{
 "generated_utc": "2026-08-29T23:26:48Z",
 "gfs_cycle_utc": "2026-08-29T18:00:00Z",
 "model": {
  "source": "NCEP GFS 0.50 degree",
  "vertical_coordinate": "constant density (isopycnic)",
  "horizon_hours": 452.5,
  "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_20260829_18Z.csv.gz",
  "trajectories_geojson_gz": "PBA_forecast_20260829_18Z.geojson.gz"
 },
 "counts": {
  "flights": 18,
  "members": 9,
  "rows": 70380
 },
 "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": 31.11,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-05 17:45:00",
    "lat": -65.19903,
    "lon": 26.41487,
    "alt_m": 12228.7
   },
   "member_spread_deg": {
    "lat": 31.93,
    "lon": 90.93
   },
   "member_spread_now_deg": {
    "lat": 8.82,
    "lon": 49.59
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "BSS54",
   "flight_id": "BSS54_2026-07-09",
   "payload_type": "WSPR",
   "seed_time": "2026-08-29 09:54:48",
   "seed_lat": 48.89583,
   "seed_lon": 80.75,
   "seed_alt_m": 13930.0,
   "seed_age_h": 13.42,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-05 17:30:00",
    "lat": 38.51722,
    "lon": -96.9817,
    "alt_m": 14438.3
   },
   "member_spread_deg": {
    "lat": 25.27,
    "lon": 115.19
   },
   "member_spread_now_deg": {
    "lat": 2.36,
    "lon": 5.15
   },
   "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": 97.85,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-05 17:30:00",
    "lat": 24.96987,
    "lon": -92.45906,
    "alt_m": 13057.7
   },
   "member_spread_deg": {
    "lat": 20.16,
    "lon": 84.13
   },
   "member_spread_now_deg": {
    "lat": 13.83,
    "lon": 10.06
   },
   "display_as": "region",
   "display_reason": "seed_age"
  },
  {
   "callsign": "DG2GG-30",
   "flight_id": "DG2GG-30_2026-08-07",
   "payload_type": "WSPR",
   "seed_time": "2026-08-29 16:41:00",
   "seed_lat": 74.58333,
   "seed_lon": -39.79167,
   "seed_alt_m": 12140.0,
   "seed_age_h": 6.65,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-05 17:45:00",
    "lat": 79.3924,
    "lon": 151.58067,
    "alt_m": 11655.5
   },
   "member_spread_deg": {
    "lat": 24.85,
    "lon": 240.56
   },
   "member_spread_now_deg": {
    "lat": 3.67,
    "lon": 4.09
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-31",
   "flight_id": "DG2GG-31_2026-08-13",
   "payload_type": "WSPR",
   "seed_time": "2026-08-29 16:47:00",
   "seed_lat": 45.72917,
   "seed_lon": -15.54167,
   "seed_alt_m": 13180.0,
   "seed_age_h": 6.55,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-05 17:45:00",
    "lat": 44.84084,
    "lon": 149.92591,
    "alt_m": 13194.0
   },
   "member_spread_deg": {
    "lat": 14.45,
    "lon": 341.68
   },
   "member_spread_now_deg": {
    "lat": 0.48,
    "lon": 5.19
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DN3LEO-13",
   "flight_id": "DN3LEO-13_2026-04-12",
   "payload_type": "WSPR",
   "seed_time": "2026-08-29 12:08:00",
   "seed_lat": 67.39583,
   "seed_lon": 49.5,
   "seed_alt_m": 12030.0,
   "seed_age_h": 11.2,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-05 17:45:00",
    "lat": 75.02329,
    "lon": 153.562,
    "alt_m": 11669.2
   },
   "member_spread_deg": {
    "lat": 18.98,
    "lon": 348.12
   },
   "member_spread_now_deg": {
    "lat": 6.13,
    "lon": 2.55
   },
   "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": 129.12,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-05 17:45:00",
    "lat": 64.2812,
    "lon": -127.70488,
    "alt_m": 12910.9
   },
   "member_spread_deg": {
    "lat": 35.27,
    "lon": 211.34
   },
   "member_spread_now_deg": {
    "lat": 12.92,
    "lon": 352.74
   },
   "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": 112.77,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-05 17:30:00",
    "lat": 72.13543,
    "lon": 49.58617,
    "alt_m": 12989.8
   },
   "member_spread_deg": {
    "lat": 34.84,
    "lon": 240.79
   },
   "member_spread_now_deg": {
    "lat": 34.1,
    "lon": 170.46
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "KC7RW-3",
   "flight_id": "KC7RW-3_2026-08-20",
   "payload_type": "WSPR",
   "seed_time": "2026-08-29 12:29:00",
   "seed_lat": 42.33333,
   "seed_lon": 53.91667,
   "seed_alt_m": 12550.0,
   "seed_age_h": 10.85,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-05 17:30:00",
    "lat": 32.57305,
    "lon": -137.45312,
    "alt_m": 12624.9
   },
   "member_spread_deg": {
    "lat": 33.74,
    "lon": 34.69
