Issued by NWS Denver/Boulder, CO
000
UXUS97 KBOU 081209
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
609 AM MDT Friday May 8, 2009
This forecast is for Friday May 8, 2009:
If the trigger temperature of 64.9 F/18.3 C is reached...then
Thermal Soaring Index....................... Fair
Maximum rate of lift........................ 244 ft/min (1.2 m/s)
Maximum height of thermals.................. 8870 ft MSL (3585 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................. 6681 ft MSL (1395 ft AGL)
Thermal soaring outlook for Saturday 05/09..... Poor
Wave Soaring Index............................. Good
Wave Soaring Index trend (to 1800 MDT)......... No change
Height of stable layer (12-18K ft MSL)......... 15644 ft MSL (10359 ft AGL)
Weak PVA/NVA (through 1800 MDT)................ Neither
Potential height of wave....................... 35621 ft MSL (30336 ft AGL)
Wave soaring outlook for Saturday 05/09........ Poor
Remarks...
Sunrise/Sunset.................... 05:51:43 / 19:59:59 MDT
Total possible sunshine........... 14 hr 8 min 17 sec (848 min 17 sec)
Altitude of sun at 12:56:02 MDT... 67.50 degrees
Upper air data from rawinsonde observation taken on 05/08/2009 at 0600 MDT
Freezing level.................. 12078 ft MSL (6793 ft AGL)
Additional freezing level....... 53722 ft MSL (48437 ft AGL)
Convective condensation level... 13267 ft MSL (7982 ft AGL)
Lifted condensation level....... 12141 ft MSL (6855 ft AGL)
Lifted index.................... +5.1
K index......................... -2.5
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 -63.9 -83.0 269 66 34 2.9 1.6 90.1 194.1 41.7 M M
45000 -58.8 -73.8 261 74 38 4.3 2.4 73.2 163.7 34.3 M M
40000 -52.4 -62.3 274 92 47 3.7 2.0 60.4 140.8 28.2 M M
38000 -50.7 -59.3 275 96 49 -3.4 -1.8 54.2 129.5 24.7 M M
36000 -50.3 -58.5 275 98 50 6.2 3.4 46.2 115.2 19.8 M M
34000 -46.6 -51.9 276 95 49 7.4 4.1 42.1 107.8 17.5 M M
32000 -42.1 -43.8 278 90 46 7.7 4.2 40.2 104.3 16.5 M M
30000 -37.1 -34.8 280 88 45 8.4 4.6 39.2 102.6 16.2 M M
29000 -34.6 -30.3 280 87 45 8.4 4.6 38.4 101.2 15.8 M M
28000 -32.0 -25.6 280 86 44 8.4 4.6 37.8 100.0 15.5 M M
27000 -29.5 -21.1 280 84 43 8.4 4.6 37.3 99.1 15.3 M M
26000 -27.0 -16.6 280 83 43 8.4 4.6 36.9 98.4 15.2 M M
25000 -24.8 -12.6 280 82 42 6.8 3.8 36.1 97.1 14.8 M M
24000 -22.6 -8.7 279 79 41 9.7 5.3 35.2 95.4 14.2 M M
23000 -20.3 -4.5 277 75 38 7.1 3.9 34.4 93.9 13.7 M M
22000 -18.1 -0.6 275 70 36 7.1 3.9 33.5 92.2 13.0 M M
