{
 "generated_utc": "2026-08-31T11:27:08Z",
 "gfs_cycle_utc": "2026-08-31T06:00:00Z",
 "model": {
  "source": "NCEP GFS 0.50 degree",
  "vertical_coordinate": "constant density (isopycnic)",
  "horizon_hours": 488.5,
  "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_20260831_06Z.csv.gz",
  "trajectories_geojson_gz": "PBA_forecast_20260831_06Z.geojson.gz"
 },
 "counts": {
  "flights": 18,
  "members": 9,
  "rows": 72180
 },
 "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": 67.11,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-07 05:45:00",
    "lat": -48.89002,
    "lon": 66.1742,
    "alt_m": 12213.0
   },
   "member_spread_deg": {
    "lat": 19.06,
    "lon": 44.91
   },
   "member_spread_now_deg": {
    "lat": 11.79,
    "lon": 83.29
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "BSS54",
   "flight_id": "BSS54_2026-07-09",
   "payload_type": "WSPR",
   "seed_time": "2026-08-31 06:11:19",
   "seed_lat": 43.52083,
   "seed_lon": 154.41667,
   "seed_alt_m": 13960.0,
   "seed_age_h": 5.15,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-07 05:45:00",
    "lat": 31.15054,
    "lon": -69.81789,
    "alt_m": 14498.8
   },
   "member_spread_deg": {
    "lat": 14.97,
    "lon": 49.87
   },
   "member_spread_now_deg": {
    "lat": 0.42,
    "lon": 2.86
   },
   "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": 133.85,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-07 05:30:00",
    "lat": 24.98266,
    "lon": -99.52232,
    "alt_m": 13133.8
   },
   "member_spread_deg": {
    "lat": 18.79,
    "lon": 76.03
   },
   "member_spread_now_deg": {
    "lat": 12.5,
    "lon": 27.68
   },
   "display_as": "region",
   "display_reason": "seed_age"
  },
  {
   "callsign": "DG2GG-30",
   "flight_id": "DG2GG-30_2026-08-07",
   "payload_type": "WSPR",
   "seed_time": "2026-08-31 10:46:00",
   "seed_lat": 60.20833,
   "seed_lon": -21.16667,
   "seed_alt_m": 12050.0,
   "seed_age_h": 0.57,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-07 10:45:00",
    "lat": 71.53697,
    "lon": -92.72591,
    "alt_m": 11973.5
   },
   "member_spread_deg": {
    "lat": 19.99,
    "lon": 167.69
   },
   "member_spread_now_deg": {
    "lat": 0.14,
    "lon": 0.29
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-31",
   "flight_id": "DG2GG-31_2026-08-13",
   "payload_type": "WSPR",
   "seed_time": "2026-08-30 15:47:00",
   "seed_lat": 50.16667,
   "seed_lon": 16.875,
   "seed_alt_m": 13220.0,
   "seed_age_h": 19.55,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-07 05:45:00",
    "lat": 56.01742,
    "lon": -140.2941,
    "alt_m": 12810.1
   },
   "member_spread_deg": {
    "lat": 21.11,
    "lon": 353.69
   },
   "member_spread_now_deg": {
    "lat": 6.77,
    "lon": 4.25
   },
   "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": 1.45,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-07 09:30:00",
    "lat": 75.38886,
    "lon": 152.69949,
    "alt_m": 11741.2
   },
   "member_spread_deg": {
    "lat": 22.57,
    "lon": 343.32
   },
   "member_spread_now_deg": {
    "lat": 0.68,
    "lon": 0.59
   },
   "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": 165.12,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-07 05:45:00",
    "lat": 63.37889,
    "lon": -162.08323,
    "alt_m": 12509.8
   },
   "member_spread_deg": {
    "lat": 26.29,
    "lon": 256.77
   },
   "member_spread_now_deg": {
    "lat": 18.3,
    "lon": 309.49
   },
   "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": 148.77,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-07 05:30:00",
    "lat": 48.45137,
    "lon": 92.86583,
    "alt_m": 13417.1
   },
   "member_spread_deg": {
    "lat": 47.47,
    "lon": 230.07
   },
   "member_spread_now_deg": {
    "lat": 32.66,
    "lon": 217.49
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "KC7RW-3",
   "flight_id": "KC7RW-3_2026-08-20",
   "payload_type": "WSPR",
   "seed_time": "2026-08-31 08:49:00",
   "seed_lat": 35.0,
   "seed_lon": 106.08333,
   "seed_alt_m": 12580.0,
   "seed_age_h": 2.52,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-07 08:15:00",
    "lat": -0.97814,
    "lon": 147.89606,
    "alt_m": 12806.5
   },
   "member_spread_deg": {
    "lat": 37.61,
    "lon": 279.38
   },
   "member_spread_now_deg": {
    "lat": 0.23,
    "lon": 0.12
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KD7FXO-1",
   "flight_id": "KD7FXO-1_2026-08-02",
