Issued by NWS Denver/Boulder, CO
000
UXUS97 KBOU 251251
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
650 AM MDT Saturday October 25, 2008
This forecast is for Saturday October 25, 2008:
If the trigger temperature of 64.2 F/17.9 C is reached...then
Thermal Soaring Index....................... Good
Maximum rate of lift........................ 559 ft/min (2.8 m/s)
Maximum height of thermals.................. 12703 ft MSL (7380 ft AGL)
Forecast maximum temperature................... 72.0 F/22.7 C
Time of trigger temperature.................... 1115 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................. 10341 ft MSL (5018 ft AGL)
Thermal soaring outlook for Sunday 10/26....... Good
Wave Soaring Index............................. Poor
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 NVA
Potential height of wave....................... 35280 ft MSL (29957 ft AGL)
Wave soaring outlook for Sunday 10/26.......... Fair
Remarks...
Sunrise/Sunset.................... 07:21:02 / 18:06:55 MDT
Total possible sunshine........... 10 hr 45 min 53 sec (645 min 53 sec)
Altitude of sun at 12:43:35 MDT... 37.84 degrees
Upper air data from numerical model forecast valid on 10/25/2008 at 0600 MDT
Freezing level.................. 12633 ft MSL (7310 ft AGL)
Convective condensation level... 24105 ft MSL (18782 ft AGL)
Lifted condensation level....... 19333 ft MSL (14010 ft AGL)
Lifted index.................... +8.8
K index......................... -9.3
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 -65.7 -86.3 325 33 17 1.9 1.0 85.6 186.1 36.6 M M
45000 -62.6 -80.7 331 47 24 3.1 1.7 67.8 154.0 28.1 M M
40000 -57.7 -71.9 350 68 35 3.3 1.8 51.7 125.1 19.6 M M
38000 -54.2 -65.6 348 73 37 6.1 3.4 47.9 118.2 17.5 M M
36000 -50.5 -58.9 346 77 40 6.1 3.4 44.9 112.7 15.8 M M
34000 -46.1 -51.0 344 78 40 8.7 4.8 43.0 109.4 14.9 M M
32000 -40.9 -41.6 342 76 39 8.7 4.8 42.1 107.9 14.7 M M
30000 -35.4 -31.7 342 73 38 7.7 4.2 40.8 105.4 14.0 M M
29000 -33.1 -27.6 343 71 37 7.7 4.2 40.0 103.9 13.5 M M
28000 -30.8 -23.4 343 70 36 7.7 4.2 39.3 102.7 13.2 M M
27000 -28.4 -19.1 344 68 35 8.0 4.4 38.5 101.4 12.7 M M
26000 -26.0 -14.8 345 66 34 8.0 4.4 37.8 100.1 12.3 M M
25000 -23.6 -10.5 346 65 33 8.0 4.4 37.2 99.0 12.0 M M
24000 -21.4 -6.5 347 62 32 6.2 3.4 36.4 97.5 11.4 M M
23000 -19.6 -3.3 345 60 31 6.3 3.4 35.0 95.1 10.4 M M
22000 -17.7 0.1 344 57 29 6.3 3.4 33.8 92.9 9.5 M M
21000 -15.8 3.6 342 54 28 6.3 3.5 32.6 90.7 8.6 M M
