Issued by NWS Denver/Boulder, CO
000
UXUS97 KBOU 260034
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
634 PM MDT Saturday October 25, 2008
This forecast is for Sunday October 26, 2008:
If the trigger temperature of 65.2 F/18.4 C is reached...then
Thermal Soaring Index....................... Fair
Maximum rate of lift........................ 217 ft/min (1.1 m/s)
Maximum height of thermals.................. 8634 ft MSL (3311 ft AGL)
Forecast maximum temperature................... 64.0 F/18.2 C
Time of trigger temperature.................... 1415 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................. 6680 ft MSL (1357 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 NVA
Potential height of wave....................... 45607 ft MSL (40284 ft AGL)
Wave soaring outlook for Monday 10/27.......... Poor
Remarks... None
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.................. 12229 ft MSL (6906 ft AGL)
Convective condensation level... 20088 ft MSL (14765 ft AGL)
Lifted condensation level....... 15228 ft MSL (9905 ft AGL)
Lifted index.................... +9.4
K index......................... +3.8
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 -68.0 -90.4 301 51 26 0.9 0.5 82.0 179.6 37.1 M M
45000 -66.0 -86.8 298 60 31 4.7 2.6 62.5 144.5 27.6 M M
40000 -58.6 -73.5 293 63 33 6.0 3.3 50.3 122.6 21.6 M M
38000 -54.1 -65.4 297 63 32 7.6 4.2 47.9 118.3 20.6 M M
36000 -49.5 -57.1 300 62 32 7.6 4.1 46.2 115.2 19.9 M M
34000 -44.7 -48.5 303 62 32 8.4 4.6 44.8 112.6 19.4 M M
32000 -39.7 -39.5 304 63 32 8.4 4.6 43.7 110.7 19.1 M M
30000 -34.6 -30.3 306 63 32 7.0 3.8 41.7 107.1 18.1 M M
29000 -32.5 -26.5 308 62 32 7.0 3.8 40.7 105.2 17.5 M M
28000 -30.5 -22.9 309 62 32 7.0 3.8 39.7 103.5 17.0 M M
27000 -28.3 -18.9 308 61 31 7.1 3.9 38.7 101.6 16.3 M M
26000 -26.2 -15.2 308 60 31 7.2 3.9 37.6 99.7 15.7 M M
25000 -24.1 -11.4 307 60 31 7.2 3.9 36.7 98.1 15.1 M M
24000 -22.0 -7.6 308 58 30 6.9 3.8 35.7 96.3 14.5 M M
23000 -20.0 -4.0 310 57 29 6.9 3.8 34.6 94.3 13.7 M M
22000 -17.9 -0.2 312 55 28 6.9 3.8 33.6 92.6 13.1 M M
21000 -15.9 3.4 312 52 27 6.6 3.6 32.5 90.6 12.3 M M
20000 -13.9 7.0 311 47 24 6.6 3.6 31.4 88.5 11.4 M M
19500 -13.0 8.6 310 45 23 6.6 3.6 30.9 87.6 11.1 M M
19000 -12.0 10.4 309 42 22 6.4 3.5 30.4 86.7 10.7 M M
18500 -11.1 12.0 307 39 20 5.8 3.2 29.7 85.5 10.2 M M
18000 -10.2 13.6 304 36 18 5.9 3.2 29.0 84.3 9.6 M M
