Soaring Forecast
National Weather Service Denver/Boulder, Colorado
541 AM MST Monday November 23, 2009
This forecast is for Monday November 23, 2009:
If the trigger temperature of 48.0 F/8.9 C is reached...then
Thermal Soaring Index....................... Poor
Maximum rate of lift........................ 0 ft/min (0.0 m/s)
Maximum height of thermals.................. 6820 ft MSL (1535 ft AGL)
Forecast maximum temperature................... 42.0 F/6.0 C
Time of trigger temperature.................... None
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................. 5787 ft MSL (501 ft AGL)
Thermal soaring outlook for Tuesday 11/24...... Fair
Wave Soaring Index............................. Good
Wave Soaring Index trend (to 1700 MST)......... No change
Height of stable layer (12-18K ft MSL)......... 18097 ft MSL (12812 ft AGL)
Weak PVA/NVA (through 1700 MST)................ Weak PVA
Potential height of wave....................... 20068 ft MSL (14783 ft AGL)
Wave soaring outlook for Tuesday 11/24......... Fair
Remarks...
Sunrise/Sunset.................... 06:53:24 / 16:38:32 MST
Total possible sunshine........... 9 hr 45 min 8 sec (585 min 8 sec)
Altitude of sun at 11:46:08 MST... 29.80 degrees
Upper air data from rawinsonde observation taken on 11/23/2009 at 0500 MST
Freezing level.................. 5529 ft MSL (244 ft AGL)
Additional freezing level....... 7871 ft MSL (2586 ft AGL)
Convective condensation level... 12900 ft MSL (7615 ft AGL)
Lifted condensation level....... 10852 ft MSL (5567 ft AGL)
Lifted index.................... +3.6
K index......................... +21.1
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 -56.8 -70.2 236 20 11 8.0 4.4 106.1 223.0 57.4 M M
45000 -52.3 -62.1 300 42 22 0.4 0.2 88.7 191.6 50.7 M M
40000 -51.0 -59.8 260 44 23 7.0 3.8 67.5 153.5 40.4 M M
38000 -49.3 -56.7 259 45 23 -0.5 -0.3 61.1 142.0 37.2 M M
36000 -48.4 -55.1 254 46 24 6.5 3.6 53.9 129.0 33.2 M M
34000 -47.6 -53.7 250 48 25 1.4 0.8 46.6 115.8 28.9 M M
32000 -47.0 -52.6 247 50 26 1.2 0.7 38.2 100.8 23.7 M M
30000 -45.3 -49.5 245 52 27 0.1 0.1 32.6 90.7 20.2 M M
29000 -46.0 -50.8 245 53 27 1.6 0.9 27.8 82.0 16.8 M M
28000 -45.5 -49.9 247 47 24 2.0 1.1 24.6 76.3 14.6 M M
27000 -45.2 -49.4 250 41 21 -6.3 -3.5 21.2 70.2 12.1 M M
26000 -44.7 -48.5 254 35 18 7.6 4.2 18.1 64.6 9.9 M M
25000 -42.3 -44.1 239 30 15 7.9 4.3 17.4 63.4 9.4 M M
24000 -39.9 -39.8 232 25 13 8.0 4.4 16.7 62.0 8.9 M M
23000 -37.3 -35.1 225 22 11 9.4 5.2 16.3 61.3 8.7 M M
