Issued by NWS Denver/Boulder, CO
000
UXUS97 KBOU 041231
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
631 AM MDT Monday May 4, 2009
This forecast is for Monday May 4, 2009:
If the trigger temperature of 61.8 F/16.6 C is reached...then
Thermal Soaring Index....................... Fair
Maximum rate of lift........................ 320 ft/min (1.6 m/s)
Maximum height of thermals.................. 11999 ft MSL (6714 ft AGL)
Forecast maximum temperature................... 67.0 F/19.9 C
Time of trigger temperature.................... 1145 MDT
Time of overdevelopment........................ None
Middle/high clouds during soaring window....... Broken/overcast thin middle
Surface winds during soaring window............ 20 mph or less
Height of the -3 thermal index................. 8640 ft MSL (3355 ft AGL)
Thermal soaring outlook for Tuesday 05/05...... Good
Wave Soaring Index............................. Fair
Wave Soaring Index trend (to 1800 MDT)......... Little change
Height of stable layer (12-18K ft MSL)......... None
Weak PVA/NVA (through 1800 MDT)................ Weak PVA
Potential height of wave....................... 19036 ft MSL (13751 ft AGL)
Wave soaring outlook for Tuesday 05/05......... Fair
Remarks... Decreasing clouds during the day
Sunrise/Sunset.................... 05:56:12 / 19:56:02 MDT
Total possible sunshine........... 13 hr 59 min 51 sec (839 min 51 sec)
Altitude of sun at 12:56:18 MDT... 66.39 degrees
Upper air data from rawinsonde observation taken on 05/04/2009 at 0600 MDT
Freezing level.................. 11676 ft MSL (6391 ft AGL)
Convective condensation level... 14365 ft MSL (9080 ft AGL)
Lifted condensation level....... 14192 ft MSL (8907 ft AGL)
Lifted index.................... -0.2
K index......................... +17.2
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 -57.4 -71.3 260 51 26 -0.1 -0.0 104.0 219.2 48.4 M M
45000 -54.1 -65.4 268 45 23 -3.7 -2.0 84.6 184.3 39.9 M M
40000 -57.7 -71.9 275 58 30 -12.1 -6.6 54.8 130.6 23.2 M M
38000 -59.8 -75.6 272 69 35 -1.9 -1.0 42.7 108.9 15.7 M M
36000 -60.0 -76.0 270 67 35 6.8 3.7 34.0 93.3 10.1 M M
34000 -55.5 -67.9 265 54 28 7.0 3.8 32.2 89.9 9.1 M M
32000 -50.3 -58.5 267 52 27 9.0 4.9 31.1 88.0 8.5 M M
30000 -44.7 -48.5 270 51 26 9.1 5.0 30.9 87.7 8.6 M M
29000 -42.0 -43.6 265 50 26 9.1 5.0 30.5 87.0 8.4 M M
28000 -39.3 -38.7 260 50 26 9.1 5.0 30.3 86.5 8.3 M M
27000 -35.9 -32.6 254 50 26 9.3 5.1 30.1 86.2 8.3 M M
26000 -33.5 -28.3 250 50 26 7.5 4.1 29.5 85.1 7.9 M M
25000 -31.3 -24.3 259 44 22 7.5 4.1 28.7 83.6 7.3 M M
