Issued by NWS Denver/Boulder, CO
000
UXUS97 KBOU 261230
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
630 AM MDT Sunday October 26, 2008
This forecast is for Sunday October 26, 2008:
If the trigger temperature of 65.9 F/18.8 C is reached...then
Thermal Soaring Index....................... Fair
Maximum rate of lift........................ 205 ft/min (1.0 m/s)
Maximum height of thermals.................. 8436 ft MSL (3113 ft AGL)
Forecast maximum temperature................... 64.0 F/18.2 C
Time of trigger temperature.................... None
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................. 6863 ft MSL (1540 ft AGL)
Thermal soaring outlook for Monday 10/27....... Good
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 PVA
Potential height of wave....................... 40178 ft MSL (34855 ft AGL)
Wave soaring outlook for Monday 10/27.......... Poor
Remarks...
Sunrise/Sunset.................... 07:22:08 / 18:05:36 MDT
Total possible sunshine........... 10 hr 43 min 29 sec (643 min 29 sec)
Altitude of sun at 12:43:29 MDT... 37.50 degrees
Upper air data from numerical model forecast valid on 10/26/2008 at 0600 MDT
Freezing level.................. 12518 ft MSL (7195 ft AGL)
Convective condensation level... 17731 ft MSL (12408 ft AGL)
Lifted condensation level....... 14458 ft MSL (9134 ft AGL)
Lifted index.................... +8.1
K index......................... +12.7
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 -66.9 -88.4 299 54 28 1.8 1.0 84.1 183.5 38.3 M M
45000 -64.0 -83.2 294 63 33 3.4 1.9 66.2 151.1 29.8 M M
40000 -58.5 -73.3 297 70 36 4.0 2.2 50.9 123.7 22.0 M M
38000 -55.1 -67.2 302 70 36 5.9 3.2 46.9 116.5 19.9 M M
36000 -51.5 -60.7 308 70 36 5.9 3.2 43.8 110.8 18.2 M M
34000 -47.1 -52.8 310 70 36 8.5 4.7 41.8 107.2 17.2 M M
32000 -42.0 -43.6 311 69 36 8.6 4.7 40.8 105.5 17.0 M M
30000 -36.9 -34.4 310 67 34 8.6 4.7 39.9 103.9 16.7 M M
29000 -33.6 -28.5 308 64 33 8.6 4.7 39.4 102.8 16.5 M M
28000 -31.1 -24.0 307 62 32 8.8 4.8 39.0 102.3 16.5 M M
27000 -28.8 -19.8 307 61 31 7.3 4.0 38.2 100.8 16.0 M M
26000 -26.6 -15.9 307 59 30 7.3 4.0 37.2 99.0 15.4 M M
25000 -24.4 -11.9 307 57 29 7.3 4.0 36.4 97.5 14.9 M M
24000 -22.4 -8.3 309 55 28 5.6 3.1 35.2 95.3 14.1 M M
23000 -20.8 -5.4 313 52 27 5.5 3.0 33.6 92.5 13.0 M M
22000 -19.1 -2.4 316 49 25 5.5 3.0 32.1 89.8 11.9 M M
21000 -17.3 0.9 318 46 23 6.5 3.5 30.8 87.4 10.9 M M
20000 -15.4 4.3 317 42 22 6.5 3.6 29.6 85.3 10.0 M M