17500 -9.4 15.1 301 32 17 5.4 3.0 28.3 83.0 9.1 M M
17000 -8.6 16.5 298 30 15 5.3 2.9 27.6 81.6 8.5 M M
16500 -7.8 18.0 295 27 14 5.2 2.9 26.9 80.3 7.8 M M
16000 -6.7 19.9 294 24 12 5.0 2.8 25.6 78.2 6.8 M M
15500 -5.9 21.4 295 22 12 5.5 3.0 24.9 76.8 6.1 M M
15000 -5.1 22.8 297 21 11 5.7 3.1 24.2 75.6 5.5 M M
14500 -4.2 24.4 301 20 10 5.9 3.2 23.6 74.4 5.0 M M
14000 -3.4 25.9 304 20 10 6.1 3.4 22.9 73.3 4.4 M M
13500 -2.5 27.5 307 19 10 6.3 3.4 22.4 72.2 3.9 M M
13000 -1.5 29.3 308 20 10 7.0 3.8 21.9 71.3 3.4 M M
12500 -0.5 31.1 309 20 10 7.0 3.8 21.4 70.5 3.0 M M
12000 0.6 33.1 308 20 10 7.5 4.1 21.0 69.8 2.6 M M
11500 1.7 35.1 307 20 10 7.4 4.1 20.6 69.1 2.3 M M
11000 2.8 37.0 305 20 11 7.5 4.1 20.3 68.5 1.9 M M
10500 3.9 39.0 303 21 11 7.5 4.1 19.9 67.8 1.6 M M
10250 4.5 40.1 302 21 11 7.2 4.0 19.7 67.5 1.4 M M
10000 5.0 41.0 302 21 11 7.0 3.9 19.5 67.1 1.2 M M
9750 5.5 41.9 302 20 10 7.1 3.9 19.3 66.7 1.0 M M
9500 6.0 42.8 301 20 10 7.0 3.9 19.1 66.4 0.8 M M
9250 6.5 43.7 301 20 10 6.8 3.7 18.9 66.0 0.6 M M
9000 7.0 44.6 301 19 10 6.6 3.6 18.6 65.5 0.3 M M
8750 7.5 45.5 302 18 9 6.8 3.7 18.4 65.1 0.1 M M
8500 8.0 46.4 302 17 9 6.4 3.5 18.2 64.7 -0.1 206 1.0
8250 8.5 47.3 302 17 9 5.8 3.2 17.9 64.2 -0.4 185 0.9
8000 8.9 48.0 302 16 8 5.7 3.1 17.6 63.6 -0.7 165 0.8
7750 9.3 48.7 302 15 8 5.9 3.2 17.3 63.1 -1.0 145 0.7
7500 9.8 49.6 302 14 7 4.6 2.5 16.9 62.5 -1.3 125 0.6
7250 10.0 50.0 303 13 6 3.3 1.8 16.5 61.6 -1.8 110 0.6
7000 10.3 50.5 303 11 6 4.0 2.2 16.0 60.8 -2.2 94 0.5
6750 10.6 51.1 304 10 5 2.7 1.5 15.5 60.0 -2.7 79 0.4
6500 10.7 51.3 301 8 4 0.4 0.2 14.9 58.8 -3.3 68 0.3
6250 10.7 51.3 292 6 3 -0.4 -0.2 14.2 57.5 -4.1 61 0.3
6000 10.6 51.1 278 5 2 0.3 0.2 13.4 56.1 -4.8 54 0.3
5750 10.1 50.2 252 4 2 -21.5 -11.8 12.2 53.9 -6.1 62 0.3
5500 7.0 44.6 216 4 2 -58.4 -32.0 8.3 47.0 -10.0 149 0.8
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
10/26/2008 at 0900 MDT | 10/26/2008 at 1200 MDT
|
K index... +4.5 | K index... -2.9
|
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 -68.6 -91.5 305 51 26 2.5 1.4 | -68.3 -90.9 305 54 28 1.7 0.9
45000 -64.2 -83.6 305 57 29 4.1 2.2 | -65.4 -85.7 304 62 32 3.8 2.1
40000 -58.1 -72.6 296 64 33 5.5 3.0 | -59.3 -74.7 303 66 34 5.8 3.2
38000 -53.9 -65.0 299 62 32 7.1 3.9 | -54.6 -66.3 305 66 34 7.8 4.3
36000 -49.6 -57.3 303 60 31 7.1 3.9 | -50.0 -58.0 307 65 33 7.8 4.3