22000 -34.5 -30.1 235 22 11 9.5 5.2 16.1 61.1 8.7 M M
21000 -31.7 -25.1 245 23 12 9.4 5.1 16.1 60.9 8.7 M M
20000 -28.9 -20.0 254 25 13 9.2 5.0 15.9 60.6 8.7 M M
19500 -27.5 -17.5 258 25 13 9.2 5.0 15.8 60.4 8.6 M M
19000 -26.1 -15.0 262 25 13 9.3 5.1 15.7 60.2 8.6 M M
18500 -24.8 -12.6 266 26 13 8.6 4.7 15.5 59.9 8.5 M M
18000 -24.1 -11.4 270 26 13 2.5 1.4 14.7 58.5 7.8 M M
17500 -23.2 -9.8 267 25 13 8.1 4.4 14.0 57.3 7.3 M M
17000 -22.1 -7.8 263 25 13 7.8 4.3 13.7 56.6 7.0 M M
16500 -20.9 -5.6 259 25 13 7.8 4.3 13.3 56.0 6.7 M M
16000 -19.2 -2.6 255 25 13 8.0 4.4 12.9 55.2 6.3 M M
15500 -18.0 -0.4 256 25 13 8.1 4.4 12.6 54.6 6.0 M M
15000 -16.8 1.8 257 26 13 8.1 4.4 12.3 54.1 5.8 M M
14500 -15.6 3.9 259 26 13 8.1 4.4 12.0 53.7 5.6 M M
14000 -14.4 6.1 260 25 13 8.1 4.4 11.8 53.2 5.4 M M
13500 -13.2 8.2 262 22 11 8.1 4.4 11.5 52.7 5.1 M M
13000 -12.0 10.4 265 19 10 8.2 4.5 11.2 52.2 4.9 M M
12500 -10.8 12.6 269 16 8 8.2 4.5 11.0 51.8 4.7 M M
12000 -9.6 14.7 275 13 7 8.2 4.5 10.8 51.4 4.5 M M
11500 -8.3 17.1 279 13 6 8.2 4.5 10.5 50.8 4.2 M M
11000 -7.1 19.2 284 12 6 8.2 4.5 10.2 50.4 4.0 M M
10500 -5.9 21.4 288 12 6 8.2 4.5 10.0 49.9 3.8 M M
10250 -5.3 22.5 291 12 6 8.2 4.5 9.8 49.7 3.7 M M
10000 -4.7 23.5 293 12 6 8.1 4.4 9.7 49.5 3.6 M M
9750 -4.1 24.6 295 12 6 7.5 4.1 9.6 49.3 3.5 M M
9500 -3.5 25.7 297 12 6 7.3 4.0 9.4 48.9 3.3 M M
9250 -3.0 26.6 298 13 7 7.3 4.0 9.2 48.6 3.1 M M
9000 -2.5 27.5 300 13 7 7.3 4.0 9.0 48.3 3.0 M M
8750 -1.9 28.6 305 13 7 7.3 4.0 8.8 47.9 2.8 M M
8500 -1.4 29.5 310 13 7 7.3 4.0 8.7 47.6 2.6 M M
8250 -0.8 30.6 315 13 7 7.3 4.0 8.5 47.3 2.4 M M
8000 -0.3 31.5 320 13 7 7.3 4.0 8.3 46.9 2.2 M M
7750 0.3 32.5 327 12 6 7.4 4.0 8.1 46.6 2.0 M M
7500 0.8 33.4 335 11 6 7.1 3.9 7.9 46.2 1.9 M M
7250 1.4 34.5 345 11 6 8.1 4.5 7.7 45.9 1.7 M M
7000 1.6 34.9 354 11 6 -6.0 -3.3 7.3 45.1 1.2 M M
6750 0.8 33.4 355 9 5 -7.8 -4.3 5.6 42.1 -0.4 86 0.4
6500 0.9 33.6 356 7 4 5.8 3.2 5.0 41.0 -1.0 76 0.4
6250 1.2 34.2 357 5 3 1.6 0.9 4.6 40.2 -1.4 59 0.3
6000 1.1 34.0 359 3 2 0.1 0.1 3.8 38.9 -2.2 53 0.3
5750 1.0 33.8 323 2 1 -4.4 -2.4 3.0 37.5 -3.0 48 0.2
5500 0.0 32.0 268 2 1 -24.1 -13.2 1.3 34.3 -4.8 71 0.4
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
11/23/2009 at 0800 MST | 11/23/2009 at 1100 MST
|
K index... +16.8 | K index... +9.9
|
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 -57.1 -70.8 282 28 14 2.4 1.3 | -56.3 -69.3 281 25 13 2.3 1.3
45000 -53.4 -64.1 287 31 16 2.3 1.3 | -52.8 -63.0 285 27 14 2.3 1.3
40000 -49.1 -56.4 283 33 17 2.9 1.6 | -48.6 -55.5 281 35 18 2.8 1.5
