{
 "generated_utc": "2026-09-03T11:25:50Z",
 "gfs_cycle_utc": "2026-09-03T06:00:00Z",
 "model": {
  "source": "NCEP GFS 0.50 degree",
  "vertical_coordinate": "constant density (isopycnic)",
  "horizon_hours": 399.5,
  "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_20260903_06Z.csv.gz",
  "trajectories_geojson_gz": "PBA_forecast_20260903_06Z.geojson.gz"
 },
 "counts": {
  "flights": 17,
  "members": 9,
  "rows": 70434
 },
 "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": 139.11,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-10 05:45:00",
    "lat": -59.17719,
    "lon": -159.66383,
    "alt_m": 12575.8
   },
   "member_spread_deg": {
    "lat": 28.24,
    "lon": 347.94
   },
   "member_spread_now_deg": {
    "lat": 18.74,
    "lon": 255.35
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "BSS54",
   "flight_id": "BSS54_2026-07-09",
   "payload_type": "WSPR",
   "seed_time": "2026-09-03 00:05:48",
   "seed_lat": 32.64583,
   "seed_lon": -134.625,
   "seed_alt_m": 14550.0,
   "seed_age_h": 11.24,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-10 05:30:00",
    "lat": 37.51206,
    "lon": -7.64754,
    "alt_m": 14615.9
   },
   "member_spread_deg": {
    "lat": 16.84,
    "lon": 154.35
   },
   "member_spread_now_deg": {
    "lat": 0.76,
    "lon": 1.77
   },
   "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": 205.85,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-10 05:30:00",
    "lat": 16.71167,
    "lon": -89.2314,
    "alt_m": 13173.8
   },
   "member_spread_deg": {
    "lat": 32.9,
    "lon": 81.98
   },
   "member_spread_now_deg": {
    "lat": 18.0,
    "lon": 41.24
   },
   "display_as": "region",
   "display_reason": "seed_age"
  },
  {
   "callsign": "DG2GG-30",
   "flight_id": "DG2GG-30_2026-08-07",
   "payload_type": "WSPR",
   "seed_time": "2026-09-03 09:41:00",
   "seed_lat": 81.97917,
   "seed_lon": 46.75,
   "seed_alt_m": 11960.0,
   "seed_age_h": 1.65,
   "float_reliable": false,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-10 09:15:00",
    "lat": 80.3983,
    "lon": 137.68962,
    "alt_m": 11687.5
   },
   "member_spread_deg": {
    "lat": 19.79,
    "lon": 293.27
   },
   "member_spread_now_deg": {
    "lat": 0.03,
    "lon": 2.93
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-31",
   "flight_id": "DG2GG-31_2026-08-13",
   "payload_type": "WSPR",
   "seed_time": "2026-09-03 07:32:00",
   "seed_lat": 49.60417,
   "seed_lon": 103.20833,
   "seed_alt_m": 13010.0,
   "seed_age_h": 3.8,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-10 07:00:00",
    "lat": 47.31847,
    "lon": -64.51007,
    "alt_m": 13006.6
   },
   "member_spread_deg": {
    "lat": 17.42,
    "lon": 88.24
   },
   "member_spread_now_deg": {
    "lat": 1.52,
    "lon": 0.98
   },
   "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": 73.45,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-10 05:30:00",
    "lat": 64.23948,
    "lon": -136.24878,
    "alt_m": 11882.5
   },
   "member_spread_deg": {
    "lat": 24.22,
    "lon": 271.93
   },
   "member_spread_now_deg": {
    "lat": 28.12,
    "lon": 91.74
   },
   "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": 237.12,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-10 05:45:00",
    "lat": 55.89776,
    "lon": -80.64893,
    "alt_m": 12672.6
   },
   "member_spread_deg": {
    "lat": 22.49,
    "lon": 318.79
   },
   "member_spread_now_deg": {
    "lat": 31.86,
    "lon": 283.69
   },
   "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": 220.77,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-10 05:30:00",
    "lat": 35.52096,
    "lon": -177.85363,
    "alt_m": 13938.3
   },
   "member_spread_deg": {
    "lat": 40.93,
    "lon": 327.58
   },
   "member_spread_now_deg": {
    "lat": 21.41,
    "lon": 175.05
   },
   "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": 3.27,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-10 07:30:00",
    "lat": -7.15637,
    "lon": 128.05723,
    "alt_m": 12822.6
   },
   "member_spread_deg": {
    "lat": 44.86,
    "lon": 310.94
   },
   "member_spread_now_deg": {
    "lat": 2.09,
    "lon": 2.08