   },
   "member_spread_now_deg": {
    "lat": 1.91,
    "lon": 2.25
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KC7RW-4",
   "flight_id": "KC7RW-4_2026-08-26",
   "payload_type": "WSPR",
   "seed_time": "2026-08-29 17:55:00",
   "seed_lat": 22.08333,
   "seed_lon": -84.41667,
   "seed_alt_m": 11320.0,
   "seed_age_h": 5.42,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-05 17:30:00",
    "lat": 26.93111,
    "lon": -87.317,
    "alt_m": 11283.7
   },
   "member_spread_deg": {
    "lat": 7.6,
    "lon": 17.15
   },
   "member_spread_now_deg": {
    "lat": 1.09,
    "lon": 0.64
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KD7FXO-1",
   "flight_id": "KD7FXO-1_2026-08-02",
   "payload_type": "WSPR",
   "seed_time": "2026-08-29 22:45:00",
   "seed_lat": 34.54167,
   "seed_lon": -134.58333,
   "seed_alt_m": 12810.0,
   "seed_age_h": 0.58,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-05 22:45:00",
    "lat": 33.40037,
    "lon": -6.99822,
    "alt_m": 12972.4
   },
   "member_spread_deg": {
    "lat": 32.44,
    "lon": 152.51
   },
   "member_spread_now_deg": {
    "lat": 0.03,
    "lon": 0.18
   },
   "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": 144.32,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-05 17:30:00",
    "lat": 64.65193,
    "lon": -172.20415,
    "alt_m": 12124.5
   },
   "member_spread_deg": {
    "lat": 30.4,
    "lon": 323.58
   },
   "member_spread_now_deg": {
    "lat": 26.14,
    "lon": 223.73
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "KI6DS-11",
   "flight_id": "KI6DS-11_2026-02-03",
   "payload_type": "WSPR",
   "seed_time": "2026-08-29 22:40:45",
   "seed_lat": 76.41661,
   "seed_lon": -143.83331,
   "seed_alt_m": 12840.0,
   "seed_age_h": 0.66,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-05 22:45:00",
    "lat": 59.9414,
    "lon": 31.91008,
    "alt_m": 12893.6
   },
   "member_spread_deg": {
    "lat": 14.93,
    "lon": 65.11
   },
   "member_spread_now_deg": {
    "lat": 0.05,
    "lon": 0.3
   },
   "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": 79.47,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-05 17:45:00",
    "lat": 46.2861,
    "lon": -85.97662,
    "alt_m": 13190.7
   },
   "member_spread_deg": {
    "lat": 20.99,
    "lon": 108.96
   },
   "member_spread_now_deg": {
    "lat": 4.98,
    "lon": 28.39
   },
   "display_as": "region",
   "display_reason": "seed_age"
  },
  {
   "callsign": "SP2ROC-41",
   "flight_id": "SP2ROC-41_2026-01-25",
   "payload_type": "WSPR",
   "seed_time": "2026-08-29 13:46:00",
   "seed_lat": 32.70833,
   "seed_lon": 38.875,
   "seed_alt_m": 16300.0,
   "seed_age_h": 9.57,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-05 17:45:00",
    "lat": 27.89238,
    "lon": -171.1597,
    "alt_m": 16302.3
   },
   "member_spread_deg": {
    "lat": 42.48,
    "lon": 347.23
   },
   "member_spread_now_deg": {
    "lat": 6.76,
    "lon": 9.34
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "VE3VRO-36",
   "flight_id": "VE3VRO-36_2026-07-30",
   "payload_type": "WSPR",
   "seed_time": "2026-08-29 08:26:00",
   "seed_lat": 44.58333,
   "seed_lon": 112.20833,
   "seed_alt_m": 12950.0,
   "seed_age_h": 14.9,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-05 17:30:00",
    "lat": 32.01382,
    "lon": -44.23131,
    "alt_m": 13727.9
   },
   "member_spread_deg": {
    "lat": 32.02,
    "lon": 165.45
   },
   "member_spread_now_deg": {
    "lat": 1.2,
    "lon": 9.57
   },
   "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": 290.35,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-05 17:30:00",
    "lat": -29.34272,
    "lon": -147.2495,
    "alt_m": 12282.6
   },
   "member_spread_deg": {
    "lat": 20.16,
    "lon": 237.97
   },
   "member_spread_now_deg": {
    "lat": 32.83,
    "lon": 91.25
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "ZS6WBT-1",
   "flight_id": "ZS6WBT-1_2026-08-19",
   "payload_type": "WSPR",
   "seed_time": "2026-08-29 21:01:00",
   "seed_lat": -23.125,
   "seed_lon": -76.0,
   "seed_alt_m": 15580.0,
   "seed_age_h": 2.32,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-05 20:30:00",
    "lat": -4.71233,
    "lon": -60.89089,
    "alt_m": 15654.2
   },
   "member_spread_deg": {
    "lat": 38.42,
    "lon": 93.21
   },
   "member_spread_now_deg": {
    "lat": 0.25,
    "lon": 2.37
   },
   "display_as": "track",
   "display_reason": "fresh"
  }
 ]
}