Issued by NWS Denver/Boulder, CO
000
UXUS97 KBOU 071232
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
632 AM MDT Thursday May 7, 2009
This forecast is for Thursday May 7, 2009:
If the trigger temperature of 70.3 F/21.3 C is reached...then
Thermal Soaring Index....................... Excellent
Maximum rate of lift........................ 1038 ft/min (5.3 m/s)
Maximum height of thermals.................. 16891 ft MSL (11606 ft AGL)
Forecast maximum temperature................... 80.0 F/27.1 C
Time of trigger temperature.................... 1100 MDT
Time of overdevelopment........................ None
Middle/high clouds during soaring window....... None
Surface winds during soaring window............ 20 mph or less
Height of the -3 thermal index................. 14198 ft MSL (8913 ft AGL)
Thermal soaring outlook for Friday 05/08....... Fair
Wave Soaring Index............................. Excellent
Wave Soaring Index trend (to 1800 MDT)......... No change
Height of stable layer (12-18K ft MSL)......... 17100 ft MSL (11815 ft AGL)
Weak PVA/NVA (through 1800 MDT)................ Neither
Potential height of wave....................... 17592 ft MSL (12307 ft AGL)
Wave soaring outlook for Friday 05/08.......... Excellent
Remarks...
Sunrise/Sunset.................... 05:52:48 / 19:59:01 MDT
Total possible sunshine........... 14 hr 6 min 13 sec (846 min 13 sec)
Altitude of sun at 12:56:05 MDT... 67.23 degrees
Upper air data from rawinsonde observation taken on 05/07/2009 at 0600 MDT
Freezing level.................. 12836 ft MSL (7551 ft AGL)
Convective condensation level... 16278 ft MSL (10993 ft AGL)
Lifted condensation level....... 16809 ft MSL (11523 ft AGL)
Lifted index.................... +0.6
K index......................... +9.6
Height Temperature Wind Wind Spd Lapse Rate ConvectionT Thermal Lift Rate
ft MSL deg C deg F Dir kt m/s C/km F/kft deg C deg F Index fpm m/s
--------------------------------------------------------------------------------
50000 -67.3 -89.1 274 68 35 -3.4 -1.8 84.4 183.9 33.2 M M
45000 -62.0 -79.6 280 97 50 1.4 0.8 67.5 153.5 25.3 M M
40000 -55.1 -67.2 285 107 55 6.1 3.4 55.6 132.1 19.2 M M
38000 -52.2 -62.0 288 99 51 -2.1 -1.1 51.2 124.1 16.7 M M
36000 -50.2 -58.4 292 92 47 7.0 3.8 45.5 113.8 13.2 M M
34000 -46.0 -50.8 295 87 45 7.2 3.9 43.2 109.8 11.9 M M
32000 -41.1 -42.0 295 86 44 9.1 5.0 41.9 107.4 11.2 M M
30000 -35.2 -31.4 295 84 43 8.1 4.4 41.0 105.9 10.9 M M
29000 -33.1 -27.6 295 81 42 6.8 3.8 39.9 103.8 10.1 M M
28000 -31.0 -23.8 295 79 41 6.9 3.8 38.8 101.8 9.4 M M
27000 -28.8 -19.8 295 77 39 9.2 5.1 38.0 100.4 8.9 M M
26000 -26.0 -14.8 295 74 38 9.0 4.9 37.8 100.0 8.8 M M
