{
 "generated_utc": "2026-09-06T23:26:53Z",
 "gfs_cycle_utc": "2026-09-06T18:00:00Z",
 "model": {
  "source": "NCEP GFS 0.50 degree",
  "vertical_coordinate": "constant density (isopycnic)",
  "horizon_hours": 483.5,
  "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_20260906_18Z.csv.gz",
  "trajectories_geojson_gz": "PBA_forecast_20260906_18Z.geojson.gz"
 },
 "counts": {
  "flights": 19,
  "members": 9,
  "rows": 88533
 },
 "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": 223.11,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-13 17:45:00",
    "lat": -66.30365,
    "lon": -64.49475,
    "alt_m": 12177.2
   },
   "member_spread_deg": {
    "lat": 34.86,
    "lon": 256.2
   },
   "member_spread_now_deg": {
    "lat": 30.83,
    "lon": 93.72
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "BSS54",
   "flight_id": "BSS54_2026-07-09",
   "payload_type": "WSPR",
   "seed_time": "2026-09-06 19:02:18",
   "seed_lat": 32.0,
   "seed_lon": -77.625,
   "seed_alt_m": 14580.0,
   "seed_age_h": 4.3,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-13 18:30:00",
    "lat": 25.42661,
    "lon": -1.7517,
    "alt_m": 14579.6
   },
   "member_spread_deg": {
    "lat": 20.69,
    "lon": 49.2
   },
   "member_spread_now_deg": {
    "lat": 0.79,
    "lon": 1.51
   },
   "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": 289.85,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-13 17:30:00",
    "lat": 6.32174,
    "lon": -53.67584,
    "alt_m": 13132.9
   },
   "member_spread_deg": {
    "lat": 32.82,
    "lon": 125.54
   },
   "member_spread_now_deg": {
    "lat": 16.52,
    "lon": 58.96
   },
   "display_as": "region",
   "display_reason": "seed_age"
  },
  {
   "callsign": "DG2GG-30",
   "flight_id": "DG2GG-30_2026-08-07",
   "payload_type": "WSPR",
   "seed_time": "2026-09-05 04:41:00",
   "seed_lat": 86.0,
   "seed_lon": 110.20833,
   "seed_alt_m": 11660.0,
   "seed_age_h": 42.65,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-13 17:45:00",
    "lat": 73.62752,
    "lon": 131.82274,
    "alt_m": 11801.5
   },
   "member_spread_deg": {
    "lat": 27.14,
    "lon": 265.27
   },
   "member_spread_now_deg": {
    "lat": 2.16,
    "lon": 30.54
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-31",
   "flight_id": "DG2GG-31_2026-08-13",
   "payload_type": "WSPR",
   "seed_time": "2026-09-06 22:32:00",
   "seed_lat": 43.125,
   "seed_lon": -143.41667,
   "seed_alt_m": 13390.0,
   "seed_age_h": 0.8,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-13 22:00:00",
    "lat": 24.1569,
    "lon": -49.41394,
    "alt_m": 13591.9
   },
   "member_spread_deg": {
    "lat": 26.32,
    "lon": 87.28
   },
   "member_spread_now_deg": {
    "lat": 0.18,
    "lon": 0.33
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-32",
   "flight_id": "DG2GG-32_2026-09-03",
   "payload_type": "WSPR",
   "seed_time": "2026-09-06 07:36:00",
   "seed_lat": 43.02083,
   "seed_lon": 80.875,
   "seed_alt_m": 13360.0,
   "seed_age_h": 15.73,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-13 17:30:00",
    "lat": 54.92665,
    "lon": -32.10384,
    "alt_m": 12818.6
   },
   "member_spread_deg": {
    "lat": 36.81,
    "lon": 309.82
   },
   "member_spread_now_deg": {
    "lat": 1.11,
    "lon": 4.31
   },
   "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": 157.45,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-13 17:30:00",
    "lat": 71.12151,
    "lon": 169.2027,
    "alt_m": 11864.7
   },
   "member_spread_deg": {
    "lat": 43.41,
    "lon": 317.8
   },
   "member_spread_now_deg": {
    "lat": 19.73,
    "lon": 313.69
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "DO3GU-47",
   "flight_id": "DO3GU-47_2026-09-03",
   "payload_type": "WSPR",
   "seed_time": "2026-09-05 13:31:52",
   "seed_lat": 46.04167,
   "seed_lon": 61.70833,
   "seed_alt_m": 13960.0,
   "seed_age_h": 33.8,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-13 17:30:00",
    "lat": 23.30726,
    "lon": 159.00454,
    "alt_m": 14608.7
   },
   "member_spread_deg": {
    "lat": 44.35,
    "lon": 166.79
   },
   "member_spread_now_deg": {
    "lat": 1.57,
    "lon": 14.89
   },
   "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": 321.12,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-13 17:45:00",
    "lat": 50.10395,
    "lon": -22.77313,
    "alt_m": 13059.6
   },
   "member_spread_deg": {
    "lat": 32.81,
    "lon": 269.52
   },
   "member_spread_now_deg": {
    "lat": 27.05,
    "lon": 231.95
   },
   "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": 304.77,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-13 17:30:00",
    "lat": 21.46255,
    "lon": 126.71207,