19500 -14.5 5.9 317 40 21 6.5 3.6 29.1 84.4 9.6 M M
19000 -13.5 7.7 316 39 20 6.5 3.6 28.6 83.4 9.2 M M
18500 -12.6 9.3 315 37 19 6.4 3.5 28.0 82.4 8.7 M M
18000 -11.6 11.1 313 35 18 6.5 3.6 27.4 81.4 8.2 M M
17500 -10.7 12.7 312 33 17 6.4 3.5 26.9 80.3 7.7 M M
17000 -9.8 14.4 310 31 16 6.4 3.5 26.3 79.3 7.2 M M
16500 -8.9 16.0 308 29 15 6.8 3.7 25.7 78.3 6.7 M M
16000 -7.3 18.9 305 26 13 7.2 4.0 25.1 77.1 6.2 M M
15500 -6.2 20.8 302 24 12 7.4 4.1 24.7 76.4 5.8 M M
15000 -5.1 22.8 301 23 12 7.5 4.1 24.3 75.7 5.5 M M
14500 -4.0 24.8 300 21 11 7.4 4.0 23.9 75.0 5.2 M M
14000 -3.0 26.6 302 20 10 7.2 3.9 23.5 74.3 4.8 M M
13500 -1.9 28.6 303 19 10 7.2 3.9 23.1 73.5 4.4 M M
13000 -0.9 30.4 306 19 10 7.1 3.9 22.6 72.7 4.0 M M
12500 0.2 32.4 309 20 10 7.1 3.9 22.2 72.0 3.6 M M
12000 1.2 34.2 310 21 11 7.4 4.1 21.8 71.2 3.2 M M
11500 2.3 36.1 309 23 12 7.4 4.0 21.4 70.6 2.9 M M
11000 3.4 38.1 307 25 13 7.1 3.9 21.0 69.8 2.5 M M
10500 4.5 40.1 304 26 13 7.0 3.9 20.6 69.1 2.1 M M
10250 5.0 41.0 303 26 14 6.7 3.7 20.4 68.7 1.9 M M
10000 5.4 41.7 303 26 13 6.5 3.6 20.1 68.2 1.7 M M
9750 5.9 42.6 302 25 13 6.6 3.6 19.9 67.7 1.4 M M
9500 6.4 43.5 302 25 13 6.4 3.5 19.6 67.3 1.2 M M
9250 6.9 44.4 302 24 12 6.1 3.4 19.3 66.8 0.9 M M
9000 7.3 45.1 303 23 12 6.0 3.3 19.1 66.3 0.7 M M
8750 7.8 46.0 303 22 11 6.2 3.4 18.8 65.8 0.4 M M
8500 8.2 46.8 304 21 11 5.4 3.0 18.5 65.3 0.1 M M
8250 8.6 47.5 305 21 11 4.4 2.4 18.1 64.6 -0.3 193 1.0
8000 8.9 48.0 306 20 10 4.4 2.4 17.7 63.8 -0.7 175 0.9
7750 9.2 48.6 307 19 10 4.5 2.4 17.3 63.1 -1.1 158 0.8
7500 9.5 49.1 308 18 9 3.2 1.7 16.8 62.3 -1.5 142 0.7
7250 9.7 49.5 308 17 9 2.1 1.2 16.3 61.3 -2.0 129 0.7
7000 9.9 49.8 308 15 8 2.6 1.5 15.7 60.3 -2.6 116 0.6
6750 10.1 50.2 309 14 7 1.6 0.9 15.2 59.3 -3.2 104 0.5
6500 10.1 50.2 310 11 6 -0.3 -0.2 14.5 58.0 -3.9 95 0.5
6250 10.1 50.2 313 8 4 -0.3 -0.2 13.7 56.6 -4.6 89 0.5
6000 10.0 50.0 319 5 3 -1.1 -0.6 12.9 55.2 -5.4 83 0.4
5750 9.7 49.5 329 3 1 -9.5 -5.2 11.9 53.3 -6.5 86 0.4
5500 8.5 47.3 271 1 0 -20.8 -11.4 9.9 49.8 -8.5 114 0.6
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
10/26/2008 at 0900 MDT | 10/26/2008 at 1200 MDT
|
K index... +3.7 | K index... -10.7
|
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 -67.6 -89.7 303 57 29 1.8 1.0 | -67.3 -89.1 304 62 32 1.2 0.6
45000 -64.5 -84.1 305 66 34 3.9 2.1 | -65.1 -85.2 305 72 37 3.4 1.9
40000 -58.7 -73.7 306 72 37 3.6 2.0 | -59.9 -75.8 314 78 40 3.1 1.7