25000 -23.8 -10.8 295 72 37 5.8 3.2 36.9 98.5 8.2 M M
24000 -22.2 -8.0 294 67 35 5.0 2.7 35.3 95.6 7.0 M M
23000 -20.6 -5.1 292 64 33 5.6 3.1 33.7 92.6 5.7 M M
22000 -18.9 -2.0 290 62 32 5.5 3.0 32.2 90.0 4.6 M M
21000 -16.9 1.6 287 59 31 7.3 4.0 31.1 88.0 3.8 M M
20000 -14.7 5.5 285 57 29 7.1 3.9 30.2 86.4 3.0 M M
19500 -13.7 7.3 283 55 28 7.1 3.9 29.7 85.5 2.6 M M
19000 -12.6 9.3 281 53 27 7.1 3.9 29.3 84.7 2.2 M M
18500 -11.5 11.3 278 51 26 7.7 4.2 28.9 84.0 1.9 M M
18000 -10.4 13.3 275 49 25 7.7 4.2 28.5 83.4 1.6 M M
17500 -9.2 15.4 273 51 26 7.9 4.3 28.2 82.7 1.3 M M
17000 -8.4 16.9 272 53 27 1.0 0.5 27.5 81.4 0.7 M M
16500 -8.2 17.2 271 55 28 6.7 3.7 26.1 79.0 -0.6 1022 5.2
16000 -7.0 19.4 270 57 30 8.1 4.5 25.9 78.5 -0.9 972 4.9
15500 -5.9 21.4 271 59 30 8.1 4.4 25.6 78.1 -1.2 923 4.7
15000 -4.3 24.3 275 58 30 4.8 2.7 25.0 76.9 -1.9 853 4.3
14500 -3.6 25.5 277 50 26 4.6 2.5 24.1 75.4 -2.7 819 4.2
14000 -2.8 27.0 280 42 22 7.9 4.3 23.4 74.2 -3.4 780 4.0
13500 -1.5 29.3 280 39 20 8.7 4.8 23.3 73.9 -3.5 726 3.7
13000 -0.2 31.6 280 35 18 8.7 4.8 23.1 73.6 -3.7 672 3.4
12500 1.1 34.0 280 32 16 8.8 4.8 23.0 73.3 -3.9 618 3.1
12000 2.4 36.3 280 28 14 8.8 4.8 22.8 73.1 -4.0 565 2.9
11500 3.7 38.7 280 21 11 8.8 4.8 22.7 72.8 -4.2 511 2.6
11000 5.0 41.0 279 14 7 8.8 4.8 22.5 72.5 -4.4 457 2.3
10500 6.3 43.3 276 15 8 8.8 4.8 22.3 72.2 -4.6 403 2.0
10250 6.9 44.4 275 15 8 8.7 4.8 22.2 72.0 -4.7 377 1.9
10000 7.6 45.7 272 14 7 8.5 4.7 22.1 71.9 -4.8 350 1.8
9750 8.2 46.8 267 13 7 8.5 4.7 22.0 71.7 -5.0 324 1.6
9500 8.8 47.8 262 12 6 8.5 4.7 21.9 71.5 -5.1 298 1.5
9250 9.4 48.9 256 12 6 8.6 4.7 21.8 71.3 -5.2 272 1.4
9000 10.1 50.2 249 11 6 8.1 4.5 21.8 71.2 -5.3 246 1.2
8750 10.7 51.3 237 9 5 10.0 5.5 21.7 71.0 -5.4 220 1.1
8500 11.2 52.2 222 9 4 -0.3 -0.2 21.5 70.7 -5.7 197 1.0
8250 10.6 51.1 205 8 4 -6.7 -3.7 20.2 68.4 -7.0 207 1.1
8000 10.6 51.1 189 9 5 4.3 2.4 19.4 66.9 -7.8 202 1.0
7750 11.1 52.0 170 9 5 7.7 4.2 19.2 66.5 -8.0 179 0.9
7500 11.6 52.9 155 11 6 6.8 3.7 18.9 66.1 -8.3 156 0.8
7250 12.1 53.8 143 13 7 7.0 3.8 18.7 65.7 -8.5 133 0.7
7000 12.6 54.7 135 15 8 7.1 3.9 18.5 65.3 -8.7 110 0.6
6750 13.1 55.6 137 14 7 6.4 3.5 18.3 64.9 -9.0 87 0.4
6500 13.5 56.3 139 14 7 4.8 2.6 18.0 64.4 -9.3 68 0.3
6250 13.8 56.8 142 13 7 3.2 1.8 17.5 63.6 -9.8 53 0.3
6000 14.1 57.4 144 13 7 6.8 3.7 17.1 62.8 -10.3 37 0.2
5750 14.3 57.7 151 11 6 -5.8 -3.2 16.7 62.1 -10.8 22 0.1
5500 12.6 54.7 162 9 4 -39.6 -21.7 14.2 57.6 -13.3 66 0.3
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
05/07/2009 at 0900 MDT | 05/07/2009 at 1200 MDT
|
K index... +7.2 | K index... +11.2
|
Height Temperature Wnd WndSpd Lapse Rate | Temperature Wnd WndSpd Lapse Rate