    "alt_m": 14202.0
   },
   "member_spread_deg": {
    "lat": 49.83,
    "lon": 335.43
   },
   "member_spread_now_deg": {
    "lat": 37.73,
    "lon": 247.25
   },
   "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": 87.27,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-13 17:30:00",
    "lat": 24.91876,
    "lon": 145.87562,
    "alt_m": 12903.2
   },
   "member_spread_deg": {
    "lat": 47.95,
    "lon": 310.67
   },
   "member_spread_now_deg": {
    "lat": 26.09,
    "lon": 334.68
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "KD7FXO-1",
   "flight_id": "KD7FXO-1_2026-08-02",
   "payload_type": "WSPR",
   "seed_time": "2026-09-06 17:05:00",
   "seed_lat": 28.66667,
   "seed_lon": -4.45833,
   "seed_alt_m": 13010.0,
   "seed_age_h": 6.25,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-13 17:30:00",
    "lat": 44.69553,
    "lon": 173.66758,
    "alt_m": 12602.0
   },
   "member_spread_deg": {
    "lat": 17.77,
    "lon": 339.2
   },
   "member_spread_now_deg": {
    "lat": 2.34,
    "lon": 1.26
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KE8RES-8",
   "flight_id": "KE8RES-8_2026-06-20",
   "payload_type": "WSPR",
   "seed_time": "2026-09-06 21:41:00",
   "seed_lat": 62.875,
   "seed_lon": -125.54167,
   "seed_alt_m": 12300.0,
   "seed_age_h": 1.65,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-13 21:15:00",
    "lat": 52.99204,
    "lon": 81.30975,
    "alt_m": 12666.7
   },
   "member_spread_deg": {
    "lat": 31.2,
    "lon": 108.86
   },
   "member_spread_now_deg": {
    "lat": 0.04,
    "lon": 2.24
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KI6DS-11",
   "flight_id": "KI6DS-11_2026-02-03",
   "payload_type": "WSPR",
   "seed_time": "2026-09-05 15:25:45",
   "seed_lat": 57.95828,
   "seed_lon": 16.20835,
   "seed_alt_m": 13120.0,
   "seed_age_h": 31.9,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-13 17:30:00",
    "lat": 67.35899,
    "lon": -116.66614,
    "alt_m": 13065.0
   },
   "member_spread_deg": {
    "lat": 21.43,
    "lon": 217.02
   },
   "member_spread_now_deg": {
    "lat": 2.11,
    "lon": 3.1
   },
   "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": 271.47,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-13 17:45:00",
    "lat": 33.79802,
    "lon": 29.99821,
    "alt_m": 13335.9
   },
   "member_spread_deg": {
    "lat": 15.78,
    "lon": 241.61
   },
   "member_spread_now_deg": {
    "lat": 16.45,
    "lon": 107.53
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "SP2ROC-41",
   "flight_id": "SP2ROC-41_2026-01-25",
   "payload_type": "WSPR",
   "seed_time": "2026-09-06 22:31:00",
   "seed_lat": 23.77083,
   "seed_lon": -160.625,
   "seed_alt_m": 16260.0,
   "seed_age_h": 0.82,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-13 22:00:00",
    "lat": 23.27227,
    "lon": -156.10132,
    "alt_m": 16325.6
   },
   "member_spread_deg": {
    "lat": 26.95,
    "lon": 335.53
   },
   "member_spread_now_deg": {
    "lat": 0.03,
    "lon": 1.08
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "VE3VRO-36",
   "flight_id": "VE3VRO-36_2026-07-30",
   "payload_type": "WSPR",
   "seed_time": "2026-09-06 20:41:00",
   "seed_lat": 38.10417,
   "seed_lon": -70.29167,
   "seed_alt_m": 13280.0,
   "seed_age_h": 2.65,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-13 20:15:00",
    "lat": 45.93351,
    "lon": 94.13609,
    "alt_m": 13313.3
   },
   "member_spread_deg": {
    "lat": 30.14,
    "lon": 111.44
   },
   "member_spread_now_deg": {
    "lat": 0.62,
    "lon": 1.69
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "W0RBO-12",
   "flight_id": "W0RBO-12_2026-05-02",
   "payload_type": "WSPR",
   "seed_time": "2026-09-06 22:50:23",
   "seed_lat": 35.18745,
   "seed_lon": -126.79164,
   "seed_alt_m": 13810.0,
   "seed_age_h": 0.49,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-13 22:45:00",
    "lat": 43.53578,
    "lon": 9.14647,
    "alt_m": 13683.4
   },
   "member_spread_deg": {
    "lat": 26.93,
    "lon": 141.73
   },
   "member_spread_now_deg": {
    "lat": 0.05,
    "lon": 0.07
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "ZS6WBT-1",
   "flight_id": "ZS6WBT-1_2026-08-19",
   "payload_type": "WSPR",
   "seed_time": "2026-09-06 14:41:00",
   "seed_lat": -26.25,
   "seed_lon": 20.70833,
   "seed_alt_m": 15570.0,
   "seed_age_h": 8.65,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-13 17:45:00",
    "lat": -26.26125,
    "lon": 107.38095,
    "alt_m": 15579.1
   },
   "member_spread_deg": {
    "lat": 17.9,
    "lon": 149.26
   },
   "member_spread_now_deg": {
    "lat": 0.39,
    "lon": 1.52
   },
   "display_as": "track",
   "display_reason": "fresh"
  }
 ]
}