   "payload_type": "WSPR",
   "seed_time": "2026-08-30 23:25:00",
   "seed_lat": 45.10417,
   "seed_lon": -99.54167,
   "seed_alt_m": 12890.0,
   "seed_age_h": 11.92,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-07 05:30:00",
    "lat": 28.37404,
    "lon": -24.3383,
    "alt_m": 13039.2
   },
   "member_spread_deg": {
    "lat": 29.77,
    "lon": 111.22
   },
   "member_spread_now_deg": {
    "lat": 3.15,
    "lon": 7.83
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KE8RES-8",
   "flight_id": "KE8RES-8_2026-06-20",
   "payload_type": "WSPR",
   "seed_time": "2026-08-30 11:11:00",
   "seed_lat": 53.6875,
   "seed_lon": 74.70833,
   "seed_alt_m": 12000.0,
   "seed_age_h": 24.15,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-07 05:45:00",
    "lat": 67.03459,
    "lon": -91.47563,
    "alt_m": 12119.7
   },
   "member_spread_deg": {
    "lat": 22.64,
    "lon": 90.16
   },
   "member_spread_now_deg": {
    "lat": 6.66,
    "lon": 0.92
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KI6DS-11",
   "flight_id": "KI6DS-11_2026-02-03",
   "payload_type": "WSPR",
   "seed_time": "2026-08-30 21:45:45",
   "seed_lat": 81.47911,
   "seed_lon": -97.12498,
   "seed_alt_m": 12900.0,
   "seed_age_h": 13.57,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-07 05:45:00",
    "lat": 48.59971,
    "lon": 40.21535,
    "alt_m": 13098.4
   },
   "member_spread_deg": {
    "lat": 33.04,
    "lon": 55.26
   },
   "member_spread_now_deg": {
    "lat": 5.51,
    "lon": 15.61
   },
   "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": 115.47,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-07 05:45:00",
    "lat": 46.49779,
    "lon": -44.48243,
    "alt_m": 12962.5
   },
   "member_spread_deg": {
    "lat": 13.46,
    "lon": 45.55
   },
   "member_spread_now_deg": {
    "lat": 13.54,
    "lon": 345.97
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "SP2ROC-41",
   "flight_id": "SP2ROC-41_2026-01-25",
   "payload_type": "WSPR",
   "seed_time": "2026-08-31 09:43:00",
   "seed_lat": 46.16667,
   "seed_lon": 91.54167,
   "seed_alt_m": 15960.0,
   "seed_age_h": 1.62,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-07 09:15:00",
    "lat": 30.43298,
    "lon": 173.70763,
    "alt_m": 16296.8
   },
   "member_spread_deg": {
    "lat": 32.23,
    "lon": 348.05
   },
   "member_spread_now_deg": {
    "lat": 0.22,
    "lon": 1.84
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "VE3VRO-36",
   "flight_id": "VE3VRO-36_2026-07-30",
   "payload_type": "WSPR",
   "seed_time": "2026-08-31 04:16:00",
   "seed_lat": 57.25,
   "seed_lon": -179.33333,
   "seed_alt_m": 13330.0,
   "seed_age_h": 7.07,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-07 05:45:00",
    "lat": 56.0543,
    "lon": -112.97233,
    "alt_m": 12971.1
   },
   "member_spread_deg": {
    "lat": 36.98,
    "lon": 110.01
   },
   "member_spread_now_deg": {
    "lat": 2.01,
    "lon": 5.33
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "W0RBO-12",
   "flight_id": "W0RBO-12_2026-05-02",
   "payload_type": "WSPR",
   "seed_time": "2026-08-31 10:15:23",
   "seed_lat": 49.31245,
   "seed_lon": 84.79169,
   "seed_alt_m": 13240.0,
   "seed_age_h": 1.08,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-07 09:45:00",
    "lat": 58.74458,
    "lon": -72.03434,
    "alt_m": 12858.5
   },
   "member_spread_deg": {
    "lat": 32.25,
    "lon": 301.39
   },
   "member_spread_now_deg": {
    "lat": 0.16,
    "lon": 0.94
   },
   "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": 326.35,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-07 05:30:00",
    "lat": -31.03219,
    "lon": -64.64505,
    "alt_m": 12194.1
   },
   "member_spread_deg": {
    "lat": 23.21,
    "lon": 251.96
   },
   "member_spread_now_deg": {
    "lat": 28.06,
    "lon": 109.72
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "ZS6WBT-1",
   "flight_id": "ZS6WBT-1_2026-08-19",
   "payload_type": "WSPR",
   "seed_time": "2026-08-30 20:26:00",
   "seed_lat": -18.0,
   "seed_lon": -59.16667,
   "seed_alt_m": 15810.0,
   "seed_age_h": 14.9,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-07 05:30:00",
    "lat": -11.00802,
    "lon": -63.29384,
    "alt_m": 15734.8
   },
   "member_spread_deg": {
    "lat": 6.06,
    "lon": 42.1
   },
   "member_spread_now_deg": {
    "lat": 4.44,
    "lon": 1.06
   },
   "display_as": "track",
   "display_reason": "fresh"
  }
 ]
}