38000 -55.2 -67.4 307 72 37 6.1 3.3 | -56.1 -69.0 312 78 40 6.8 3.7
36000 -51.1 -60.0 309 72 37 6.1 3.3 | -51.5 -60.7 309 77 40 6.8 3.7
34000 -46.7 -52.1 310 72 37 8.2 4.5 | -46.9 -52.4 309 75 39 8.0 4.4
32000 -41.8 -43.2 310 71 37 8.1 4.5 | -42.1 -43.8 309 74 38 8.0 4.4
30000 -36.7 -34.1 311 71 36 8.7 4.8 | -36.9 -34.4 310 71 37 9.1 5.0
29000 -34.1 -29.4 311 70 36 8.7 4.8 | -34.2 -29.6 310 70 36 9.1 5.0
28000 -31.4 -24.5 312 70 36 8.8 4.8 | -31.4 -24.5 310 68 35 9.2 5.0
27000 -29.1 -20.4 312 69 36 7.3 4.0 | -29.0 -20.2 310 65 34 7.4 4.1
26000 -26.9 -16.4 312 68 35 7.3 4.0 | -26.8 -16.2 311 62 32 7.4 4.0
25000 -24.7 -12.5 311 66 34 7.3 4.0 | -24.6 -12.3 311 58 30 7.4 4.0
24000 -22.7 -8.9 311 63 33 5.5 3.0 | -22.5 -8.5 312 56 29 6.4 3.5
23000 -21.1 -6.0 311 59 30 5.5 3.0 | -20.6 -5.1 314 55 28 6.4 3.5
22000 -19.4 -2.9 312 55 28 5.5 3.0 | -18.7 -1.7 315 55 28 6.4 3.5
21000 -17.6 0.3 311 51 26 6.5 3.6 | -16.9 1.6 315 54 28 5.7 3.1
20000 -15.7 3.7 308 47 24 6.5 3.6 | -15.2 4.6 314 53 27 5.7 3.1
19500 -14.2 6.4 307 44 23 6.5 3.6 | -13.9 7.0 313 52 27 5.8 3.2
19000 -13.2 8.2 305 42 22 6.7 3.7 | -13.1 8.4 313 50 26 4.4 2.4
18500 -12.2 10.0 305 41 21 6.7 3.7 | -12.5 9.5 313 48 25 4.3 2.4
18000 -11.2 11.8 304 39 20 6.6 3.6 | -11.8 10.8 313 46 24 5.0 2.7
17500 -10.3 13.5 304 38 20 6.3 3.5 | -10.9 12.4 314 45 23 6.3 3.5
17000 -9.4 15.1 304 37 19 6.3 3.4 | -10.0 14.0 316 43 22 6.2 3.4
16500 -8.4 16.9 305 36 19 6.9 3.8 | -9.0 15.8 318 42 22 7.0 3.8
16000 -7.4 18.7 305 35 18 6.9 3.8 | -8.0 17.6 320 42 22 6.9 3.8
15500 -6.4 20.5 305 34 18 6.7 3.7 | -6.9 19.6 322 42 21 7.2 3.9
15000 -5.4 22.3 304 33 17 6.5 3.6 | -5.8 21.6 322 40 21 7.3 4.0
14500 -4.4 24.1 304 32 16 6.4 3.5 | -4.7 23.5 323 38 20 7.1 3.9
14000 -3.5 25.7 304 31 16 6.1 3.3 | -3.7 25.3 321 36 18 7.0 3.8
13500 -2.6 27.3 304 30 15 5.9 3.2 | -2.7 27.1 320 33 17 7.0 3.8
13000 -1.8 28.8 303 28 14 5.3 2.9 | -1.7 28.9 317 31 16 6.9 3.8
12500 -1.1 30.0 301 26 13 5.5 3.0 | -0.7 30.7 313 30 15 7.0 3.8
12000 -0.2 31.6 298 25 13 6.9 3.8 | 0.3 32.5 308 29 15 7.0 3.9
11500 0.8 33.4 293 24 12 6.8 3.7 | 1.3 34.3 304 29 15 6.6 3.6
11000 1.7 35.1 290 23 12 6.1 3.3 | 2.1 35.8 300 27 14 4.4 2.4
10500 2.7 36.9 286 22 11 5.5 3.0 | 2.7 36.9 296 25 13 3.1 1.7
10250 3.0 37.4 285 21 11 3.2 1.8 | 2.7 36.9 294 23 12 -0.8 -0.4
10000 3.2 37.8 286 19 10 2.2 1.2 | 2.6 36.7 292 21 11 -1.8 -1.0
9750 3.3 37.9 286 16 8 2.8 1.5 | 2.5 36.5 290 19 10 -1.2 -0.6