38000 -47.7 -53.9 281 34 17 0.7 0.4 | -47.2 -53.0 281 38 19 1.1 0.6
36000 -47.2 -53.0 277 34 18 0.7 0.4 | -46.5 -51.7 284 36 19 1.1 0.6
34000 -46.8 -52.2 274 35 18 0.7 0.4 | -45.7 -50.3 288 35 18 1.2 0.7
32000 -46.1 -51.0 274 34 17 1.1 0.6 | -45.2 -49.4 293 34 17 0.8 0.4
30000 -45.4 -49.7 274 32 17 1.0 0.6 | -44.7 -48.5 297 33 17 0.6 0.3
29000 -44.9 -48.8 269 29 15 2.1 1.1 | -44.2 -47.6 294 30 15 2.3 1.2
28000 -44.3 -47.7 260 25 13 2.1 1.1 | -43.5 -46.3 288 27 14 2.3 1.3
27000 -43.7 -46.7 247 22 11 2.0 1.1 | -42.8 -45.0 279 24 12 2.3 1.2
26000 -42.8 -45.0 236 20 10 5.0 2.7 | -42.1 -43.8 270 22 11 3.8 2.1
25000 -41.4 -42.5 234 19 10 4.7 2.6 | -41.0 -41.8 264 20 10 3.7 2.0
24000 -40.0 -40.0 231 17 9 4.6 2.5 | -39.9 -39.8 256 17 9 3.6 2.0
23000 -38.4 -37.1 228 16 8 8.2 4.5 | -38.6 -37.5 248 16 8 6.5 3.6
22000 -36.1 -33.0 228 16 8 7.8 4.3 | -36.7 -34.1 250 17 9 6.4 3.5
21000 -33.7 -28.7 227 16 8 7.9 4.3 | -34.8 -30.6 251 17 9 6.4 3.5
20000 -31.4 -24.5 232 16 8 7.9 4.3 | -32.8 -27.0 261 17 9 6.9 3.8
19500 -30.2 -22.4 237 15 8 7.9 4.3 | -31.8 -25.2 270 17 9 6.9 3.8
19000 -29.0 -20.2 242 15 8 7.9 4.3 | -30.7 -23.3 279 17 9 6.9 3.8
18500 -27.9 -18.2 248 16 8 7.9 4.3 | -29.2 -20.6 292 19 10 6.9 3.8
18000 -26.7 -16.1 253 16 8 7.5 4.1 | -28.2 -18.8 300 20 10 6.8 3.8
17500 -25.1 -13.2 263 16 8 7.3 4.0 | -27.2 -17.0 307 22 11 6.8 3.8
17000 -24.0 -11.2 271 16 8 6.4 3.5 | -26.1 -15.0 313 24 12 7.2 3.9
16500 -23.1 -9.6 279 16 8 6.1 3.3 | -25.0 -13.0 315 24 13 7.3 4.0
16000 -22.2 -8.0 287 17 9 6.0 3.3 | -23.9 -11.0 318 25 13 7.3 4.0
15500 -21.4 -6.5 294 18 9 5.8 3.2 | -22.9 -9.2 319 24 13 7.2 4.0
15000 -20.5 -4.9 301 20 10 6.0 3.3 | -21.8 -7.2 321 24 12 7.2 3.9
14500 -19.5 -3.1 306 22 11 7.0 3.9 | -20.8 -5.4 323 23 12 7.0 3.9
14000 -18.5 -1.3 309 24 12 7.0 3.9 | -19.7 -3.5 325 22 12 7.1 3.9
13500 -17.3 0.9 312 25 13 8.1 4.4 | -18.6 -1.5 327 22 11 7.7 4.2
13000 -16.2 2.8 313 25 13 8.0 4.4 | -17.5 0.5 329 22 11 7.6 4.2
12500 -15.0 5.0 314 25 13 7.9 4.3 | -16.4 2.5 331 22 11 7.5 4.1
12000 -13.8 7.2 315 25 13 7.9 4.3 | -15.3 4.5 334 22 12 7.6 4.2
11500 -12.7 9.1 315 24 12 8.2 4.5 | -14.0 6.8 335 22 11 8.5 4.6
11000 -11.5 11.3 316 23 12 8.2 4.5 | -12.8 9.0 336 22 11 8.6 4.7
10500 -10.3 13.5 316 21 11 7.7 4.2 | -11.4 11.5 336 21 11 9.2 5.1
10250 -9.7 14.5 316 21 11 7.8 4.3 | -10.8 12.6 335 21 11 9.2 5.0
10000 -9.2 15.4 316 20 10 7.5 4.1 | -10.1 13.8 334 20 10 9.1 5.0
9750 -8.6 16.5 316 19 10 6.9 3.8 | -9.4 15.1 334 20 10 9.0 5.0
9500 -8.1 17.4 317 18 9 6.8 3.7 | -8.7 16.3 334 20 10 9.0 5.0
