{
 "generated_utc": "2026-08-28T05:26:48Z",
 "gfs_cycle_utc": "2026-08-28T00:00:00Z",
 "model": {
  "source": "NCEP GFS 0.50 degree",
  "vertical_coordinate": "constant density (isopycnic)",
  "horizon_hours": 459.0,
  "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_20260828_00Z.csv.gz",
  "trajectories_geojson_gz": "PBA_forecast_20260828_00Z.geojson.gz"
 },
 "counts": {
  "flights": 18,
  "members": 9,
  "rows": 71658
 },
 "flights": [
  {
   "callsign": "AG6NS-23",
   "flight_id": "AG6NS-23_2026-02-07",
   "payload_type": "WSPR",
   "seed_time": "2026-08-26 23:18:40",
   "seed_lat": -70.79167,
   "seed_lon": -148.58332,
   "seed_alt_m": 12300.0,
   "seed_age_h": 30.02,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-03 23:45:00",
    "lat": -66.57495,
    "lon": -63.88192,
    "alt_m": 11998.8
   },
   "member_spread_deg": {
    "lat": 18.73,
    "lon": 27.49
   },
   "member_spread_now_deg": {
    "lat": 3.46,
    "lon": 11.77
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "BSS54",
   "flight_id": "BSS54_2026-07-09",
   "payload_type": "WSPR",
   "seed_time": "2026-08-27 14:01:48",
   "seed_lat": 43.125,
   "seed_lon": 21.54167,
   "seed_alt_m": 14180.0,
   "seed_age_h": 15.3,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-03 23:30:00",
    "lat": 36.85967,
    "lon": -117.87191,
    "alt_m": 14428.8
   },
   "member_spread_deg": {
    "lat": 26.02,
    "lon": 325.71
   },
   "member_spread_now_deg": {
    "lat": 0.57,
    "lon": 7.7
   },
   "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": 55.85,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-03 23:30:00",
    "lat": 31.95975,
    "lon": -95.30839,
    "alt_m": 13116.8
   },
   "member_spread_deg": {
    "lat": 12.53,
    "lon": 53.62
   },
   "member_spread_now_deg": {
    "lat": 5.68,
    "lon": 6.6
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-30",
   "flight_id": "DG2GG-30_2026-08-07",
   "payload_type": "WSPR",
   "seed_time": "2026-08-27 22:51:00",
   "seed_lat": 69.58333,
   "seed_lon": -114.33333,
   "seed_alt_m": 12310.0,
   "seed_age_h": 6.48,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-03 23:45:00",
    "lat": 67.10016,
    "lon": 158.38201,
    "alt_m": 11775.5
   },
   "member_spread_deg": {
    "lat": 32.94,
    "lon": 290.83
   },
   "member_spread_now_deg": {
    "lat": 3.95,
    "lon": 10.8
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-31",
   "flight_id": "DG2GG-31_2026-08-13",
   "payload_type": "WSPR",
   "seed_time": "2026-08-27 21:37:00",
   "seed_lat": 44.35417,
   "seed_lon": -69.45833,
   "seed_alt_m": 13180.0,
   "seed_age_h": 7.72,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-03 23:30:00",
    "lat": 51.23629,
    "lon": 116.54386,
    "alt_m": 13192.7
   },
   "member_spread_deg": {
    "lat": 18.64,
    "lon": 167.97
   },
   "member_spread_now_deg": {
    "lat": 0.42,
    "lon": 4.85
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DN3LEO-13",
   "flight_id": "DN3LEO-13_2026-04-12",
   "payload_type": "WSPR",
   "seed_time": "2026-08-26 13:38:00",
   "seed_lat": 83.20833,
   "seed_lon": -24.91667,
   "seed_alt_m": 11920.0,
   "seed_age_h": 39.7,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-03 23:45:00",
    "lat": 55.21485,
    "lon": 171.64223,
    "alt_m": 11879.2
   },
   "member_spread_deg": {
    "lat": 29.13,
    "lon": 134.27
   },
   "member_spread_now_deg": {
    "lat": 14.04,
    "lon": 6.51
   },
   "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": 87.12,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-03 23:45:00",
    "lat": 48.11413,
    "lon": 177.61219,
    "alt_m": 12551.2
   },
   "member_spread_deg": {
    "lat": 30.45,
    "lon": 352.89
   },
   "member_spread_now_deg": {
    "lat": 21.44,
    "lon": 90.23
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "K5NOT-11",
   "flight_id": "K5NOT-11_2026-06-20",
   "payload_type": "WSPR",
   "seed_time": "2026-08-15 20:50:37",
   "seed_lat": 40.97911,
   "seed_lon": -75.41666,
   "seed_alt_m": 13300.0,
   "seed_age_h": 296.49,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-03 23:45:00",
    "lat": 36.9557,
    "lon": 22.23258,
    "alt_m": 12993.4
   },
   "member_spread_deg": {
    "lat": 54.83,
    "lon": 300.98
   },
   "member_spread_now_deg": {
    "lat": 46.27,
    "lon": 216.63
   },
   "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": 70.77,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-03 23:30:00",
    "lat": 52.87612,
    "lon": 24.34861,
    "alt_m": 13396.4
   },
   "member_spread_deg": {
    "lat": 21.56,
