Issued by NWS Denver/Boulder, CO
000
UXUS97 KBOU 281242
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
642 AM MDT Tuesday October 28, 2008
This forecast is for Tuesday October 28, 2008:
If the trigger temperature of 70.3 F/21.3 C is reached...then
Thermal Soaring Index....................... Good
Maximum rate of lift........................ 697 ft/min (3.5 m/s)
Maximum height of thermals.................. 13303 ft MSL (8018 ft AGL)
Forecast maximum temperature................... 74.0 F/23.8 C
Time of trigger temperature.................... 1330 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................. 7369 ft MSL (2084 ft AGL)
Thermal soaring outlook for Wednesday 10/29.... Excellent
Wave Soaring Index............................. Poor
Wave Soaring Index trend (to 1800 MDT)......... No change
Height of stable layer (12-18K ft MSL)......... None
Weak PVA/NVA (through 1800 MDT)................ Weak NVA
Potential height of wave....................... 16130 ft MSL (10845 ft AGL)
Wave soaring outlook for Wednesday 10/29....... Poor
Remarks...
Sunrise/Sunset.................... 07:24:20 / 18:03:02 MDT
Total possible sunshine........... 10 hr 38 min 42 sec (638 min 42 sec)
Altitude of sun at 12:43:20 MDT... 36.83 degrees
Upper air data from rawinsonde observation taken on 10/28/2008 at 0600 MDT
Freezing level.................. 13044 ft MSL (7759 ft AGL)
Additional freezing level....... 53776 ft MSL (48491 ft AGL)
Convective condensation level... 29911 ft MSL (24626 ft AGL)
Lifted condensation level....... 25357 ft MSL (20072 ft AGL)
Lifted index.................... +7.9
K index......................... -10.1
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 -65.8 -86.4 300 33 17 5.8 3.2 88.2 190.8 37.2 M M
45000 -64.1 -83.4 320 33 17 4.1 2.3 65.8 150.4 26.2 M M
40000 -58.9 -74.0 324 34 17 5.4 2.9 50.9 123.7 18.2 M M
38000 -55.5 -67.9 316 36 18 5.7 3.1 47.2 116.9 16.2 M M
36000 -52.7 -62.9 308 39 20 4.2 2.3 42.8 109.1 13.6 M M
34000 -49.0 -56.2 305 41 21 6.6 3.6 39.6 103.3 11.7 M M
32000 -43.6 -46.5 305 42 21 9.5 5.2 38.0 100.4 10.8 M M
30000 -38.2 -36.8 305 37 19 7.6 4.1 37.4 99.4 10.7 M M
29000 -36.0 -32.8 308 35 18 7.5 4.1 36.5 97.7 10.1 M M
28000 -33.7 -28.7 311 33 17 8.0 4.4 35.7 96.2 9.6 M M
27000 -31.0 -23.8 314 32 16 9.3 5.1 35.5 95.9 9.5 M M
26000 -28.5 -19.3 310 31 16 6.1 3.4 34.9 94.8 9.2 M M
25000 -26.5 -15.7 305 30 15 6.4 3.5 33.7 92.6 8.3 M M
24000 -24.4 -11.9 305 28 14 7.9 4.3 32.6 90.7 7.6 M M