ft MSL deg C deg F Dir kt m/s C/km F/kft | deg C deg F Dir kt m/s C/km F/kft
--------------------------------------------------------------------------------
50000 -62.6 -80.7 282 56 29 1.6 0.9 | -63.8 -82.8 279 58 30 1.5 0.8
45000 -59.9 -75.8 287 93 48 3.1 1.7 | -61.1 -78.0 282 87 45 3.6 2.0
40000 -55.2 -67.4 288 102 52 2.9 1.6 | -55.7 -68.3 284 91 47 3.4 1.9
38000 -52.3 -62.1 289 100 51 5.2 2.9 | -51.9 -61.4 284 88 45 5.8 3.2
36000 -48.8 -55.8 290 96 50 5.2 2.8 | -48.4 -55.1 283 84 43 5.8 3.2
34000 -45.0 -49.0 290 92 47 7.2 4.0 | -44.4 -47.9 282 81 42 7.2 3.9
32000 -40.7 -41.3 289 86 44 7.2 4.0 | -40.1 -40.2 281 78 40 7.2 4.0
30000 -36.5 -33.7 289 80 41 6.9 3.8 | -35.7 -32.3 280 73 37 7.6 4.1
29000 -34.4 -29.9 290 76 39 6.9 3.8 | -33.4 -28.1 279 69 36 7.6 4.2
28000 -32.3 -26.1 291 73 38 7.0 3.8 | -31.2 -24.2 279 66 34 7.6 4.2
27000 -30.2 -22.4 292 70 36 7.2 3.9 | -29.0 -20.2 278 63 32 6.8 3.8
26000 -28.0 -18.4 291 67 34 7.2 3.9 | -27.0 -16.6 279 60 31 6.8 3.7
25000 -25.9 -14.6 290 64 33 7.2 3.9 | -25.0 -13.0 279 58 30 6.8 3.7
24000 -23.7 -10.7 289 61 31 7.8 4.3 | -22.8 -9.0 279 55 29 7.7 4.2
23000 -21.3 -6.3 287 58 30 7.7 4.2 | -20.5 -4.9 277 52 27 7.7 4.2
22000 -19.0 -2.2 286 56 29 7.7 4.2 | -18.2 -0.8 276 49 25 7.7 4.2
21000 -16.7 1.9 285 53 27 7.5 4.1 | -15.8 3.6 274 46 24 8.1 4.4
20000 -14.4 6.1 284 51 26 7.5 4.1 | -13.4 7.9 271 43 22 8.1 4.4
19500 -12.7 9.1 283 50 26 7.5 4.1 | -11.5 11.3 269 41 21 8.1 4.4
19000 -11.6 11.1 283 49 25 7.2 4.0 | -10.3 13.5 268 40 20 7.1 3.9
18500 -10.6 12.9 283 48 25 6.9 3.8 | -9.4 15.1 269 38 20 6.4 3.5
18000 -9.6 14.7 283 47 24 6.9 3.8 | -8.4 16.9 269 37 19 6.4 3.5
17500 -8.6 16.5 283 46 24 6.5 3.6 | -7.6 18.3 270 36 19 4.7 2.6
17000 -7.6 18.3 282 44 23 6.5 3.6 | -6.9 19.6 271 36 19 4.9 2.7
16500 -6.7 19.9 282 42 22 6.4 3.5 | -6.2 20.8 272 36 18 5.3 2.9
16000 -5.8 21.6 282 41 21 6.3 3.4 | -5.4 22.3 273 36 19 5.6 3.1
15500 -4.9 23.2 281 39 20 6.4 3.5 | -4.6 23.7 275 36 19 5.8 3.2
15000 -3.9 25.0 281 37 19 6.8 3.7 | -3.7 25.3 275 35 18 6.5 3.6
14500 -2.9 26.8 281 36 19 6.8 3.7 | -2.8 27.0 274 33 17 6.6 3.6
14000 -1.9 28.6 282 34 18 6.9 3.8 | -1.8 28.8 274 31 16 7.7 4.2
13500 -0.9 30.4 282 33 17 6.9 3.8 | -0.7 30.7 273 28 15 7.6 4.2
13000 0.2 32.4 283 31 16 7.6 4.2 | 0.5 32.9 272 26 13 8.7 4.8
12500 1.3 34.3 283 29 15 7.6 4.2 | 1.7 35.1 271 24 12 8.7 4.8
12000 2.5 36.5 284 27 14 8.0 4.4 | 3.0 37.4 270 21 11 8.9 4.9
11500 3.7 38.7 284 25 13 8.1 4.5 | 4.3 39.7 270 19 10 9.0 4.9
11000 4.9 40.8 285 23 12 8.3 4.5 | 5.6 42.1 270 18 9 8.5 4.7
10500 6.1 43.0 286 22 11 8.3 4.6 | 6.9 44.4 269 16 8 8.4 4.6
10250 6.7 44.1 286 21 11 8.3 4.6 | 7.5 45.5 269 15 8 8.3 4.6
10000 7.3 45.1 287 19 10 8.4 4.6 | 8.1 46.6 268 13 7 8.1 4.4