24000 -29.0 -20.2 255 39 20 7.8 4.3 27.8 82.1 6.7 M M
23000 -26.7 -16.1 255 34 18 8.0 4.4 27.1 80.8 6.2 M M
22000 -24.3 -11.7 255 30 15 8.0 4.4 26.5 79.8 5.8 M M
21000 -21.9 -7.4 255 36 19 8.0 4.4 25.8 78.5 5.2 M M
20000 -19.6 -3.3 255 42 22 7.5 4.1 25.1 77.3 4.6 M M
19500 -18.5 -1.3 256 43 22 7.5 4.1 24.7 76.5 4.3 M M
19000 -17.4 0.7 258 43 22 7.6 4.1 24.3 75.8 4.0 M M
18500 -16.3 2.7 259 44 23 6.7 3.7 23.9 75.0 3.6 M M
18000 -15.4 4.3 258 43 22 6.4 3.5 23.3 73.9 3.1 M M
17500 -14.4 6.1 256 42 22 6.4 3.5 22.7 72.9 2.6 M M
17000 -13.5 7.7 255 41 21 6.1 3.3 22.2 72.0 2.1 M M
16500 -12.3 9.9 256 39 20 10.5 5.7 21.9 71.4 1.9 M M
16000 -10.8 12.6 259 37 19 11.0 6.0 22.0 71.7 2.0 M M
15500 -9.5 14.9 263 35 18 4.8 2.6 21.9 71.3 1.8 M M
15000 -8.7 16.3 267 33 17 6.9 3.8 21.1 70.1 1.2 M M
14500 -7.6 18.3 272 30 16 6.6 3.6 20.6 69.1 0.8 M M
14000 -5.8 21.6 280 28 14 9.4 5.2 20.2 68.4 0.4 M M
13500 -4.5 23.9 280 27 14 9.3 5.1 20.1 68.2 0.3 M M
13000 -3.1 26.4 280 26 14 9.3 5.1 20.0 68.1 0.2 M M
12500 -1.7 28.9 280 26 13 9.6 5.2 20.0 68.0 0.2 M M
12000 -0.5 31.1 280 25 13 6.6 3.6 19.8 67.6 -0.1 512 2.6
11500 0.5 32.9 282 23 12 6.5 3.5 19.3 66.7 -0.5 467 2.4
11000 1.5 34.7 284 22 11 3.2 1.8 18.8 65.8 -1.0 423 2.1
10500 1.7 35.1 287 21 11 6.5 3.6 17.6 63.7 -2.2 401 2.0
10250 2.3 36.1 288 20 11 8.7 4.8 17.5 63.4 -2.4 377 1.9
10000 2.9 37.2 289 20 10 8.7 4.8 17.4 63.3 -2.5 350 1.8
9750 3.6 38.5 287 18 10 8.6 4.7 17.3 63.1 -2.6 324 1.6
9500 4.2 39.6 285 17 9 8.7 4.7 17.2 63.0 -2.7 297 1.5
9250 4.8 40.6 282 16 8 8.7 4.8 17.1 62.8 -2.8 271 1.4
9000 5.5 41.9 279 15 8 8.7 4.8 17.1 62.7 -2.9 244 1.2
8750 6.1 43.0 278 14 7 8.7 4.8 17.0 62.6 -3.0 218 1.1
8500 6.8 44.2 277 13 7 8.7 4.8 16.9 62.4 -3.1 191 1.0
8250 7.4 45.3 276 12 6 8.7 4.8 16.8 62.3 -3.2 165 0.8
8000 8.0 46.4 274 11 6 8.7 4.8 16.7 62.1 -3.3 138 0.7
7750 8.7 47.7 268 12 6 8.7 4.8 16.6 62.0 -3.4 112 0.6
7500 9.3 48.7 263 13 7 8.7 4.7 16.5 61.8 -3.5 85 0.4
7250 9.9 49.8 258 15 8 8.8 4.8 16.5 61.6 -3.6 59 0.3
7000 10.6 51.1 255 16 8 8.4 4.6 16.4 61.5 -3.7 32 0.2
6750 11.1 52.0 254 15 8 6.2 3.4 16.2 61.2 -3.9 9 0.0
6500 11.5 52.7 253 14 7 4.8 2.6 15.8 60.5 -4.3 M M
6250 11.8 53.2 251 12 6 5.7 3.1 15.5 59.9 -4.7 M M
6000 12.2 54.0 250 11 6 3.6 2.0 15.2 59.3 -5.1 M M
5750 12.0 53.6 238 9 5 -10.5 -5.7 14.3 57.7 -6.0 M M
5500 10.5 50.9 219 7 4 -24.0 -13.2 12.1 53.9 -8.2 M M
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
05/04/2009 at 0900 MDT | 05/04/2009 at 1200 MDT
|
K index... +20.4 | K index... +17.5
|