23000 -22.0 -7.6 305 27 14 7.9 4.3 31.9 89.5 7.1 M M
22000 -19.6 -3.3 305 25 13 7.9 4.3 31.4 88.5 6.7 M M
21000 -17.3 0.9 309 23 12 6.2 3.4 30.7 87.2 6.2 M M
20000 -16.4 2.5 314 21 11 3.0 1.6 28.3 82.9 4.2 M M
19500 -15.5 4.1 323 21 11 9.2 5.0 27.7 81.8 3.6 M M
19000 -14.2 6.4 330 21 11 9.7 5.3 27.5 81.6 3.4 M M
18500 -12.8 9.0 332 20 11 9.2 5.0 27.5 81.4 3.4 M M
18000 -11.4 11.5 334 20 10 9.2 5.0 27.4 81.3 3.4 M M
17500 -10.0 14.0 330 21 11 9.2 5.0 27.3 81.1 3.3 M M
17000 -8.7 16.3 325 21 11 7.9 4.3 27.2 81.0 3.2 M M
16500 -7.7 18.1 320 22 12 6.9 3.8 26.7 80.0 2.8 M M
16000 -6.1 21.0 315 24 12 6.8 3.7 26.0 78.7 2.1 M M
15500 -5.1 22.8 315 23 12 6.8 3.7 25.5 77.8 1.7 M M
15000 -4.1 24.6 316 23 12 6.8 3.7 25.0 77.0 1.2 M M
14500 -3.1 26.4 326 22 11 6.7 3.7 24.5 76.1 0.8 M M
14000 -2.1 28.2 335 22 11 7.8 4.3 24.1 75.3 0.4 M M
13500 -0.9 30.4 336 22 11 7.8 4.3 23.7 74.7 0.1 M M
13000 0.3 32.5 337 21 11 7.8 4.3 23.4 74.1 -0.2 659 3.3
12500 1.4 34.5 338 21 11 7.8 4.3 23.1 73.6 -0.5 609 3.1
12000 2.7 36.9 339 21 11 9.0 5.0 22.9 73.2 -0.7 558 2.8
11500 4.1 39.4 338 18 9 9.5 5.2 22.8 73.1 -0.7 499 2.5
11000 5.6 42.1 336 15 8 9.6 5.2 22.8 73.0 -0.8 441 2.2
10500 7.0 44.6 333 13 7 6.9 3.8 22.7 72.8 -0.8 385 2.0
10250 7.4 45.3 329 12 6 5.7 3.1 22.3 72.2 -1.1 363 1.8
10000 7.9 46.2 325 11 6 6.2 3.4 22.1 71.7 -1.3 341 1.7
9750 8.4 47.1 319 10 5 6.1 3.4 21.8 71.2 -1.6 319 1.6
9500 8.9 48.0 313 10 5 6.5 3.6 21.5 70.7 -1.8 297 1.5
9250 9.4 48.9 306 9 5 7.6 4.2 21.3 70.3 -2.0 273 1.4
9000 10.0 50.0 299 9 5 8.2 4.5 21.2 70.1 -2.1 248 1.3
8750 10.7 51.3 299 8 4 8.0 4.4 21.0 69.9 -2.3 222 1.1
8500 11.3 52.3 298 6 3 8.1 4.4 20.9 69.6 -2.4 197 1.0
8250 11.9 53.4 297 5 3 8.0 4.4 20.8 69.4 -2.5 171 0.9
8000 12.5 54.5 294 4 2 8.0 4.4 20.7 69.2 -2.6 146 0.7
7750 13.1 55.6 286 3 2 8.0 4.4 20.5 68.9 -2.8 120 0.6
7500 13.7 56.7 273 3 1 8.1 4.5 20.4 68.7 -2.9 95 0.5
7250 14.3 57.7 252 2 1 7.8 4.3 20.3 68.5 -3.1 69 0.4
7000 14.9 58.8 226 2 1 9.1 5.0 20.1 68.2 -3.2 44 0.2
6750 15.5 59.9 220 3 1 4.1 2.3 20.0 68.0 -3.3 18 0.1
6500 15.5 59.9 218 3 2 -1.3 -0.7 19.3 66.7 -4.1 11 0.1
6250 15.3 59.5 216 4 2 -4.1 -2.3 18.4 65.1 -5.0 8 0.0
6000 14.6 58.3 215 5 3 -15.8 -8.7 16.9 62.5 -6.5 24 0.1
5750 12.5 54.5 215 3 2 -37.3 -20.5 14.3 57.7 -9.3 78 0.4
5500 8.2 46.8 215 2 1 -75.5 -41.4 9.4 48.9 -14.3 199 1.0
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
10/28/2008 at 0900 MDT | 10/28/2008 at 1200 MDT
|
K index... +5.3 | K index... +8.0
|