9500 3.5 38.3 287 14 7 1.6 0.9 | 2.3 36.1 287 17 9 -2.6 -1.4
9250 3.5 38.3 290 12 6 -0.3 -0.2 | 2.0 35.6 284 14 7 -4.3 -2.3
9000 3.5 38.3 296 9 5 -0.4 -0.2 | 1.7 35.1 281 11 6 -4.1 -2.3
8750 3.4 38.1 306 6 3 -0.7 -0.4 | 1.4 34.5 275 8 4 -4.2 -2.3
8500 3.4 38.1 328 4 2 0.8 0.4 | 1.1 34.0 267 5 3 -0.9 -0.5
8250 3.6 38.5 004 4 2 2.3 1.3 | 1.2 34.2 277 2 1 1.8 1.0
8000 3.7 38.7 030 6 3 1.8 1.0 | 1.3 34.3 055 1 1 0.2 0.1
7750 3.8 38.8 044 8 4 2.4 1.3 | 1.4 34.5 074 4 2 3.8 2.1
7500 4.1 39.4 050 10 5 3.7 2.0 | 1.9 35.4 074 6 3 9.1 5.0
7250 4.4 39.9 052 12 6 4.3 2.4 | 2.6 36.7 072 6 3 9.8 5.4
7000 4.7 40.5 054 14 7 3.9 2.1 | 3.4 38.1 070 6 3 9.7 5.3
6750 5.0 41.0 055 15 8 5.5 3.0 | 4.1 39.4 069 6 3 10.1 5.5
6500 5.5 41.9 058 14 7 7.2 3.9 | 4.9 40.8 068 6 3 10.7 5.9
6250 6.0 42.8 061 13 6 6.4 3.5 | 5.7 42.3 067 6 3 9.3 5.1
6000 6.5 43.7 065 11 6 7.9 4.3 | 6.4 43.5 066 6 3 14.1 7.7
5750 7.2 45.0 067 9 5 10.1 5.6 | 7.8 46.0 065 6 3 20.2 11.1
5500 7.9 46.2 069 7 4 9.9 5.4 | 9.2 48.6 065 7 3 16.3 8.9
10/26/2008 at 1500 MDT | 10/26/2008 at 1800 MDT
|
K index... +3.0 | K index... -1.8
|
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 -67.5 -89.5 310 60 31 1.9 1.0 | -66.7 -88.1 316 59 30 1.4 0.8
45000 -64.4 -83.9 310 73 38 2.9 1.6 | -64.3 -83.7 321 76 39 2.8 1.5
40000 -60.0 -76.0 318 83 43 2.4 1.3 | -60.1 -76.2 321 83 43 2.4 1.3
38000 -56.1 -69.0 317 80 41 7.0 3.8 | -56.5 -69.7 324 82 42 6.5 3.6
36000 -51.4 -60.5 315 75 39 7.0 3.8 | -52.1 -61.8 328 80 41 6.5 3.6
34000 -46.7 -52.1 315 74 38 8.3 4.5 | -47.2 -53.0 327 78 40 9.1 5.0
32000 -41.7 -43.1 317 75 38 8.3 4.5 | -41.8 -43.2 323 76 39 9.1 5.0
30000 -36.8 -34.2 318 75 38 8.2 4.5 | -36.6 -33.9 322 75 39 8.2 4.5
29000 -34.3 -29.7 319 74 38 8.2 4.5 | -34.2 -29.6 322 74 38 8.2 4.5
28000 -31.9 -25.4 319 74 38 8.3 4.5 | -31.7 -25.1 323 73 38 8.3 4.5
27000 -29.6 -21.3 320 72 37 7.3 4.0 | -29.5 -21.1 325 71 37 6.9 3.8
26000 -27.4 -17.3 321 69 36 7.3 4.0 | -27.5 -17.5 327 69 35 6.9 3.8
25000 -25.2 -13.4 322 66 34 7.3 4.0 | -25.4 -13.7 331 66 34 6.9 3.8
24000 -23.2 -9.8 322 63 32 6.3 3.4 | -23.4 -10.1 331 63 32 6.8 3.7
23000 -21.3 -6.3 319 59 30 6.3 3.4 | -21.3 -6.3 327 59 30 6.8 3.7
22000 -19.4 -2.9 315 55 28 6.3 3.4 | -19.3 -2.7 323 55 28 6.8 3.7
21000 -17.4 0.7 314 53 27 6.7 3.7 | -17.4 0.7 322 54 28 5.8 3.2
20000 -15.4 4.3 314 51 26 6.7 3.7 | -15.7 3.7 325 55 28 5.8 3.2
19500 -14.4 6.1 314 50 26 6.6 3.6 | -14.4 6.1 326 55 29 5.7 3.1
19000 -13.2 8.2 316 49 25 2.4 1.3 | -13.5 7.7 328 56 29 6.4 3.5