    "lon": 345.04
   },
   "member_spread_now_deg": {
    "lat": 36.55,
    "lon": 51.48
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KC7RW-3",
   "flight_id": "KC7RW-3_2026-08-20",
   "payload_type": "WSPR",
   "seed_time": "2026-08-27 11:49:00",
   "seed_lat": 31.89583,
   "seed_lon": 23.625,
   "seed_alt_m": 12710.0,
   "seed_age_h": 17.52,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-03 23:45:00",
    "lat": 44.38907,
    "lon": -103.37322,
    "alt_m": 12801.1
   },
   "member_spread_deg": {
    "lat": 45.68,
    "lon": 345.98
   },
   "member_spread_now_deg": {
    "lat": 2.4,
    "lon": 3.98
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KD7FXO-1",
   "flight_id": "KD7FXO-1_2026-08-02",
   "payload_type": "WSPR",
   "seed_time": "2026-08-28 04:25:00",
   "seed_lat": 27.08333,
   "seed_lon": -164.41667,
   "seed_alt_m": 12960.0,
   "seed_age_h": 0.92,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-04 04:00:00",
    "lat": 32.14408,
    "lon": -83.10602,
    "alt_m": 13075.4
   },
   "member_spread_deg": {
    "lat": 11.66,
    "lon": 49.54
   },
   "member_spread_now_deg": {
    "lat": 0.37,
    "lon": 0.59
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KE8RES-8",
   "flight_id": "KE8RES-8_2026-06-20",
   "payload_type": "WSPR",
   "seed_time": "2026-08-23 23:01:00",
   "seed_lat": 73.33333,
   "seed_lon": -150.25,
   "seed_alt_m": 11900.0,
   "seed_age_h": 102.32,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-03 23:30:00",
    "lat": 71.52751,
    "lon": 131.38286,
    "alt_m": 12384.8
   },
   "member_spread_deg": {
    "lat": 31.84,
    "lon": 330.21
   },
   "member_spread_now_deg": {
    "lat": 20.74,
    "lon": 232.92
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "KI6DS-11",
   "flight_id": "KI6DS-11_2026-02-03",
   "payload_type": "WSPR",
   "seed_time": "2026-08-28 04:55:45",
   "seed_lat": 73.18745,
   "seed_lon": 179.45835,
   "seed_alt_m": 12780.0,
   "seed_age_h": 0.41,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-04 05:00:00",
    "lat": 64.54444,
    "lon": -6.35654,
    "alt_m": 12813.8
   },
   "member_spread_deg": {
    "lat": 24.32,
    "lon": 175.23
   },
   "member_spread_now_deg": {
    "lat": 0.11,
    "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": 37.47,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-03 23:45:00",
    "lat": 56.33279,
    "lon": -149.40295,
    "alt_m": 13392.6
   },
   "member_spread_deg": {
    "lat": 22.26,
    "lon": 50.43
   },
   "member_spread_now_deg": {
    "lat": 3.55,
    "lon": 14.25
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "SP2ROC-41",
   "flight_id": "SP2ROC-41_2026-01-25",
   "payload_type": "WSPR",
   "seed_time": "2026-08-27 15:48:00",
   "seed_lat": 37.375,
   "seed_lon": 9.16667,
   "seed_alt_m": 16440.0,
   "seed_age_h": 13.53,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-03 23:45:00",
    "lat": 37.04846,
    "lon": 168.77724,
    "alt_m": 16472.1
   },
   "member_spread_deg": {
    "lat": 33.58,
    "lon": 342.95
   },
   "member_spread_now_deg": {
    "lat": 4.3,
    "lon": 8.85
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "VE3VRO-36",
   "flight_id": "VE3VRO-36_2026-07-30",
   "payload_type": "WSPR",
   "seed_time": "2026-08-28 04:41:00",
   "seed_lat": 50.1875,
   "seed_lon": 70.91667,
   "seed_alt_m": 12950.0,
   "seed_age_h": 0.65,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-04 04:15:00",
    "lat": 42.23232,
    "lon": -97.37244,
    "alt_m": 13544.3
   },
   "member_spread_deg": {
    "lat": 25.58,
    "lon": 66.88
   },
   "member_spread_now_deg": {
    "lat": 0.02,
    "lon": 0.14
   },
   "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": 248.35,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-03 23:30:00",
    "lat": -35.44772,
    "lon": 143.06716,
    "alt_m": 12008.1
   },
   "member_spread_deg": {
    "lat": 26.52,
    "lon": 357.5
   },
   "member_spread_now_deg": {
    "lat": 11.21,
    "lon": 135.22
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "ZS6WBT-1",
   "flight_id": "ZS6WBT-1_2026-08-19",
   "payload_type": "WSPR",
   "seed_time": "2026-08-28 01:21:00",
   "seed_lat": -25.875,
   "seed_lon": -135.66667,
   "seed_alt_m": 15340.0,
   "seed_age_h": 3.98,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-04 00:45:00",
    "lat": -12.91216,
    "lon": -71.83718,
    "alt_m": 15610.0
   },
   "member_spread_deg": {
    "lat": 41.97,
    "lon": 194.4
   },
   "member_spread_now_deg": {
    "lat": 0.73,
    "lon": 4.99
   },
   "display_as": "track",
   "display_reason": "fresh"
  }
 ]
}