9250 -7.6 18.3 317 17 9 7.0 3.8 | -8.0 17.6 334 19 10 9.0 5.0
9000 -7.1 19.2 317 17 9 6.4 3.5 | -7.4 18.7 334 19 10 9.1 5.0
8750 -6.7 19.9 319 16 8 5.9 3.2 | -6.7 19.9 335 19 10 9.1 5.0
8500 -6.3 20.7 322 16 8 6.1 3.4 | -6.0 21.2 336 18 9 9.2 5.0
8250 -5.8 21.6 325 15 8 5.8 3.2 | -5.3 22.5 338 18 9 8.9 4.9
8000 -5.4 22.3 328 15 8 5.1 2.8 | -4.7 23.5 339 17 9 8.4 4.6
7750 -5.1 22.8 334 15 8 4.8 2.6 | -4.1 24.6 341 17 9 8.4 4.6
7500 -4.7 23.5 339 16 8 4.9 2.7 | -3.4 25.9 343 16 8 8.4 4.6
7250 -4.4 24.1 343 16 8 4.9 2.7 | -2.8 27.0 344 16 8 7.8 4.3
7000 -4.0 24.8 349 16 8 4.9 2.7 | -2.3 27.9 345 15 8 7.3 4.0
6750 -3.7 25.3 354 17 9 4.9 2.7 | -1.7 28.9 347 14 7 7.9 4.3
6500 -3.3 26.1 359 17 9 4.8 2.6 | -1.2 29.8 348 13 7 6.3 3.4
6250 -3.0 26.6 360 15 8 4.6 2.5 | -0.9 30.4 348 11 6 4.7 2.6
6000 -2.7 27.1 360 12 6 4.3 2.4 | -0.6 30.9 347 9 4 4.4 2.4
5750 -2.3 27.9 360 9 5 5.4 3.0 | -0.3 31.5 345 6 3 6.9 3.8
5500 -1.8 28.8 360 7 4 9.2 5.0 | 0.4 32.7 344 6 3 14.0 7.7
11/23/2009 at 1400 MST | 11/23/2009 at 1700 MST
|
K index... +15.4 | K index... +16.1
|
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 -56.3 -69.3 273 25 13 2.6 1.4 | -56.8 -70.2 290 22 11 2.7 1.5
45000 -52.4 -62.3 279 24 12 2.6 1.4 | -52.7 -62.9 291 27 14 2.7 1.5
40000 -48.6 -55.5 291 37 19 2.5 1.4 | -49.2 -56.6 304 39 20 2.3 1.3
38000 -47.3 -53.1 294 42 22 1.3 0.7 | -47.9 -54.2 308 43 22 1.5 0.8
36000 -46.4 -51.5 297 41 21 1.4 0.7 | -46.9 -52.4 312 41 21 1.6 0.9
34000 -45.5 -49.9 300 40 21 1.4 0.8 | -46.0 -50.8 317 39 20 1.5 0.8
32000 -44.9 -48.8 304 38 20 0.9 0.5 | -45.2 -49.4 321 38 19 1.1 0.6
30000 -44.3 -47.7 309 36 19 0.8 0.4 | -44.5 -48.1 325 37 19 1.1 0.6
29000 -43.7 -46.7 309 35 18 2.7 1.5 | -44.0 -47.2 325 37 19 1.8 1.0
28000 -42.9 -45.2 309 34 18 2.7 1.5 | -43.5 -46.3 325 36 18 1.8 1.0
27000 -42.1 -43.8 308 33 17 2.7 1.5 | -42.9 -45.2 325 35 18 1.8 1.0
26000 -41.2 -42.2 308 32 16 2.9 1.6 | -42.4 -44.3 326 34 17 1.6 0.9
25000 -40.4 -40.7 310 30 16 2.9 1.6 | -41.9 -43.4 329 31 16 1.6 0.9
24000 -39.5 -39.1 311 29 15 2.9 1.6 | -41.4 -42.5 333 28 15 1.6 0.9
23000 -38.5 -37.3 314 27 14 4.8 2.6 | -40.6 -41.1 337 26 13 7.9 4.3
22000 -37.1 -34.8 317 26 13 4.9 2.7 | -38.4 -37.1 342 25 13 7.3 4.0
21000 -35.6 -32.1 321 24 12 4.9 2.7 | -36.2 -33.2 348 25 13 7.3 4.0
20000 -33.9 -29.0 326 24 12 6.6 3.6 | -33.9 -29.0 349 25 13 7.8 4.3
19500 -32.9 -27.2 329 24 12 6.7 3.7 | -32.8 -27.0 347 25 13 7.8 4.3
19000 -31.9 -25.4 331 24 13 6.7 3.7 | -31.6 -24.9 346 26 13 7.8 4.3