34000 -44.9 -48.8 306 60 31 8.4 4.6 | -45.1 -49.2 309 64 33 8.3 4.6
32000 -39.8 -39.6 309 61 32 8.4 4.6 | -40.1 -40.2 311 64 33 8.3 4.6
30000 -34.5 -30.1 311 61 32 7.6 4.2 | -35.4 -31.7 312 63 32 7.5 4.1
29000 -32.2 -26.0 312 61 31 7.6 4.2 | -32.6 -26.7 312 62 32 7.5 4.1
28000 -30.0 -22.0 313 61 31 7.7 4.2 | -30.4 -22.7 311 61 31 7.6 4.1
27000 -27.9 -18.2 313 61 31 6.8 3.7 | -28.3 -18.9 312 61 32 7.0 3.8
26000 -25.9 -14.6 312 61 31 6.8 3.7 | -26.2 -15.2 312 62 32 7.0 3.8
25000 -23.8 -10.8 311 61 31 6.8 3.7 | -24.1 -11.4 312 62 32 7.0 3.8
24000 -22.0 -7.6 310 60 31 5.9 3.2 | -22.2 -8.0 313 62 32 6.3 3.5
23000 -20.2 -4.4 309 57 29 5.9 3.2 | -20.3 -4.5 313 59 31 6.3 3.5
22000 -18.5 -1.3 308 54 28 5.9 3.2 | -18.4 -1.1 313 57 29 6.4 3.5
21000 -16.8 1.8 307 51 26 5.5 3.0 | -16.7 1.9 314 54 28 5.0 2.7
20000 -15.2 4.6 307 46 24 5.4 3.0 | -15.3 4.5 316 49 25 5.0 2.7
19500 -14.4 6.1 307 44 23 5.5 3.0 | -14.5 5.9 317 47 24 5.0 2.7
19000 -13.5 7.7 307 42 21 5.8 3.2 | -13.8 7.2 318 45 23 5.5 3.0
18500 -12.6 9.3 306 40 20 6.5 3.5 | -12.9 8.8 317 44 23 6.2 3.4
18000 -11.7 10.9 306 38 19 6.5 3.5 | -11.9 10.6 317 43 22 6.2 3.4
17500 -10.7 12.7 305 36 18 6.3 3.5 | -11.0 12.2 317 42 21 6.8 3.7
17000 -9.8 14.4 305 34 18 6.3 3.5 | -10.0 14.0 317 41 21 6.7 3.7
16500 -8.4 16.9 305 32 17 6.3 3.5 | -9.0 15.8 316 40 21 6.8 3.7
16000 -7.4 18.7 306 31 16 6.3 3.5 | -7.4 18.7 315 38 20 6.8 3.8
15500 -6.5 20.3 306 30 16 6.1 3.3 | -6.4 20.5 314 36 19 7.0 3.8
15000 -5.6 21.9 307 29 15 6.0 3.3 | -5.4 22.3 313 35 18 7.0 3.9
14500 -4.8 23.4 308 28 15 6.1 3.4 | -4.3 24.3 312 33 17 6.8 3.7
14000 -3.8 25.2 308 27 14 6.3 3.4 | -3.4 25.9 313 31 16 6.7 3.7
13500 -2.9 26.8 308 26 14 6.1 3.3 | -2.4 27.7 313 29 15 6.8 3.7
13000 -2.1 28.2 308 25 13 5.4 3.0 | -1.4 29.5 311 29 15 7.1 3.9
12500 -1.4 29.5 308 23 12 5.6 3.1 | -0.4 31.3 308 30 15 6.9 3.8
12000 -0.4 31.3 309 21 11 6.6 3.6 | 0.5 32.9 305 30 15 6.1 3.4
11500 0.5 32.9 310 20 10 6.6 3.6 | 1.4 34.5 300 30 16 5.9 3.2
11000 1.5 34.7 311 18 9 7.0 3.8 | 2.1 35.8 298 28 14 4.4 2.4
10500 2.5 36.5 311 17 9 6.6 3.6 | 2.7 36.9 296 24 13 3.2 1.8
10250 3.0 37.4 312 16 8 5.5 3.0 | 2.8 37.0 295 22 11 -0.2 -0.1
10000 3.4 38.1 312 15 8 5.0 2.8 | 2.8 37.0 294 20 10 -1.1 -0.6
9750 3.8 38.8 313 14 7 5.4 3.0 | 2.7 36.9 292 17 9 -0.6 -0.3
9500 4.1 39.4 313 13 7 4.4 2.4 | 2.6 36.7 290 15 8 -1.5 -0.8
9250 4.4 39.9 315 12 6 3.1 1.7 | 2.5 36.5 288 12 6 -2.7 -1.5