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 -65.0 -85.0 328 29 15 1.3 0.7 | -64.9 -84.8 336 28 15 1.4 0.8
45000 -62.7 -80.9 322 37 19 3.2 1.7 | -62.3 -80.1 332 37 19 3.8 2.1
40000 -58.0 -72.4 309 35 18 3.4 1.9 | -56.6 -69.9 317 40 21 3.8 2.1
38000 -54.8 -66.6 312 36 18 5.5 3.0 | -54.0 -65.2 319 36 19 4.3 2.4
36000 -51.1 -60.0 315 37 19 5.5 3.0 | -51.1 -60.0 323 32 16 4.3 2.4
34000 -47.5 -53.5 316 37 19 6.2 3.4 | -47.6 -53.7 324 29 15 6.6 3.6
32000 -43.8 -46.8 315 36 19 6.2 3.4 | -43.6 -46.5 324 27 14 6.6 3.6
30000 -39.4 -38.9 316 36 19 7.8 4.3 | -39.2 -38.6 324 27 14 7.7 4.2
29000 -37.1 -34.8 318 36 19 7.8 4.3 | -36.9 -34.4 323 27 14 7.7 4.2
28000 -34.7 -30.5 319 37 19 7.8 4.3 | -34.6 -30.3 323 27 14 7.7 4.2
27000 -32.3 -26.1 319 35 18 8.2 4.5 | -32.3 -26.1 322 26 14 7.9 4.3
26000 -29.8 -21.6 318 33 17 8.2 4.5 | -29.9 -21.8 320 26 13 7.9 4.3
25000 -27.3 -17.1 317 30 16 8.2 4.5 | -27.5 -17.5 319 25 13 7.9 4.3
24000 -24.9 -12.8 317 28 14 8.0 4.4 | -25.2 -13.4 319 23 12 7.8 4.3
23000 -22.5 -8.5 318 25 13 8.0 4.4 | -22.8 -9.0 320 20 10 7.8 4.3
22000 -20.1 -4.2 319 22 11 8.1 4.5 | -20.5 -4.9 322 17 9 7.9 4.3
21000 -17.9 -0.2 321 20 10 7.0 3.9 | -18.3 -0.9 326 15 8 7.4 4.0
20000 -15.8 3.6 322 19 10 7.1 3.9 | -16.1 3.0 333 13 7 7.4 4.1
19500 -14.8 5.4 323 18 9 7.0 3.9 | -14.4 6.1 340 12 6 7.5 4.1
19000 -13.7 7.3 323 18 9 8.1 4.4 | -13.3 8.1 343 12 6 7.9 4.4
18500 -11.8 10.8 321 18 9 8.3 4.6 | -12.1 10.2 345 12 6 7.9 4.3
18000 -10.6 12.9 321 18 9 8.0 4.4 | -10.9 12.4 347 12 6 8.1 4.4
17500 -9.4 15.1 320 18 9 7.9 4.4 | -9.7 14.5 347 12 6 8.1 4.4
17000 -8.2 17.2 320 18 9 8.0 4.4 | -8.5 16.7 348 12 6 8.0 4.4
16500 -7.0 19.4 320 18 9 8.0 4.4 | -7.3 18.9 348 12 6 7.9 4.4
16000 -5.9 21.4 319 18 9 8.1 4.4 | -6.1 21.0 347 12 6 8.0 4.4
15500 -4.8 23.4 319 18 9 6.9 3.8 | -5.0 23.0 345 12 6 7.4 4.1
15000 -3.7 25.3 318 17 9 7.0 3.8 | -3.9 25.0 342 12 6 7.5 4.1
14500 -2.7 27.1 318 16 8 7.4 4.0 | -2.8 27.0 339 11 6 7.2 3.9
14000 -1.6 29.1 318 15 8 7.4 4.1 | -1.7 28.9 335 11 6 7.2 3.9
13500 -0.5 31.1 319 14 7 7.6 4.2 | -0.7 30.7 331 10 5 7.4 4.1
13000 0.6 33.1 319 13 7 7.6 4.2 | 0.4 32.7 329 10 5 7.6 4.1
12500 1.7 35.1 321 12 6 7.9 4.3 | 1.5 34.7 328 10 5 8.1 4.4
12000 2.9 37.2 321 11 6 8.0 4.4 | 2.8 37.0 326 10 5 8.4 4.6
11500 4.1 39.4 321 11 5 8.3 4.5 | 4.1 39.4 325 10 5 8.5 4.7
11000 5.4 41.7 319 11 5 8.4 4.6 | 5.3 41.5 321 11 6 8.5 4.7
10500 6.6 43.9 316 11 5 8.2 4.5 | 6.6 43.9 317 12 6 8.6 4.7
10250 7.2 45.0 315 10 5 8.0 4.4 | 7.3 45.1 316 12 6 8.7 4.8