20000 -13.9 7.0 341 52 27 6.3 3.5 31.3 88.4 7.6 M M
19500 -13.0 8.6 340 51 26 6.3 3.5 30.8 87.4 7.2 M M
19000 -12.1 10.2 339 49 25 6.2 3.4 30.2 86.4 6.7 M M
18500 -10.9 12.4 338 48 25 9.0 4.9 29.9 85.8 6.5 M M
18000 -9.6 14.7 336 46 24 8.7 4.8 29.7 85.4 6.3 M M
17500 -8.3 17.1 335 44 23 6.8 3.7 29.5 85.1 6.2 M M
17000 -7.6 18.3 333 41 21 5.4 3.0 28.7 83.7 5.5 M M
16500 -6.8 19.8 331 37 19 5.3 2.9 28.0 82.4 4.9 M M
16000 -5.8 21.6 328 33 17 4.1 2.2 26.6 79.9 3.7 M M
15500 -5.2 22.6 327 30 15 4.5 2.5 25.7 78.2 2.9 M M
15000 -4.4 24.1 326 27 14 6.0 3.3 25.0 76.9 2.3 M M
14500 -3.5 25.7 326 24 12 5.9 3.3 24.3 75.8 1.7 M M
14000 -2.5 27.5 326 22 11 6.7 3.7 23.8 74.8 1.2 M M
13500 -1.5 29.3 327 20 10 6.7 3.7 23.3 73.9 0.7 M M
13000 -0.6 30.9 328 17 9 6.2 3.4 22.7 72.9 0.3 M M
12500 0.4 32.7 326 15 8 6.2 3.4 22.1 71.8 -0.3 537 2.7
12000 1.3 34.3 325 13 7 6.3 3.4 21.6 70.8 -0.8 494 2.5
11500 2.2 36.0 325 12 6 6.4 3.5 21.0 69.8 -1.3 451 2.3
11000 3.1 37.6 324 11 6 4.6 2.5 20.4 68.7 -1.9 411 2.1
10500 3.7 38.7 324 11 6 4.2 2.3 19.5 67.1 -2.8 377 1.9
10250 4.1 39.4 324 11 6 5.0 2.7 19.1 66.4 -3.2 360 1.8
10000 4.5 40.1 325 12 6 6.4 3.5 18.8 65.8 -3.5 340 1.7
9750 5.0 41.0 326 12 6 6.8 3.7 18.5 65.4 -3.7 317 1.6
9500 5.5 41.9 327 13 7 6.5 3.6 18.3 64.9 -4.0 295 1.5
9250 6.0 42.8 327 14 7 7.3 4.0 18.1 64.5 -4.2 273 1.4
9000 6.5 43.7 324 15 8 8.3 4.5 17.9 64.2 -4.4 248 1.3
8750 7.1 44.8 321 17 9 8.2 4.5 17.8 64.0 -4.5 223 1.1
8500 7.7 45.9 319 19 10 8.4 4.6 17.7 63.8 -4.7 197 1.0
8250 8.3 46.9 316 20 10 6.8 3.7 17.5 63.6 -4.8 172 0.9
8000 8.8 47.8 310 21 11 5.3 2.9 17.2 63.0 -5.1 152 0.8
7750 9.2 48.6 305 23 12 5.9 3.2 16.9 62.4 -5.5 132 0.7
7500 9.6 49.3 300 24 13 5.2 2.8 16.6 61.9 -5.8 113 0.6
7250 9.9 49.8 297 25 13 3.6 2.0 16.2 61.1 -6.2 96 0.5
7000 10.1 50.2 295 24 12 2.5 1.4 15.7 60.2 -6.7 82 0.4
6750 10.3 50.5 292 23 12 4.2 2.3 15.2 59.3 -7.3 68 0.3
6500 10.6 51.1 290 22 11 -1.3 -0.7 14.7 58.4 -7.8 54 0.3
6250 10.1 50.2 285 19 10 -8.3 -4.6 13.4 56.2 -9.0 60 0.3
6000 9.6 49.3 278 15 8 -3.2 -1.8 12.2 54.0 -10.3 68 0.3
5750 9.1 48.4 266 12 6 -17.9 -9.8 11.0 51.8 -11.5 76 0.4
5500 6.1 43.0 247 9 5 -62.3 -34.2 7.3 45.1 -15.3 157 0.8
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
10/25/2008 at 0900 MDT | 10/25/2008 at 1200 MDT
|
K index... -3.8 | K index... +7.4
|
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 -66.3 -87.3 310 32 16 2.0 1.1 | -67.0 -88.6 308 33 17 0.6 0.3
45000 -62.8 -81.0 324 46 24 3.2 1.8 | -64.9 -84.8 326 42 22 4.6 2.5