9000 4.6 40.3 319 11 6 3.0 1.6 | 2.3 36.1 286 10 5 -2.6 -1.4
8750 4.9 40.8 324 10 5 3.0 1.7 | 2.1 35.8 281 7 3 -2.8 -1.5
8500 5.1 41.2 331 8 4 2.7 1.5 | 1.9 35.4 274 4 2 -0.8 -0.5
8250 5.3 41.5 344 7 4 2.5 1.4 | 1.9 35.4 305 2 1 1.0 0.6
8000 5.5 41.9 001 7 3 2.5 1.4 | 1.9 35.4 018 2 1 -0.2 -0.1
7750 5.7 42.3 019 7 3 2.7 1.5 | 1.9 35.4 045 4 2 2.9 1.6
7500 5.9 42.6 033 8 4 3.1 1.7 | 2.3 36.1 049 5 3 8.7 4.8
7250 6.1 43.0 041 9 5 3.4 1.9 | 3.0 37.4 047 6 3 9.9 5.5
7000 6.4 43.5 047 10 5 3.1 1.7 | 3.8 38.8 046 6 3 9.6 5.3
6750 6.6 43.9 051 12 6 4.0 2.2 | 4.5 40.1 045 6 3 10.0 5.5
6500 6.9 44.4 051 11 6 4.6 2.5 | 5.2 41.4 044 6 3 10.5 5.8
6250 7.3 45.1 052 11 6 4.9 2.7 | 6.0 42.8 044 6 3 9.3 5.1
6000 7.6 45.7 052 11 6 3.2 1.7 | 6.8 44.2 044 6 3 13.4 7.4
5750 7.7 45.9 053 9 5 -0.3 -0.1 | 8.1 46.6 044 6 3 19.5 10.7
5500 7.6 45.7 056 7 3 -0.6 -0.3 | 9.5 49.1 044 6 3 17.3 9.5
10/26/2008 at 1500 MDT | 10/26/2008 at 1800 MDT
|
K index... -1.2 | K index... -2.1
|
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 -68.0 -90.4 307 50 26 1.5 0.8 | -67.2 -89.0 309 53 28 1.4 0.8
45000 -65.2 -85.4 309 64 33 4.0 2.2 | -64.7 -84.5 316 68 35 3.6 2.0
40000 -58.8 -73.8 308 71 37 5.7 3.1 | -59.0 -74.2 312 77 40 5.0 2.8
38000 -54.2 -65.6 308 71 37 7.7 4.2 | -54.6 -66.3 312 76 39 7.3 4.0
36000 -49.6 -57.3 308 72 37 7.7 4.2 | -50.3 -58.5 313 74 38 7.3 4.0
34000 -45.0 -49.0 309 70 36 7.7 4.2 | -45.6 -50.1 314 71 37 8.1 4.5
32000 -40.4 -40.7 312 65 33 7.7 4.3 | -40.7 -41.3 316 68 35 8.1 4.5
30000 -35.7 -32.3 314 63 33 7.7 4.3 | -36.1 -33.0 322 66 34 5.9 3.2
29000 -32.8 -27.0 315 64 33 7.7 4.3 | -34.4 -29.9 325 65 34 5.9 3.2
28000 -30.5 -22.9 316 64 33 7.9 4.3 | -32.6 -26.7 328 66 34 5.6 3.1
27000 -28.5 -19.3 317 63 33 6.4 3.5 | -30.3 -22.5 329 64 33 8.5 4.6
26000 -26.6 -15.9 317 62 32 6.4 3.5 | -27.7 -17.9 328 61 32 8.5 4.6
25000 -24.6 -12.3 317 60 31 6.4 3.5 | -25.2 -13.4 327 59 30 8.5 4.6
24000 -22.8 -9.0 318 57 29 6.0 3.3 | -22.9 -9.2 329 57 30 7.3 4.0
23000 -21.0 -5.8 320 52 27 6.0 3.3 | -20.7 -5.3 332 57 29 7.3 4.0
22000 -19.2 -2.6 322 48 25 6.0 3.3 | -18.5 -1.3 335 57 29 7.4 4.0
21000 -17.3 0.9 326 48 25 6.6 3.6 | -16.6 2.1 337 56 29 6.1 3.3
20000 -15.3 4.5 329 51 26 6.6 3.6 | -14.7 5.5 338 53 27 6.1 3.3
19500 -14.3 6.3 330 52 27 6.6 3.6 | -13.8 7.2 338 52 27 6.0 3.3
19000 -13.3 8.1 332 54 28 6.7 3.7 | -12.9 8.8 339 51 26 5.1 2.8
