{
 "generated_utc": "2026-09-02T11:25:31Z",
 "gfs_cycle_utc": "2026-09-02T06:00:00Z",
 "model": {
  "source": "NCEP GFS 0.50 degree",
  "vertical_coordinate": "constant density (isopycnic)",
  "horizon_hours": 375.5,
  "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_20260902_06Z.csv.gz",
  "trajectories_geojson_gz": "PBA_forecast_20260902_06Z.geojson.gz"
 },
 "counts": {
  "flights": 16,
  "members": 9,
  "rows": 65430
 },
 "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": 115.11,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-09 05:45:00",
    "lat": -66.04862,
    "lon": 104.02868,
    "alt_m": 12354.6
   },
   "member_spread_deg": {
    "lat": 36.21,
    "lon": 93.4
   },
   "member_spread_now_deg": {
    "lat": 15.59,
    "lon": 281.8
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "BSS54",
   "flight_id": "BSS54_2026-07-09",
   "payload_type": "WSPR",
   "seed_time": "2026-08-31 23:04:18",
   "seed_lat": 53.97917,
   "seed_lon": 172.375,
   "seed_alt_m": 13860.0,
   "seed_age_h": 36.26,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-09 05:30:00",
    "lat": 37.5118,
    "lon": -49.79125,
    "alt_m": 14352.6
   },
   "member_spread_deg": {
    "lat": 23.75,
    "lon": 78.97
   },
   "member_spread_now_deg": {
    "lat": 16.37,
    "lon": 13.71
   },
   "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": 181.85,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-09 05:30:00",
    "lat": 18.2627,
    "lon": -87.34482,
    "alt_m": 13151.2
   },
   "member_spread_deg": {
    "lat": 13.44,
    "lon": 48.93
   },
   "member_spread_now_deg": {
    "lat": 15.6,
    "lon": 27.37
   },
   "display_as": "region",
   "display_reason": "seed_age"
  },
  {
   "callsign": "DG2GG-30",
   "flight_id": "DG2GG-30_2026-08-07",
   "payload_type": "WSPR",
   "seed_time": "2026-09-01 15:06:00",
   "seed_lat": 68.20833,
   "seed_lon": 3.5,
   "seed_alt_m": 12060.0,
   "seed_age_h": 20.23,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-09 05:30:00",
    "lat": 68.78891,
    "lon": 58.18065,
    "alt_m": 11945.7
   },
   "member_spread_deg": {
    "lat": 15.56,
    "lon": 238.44
   },
   "member_spread_now_deg": {
    "lat": 7.08,
    "lon": 9.7
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-31",
   "flight_id": "DG2GG-31_2026-08-13",
   "payload_type": "WSPR",
   "seed_time": "2026-09-02 07:37:00",
   "seed_lat": 46.54167,
   "seed_lon": 66.41667,
   "seed_alt_m": 13020.0,
   "seed_age_h": 3.72,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-09 07:00:00",
    "lat": 49.18502,
    "lon": -106.19733,
    "alt_m": 13124.9
   },
   "member_spread_deg": {
    "lat": 40.46,
    "lon": 71.06
   },
   "member_spread_now_deg": {
    "lat": 0.18,
    "lon": 0.92
   },
   "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": 49.45,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-09 05:30:00",
    "lat": 56.54019,
    "lon": 143.37459,
    "alt_m": 11764.9
   },
   "member_spread_deg": {
    "lat": 26.12,
    "lon": 317.38
   },
   "member_spread_now_deg": {
    "lat": 19.41,
    "lon": 92.92
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "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": 213.12,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-09 05:45:00",
    "lat": 59.91423,
    "lon": -112.2899,
    "alt_m": 12797.0
   },
   "member_spread_deg": {
    "lat": 21.44,
    "lon": 314.22
   },
   "member_spread_now_deg": {
    "lat": 25.65,
    "lon": 284.85
   },
   "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": 196.77,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-09 05:30:00",
    "lat": 36.67657,
    "lon": 175.87514,
    "alt_m": 13740.4
   },
   "member_spread_deg": {
    "lat": 46.75,
    "lon": 342.96
   },
   "member_spread_now_deg": {
    "lat": 23.31,
    "lon": 349.3
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "KC7RW-3",
   "flight_id": "KC7RW-3_2026-08-20",
   "payload_type": "WSPR",
   "seed_time": "2026-09-02 07:19:00",
   "seed_lat": 32.375,