40000 -58.0 -72.4 349 65 33 3.9 2.1 | -58.1 -72.6 338 57 29 5.7 3.1
38000 -54.1 -65.4 345 62 32 6.7 3.7 | -53.8 -64.8 335 57 30 7.3 4.0
36000 -50.1 -58.2 340 60 31 6.7 3.7 | -49.4 -56.9 333 58 30 7.3 4.0
34000 -45.4 -49.7 336 59 30 8.7 4.8 | -44.6 -48.3 330 58 30 8.3 4.5
32000 -39.5 -39.1 334 60 31 8.8 4.8 | -39.7 -39.5 327 58 30 8.3 4.6
30000 -34.7 -30.5 334 61 32 7.5 4.1 | -34.5 -30.1 326 58 30 7.2 4.0
29000 -32.5 -26.5 334 62 32 7.5 4.1 | -32.4 -26.3 326 58 30 7.3 4.0
28000 -30.3 -22.5 335 63 32 7.6 4.2 | -30.2 -22.4 326 58 30 7.3 4.0
27000 -28.3 -18.9 335 62 32 6.4 3.5 | -28.1 -18.6 326 57 29 6.9 3.8
26000 -26.4 -15.5 335 60 31 6.4 3.5 | -26.1 -15.0 325 56 29 6.9 3.8
25000 -24.5 -12.1 335 58 30 6.4 3.5 | -24.0 -11.2 325 55 28 6.9 3.8
24000 -22.6 -8.7 335 57 29 6.7 3.7 | -22.0 -7.6 324 54 28 7.0 3.8
23000 -20.6 -5.1 335 56 29 6.7 3.7 | -19.9 -3.8 324 52 27 7.0 3.8
22000 -18.6 -1.5 335 55 28 6.7 3.7 | -17.9 -0.2 323 50 26 7.0 3.9
21000 -16.4 2.5 335 54 28 7.9 4.3 | -15.8 3.6 323 49 25 6.8 3.7
20000 -14.1 6.6 336 52 27 7.9 4.3 | -13.9 7.0 323 49 25 6.8 3.7
19500 -12.9 8.8 336 52 27 7.9 4.3 | -12.9 8.8 323 49 25 6.8 3.7
19000 -11.7 10.9 336 51 26 7.9 4.3 | -11.9 10.6 323 49 25 6.7 3.7
18500 -10.5 13.1 336 50 26 7.7 4.2 | -10.9 12.4 322 48 25 6.6 3.6
18000 -9.4 15.1 337 48 25 7.8 4.3 | -9.9 14.2 322 47 24 6.6 3.6
17500 -8.2 17.2 337 46 23 7.6 4.2 | -9.0 15.8 322 46 23 6.9 3.8
17000 -6.5 20.3 336 42 22 7.6 4.2 | -7.4 18.7 322 43 22 6.9 3.8
16500 -5.4 22.3 335 39 20 6.8 3.8 | -6.3 20.7 323 41 21 8.2 4.5
16000 -4.4 24.1 334 37 19 6.7 3.7 | -5.1 22.8 323 39 20 8.2 4.5
15500 -3.4 25.9 332 34 18 6.4 3.5 | -3.9 25.0 323 36 19 8.1 4.4
15000 -2.5 27.5 331 31 16 6.0 3.3 | -2.6 27.3 323 34 17 8.0 4.4
14500 -1.6 29.1 329 29 15 5.8 3.2 | -1.4 29.5 322 31 16 7.8 4.3
14000 -0.8 30.6 329 26 13 4.5 2.5 | -0.3 31.5 322 28 15 7.3 4.0
13500 -0.1 31.8 329 23 12 4.5 2.5 | 0.8 33.4 322 26 13 7.3 4.0
13000 0.6 33.1 331 21 11 5.5 3.0 | 1.9 35.4 322 23 12 6.7 3.7
12500 1.5 34.7 333 18 10 5.3 2.9 | 2.9 37.2 321 19 10 6.8 3.7
12000 2.3 36.1 336 17 9 6.5 3.5 | 3.9 39.0 318 16 8 6.0 3.3
11500 3.3 37.9 339 15 8 6.4 3.5 | 4.8 40.6 314 13 7 6.1 3.3
11000 4.3 39.7 342 13 7 6.9 3.8 | 5.8 42.4 309 11 6 6.3 3.5
10500 5.3 41.5 342 11 6 6.9 3.8 | 6.7 44.1 302 9 5 6.2 3.4
10250 5.8 42.4 343 10 5 6.9 3.8 | 7.2 45.0 297 9 4 6.9 3.8
10000 6.3 43.3 341 9 5 6.8 3.7 | 7.8 46.0 297 9 4 7.7 4.2
9750 6.9 44.4 339 8 4 6.8 3.7 | 8.3 46.9 296 9 4 7.5 4.1
9500 7.4 45.3 336 7 4 6.9 3.8 | 8.9 48.0 295 9 4 7.5 4.1