18500 -30.9 -23.6 334 25 13 6.7 3.7 | -30.4 -22.7 345 27 14 7.9 4.3
18000 -29.3 -20.7 336 25 13 7.7 4.2 | -29.3 -20.7 343 27 14 6.9 3.8
17500 -28.2 -18.8 337 26 13 7.6 4.2 | -27.8 -18.0 341 27 14 6.5 3.6
17000 -27.1 -16.8 337 26 13 7.3 4.0 | -26.9 -16.4 340 26 14 6.5 3.6
16500 -26.0 -14.8 335 27 14 7.2 4.0 | -25.9 -14.6 340 26 13 6.5 3.6
16000 -25.0 -13.0 334 27 14 7.5 4.1 | -24.9 -12.8 339 26 13 7.3 4.0
15500 -23.8 -10.8 333 27 14 8.0 4.4 | -23.8 -10.8 339 26 13 7.8 4.3
15000 -22.6 -8.7 331 27 14 8.2 4.5 | -22.6 -8.7 339 26 13 8.0 4.4
14500 -21.3 -6.3 330 26 13 8.8 4.9 | -21.4 -6.5 338 26 13 8.3 4.6
14000 -20.0 -4.0 329 25 13 8.8 4.8 | -20.2 -4.4 337 26 13 8.3 4.6
13500 -18.7 -1.7 327 25 13 8.5 4.6 | -18.9 -2.0 336 26 13 8.3 4.6
13000 -17.5 0.5 326 24 12 8.5 4.6 | -17.7 0.1 334 26 13 8.3 4.6
12500 -16.3 2.7 325 23 12 7.9 4.4 | -16.5 2.3 332 26 13 8.2 4.5
12000 -15.1 4.8 324 22 12 8.0 4.4 | -15.3 4.5 331 25 13 8.2 4.5
11500 -13.9 7.0 323 22 11 8.6 4.7 | -14.0 6.8 329 25 13 8.2 4.5
11000 -12.6 9.3 324 21 11 8.5 4.6 | -12.8 9.0 327 24 12 8.5 4.6
10500 -11.4 11.5 326 20 10 8.1 4.4 | -11.5 11.3 326 23 12 8.8 4.8
10250 -10.8 12.6 327 19 10 8.1 4.5 | -10.9 12.4 325 22 12 8.8 4.8
10000 -10.2 13.6 328 19 10 8.1 4.4 | -10.2 13.6 325 22 11 8.9 4.9
9750 -9.6 14.7 330 18 9 8.0 4.4 | -9.6 14.7 325 21 11 8.9 4.9
9500 -9.0 15.8 332 18 9 8.0 4.4 | -8.9 16.0 325 21 11 8.9 4.9
9250 -8.5 16.7 334 17 9 8.0 4.4 | -8.3 17.1 325 20 10 8.9 4.9
9000 -7.9 17.8 336 16 8 8.2 4.5 | -7.6 18.3 325 20 10 8.6 4.7
8750 -7.3 18.9 339 16 8 8.3 4.6 | -7.0 19.4 325 19 10 8.5 4.7
8500 -6.6 20.1 342 15 8 8.2 4.5 | -6.4 20.5 326 18 9 8.6 4.7
8250 -6.0 21.2 345 14 7 8.5 4.7 | -5.8 21.6 326 18 9 8.3 4.5
8000 -5.4 22.3 347 14 7 9.1 5.0 | -5.2 22.6 328 16 8 7.9 4.3
7750 -4.7 23.5 348 14 7 9.1 5.0 | -4.6 23.7 330 15 8 8.0 4.4
7500 -4.0 24.8 350 13 7 9.1 5.0 | -4.0 24.8 332 14 7 8.0 4.4
7250 -3.3 26.1 351 13 7 9.5 5.2 | -3.4 25.9 335 13 7 8.0 4.4
7000 -2.6 27.3 353 12 6 9.8 5.3 | -2.8 27.0 338 12 6 8.1 4.4
6750 -1.9 28.6 356 12 6 9.9 5.4 | -2.2 28.0 343 11 6 8.1 4.4
6500 -1.2 29.8 358 11 6 9.3 5.1 | -1.7 28.9 347 10 5 7.4 4.1
6250 -0.5 31.1 360 10 5 8.6 4.7 | -1.2 29.8 352 8 4 6.7 3.7
6000 0.1 32.2 002 9 5 8.7 4.8 | -0.7 30.7 360 6 3 7.3 4.0
5750 0.7 33.3 006 8 4 8.8 4.8 | -0.1 31.8 014 5 2 5.6 3.1
5500 1.3 34.3 004 7 4 9.0 5.0 | 0.1 32.2 014 3 2 1.5 0.8
________________________________________________________________________________
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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