18500 -12.3 9.9 330 51 27 6.8 3.8 | -12.3 9.9 338 47 24 4.1 2.3
18000 -11.3 11.7 329 49 25 6.9 3.8 | -11.7 10.9 336 43 22 3.7 2.0
17500 -10.3 13.5 327 47 24 6.0 3.3 | -10.9 12.4 335 40 20 7.2 3.9
17000 -9.4 15.1 325 45 23 6.0 3.3 | -9.9 14.2 333 36 18 6.9 3.8
16500 -8.5 16.7 322 43 22 5.1 2.8 | -8.9 16.0 331 32 17 4.9 2.7
16000 -7.6 18.3 319 41 21 4.2 2.3 | -8.1 17.4 329 34 17 3.7 2.0
15500 -6.9 19.6 317 40 21 5.3 2.9 | -7.5 18.5 327 34 18 4.1 2.3
15000 -6.1 21.0 316 38 20 5.6 3.1 | -7.0 19.4 322 33 17 4.2 2.3
14500 -5.3 22.5 314 36 19 6.5 3.6 | -6.3 20.7 318 32 16 6.1 3.4
14000 -4.2 24.4 312 34 18 7.3 4.0 | -5.3 22.5 315 29 15 7.3 4.0
13500 -3.2 26.2 310 32 16 7.4 4.1 | -4.2 24.4 313 27 14 7.7 4.2
13000 -2.1 28.2 307 31 16 7.5 4.1 | -3.1 26.4 311 26 13 8.2 4.5
12500 -1.0 30.2 303 30 15 7.6 4.2 | -1.9 28.6 310 25 13 8.1 4.4
12000 0.1 32.2 301 29 15 8.0 4.4 | -0.7 30.7 310 24 12 7.9 4.3
11500 1.3 34.3 299 27 14 7.8 4.3 | 0.4 32.7 310 23 12 6.6 3.6
11000 2.3 36.1 299 25 13 6.6 3.6 | 1.1 34.0 311 22 11 3.7 2.0
10500 3.3 37.9 300 23 12 4.7 2.6 | 1.6 34.9 311 20 10 2.0 1.1
10250 3.4 38.1 300 21 11 -0.8 -0.5 | 1.6 34.9 312 18 9 -1.2 -0.7
10000 3.2 37.8 301 19 10 -2.2 -1.2 | 1.5 34.7 312 16 8 -1.0 -0.6
9750 3.1 37.6 301 17 9 -1.6 -0.9 | 1.4 34.5 312 14 7 -1.3 -0.7
9500 2.9 37.2 302 14 7 -2.8 -1.5 | 1.3 34.3 313 12 6 -0.1 -0.0
9250 2.6 36.7 307 11 6 -4.4 -2.4 | 1.4 34.5 318 9 5 1.2 0.6
9000 2.3 36.1 319 7 4 -4.2 -2.3 | 1.4 34.5 329 6 3 0.5 0.3
8750 1.9 35.4 347 5 2 -4.9 -2.7 | 1.5 34.7 351 4 2 1.9 1.0
8500 1.7 35.1 032 4 2 3.7 2.0 | 1.8 35.2 020 4 2 6.8 3.7
8250 2.4 36.3 033 5 2 10.8 5.9 | 2.4 36.3 028 5 2 9.2 5.0
8000 3.1 37.6 034 5 3 8.8 4.8 | 3.1 37.6 034 6 3 8.4 4.6
7750 3.8 38.8 035 5 3 9.5 5.2 | 3.7 38.7 038 7 4 9.2 5.0
7500 4.5 40.1 035 5 3 9.8 5.4 | 4.5 40.1 038 7 4 9.9 5.4
7250 5.2 41.4 035 5 3 9.9 5.4 | 5.2 41.4 038 8 4 9.8 5.4
7000 6.0 42.8 035 6 3 9.8 5.4 | 5.9 42.6 038 9 4 9.7 5.3
6750 6.7 44.1 035 6 3 10.2 5.6 | 6.6 43.9 038 9 5 9.4 5.2
6500 7.5 45.5 034 6 3 10.7 5.9 | 7.3 45.1 038 9 5 9.2 5.0
6250 8.3 46.9 034 6 3 9.8 5.4 | 8.0 46.4 038 10 5 9.5 5.2
6000 9.0 48.2 033 6 3 12.9 7.1 | 8.7 47.7 038 10 5 8.3 4.6
5750 10.2 50.4 033 6 3 17.8 9.8 | 9.3 48.7 037 9 5 7.0 3.8
5500 11.5 52.7 033 6 3 16.9 9.3 | 9.8 49.6 036 8 4 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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