9250 7.9 46.2 332 7 3 6.5 3.6 | 9.5 49.1 295 9 4 7.7 4.2
9000 8.3 46.9 324 6 3 6.2 3.4 | 10.0 50.0 295 9 5 7.8 4.3
8750 8.8 47.8 316 6 3 6.3 3.5 | 10.6 51.1 296 10 5 7.8 4.3
8500 9.3 48.7 309 7 3 6.4 3.5 | 11.2 52.2 296 11 6 7.6 4.2
8250 9.8 49.6 303 7 4 7.3 4.0 | 11.7 53.1 296 12 6 6.8 3.7
8000 10.4 50.7 302 9 4 7.8 4.3 | 12.2 54.0 295 14 7 6.3 3.4
7750 10.9 51.6 301 10 5 8.1 4.4 | 12.7 54.9 295 15 8 6.5 3.6
7500 11.5 52.7 300 11 6 6.6 3.6 | 13.1 55.6 294 17 9 6.1 3.3
7250 11.9 53.4 297 13 7 4.1 2.2 | 13.5 56.3 293 16 8 5.5 3.0
7000 12.2 54.0 295 15 8 3.3 1.8 | 13.9 57.0 290 14 7 5.4 3.0
6750 12.4 54.3 293 18 9 4.7 2.6 | 14.3 57.7 287 12 6 5.4 2.9
6500 12.6 54.7 291 19 10 -5.0 -2.7 | 14.7 58.5 283 10 5 5.9 3.2
6250 11.7 53.1 283 16 8 -13.5 -7.4 | 15.2 59.4 282 9 4 6.6 3.6
6000 10.8 51.4 272 14 7 -10.6 -5.8 | 15.7 60.3 280 7 4 5.5 3.0
5750 9.9 49.8 256 12 6 -13.7 -7.5 | 16.1 61.0 277 5 3 9.4 5.2
5500 8.6 47.5 241 10 5 -19.2 -10.6 | 17.2 63.0 275 5 3 20.3 11.2
10/25/2008 at 1500 MDT | 10/25/2008 at 1800 MDT
|
K index... +14.3 | K index... +13.1
|
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 -68.4 -91.1 298 31 16 1.4 0.8 | -69.2 -92.6 300 38 20 1.3 0.7
45000 -65.1 -85.2 316 38 20 5.3 2.9 | -66.2 -87.2 309 50 26 6.0 3.3
40000 -57.1 -70.8 327 51 26 6.3 3.5 | -56.7 -70.1 316 49 25 6.5 3.6
38000 -52.9 -63.2 326 52 27 7.1 3.9 | -52.6 -62.7 315 48 25 6.9 3.8
36000 -48.7 -55.7 325 53 27 7.0 3.9 | -48.5 -55.3 315 46 24 6.8 3.8
34000 -44.0 -47.2 322 54 28 8.2 4.5 | -44.1 -47.4 315 46 24 7.8 4.3
32000 -39.1 -38.4 318 56 29 8.2 4.5 | -39.5 -39.1 315 47 24 7.8 4.3
30000 -34.0 -29.2 317 57 29 7.3 4.0 | -34.3 -29.7 313 49 25 7.7 4.2
29000 -31.8 -25.2 317 58 30 7.3 4.0 | -32.0 -25.6 312 50 26 7.7 4.2
28000 -29.7 -21.5 317 58 30 7.3 4.0 | -29.7 -21.5 311 52 27 7.8 4.3
27000 -27.6 -17.7 317 58 30 6.9 3.8 | -27.6 -17.7 311 53 27 7.0 3.8
26000 -25.5 -13.9 316 56 29 6.9 3.8 | -25.5 -13.9 312 54 28 7.0 3.9
25000 -23.5 -10.3 316 55 28 6.9 3.8 | -23.4 -10.1 312 56 29 7.0 3.9
24000 -21.5 -6.7 316 54 28 6.7 3.7 | -21.4 -6.5 313 55 28 6.5 3.6
23000 -19.5 -3.1 317 53 27 6.7 3.7 | -19.5 -3.1 314 53 27 6.5 3.6
22000 -17.5 0.5 317 52 27 6.7 3.7 | -17.6 0.3 315 51 26 6.5 3.6
21000 -15.5 4.1 318 51 26 7.1 3.9 | -15.6 3.9 316 47 24 6.9 3.8
20000 -13.4 7.9 319 50 26 7.1 3.9 | -13.5 7.7 318 42 22 7.0 3.8
19500 -12.4 9.7 320 49 25 7.1 3.9 | -12.5 9.5 319 40 21 7.0 3.8
19000 -11.3 11.7 321 49 25 7.0 3.9 | -11.4 11.5 320 37 19 7.4 4.0