9750 8.0 46.4 288 18 9 8.4 4.6 | 8.7 47.7 267 12 6 8.0 4.4
9500 8.6 47.5 288 17 9 8.5 4.6 | 9.3 48.7 265 11 6 8.1 4.4
9250 9.3 48.7 289 16 8 8.4 4.6 | 9.9 49.8 263 10 5 7.7 4.2
9000 9.9 49.8 290 14 7 8.2 4.5 | 10.5 50.9 261 9 5 7.3 4.0
8750 10.5 50.9 291 13 7 8.0 4.4 | 11.1 52.0 257 7 4 7.2 4.0
8500 11.1 52.0 291 11 6 8.3 4.6 | 11.6 52.9 252 6 3 7.3 4.0
8250 11.7 53.1 292 10 5 7.4 4.1 | 12.2 54.0 244 5 2 7.1 3.9
8000 12.2 54.0 293 8 4 6.2 3.4 | 12.7 54.9 234 4 2 7.0 3.8
7750 12.7 54.9 293 6 3 6.3 3.4 | 13.2 55.8 219 3 1 7.0 3.8
7500 13.1 55.6 295 5 2 6.3 3.5 | 13.7 56.7 192 2 1 7.1 3.9
7250 13.6 56.5 294 3 1 5.3 2.9 | 14.3 57.7 166 2 1 8.3 4.5
7000 13.9 57.0 258 1 1 4.3 2.3 | 14.9 58.8 154 2 1 9.0 5.0
6750 14.2 57.6 172 2 1 5.0 2.7 | 15.6 60.1 142 2 1 8.7 4.8
6500 14.5 58.1 152 3 2 3.3 1.8 | 16.2 61.2 130 2 1 9.4 5.2
6250 14.6 58.3 152 4 2 0.2 0.1 | 16.9 62.4 125 2 1 10.4 5.7
6000 14.5 58.1 157 4 2 -0.6 -0.3 | 17.7 63.9 123 2 1 10.2 5.6
5750 14.3 57.7 161 4 2 0.3 0.2 | 18.4 65.1 120 2 1 11.1 6.1
5500 14.5 58.1 164 4 2 8.5 4.7 | 19.4 66.9 113 2 1 17.1 9.4
05/07/2009 at 1500 MDT | 05/07/2009 at 1800 MDT
|
K index... +13.1 | K index... +14.1
|
Height Temperature Wnd WndSpd Lapse Rate | Temperature Wnd WndSpd Lapse Rate
ft MSL deg C deg F Dir kt m/s C/km F/kft | deg C deg F Dir kt m/s C/km F/kft
--------------------------------------------------------------------------------
50000 -64.5 -84.1 281 62 32 1.2 0.7 | -62.6 -80.7 284 62 32 0.3 0.2
45000 -61.9 -79.4 279 89 46 4.2 2.3 | -61.4 -78.5 282 93 48 3.5 1.9
40000 -55.7 -68.3 277 86 44 4.2 2.3 | -56.2 -69.2 280 93 48 3.3 1.8
38000 -52.2 -62.0 278 83 43 6.0 3.3 | -53.1 -63.6 280 89 46 5.4 3.0
36000 -48.1 -54.6 278 78 40 6.0 3.3 | -49.4 -56.9 280 82 42 5.4 3.0
34000 -44.1 -47.4 278 74 38 7.1 3.9 | -45.7 -50.3 280 77 40 6.9 3.8
32000 -39.8 -39.6 276 70 36 7.2 3.9 | -41.5 -42.7 280 71 37 6.9 3.8
30000 -35.5 -31.9 275 68 35 7.2 3.9 | -37.0 -34.6 282 66 34 8.0 4.4
29000 -33.4 -28.1 275 67 35 7.2 4.0 | -34.6 -30.3 283 64 33 8.0 4.4
28000 -31.3 -24.3 275 67 34 7.2 4.0 | -32.2 -26.0 285 62 32 8.0 4.4
27000 -29.1 -20.4 276 66 34 7.2 4.0 | -29.8 -21.6 285 60 31 8.2 4.5
26000 -26.9 -16.4 275 64 33 7.3 4.0 | -27.3 -17.1 284 58 30 8.3 4.5
25000 -24.8 -12.6 275 63 32 7.3 4.0 | -24.9 -12.8 283 56 29 8.3 4.5
24000 -22.5 -8.5 274 61 31 7.8 4.3 | -22.5 -8.5 281 53 27 7.6 4.2
23000 -20.2 -4.4 272 58 30 7.8 4.3 | -20.2 -4.4 277 49 25 7.7 4.2
22000 -17.9 -0.2 270 55 28 7.8 4.3 | -17.9 -0.2 273 45 23 7.7 4.2
21000 -15.5 4.1 268 51 26 7.9 4.3 | -15.7 3.7 271 43 22 6.8 3.8
20000 -13.1 8.4 267 46 24 7.9 4.3 | -13.6 7.5 274 42 22 6.9 3.8
19500 -11.9 10.6 266 44 23 7.9 4.3 | -12.6 9.3 275 41 21 6.9 3.8