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 -56.7 -70.1 274 44 23 0.9 0.5 | -57.4 -71.3 275 40 21 0.9 0.5
45000 -55.3 -67.5 272 59 30 -0.6 -0.3 | -56.0 -68.8 284 60 31 -0.6 -0.3
40000 -56.7 -70.1 289 70 36 -0.9 -0.5 | -57.1 -70.8 299 82 42 -0.7 -0.4
38000 -56.4 -69.5 288 66 34 1.6 0.9 | -56.3 -69.3 302 89 46 3.1 1.7
36000 -55.5 -67.9 279 54 28 1.6 0.9 | -54.4 -65.9 304 93 48 3.1 1.7
34000 -54.0 -65.2 268 46 24 8.3 4.5 | -52.1 -61.8 306 96 50 8.2 4.5
32000 -49.3 -56.7 271 49 25 7.7 4.2 | -46.7 -52.1 308 90 46 7.9 4.3
30000 -44.0 -47.2 273 51 26 8.4 4.6 | -42.2 -44.0 307 82 42 6.8 3.7
29000 -41.5 -42.7 275 51 26 8.4 4.6 | -40.2 -40.4 303 75 39 6.8 3.7
28000 -39.0 -38.2 277 51 26 8.4 4.6 | -38.1 -36.6 299 69 35 6.8 3.7
27000 -36.5 -33.7 278 51 26 8.2 4.5 | -36.1 -33.0 293 63 33 7.8 4.3
26000 -34.1 -29.4 279 48 25 8.1 4.4 | -33.6 -28.5 291 61 31 8.2 4.5
25000 -31.7 -25.1 279 45 23 8.1 4.5 | -31.2 -24.2 289 58 30 8.2 4.5
24000 -29.3 -20.7 279 43 22 7.9 4.3 | -28.7 -19.7 286 56 29 7.6 4.1
23000 -27.0 -16.6 280 42 22 7.5 4.1 | -26.8 -16.2 284 52 27 6.6 3.6
22000 -24.8 -12.6 280 42 22 7.5 4.1 | -24.8 -12.6 282 48 25 6.6 3.6
21000 -22.6 -8.7 281 41 21 7.2 4.0 | -22.8 -9.0 279 44 23 7.4 4.0
20000 -20.5 -4.9 282 40 21 7.2 3.9 | -20.6 -5.1 281 40 21 7.6 4.1
19500 -19.4 -2.9 282 40 20 7.2 3.9 | -19.5 -3.1 282 39 20 7.6 4.1
19000 -18.4 -1.1 283 39 20 7.2 3.9 | -18.3 -0.9 282 37 19 7.6 4.2
18500 -17.3 0.9 283 38 20 7.1 3.9 | -17.2 1.0 283 35 18 7.6 4.2
18000 -16.3 2.7 283 37 19 7.0 3.9 | -16.1 3.0 284 34 17 7.7 4.2
17500 -15.2 4.6 283 35 18 7.0 3.9 | -14.9 5.2 285 32 17 7.7 4.2
17000 -14.2 6.4 283 33 17 6.8 3.7 | -13.3 8.1 286 30 16 7.0 3.9
16500 -12.7 9.1 283 32 16 6.9 3.8 | -12.3 9.9 287 29 15 7.0 3.9
16000 -11.7 10.9 284 31 16 7.3 4.0 | -11.3 11.7 287 29 15 7.0 3.9
15500 -10.6 12.9 284 31 16 7.2 4.0 | -10.2 13.6 287 28 14 7.0 3.9
15000 -9.4 15.1 284 30 15 8.3 4.6 | -9.2 15.4 287 27 14 7.1 3.9
14500 -8.2 17.2 284 28 14 8.3 4.5 | -8.1 17.4 287 26 13 7.1 3.9
14000 -7.0 19.4 283 26 14 8.2 4.5 | -7.1 19.2 286 25 13 7.5 4.1
13500 -5.8 21.6 283 26 13 8.2 4.5 | -6.0 21.2 286 25 13 7.6 4.2
13000 -4.6 23.7 283 25 13 8.0 4.4 | -4.8 23.4 285 25 13 7.8 4.3
12500 -3.4 25.9 283 25 13 7.9 4.4 | -3.7 25.3 285 24 13 7.9 4.4
12000 -2.2 28.0 282 24 13 7.7 4.2 | -2.5 27.5 285 24 12 8.1 4.5
11500 -1.1 30.0 281 24 12 7.6 4.2 | -1.3 29.7 285 23 12 8.3 4.5
11000 0.0 32.0 280 23 12 7.6 4.2 | -0.1 31.8 285 22 11 8.4 4.6
10500 1.1 34.0 280 22 12 7.6 4.2 | 1.1 34.0 286 21 11 8.5 4.7
10250 1.7 35.1 280 22 11 7.6 4.2 | 1.8 35.2 287 20 10 8.5 4.7