18500 -10.3 13.5 321 48 25 6.9 3.8 | -10.3 13.5 322 38 19 8.2 4.5
18000 -9.3 15.3 321 46 24 6.9 3.8 | -9.0 15.8 324 39 20 8.3 4.5
17500 -8.3 17.1 321 45 23 7.1 3.9 | -7.9 17.8 325 39 20 7.6 4.2
17000 -6.7 19.9 321 43 22 7.1 3.9 | -6.7 19.9 325 40 20 7.5 4.1
16500 -5.6 21.9 321 42 21 7.4 4.0 | -5.6 21.9 325 40 21 7.6 4.2
16000 -4.6 23.7 320 40 21 7.4 4.0 | -3.9 25.0 326 39 20 7.7 4.2
15500 -3.5 25.7 320 39 20 7.6 4.1 | -2.8 27.0 326 38 20 7.7 4.2
15000 -2.3 27.9 319 38 19 7.7 4.2 | -1.7 28.9 325 37 19 7.7 4.2
14500 -1.2 29.8 318 36 19 7.7 4.2 | -0.5 31.1 325 35 18 7.5 4.1
14000 -0.1 31.8 317 34 18 7.7 4.2 | 0.5 32.9 324 33 17 7.1 3.9
13500 1.1 34.0 316 32 17 7.7 4.2 | 1.6 34.9 322 31 16 7.1 3.9
13000 2.2 36.0 315 30 16 7.5 4.1 | 2.6 36.7 320 28 14 6.6 3.6
12500 3.3 37.9 314 28 14 7.5 4.1 | 3.6 38.5 318 25 13 6.6 3.6
12000 4.5 40.1 314 26 13 7.3 4.0 | 4.6 40.3 318 23 12 7.2 4.0
11500 5.6 42.1 313 23 12 7.4 4.1 | 5.6 42.1 318 22 11 7.1 3.9
11000 6.6 43.9 312 20 11 6.0 3.3 | 6.7 44.1 318 22 11 7.7 4.2
10500 7.5 45.5 311 19 10 6.0 3.3 | 7.9 46.2 317 23 12 7.7 4.3
10250 8.0 46.4 310 18 9 6.7 3.7 | 8.5 47.3 316 23 12 7.4 4.1
10000 8.5 47.3 308 18 9 7.4 4.1 | 9.0 48.2 312 24 13 7.1 3.9
9750 9.1 48.4 306 19 10 7.3 4.0 | 9.5 49.1 308 26 13 7.1 3.9
9500 9.6 49.3 305 19 10 7.3 4.0 | 10.1 50.2 304 28 14 7.2 3.9
9250 10.2 50.4 303 19 10 7.3 4.0 | 10.6 51.1 301 29 15 6.8 3.7
9000 10.7 51.3 303 19 10 7.2 4.0 | 11.1 52.0 298 30 15 6.5 3.6
8750 11.3 52.3 304 19 10 7.2 3.9 | 11.6 52.9 295 30 16 6.6 3.6
8500 11.8 53.2 304 19 10 7.4 4.1 | 12.1 53.8 292 31 16 6.6 3.6
8250 12.4 54.3 304 18 10 8.7 4.8 | 12.6 54.7 290 31 16 7.4 4.0
8000 13.1 55.6 305 18 9 9.4 5.2 | 13.2 55.8 289 30 15 7.9 4.4
7750 13.8 56.8 306 18 9 9.1 5.0 | 13.8 56.8 288 28 15 7.7 4.2
7500 14.5 58.1 306 17 9 9.5 5.2 | 14.4 57.9 288 27 14 8.2 4.5
7250 15.2 59.4 307 17 9 10.0 5.5 | 15.0 59.0 287 26 13 9.1 5.0
7000 16.0 60.8 308 16 8 10.0 5.5 | 15.7 60.3 287 25 13 9.3 5.1
6750 16.7 62.1 309 16 8 10.0 5.5 | 16.4 61.5 288 24 12 9.3 5.1
6500 17.5 63.5 310 16 8 10.1 5.5 | 17.1 62.8 288 23 12 9.1 5.0
6250 18.2 64.8 310 15 8 10.4 5.7 | 17.7 63.9 288 21 11 8.5 4.6
6000 19.0 66.2 311 15 8 9.7 5.3 | 18.4 65.1 289 19 10 9.6 5.3
5750 19.8 67.6 312 14 7 12.1 6.6 | 19.0 66.2 290 17 9 5.6 3.1
5500 20.9 69.6 313 13 7 19.3 10.6 | 19.0 66.2 291 13 7 -8.0 -4.4
________________________________________________________________________________
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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