18500 -12.8 9.0 320 49 25 2.4 1.3 | -12.6 9.3 331 55 28 6.3 3.5
18000 -12.5 9.5 323 49 25 3.9 2.1 | -11.6 11.1 333 55 28 5.9 3.2
17500 -11.6 11.1 323 46 24 6.6 3.6 | -10.8 12.6 333 53 27 5.1 2.8
17000 -10.6 12.9 322 42 22 6.8 3.7 | -10.1 13.8 333 52 27 5.2 2.8
16500 -9.8 14.4 322 41 21 3.5 1.9 | -9.4 15.1 332 50 26 3.6 2.0
16000 -9.3 15.3 322 41 21 3.7 2.0 | -8.9 16.0 331 48 25 3.7 2.0
15500 -8.6 16.5 322 40 21 6.9 3.8 | -8.3 17.1 329 46 24 4.7 2.6
15000 -7.5 18.5 320 37 19 7.6 4.2 | -7.6 18.3 325 42 22 5.0 2.7
14500 -6.4 20.5 319 35 18 8.2 4.5 | -6.8 19.8 321 39 20 6.2 3.4
14000 -5.1 22.8 318 33 17 8.5 4.7 | -5.8 21.6 320 36 19 7.1 3.9
13500 -3.9 25.0 318 31 16 8.3 4.6 | -4.7 23.5 318 33 17 7.2 4.0
13000 -2.7 27.1 318 29 15 7.8 4.3 | -3.7 25.3 318 30 15 7.3 4.0
12500 -1.6 29.1 318 27 14 7.8 4.3 | -2.6 27.3 317 26 14 6.9 3.8
12000 -0.5 31.1 319 25 13 7.5 4.1 | -1.8 28.8 318 24 12 5.9 3.2
11500 0.6 33.1 321 24 12 7.1 3.9 | -0.9 30.4 320 21 11 5.6 3.1
11000 1.6 34.9 323 22 11 5.9 3.3 | -0.2 31.6 322 19 10 4.6 2.5
10500 2.5 36.5 324 21 11 4.0 2.2 | 0.4 32.7 325 17 9 3.9 2.2
10250 2.6 36.7 324 19 10 0.4 0.2 | 0.6 33.1 325 16 8 2.7 1.5
10000 2.6 36.7 323 18 9 0.2 0.1 | 0.9 33.6 325 15 8 2.8 1.5
9750 2.6 36.7 322 17 9 0.6 0.3 | 1.1 34.0 325 13 7 2.8 1.5
9500 2.6 36.7 321 16 8 -0.8 -0.4 | 1.3 34.3 325 12 6 2.6 1.4
9250 2.5 36.5 324 12 6 -2.1 -1.2 | 1.4 34.5 324 10 5 2.6 1.4
9000 2.3 36.1 329 8 4 -2.0 -1.1 | 1.6 34.9 323 7 4 2.3 1.3
8750 2.2 36.0 341 5 3 -1.1 -0.6 | 1.8 35.2 321 5 3 3.3 1.8
8500 2.3 36.1 009 3 2 4.6 2.5 | 2.2 36.0 327 3 2 6.3 3.4
8250 2.8 37.0 028 4 2 7.9 4.3 | 2.7 36.9 348 3 1 7.6 4.1
8000 3.3 37.9 042 4 2 6.7 3.7 | 3.3 37.9 016 3 1 6.8 3.8
7750 3.9 39.0 051 5 3 8.3 4.5 | 3.8 38.8 039 3 2 8.4 4.6
7500 4.6 40.3 052 5 3 10.0 5.5 | 4.5 40.1 041 4 2 9.9 5.4
7250 5.3 41.5 052 5 3 9.9 5.4 | 5.3 41.5 042 4 2 9.6 5.3
7000 6.1 43.0 052 5 3 10.0 5.5 | 6.0 42.8 043 4 2 9.7 5.3
6750 6.8 44.2 052 6 3 10.0 5.5 | 6.7 44.1 043 5 2 9.6 5.3
6500 7.6 45.7 051 6 3 10.3 5.7 | 7.4 45.3 043 5 3 9.6 5.3
6250 8.3 46.9 051 6 3 9.1 5.0 | 8.2 46.8 042 6 3 9.8 5.4
6000 9.1 48.4 050 6 3 13.6 7.5 | 8.8 47.8 042 6 3 7.8 4.3
5750 10.4 50.7 050 6 3 19.1 10.5 | 9.3 48.7 041 5 3 5.8 3.2
5500 11.7 53.1 049 6 3 14.9 8.2 | 9.8 49.6 039 5 2 7.3 4.0
________________________________________________________________________________
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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