10000 2.3 36.1 280 22 11 7.7 4.2 | 2.4 36.3 287 20 10 8.6 4.7
9750 2.8 37.0 282 22 11 7.8 4.3 | 3.0 37.4 289 19 10 8.7 4.8
9500 3.4 38.1 283 22 12 7.8 4.3 | 3.7 38.7 290 18 9 8.7 4.8
9250 4.0 39.2 285 23 12 7.7 4.2 | 4.3 39.7 291 18 9 8.7 4.8
9000 4.5 40.1 286 23 12 7.1 3.9 | 5.0 41.0 293 17 9 8.7 4.8
8750 5.0 41.0 287 24 12 6.7 3.7 | 5.6 42.1 295 16 8 8.7 4.8
8500 5.5 41.9 288 24 13 6.7 3.7 | 6.3 43.3 297 16 8 8.7 4.8
8250 6.0 42.8 289 25 13 7.2 4.0 | 6.9 44.4 299 15 8 8.7 4.8
8000 6.6 43.9 289 25 13 8.1 4.5 | 7.6 45.7 301 14 7 8.6 4.7
7750 7.2 45.0 289 24 12 8.3 4.5 | 8.2 46.8 304 13 7 8.6 4.7
7500 7.8 46.0 289 23 12 8.2 4.5 | 8.8 47.8 307 12 6 8.5 4.6
7250 8.4 47.1 289 22 11 8.2 4.5 | 9.4 48.9 311 11 6 9.2 5.1
7000 9.0 48.2 290 21 11 8.0 4.4 | 10.1 50.2 313 10 5 9.9 5.5
6750 9.6 49.3 291 20 10 8.6 4.7 | 10.8 51.4 316 9 4 9.7 5.3
6500 10.2 50.4 291 19 10 6.4 3.5 | 11.6 52.9 320 8 4 9.9 5.4
6250 10.4 50.7 291 17 9 1.4 0.7 | 12.3 54.1 323 7 4 10.2 5.6
6000 10.4 50.7 288 13 7 -0.2 -0.1 | 13.0 55.4 325 6 3 10.3 5.7
5750 10.3 50.5 283 9 5 0.4 0.2 | 13.8 56.8 326 6 3 10.0 5.5
5500 10.4 50.7 271 5 3 2.8 1.5 | 14.6 58.3 328 6 3 14.2 7.8
05/04/2009 at 1500 MDT | 05/04/2009 at 1800 MDT
|
K index... +18.9 | K index... +17.0
|
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 -58.6 -73.5 286 45 23 -1.2 -0.7 | -59.5 -75.1 291 50 26 -2.0 -1.1
45000 -60.4 -76.7 294 72 37 -0.4 -0.2 | -62.4 -80.3 295 81 42 -0.8 -0.4
40000 -61.0 -77.8 310 90 46 -0.5 -0.3 | -62.1 -79.8 317 102 53 0.4 0.2
38000 -58.5 -73.3 311 95 49 6.9 3.8 | -58.6 -73.5 314 100 51 8.1 4.5
36000 -54.4 -65.9 311 99 51 6.9 3.8 | -53.8 -64.8 306 93 48 8.1 4.5
34000 -50.0 -58.0 310 100 51 8.2 4.5 | -48.9 -56.0 299 87 45 8.1 4.5
32000 -45.1 -49.2 306 94 49 8.2 4.5 | -44.0 -47.2 296 82 42 8.2 4.5
30000 -39.8 -39.6 303 87 45 7.4 4.1 | -38.6 -37.5 294 76 39 8.0 4.4
29000 -37.6 -35.7 302 82 42 7.4 4.1 | -36.2 -33.2 293 74 38 8.0 4.4
28000 -35.4 -31.7 302 78 40 7.4 4.1 | -33.9 -29.0 292 71 36 8.0 4.4
27000 -33.1 -27.6 301 73 37 7.7 4.2 | -31.6 -24.9 292 68 35 6.7 3.7
26000 -30.8 -23.4 298 67 35 7.7 4.2 | -29.5 -21.1 292 65 34 6.9 3.8
25000 -28.5 -19.3 295 62 32 7.7 4.2 | -27.5 -17.5 292 62 32 6.9 3.8
24000 -26.2 -15.2 292 57 29 6.9 3.8 | -25.5 -13.9 292 59 30 6.5 3.6
23000 -24.3 -11.7 291 54 28 6.4 3.5 | -23.6 -10.5 290 55 29 6.4 3.5
22000 -22.4 -8.3 291 51 26 6.4 3.5 | -21.7 -7.1 288 52 27 6.4 3.5
21000 -20.6 -5.1 290 48 25 5.7 3.1 | -19.8 -3.6 286 48 25 5.9 3.3
20000 -18.9 -2.0 288 44 23 5.7 3.1 | -18.0 -0.4 287 44 22 6.0 3.3
19500 -18.1 -0.6 287 42 22 5.7 3.1 | -17.1 1.2 288 42 21 6.0 3.3
