:00",
   "seed_lat": -31.08333,
   "seed_lon": -6.04167,
   "seed_alt_m": 15450.0,
   "seed_age_h": 1.15,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-11 09:45:00",
    "lat": -24.53499,
    "lon": 57.91153,
    "alt_m": 15410.7
   },
   "member_spread_deg": {
    "lat": 18.51,
    "lon": 322.7
   },
   "member_spread_now_deg": {
    "lat": 0.11,
    "lon": 0.18
   },
   "display_as": "track",
   "display_reason": "fresh"
  }
 ]
}