19000 -10.2 13.6 265 40 21 6.8 3.7 | -11.1 12.0 278 41 21 6.4 3.5
18500 -9.3 15.3 265 37 19 6.0 3.3 | -10.2 13.6 279 40 20 6.0 3.3
18000 -8.4 16.9 266 34 18 6.0 3.3 | -9.3 15.3 281 38 20 5.9 3.3
17500 -7.5 18.5 267 33 17 5.6 3.1 | -8.3 17.1 282 37 19 7.1 3.9
17000 -6.7 19.9 269 32 17 5.7 3.1 | -7.3 18.9 282 36 18 7.0 3.8
16500 -5.8 21.6 272 32 17 6.1 3.4 | -6.3 20.7 283 34 18 7.0 3.8
16000 -4.9 23.2 273 32 16 6.4 3.5 | -5.2 22.6 283 32 17 7.0 3.8
15500 -4.0 24.8 274 31 16 6.7 3.7 | -4.2 24.4 283 30 15 7.2 4.0
15000 -3.0 26.6 274 30 16 7.7 4.2 | -3.1 26.4 283 28 14 8.0 4.4
14500 -1.9 28.6 274 29 15 7.7 4.2 | -1.9 28.6 284 25 13 8.0 4.4
14000 -0.7 30.7 273 27 14 8.7 4.8 | -0.7 30.7 284 23 12 9.0 4.9
13500 0.6 33.1 271 26 13 8.5 4.7 | 0.6 33.1 283 21 11 8.8 4.9
13000 1.9 35.4 270 24 12 9.6 5.2 | 1.9 35.4 283 19 10 9.6 5.3
12500 3.3 37.9 270 23 12 9.6 5.3 | 3.3 37.9 283 19 10 9.6 5.3
12000 4.7 40.5 270 22 11 9.3 5.1 | 4.8 40.6 283 18 9 9.7 5.3
11500 6.1 43.0 271 20 10 9.2 5.1 | 6.2 43.2 283 18 9 9.7 5.3
11000 7.4 45.3 271 19 10 8.9 4.9 | 7.7 45.9 284 18 9 9.8 5.4
10500 8.7 47.7 271 17 9 8.9 4.9 | 9.2 48.6 284 17 9 9.9 5.4
10250 9.4 48.9 271 16 8 8.8 4.8 | 9.9 49.8 284 17 9 9.9 5.4
10000 10.0 50.0 270 15 8 8.4 4.6 | 10.6 51.1 284 17 9 9.8 5.4
9750 10.6 51.1 270 14 7 8.3 4.5 | 11.4 52.5 284 17 9 9.8 5.4
9500 11.3 52.3 269 13 7 8.3 4.6 | 12.1 53.8 284 17 9 9.8 5.4
9250 11.9 53.4 268 12 6 8.3 4.5 | 12.8 55.0 284 17 9 9.8 5.4
9000 12.5 54.5 268 11 5 8.2 4.5 | 13.6 56.5 284 17 9 9.8 5.4
8750 13.1 55.6 267 9 5 8.2 4.5 | 14.3 57.7 285 17 9 9.8 5.4
8500 13.7 56.7 267 8 4 8.1 4.4 | 15.0 59.0 285 17 9 9.8 5.4
8250 14.3 57.7 267 7 4 8.5 4.7 | 15.8 60.4 285 17 9 9.8 5.4
8000 15.0 59.0 267 6 3 9.1 5.0 | 16.5 61.7 285 17 9 9.7 5.3
7750 15.6 60.1 268 6 3 9.2 5.0 | 17.2 63.0 285 17 9 9.7 5.3
7500 16.3 61.3 269 5 3 9.1 5.0 | 18.0 64.4 285 16 8 9.7 5.3
7250 16.9 62.4 270 5 2 9.6 5.2 | 18.7 65.7 285 16 8 9.8 5.4
7000 17.7 63.9 271 4 2 10.0 5.5 | 19.4 66.9 286 16 8 9.9 5.5
6750 18.4 65.1 272 4 2 9.8 5.4 | 20.2 68.4 286 16 8 9.9 5.4
6500 19.1 66.4 273 4 2 10.0 5.5 | 20.9 69.6 286 16 8 9.9 5.5
6250 19.9 67.8 275 4 2 10.3 5.7 | 21.6 70.9 286 15 8 10.0 5.5
6000 20.7 69.3 275 4 2 10.8 5.9 | 22.4 72.3 286 14 7 10.2 5.6
5750 21.5 70.7 277 3 2 9.7 5.3 | 23.1 73.6 286 14 7 9.7 5.3
5500 22.2 72.0 278 3 2 13.4 7.4 | 23.9 75.0 286 13 7 11.2 6.2
________________________________________________________________________________
This product is issued twice per day, once by approximately 0630 MST/0730 MDT
(1330 UTC) and again by approximately 1830 MST/1930 MDT (0130 UTC). It is not
continuously monitored nor updated after its initial issuance.
The information contained herein is based on rawinsonde observation and/or