19000 -17.2 1.0 286 40 21 5.7 3.1 | -16.2 2.8 289 39 20 6.0 3.3
18500 -16.4 2.5 285 38 20 5.2 2.9 | -15.4 4.3 289 37 19 5.3 2.9
18000 -15.7 3.7 283 35 18 5.0 2.7 | -14.6 5.7 286 34 18 5.0 2.8
17500 -15.0 5.0 280 31 16 5.1 2.8 | -13.9 7.0 284 32 16 5.1 2.8
17000 -14.1 6.6 278 27 14 7.0 3.9 | -13.1 8.4 279 29 15 5.7 3.2
16500 -12.6 9.3 272 23 12 7.1 3.9 | -12.3 9.9 273 26 13 5.6 3.1
16000 -11.5 11.3 271 20 11 7.6 4.2 | -10.9 12.4 266 23 12 7.1 3.9
15500 -10.4 13.3 271 19 10 7.6 4.2 | -9.9 14.2 262 21 11 7.1 3.9
15000 -9.2 15.4 274 17 9 7.8 4.3 | -8.7 16.3 261 20 10 8.6 4.7
14500 -8.1 17.4 278 17 9 7.8 4.3 | -7.5 18.5 263 18 9 8.5 4.7
14000 -6.9 19.6 283 16 8 8.1 4.5 | -6.2 20.8 265 17 9 8.3 4.6
13500 -5.7 21.7 289 16 8 8.2 4.5 | -5.0 23.0 268 16 8 8.3 4.6
13000 -4.5 23.9 296 15 8 8.8 4.8 | -3.7 25.3 272 14 7 8.6 4.7
12500 -3.2 26.2 302 14 7 9.0 4.9 | -2.4 27.7 277 14 7 8.7 4.7
12000 -1.9 28.6 307 14 7 9.6 5.3 | -1.1 30.0 282 14 7 8.9 4.9
11500 -0.4 31.3 309 14 7 9.9 5.4 | 0.2 32.4 287 14 7 9.0 4.9
11000 1.0 33.8 310 14 7 9.8 5.3 | 1.5 34.7 292 13 7 9.2 5.0
10500 2.5 36.5 312 14 7 9.6 5.3 | 2.9 37.2 295 13 7 9.3 5.1
10250 3.2 37.8 313 14 7 9.6 5.3 | 3.6 38.5 296 13 7 9.3 5.1
10000 3.9 39.0 313 14 7 9.7 5.3 | 4.3 39.7 298 13 6 9.4 5.2
9750 4.7 40.5 314 14 7 9.8 5.4 | 5.0 41.0 300 12 6 9.5 5.2
9500 5.4 41.7 315 14 7 9.8 5.4 | 5.7 42.3 302 12 6 9.5 5.2
9250 6.1 43.0 316 14 7 9.8 5.4 | 6.3 43.3 304 12 6 9.5 5.2
9000 6.9 44.4 316 13 7 9.9 5.4 | 7.0 44.6 306 12 6 9.5 5.2
8750 7.6 45.7 317 13 7 9.9 5.4 | 7.7 45.9 306 12 6 9.6 5.2
8500 8.3 46.9 318 13 7 9.9 5.4 | 8.5 47.3 307 12 6 9.5 5.2
8250 9.1 48.4 319 13 7 10.0 5.5 | 9.2 48.6 308 12 6 9.8 5.4
8000 9.8 49.6 320 13 7 10.2 5.6 | 9.9 49.8 309 12 6 10.2 5.6
7750 10.6 51.1 320 13 7 10.2 5.6 | 10.7 51.3 310 12 6 10.2 5.6
7500 11.3 52.3 321 13 7 10.2 5.6 | 11.4 52.5 311 12 6 10.2 5.6
7250 12.1 53.8 321 13 7 10.1 5.5 | 12.2 54.0 312 12 6 9.9 5.5
7000 12.9 55.2 322 13 7 9.9 5.4 | 12.9 55.2 313 12 6 9.7 5.3
6750 13.6 56.5 323 13 7 9.9 5.4 | 13.6 56.5 314 12 6 9.8 5.4
6500 14.4 57.9 323 13 7 10.0 5.5 | 14.4 57.9 315 11 6 9.8 5.4
6250 15.1 59.2 324 13 7 10.3 5.6 | 15.1 59.2 316 11 6 10.1 5.5
6000 15.9 60.6 325 12 6 10.7 5.9 | 15.9 60.6 317 11 6 10.2 5.6
5750 16.7 62.1 325 12 6 9.5 5.2 | 16.6 61.9 318 10 5 9.9 5.5
5500 17.5 63.5 326 12 6 15.1 8.3 | 17.4 63.3 319 10 5 12.3 6.8
________________________________________________________________________________
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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