10000 7.8 46.0 313 10 5 8.1 4.4 | 7.9 46.2 314 12 6 8.7 4.8
9750 8.5 47.3 311 9 5 8.0 4.4 | 8.6 47.5 312 12 6 8.6 4.7
9500 9.0 48.2 309 9 5 7.3 4.0 | 9.2 48.6 310 12 6 7.9 4.4
9250 9.6 49.3 308 8 4 6.9 3.8 | 9.8 49.6 310 11 6 7.6 4.2
9000 10.1 50.2 306 6 3 7.1 3.9 | 10.3 50.5 309 10 5 7.7 4.2
8750 10.7 51.3 302 5 3 6.6 3.6 | 10.9 51.6 308 9 5 7.5 4.1
8500 11.1 52.0 296 4 2 5.7 3.1 | 11.5 52.7 307 9 4 7.1 3.9
8250 11.5 52.7 286 4 2 5.4 3.0 | 12.0 53.6 307 8 4 6.8 3.7
8000 11.9 53.4 271 3 2 5.6 3.1 | 12.5 54.5 307 7 4 7.2 4.0
7750 12.3 54.1 250 3 1 5.1 2.8 | 13.0 55.4 308 6 3 5.8 3.2
7500 12.7 54.9 260 2 1 4.4 2.4 | 13.4 56.1 309 5 3 4.3 2.3
7250 13.0 55.4 275 2 1 4.8 2.7 | 13.7 56.7 312 5 2 4.7 2.6
7000 13.3 55.9 292 2 1 3.7 2.0 | 14.1 57.4 316 4 2 4.0 2.2
6750 13.5 56.3 298 2 1 -0.0 -0.0 | 14.3 57.7 323 3 1 0.9 0.5
6500 13.4 56.1 287 2 1 -3.2 -1.7 | 14.2 57.6 338 2 1 -0.1 -0.1
6250 13.2 55.8 278 2 1 1.6 0.9 | 14.2 57.6 004 2 1 -1.6 -0.9
6000 13.1 55.6 269 2 1 -14.4 -7.9 | 14.2 57.6 038 2 1 5.3 2.9
5750 10.9 51.6 250 3 1 -34.4 -18.9 | 15.0 59.0 037 2 1 14.4 7.9
5500 8.7 47.7 235 3 2 -20.3 -11.1 | 15.9 60.6 034 2 1 8.6 4.7
10/28/2008 at 1500 MDT | 10/28/2008 at 1800 MDT
|
K index... +9.2 | 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 -84.1 332 27 14 1.8 1.0 | -65.2 -85.4 333 27 14 2.2 1.2
45000 -61.4 -78.5 336 37 19 3.7 2.0 | -61.6 -78.9 334 34 18 3.5 1.9
40000 -55.9 -68.6 323 44 23 3.7 2.0 | -56.4 -69.5 335 43 22 3.4 1.9
38000 -54.1 -65.4 325 39 20 2.9 1.6 | -54.4 -65.9 335 41 21 3.4 1.9
36000 -52.2 -62.0 329 33 17 2.8 1.6 | -52.4 -62.3 335 38 19 3.4 1.9
34000 -48.6 -55.5 332 30 15 7.7 4.2 | -48.3 -54.9 335 33 17 7.9 4.4
32000 -44.0 -47.2 336 28 14 7.7 4.2 | -43.5 -46.3 337 29 15 8.0 4.4
30000 -39.2 -38.6 333 26 13 8.2 4.5 | -38.5 -37.3 340 26 13 8.7 4.8
29000 -36.7 -34.1 330 25 13 8.2 4.5 | -35.9 -32.6 342 25 13 8.7 4.8
28000 -34.2 -29.6 327 24 12 8.4 4.6 | -33.3 -27.9 344 24 12 9.1 5.0
27000 -32.1 -25.8 328 22 11 6.5 3.6 | -31.3 -24.3 343 21 11 5.8 3.2
26000 -30.2 -22.4 331 19 10 6.5 3.6 | -29.5 -21.1 341 17 9 5.9 3.2
25000 -28.2 -18.8 335 16 8 6.5 3.6 | -27.8 -18.0 337 14 7 5.8 3.2
24000 -26.0 -14.8 340 14 7 8.0 4.4 | -25.8 -14.4 339 11 6 7.3 4.0
23000 -23.6 -10.5 346 13 6 8.0 4.4 | -23.6 -10.5 348 9 5 7.3 4.0
22000 -21.2 -6.2 353 11 6 8.0 4.4 | -21.4 -6.5 001 8 4 7.2 3.9
21000 -18.7 -1.7 359 10 5 8.4 4.6 | -19.0 -2.2 006 7 4 8.6 4.7
20000 -16.2 2.8 003 9 5 8.4 4.6 | -16.4 2.5 008 7 3 8.6 4.7
19500 -14.3 6.3 007 8 4 8.4 4.6 | -15.1 4.8 009 6 3 8.6 4.7