numerical weather prediction model data taken near the old Stapleton
Airport site in Denver, Colorado at
North Latitude: 39 deg 46 min 5.016 sec
West Longitude: 104 deg 52 min 9.984 sec
Elevation: 5285 feet (1611 meters)
and may not be representative of other areas along the Front Range of the
Colorado Rocky Mountains. Note that some elevations in numerical weather
prediction models differ from actual station elevations, which can lead to
data which appear to be below ground. Erroneous data such as these should
not be used.
The content and format of this report as well as the issuance times are subject
to change without prior notice. Comments and suggestions are welcome and should
be directed to one of the addresses or phone numbers shown at the bottom of this
page. To expedite a response to comments, be sure to mention your interest in
the soaring forecast.
DEFINITIONS:
Convective Condensation Level - The height to which an air parcel possessing the
average saturation mixing ratio in the lowest 4000 feet of the airmass,
if heated sufficiently from below, will rise dry adiabatically until it
just becomes saturated. It estimates the base of cumulus clouds that are
produced by surface heating only.
Convection Temperature (ConvectionT) - The surface temperature required to make
the airmass dry adiabatic up to the given level. It can be considered a
"trigger temperature" for that level.
Freezing Level - The height where the temperature is zero degrees Celsius.
Height of Stable Layer - The height (between 12,000 and 18,000 feet above
mean sea level) where the smallest lapse rate exists. The location and
existence of this feature is important in the generation of mountain
waves.
K Index - A measure of stability which combines the temperature difference
between approximately 5,000 and 18,000 feet above the surface, the amount
of moisture at approximately 5,000 feet above the surface, and a measure
of the dryness at approximately 10,000 feet above the surface. Larger
positive numbers indicate more instability and a greater likelihood of
thunderstorm development. One interpretation of K index values regarding
soaring in the western United States is given in WMO Technical Note 158
and is reproduced in the following table:
below -10 no or weak thermals
-10 to 5 dry thermals or 1/8 cumulus with moderate thermals
5 to 15 good soaring conditions
15 to 20 good soaring conditions with occasional showers
20 to 30 excellent soaring conditions, but increasing
probability of showers and thunderstorms
above 30 more than 60 percent probability of thunderstorms
Lapse Rate - The change with height of the temperature. Negative values indicate
inversions.