   "seed_lon": 112.58333,
   "seed_alt_m": 12680.0,
   "seed_age_h": 4.02,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-09 06:45:00",
    "lat": 37.08949,
    "lon": 144.48924,
    "alt_m": 12813.5
   },
   "member_spread_deg": {
    "lat": 60.37,
    "lon": 230.73
   },
   "member_spread_now_deg": {
    "lat": 1.44,
    "lon": 1.37
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KD7FXO-1",
   "flight_id": "KD7FXO-1_2026-08-02",
   "payload_type": "WSPR",
   "seed_time": "2026-09-02 10:45:00",
   "seed_lat": 27.625,
   "seed_lon": -60.45833,
   "seed_alt_m": 13070.0,
   "seed_age_h": 0.58,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-09 10:15:00",
    "lat": 33.55571,
    "lon": 8.1755,
    "alt_m": 12904.7
   },
   "member_spread_deg": {
    "lat": 14.43,
    "lon": 97.66
   },
   "member_spread_now_deg": {
    "lat": 0.09,
    "lon": 0.01
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KE8RES-8",
   "flight_id": "KE8RES-8_2026-06-20",
   "payload_type": "WSPR",
   "seed_time": "2026-09-02 04:26:00",
   "seed_lat": 66.25,
   "seed_lon": 146.66667,
   "seed_alt_m": 12460.0,
   "seed_age_h": 6.9,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-09 05:30:00",
    "lat": 58.18194,
    "lon": -74.26046,
    "alt_m": 12030.3
   },
   "member_spread_deg": {
    "lat": 18.12,
    "lon": 213.02
   },
   "member_spread_now_deg": {
    "lat": 3.2,
    "lon": 1.14
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KI6DS-11",
   "flight_id": "KI6DS-11_2026-02-03",
   "payload_type": "WSPR",
   "seed_time": "2026-09-02 10:53:15",
   "seed_lat": 62.91661,
   "seed_lon": -39.79165,
   "seed_alt_m": 13015.0,
   "seed_age_h": 0.45,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-09 11:00:00",
    "lat": 47.61423,
    "lon": 57.21654,
    "alt_m": 13205.6
   },
   "member_spread_deg": {
    "lat": 13.62,
    "lon": 63.39
   },
   "member_spread_now_deg": {
    "lat": 0.1,
    "lon": 0.14
   },
   "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": 163.47,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-09 05:45:00",
    "lat": 38.80127,
    "lon": -25.90213,
    "alt_m": 13599.5
   },
   "member_spread_deg": {
    "lat": 23.57,
    "lon": 87.38
   },
   "member_spread_now_deg": {
    "lat": 20.49,
    "lon": 47.4
   },
   "display_as": "region",
   "display_reason": "seed_age"
  },
  {
   "callsign": "SP2ROC-41",
   "flight_id": "SP2ROC-41_2026-01-25",
   "payload_type": "WSPR",
   "seed_time": "2026-09-01 23:21:00",
   "seed_lat": 40.39583,
   "seed_lon": 126.58333,
   "seed_alt_m": 16040.0,
   "seed_age_h": 11.98,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-09 05:45:00",
    "lat": 37.63525,
    "lon": -169.05081,
    "alt_m": 16031.5
   },
   "member_spread_deg": {
    "lat": 35.61,
    "lon": 169.18
   },
   "member_spread_now_deg": {
    "lat": 3.57,
    "lon": 15.78
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "VE3VRO-36",
   "flight_id": "VE3VRO-36_2026-07-30",
   "payload_type": "WSPR",
   "seed_time": "2026-09-02 02:36:00",
   "seed_lat": 39.8125,
   "seed_lon": -156.66667,
   "seed_alt_m": 13650.0,
   "seed_age_h": 8.73,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-09 05:30:00",
    "lat": 44.91606,
    "lon": 12.20098,
    "alt_m": 13370.8
   },
   "member_spread_deg": {
    "lat": 15.44,
    "lon": 123.18
   },
   "member_spread_now_deg": {
    "lat": 1.85,
    "lon": 2.6
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "ZS6WBT-1",
   "flight_id": "ZS6WBT-1_2026-08-19",
   "payload_type": "WSPR",
   "seed_time": "2026-09-02 10:36:00",
   "seed_lat": -21.4375,
   "seed_lon": -30.04167,
   "seed_alt_m": 15700.0,
   "seed_age_h": 0.73,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-09 10:00:00",
    "lat": -36.65828,
    "lon": 36.6511,
    "alt_m": 15298.0
   },
   "member_spread_deg": {
    "lat": 24.96,
    "lon": 21.28
   },
   "member_spread_now_deg": {
    "lat": 0.05,
    "lon": 0.18
   },
   "display_as": "track",
   "display_reason": "fresh"
  }
 ]
}