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KD7FXO-1",
   "flight_id": "KD7FXO-1_2026-08-02",
   "payload_type": "WSPR",
   "seed_time": "2026-09-03 10:35:00",
   "seed_lat": 27.25,
   "seed_lon": -55.41667,
   "seed_alt_m": 13110.0,
   "seed_age_h": 0.75,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-10 10:00:00",
    "lat": 36.31386,
    "lon": 29.34822,
    "alt_m": 12834.9
   },
   "member_spread_deg": {
    "lat": 12.09,
    "lon": 107.12
   },
   "member_spread_now_deg": {
    "lat": 0.06,
    "lon": 0.11
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KE8RES-8",
   "flight_id": "KE8RES-8_2026-06-20",
   "payload_type": "WSPR",
   "seed_time": "2026-09-03 05:46:00",
   "seed_lat": 56.66667,
   "seed_lon": 150.91667,
   "seed_alt_m": 12260.0,
   "seed_age_h": 5.57,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-10 05:45:00",
    "lat": 78.2496,
    "lon": -91.97818,
    "alt_m": 11805.7
   },
   "member_spread_deg": {
    "lat": 20.31,
    "lon": 73.3
   },
   "member_spread_now_deg": {
    "lat": 2.22,
    "lon": 0.61
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KI6DS-11",
   "flight_id": "KI6DS-11_2026-02-03",
   "payload_type": "WSPR",
   "seed_time": "2026-09-03 10:55:45",
   "seed_lat": 60.14578,
   "seed_lon": -31.08331,
   "seed_alt_m": 12960.0,
   "seed_age_h": 0.41,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-10 11:00:00",
    "lat": 60.25216,
    "lon": 74.42959,
    "alt_m": 13146.2
   },
   "member_spread_deg": {
    "lat": 10.18,
    "lon": 17.32
   },
   "member_spread_now_deg": {
    "lat": 0.1,
    "lon": 0.05
   },
   "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": 187.47,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-10 05:45:00",
    "lat": 38.87134,
    "lon": -29.91882,
    "alt_m": 13481.2
   },
   "member_spread_deg": {
    "lat": 34.56,
    "lon": 96.99
   },
   "member_spread_now_deg": {
    "lat": 10.9,
    "lon": 51.92
   },
   "display_as": "region",
   "display_reason": "seed_age"
  },
  {
   "callsign": "SP2ROC-41",
   "flight_id": "SP2ROC-41_2026-01-25",
   "payload_type": "WSPR",
   "seed_time": "2026-09-03 05:23:00",
   "seed_lat": 40.45833,
   "seed_lon": 159.66667,
   "seed_alt_m": 16100.0,
   "seed_age_h": 5.95,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-10 05:30:00",
    "lat": 36.8872,
    "lon": -167.19184,
    "alt_m": 16294.9
   },
   "member_spread_deg": {
    "lat": 28.5,
    "lon": 334.31
   },
   "member_spread_now_deg": {
    "lat": 0.69,
    "lon": 5.89
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "VE3VRO-36",
   "flight_id": "VE3VRO-36_2026-07-30",
   "payload_type": "WSPR",
   "seed_time": "2026-09-03 02:51:00",
   "seed_lat": 51.125,
   "seed_lon": -157.875,
   "seed_alt_m": 13550.0,
   "seed_age_h": 8.48,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-10 05:45:00",
    "lat": 47.87808,
    "lon": 26.44594,
    "alt_m": 13268.3
   },
   "member_spread_deg": {
    "lat": 32.07,
    "lon": 137.33
   },
   "member_spread_now_deg": {
    "lat": 2.35,
    "lon": 4.24
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "W0RBO-12",
   "flight_id": "W0RBO-12_2026-05-02",
   "payload_type": "WSPR",
   "seed_time": "2026-09-03 05:05:23",
   "seed_lat": 44.39578,
   "seed_lon": 161.87502,
   "seed_alt_m": 13300.0,
   "seed_age_h": 6.24,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-10 05:30:00",
    "lat": 51.83977,
    "lon": -51.15134,
    "alt_m": 13211.3
   },
   "member_spread_deg": {
    "lat": 43.81,
    "lon": 106.06
   },
   "member_spread_now_deg": {
    "lat": 3.09,
    "lon": 6.58
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "ZS6WBT-1",
   "flight_id": "ZS6WBT-1_2026-08-19",
   "payload_type": "WSPR",
   "seed_time": "2026-09-02 17:41:00",
   "seed_lat": -22.60417,
   "seed_lon": -26.08333,
   "seed_alt_m": 15680.0,
   "seed_age_h": 17.65,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-10 05:45:00",
    "lat": -22.85122,
    "lon": 27.09384,
    "alt_m": 15691.0
   },
   "member_spread_deg": {
    "lat": 20.26,
    "lon": 31.14
   },
   "member_spread_now_deg": {
    "lat": 3.48,
    "lon": 1.75
   },
   "display_as": "track",
   "display_reason": "fresh"
  }
 ]
}