Lifted Condensation Level - The height to which an air parcel possessing the
average dew point in the lowest 4000 feet of the airmass and the forecast
maximum temperature must be lifted dry adiabatically to attain saturation.
Lifted Index - The difference between the environmental temperature at a level
approximately 18,000 feet above the surface and the temperature of an air
parcel lifted dry adiabatically from the surface to its lifted condensation
level and then pseudoadiabatically thereafter to this same level. The
parcel`s initial temperature is the forecast maximum temperature and its
dew point is the average dew point in the lowest 4000 feet of the airmass.
Negative values are indicative of instability with positive values showing
stable conditions.
Lift Rate - An experimental estimate of the strength of thermals. It is
computed the same way as the maximum rate of lift but uses the actual
level rather than the maximum height of thermals in the calculation.
Also, none of the empirical adjustments based on cloudiness and K-index
are applied to these calculations.
Maximum Height of Thermals - The height where the dry adiabat through the
forecast maximum temperature intersects the environmental temperature.
Maximum Rate of Lift - An estimate of the maximum strength of thermals. It
is computed from an empirical formula which combines the expected maximum
height of thermals with the difference in the environmental temperatures
between the maximum height of thermals and the temperature 4,000 feet
above the ground. After this computation, further empirical adjustments
are made based on the value of the K-index and the amount and opacity of
middle and high level cloudiness expected between the time of trigger
temperature and the time of overdevelopment.
Middle/High Clouds - The amount and opacity of middle (altostratus, altocumulus)
or high (cirrus, cirrostatus, cirrocumulus) clouds. Broken means that
between 60% and 90% of the sky is covered by the cloud, with overcast
conditions occurring when more than 90% of the sky is covered by the cloud.
Thin implies that the clouds are predominantly transparent, meaning that
some sunlight is reaching the ground, in contrast to opaque which suggests
that little sunlight is reaching the ground.
Potential Height of Wave - The minimum of the following two heights:
1. Level above the height of stable layer (or 14,000 feet if none exists)
where the wind direction changes by 30 degrees or more
2. Level above the height of stable layer (or 14,000 feet if none exists)
where the wind speed no longer increases with height
PVA/NVA - Positive vorticity advection (PVA)/negative vorticity advection (NVA)
on the 500 millibar isobaric surface (approximately 18,000 feet above mean
sea level). Weak PVA has been shown to assist in mountain wave soaring.
Soaring Window - The time between the time the trigger temperature is reached
and the time of overdevelopment.
Thermal Index - The difference between the environmental temperature and the
temperature at a particular level determined by following the dry adiabat
through the forecast maximum temperature up to that level. Negative values
are indicative of thermal lift.
Thermal Soaring Index - An adjective rating (for sailplanes) based on the
computed maximum rate of lift, and the wind speed and middle and high
cloud cover expected during the soaring window (the time of the trigger
temperature and the time of overdevelopment) according to the following:
Maximum rate of lift Adjective Rating
>= 800 fpm Excellent
>= 400 and < 800 fpm Good
>= 200 and < 400 fpm Fair
< 200 fpm Poor
Time of Overdevelopment - The time one or more of the following phenomena,
which essentially shut off thermal lift, is expected to occur:
1. formation of broken to overcast convective cloud cover
2. formation of scattered to numerous downbursts
3. initiation of widespread precipitation
Time of Trigger Temperature - The time the surface temperature is expected to
reach the trigger temperature.
Trigger Temperature - The surface temperature required to make the first 4000
feet of the atmosphere dry adiabatic.
Wave Soaring Index - An empirical, adjective rating (for sailplanes) which
attempts to combine a variety of phenomena important in mountain wave
soaring into a single index number. Objective points are assigned to
these phenomena: wind speed and direction at 14,000 ft MSL, the static
stability in the 12,000-18,000 ft MSL layer, the wind speed gradient above
the stable layer, jet stream location and frontal and upper trough
movements.
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