19000 -13.1 8.4 004 8 4 8.0 4.4 | -13.9 7.0 008 6 3 8.1 4.5
18500 -11.9 10.6 358 8 4 8.1 4.4 | -12.1 10.2 354 6 3 8.0 4.4
18000 -10.7 12.7 352 7 4 7.7 4.2 | -10.9 12.4 345 7 3 7.4 4.0
17500 -9.6 14.7 347 8 4 7.7 4.2 | -9.9 14.2 338 8 4 7.2 3.9
17000 -8.5 16.7 343 8 4 7.6 4.2 | -8.8 16.2 331 8 4 7.2 3.9
16500 -7.4 18.7 340 8 4 7.3 4.0 | -7.8 18.0 330 10 5 7.2 3.9
16000 -6.3 20.7 338 8 4 7.3 4.0 | -6.7 19.9 330 11 6 7.1 3.9
15500 -5.1 22.8 337 9 5 8.3 4.5 | -5.6 21.9 329 12 6 8.0 4.4
15000 -3.9 25.0 336 9 5 8.2 4.5 | -4.5 23.9 328 12 6 7.9 4.3
14500 -2.7 27.1 334 10 5 7.9 4.4 | -3.3 26.1 328 13 6 8.8 4.8
14000 -1.5 29.3 332 10 5 7.9 4.3 | -2.0 28.4 328 12 6 8.9 4.9
13500 -0.3 31.5 331 11 6 7.9 4.3 | -0.7 30.7 328 12 6 9.0 5.0
13000 0.8 33.4 329 11 6 7.9 4.3 | 0.7 33.3 328 11 6 9.1 5.0
12500 2.0 35.6 328 11 6 8.3 4.6 | 2.1 35.8 329 11 5 8.9 4.9
12000 3.3 37.9 327 11 6 8.6 4.7 | 3.4 38.1 331 10 5 8.7 4.8
11500 4.6 40.3 327 11 5 8.7 4.8 | 4.6 40.3 334 9 5 8.8 4.8
11000 5.9 42.6 328 10 5 8.7 4.8 | 6.0 42.8 339 9 5 8.8 4.8
10500 7.1 44.8 329 10 5 8.7 4.8 | 7.3 45.1 345 8 4 8.6 4.7
10250 7.8 46.0 331 10 5 8.8 4.8 | 7.9 46.2 348 8 4 8.4 4.6
10000 8.4 47.1 332 9 5 8.8 4.8 | 8.6 47.5 352 8 4 8.4 4.6
9750 9.1 48.4 334 9 5 8.8 4.8 | 9.2 48.6 356 7 4 8.4 4.6
9500 9.7 49.5 336 9 5 8.8 4.8 | 9.8 49.6 360 7 4 8.1 4.4
9250 10.4 50.7 339 9 4 8.8 4.8 | 10.4 50.7 006 7 4 7.8 4.3
9000 11.1 52.0 341 8 4 8.9 4.9 | 11.0 51.8 011 7 3 7.9 4.3
8750 11.7 53.1 344 8 4 8.6 4.7 | 11.6 52.9 018 6 3 7.8 4.3
8500 12.3 54.1 348 8 4 7.9 4.3 | 12.2 54.0 024 6 3 7.5 4.1
8250 12.9 55.2 352 7 4 7.6 4.2 | 12.8 55.0 032 6 3 7.4 4.0
8000 13.5 56.3 357 7 4 7.9 4.3 | 13.3 55.9 040 5 3 7.3 4.0
7750 14.0 57.2 002 7 3 7.1 3.9 | 13.9 57.0 049 5 3 7.7 4.2
7500 14.5 58.1 011 6 3 6.1 3.4 | 14.5 58.1 058 5 3 8.3 4.6
7250 15.0 59.0 023 5 3 6.2 3.4 | 15.1 59.2 068 5 2 8.4 4.6
7000 15.5 59.9 038 5 2 6.2 3.4 | 15.7 60.3 078 5 2 8.4 4.6
6750 16.0 60.8 050 5 2 7.3 4.0 | 16.3 61.3 086 5 2 8.9 4.9
6500 16.5 61.7 051 4 2 8.3 4.5 | 17.0 62.6 082 5 2 9.1 5.0
6250 17.1 62.8 053 4 2 7.2 3.9 | 17.6 63.7 079 5 2 9.7 5.3
6000 17.7 63.9 055 4 2 10.5 5.8 | 18.3 64.9 075 5 2 6.9 3.8
5750 18.7 65.7 055 4 2 15.5 8.5 | 18.6 65.5 074 4 2 1.7 0.9
5500 19.8 67.6 054 4 2 14.2 7.8 | 18.7 65.7 072 3 2 1.8 1.0
________________________________________________________________________________
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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