21000 -16.3 2.7 273 66 34 4.1 2.3 32.2 90.0 12.1 M M
20000 -14.8 5.4 270 61 32 7.4 4.1 30.6 87.0 10.8 M M
19500 -13.7 7.3 266 60 31 7.1 3.9 30.1 86.1 10.5 M M
19000 -12.7 9.1 262 59 30 7.1 3.9 29.6 85.3 10.1 M M
18500 -11.7 10.9 260 58 30 6.1 3.3 29.1 84.4 9.7 M M
18000 -10.8 12.6 261 58 30 5.7 3.1 28.4 83.2 9.2 M M
17500 -9.8 14.4 262 58 30 7.8 4.3 27.9 82.2 8.8 M M
17000 -8.0 17.6 263 59 30 7.6 4.2 27.4 81.3 8.4 M M
16500 -6.9 19.6 264 59 30 4.8 2.6 27.0 80.6 8.1 M M
16000 -6.4 20.5 265 59 30 2.1 1.2 25.9 78.6 7.2 M M
15500 -6.5 20.3 268 59 30 0.6 0.3 24.2 75.6 5.7 M M
15000 -6.1 21.0 270 58 30 3.9 2.1 23.1 73.5 4.7 M M
14500 -5.5 22.1 270 55 28 3.9 2.1 22.1 71.8 3.7 M M
14000 -4.9 23.2 270 51 26 7.4 4.1 21.3 70.3 2.9 M M
13500 -3.6 25.5 271 46 24 8.8 4.8 21.1 70.0 2.8 M M
13000 -2.3 27.9 272 41 21 8.9 4.9 21.0 69.7 2.7 M M
12500 -1.0 30.2 273 36 19 8.9 4.9 20.8 69.5 2.5 M M
12000 0.4 32.7 275 32 16 8.9 4.9 20.7 69.3 2.4 M M
11500 1.7 35.1 278 28 15 8.9 4.9 20.6 69.0 2.3 M M
11000 3.0 37.4 283 25 13 8.7 4.8 20.4 68.8 2.1 M M
10500 4.0 39.2 288 22 12 6.4 3.5 20.0 68.1 1.7 M M
10250 4.5 40.1 292 21 11 6.7 3.7 19.8 67.6 1.4 M M
10000 4.9 40.8 299 16 8 7.0 3.9 19.6 67.2 1.1 M M
9750 5.4 41.7 296 15 8 7.4 4.1 19.4 66.8 0.9 M M
9500 5.9 42.6 293 14 7 7.3 4.0 19.2 66.5 0.7 M M
9250 6.4 43.5 289 13 7 7.6 4.2 19.0 66.2 0.4 M M
9000 6.9 44.4 284 12 6 6.9 3.8 18.8 65.8 0.2 M M
8750 7.2 45.0 278 10 5 2.3 1.3 18.4 65.2 -0.2 235 1.2
8500 7.1 44.8 267 8 4 -4.8 -2.6 17.6 63.6 -1.1 230 1.2
8250 6.9 44.4 250 6 3 -0.2 -0.1 16.5 61.7 -2.0 229 1.2
8000 7.3 45.1 224 5 3 8.8 4.8 16.1 61.1 -2.3 210 1.1
7750 7.9 46.2 209 5 2 9.4 5.2 16.1 61.0 -2.4 183 0.9
7500 8.6 47.5 192 5 2 9.4 5.1 16.1 60.9 -2.5 155 0.8
7250 9.3 48.7 177 5 3 9.1 5.0 16.0 60.9 -2.6 128 0.6
7000 9.9 49.8 165 6 3 10.5 5.8 16.0 60.8 -2.6 100 0.5
6750 10.6 51.1 167 4 2 5.1 2.8 16.0 60.8 -2.7 73 0.4
6500 10.5 50.9 180 1 1 -5.7 -3.1 15.2 59.3 -3.6 69 0.4
6250 10.1 50.2 322 1 1 -0.6 -0.3 14.0 57.3 -4.7 74 0.4
6000 10.4 50.7 334 4 2 7.5 4.1 13.7 56.6 -5.1 57 0.3
5750 10.9 51.6 336 4 2 8.0 4.4 13.5 56.3 -5.4 34 0.2
5500 11.3 52.3 338 4 2 1.6 0.9 13.2 55.8 -5.7 15 0.1
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
05/08/2009 at 0900 MDT | 05/08/2009 at 1200 MDT
|
K index... +7.5 | K index... +12.1
|
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 -60.7 -77.3 271 59 30 2.7 1.5 | -61.5 -78.7 267 59 30 2.4 1.3
45000 -56.7 -70.1 272 86 44 0.9 0.5 | -57.8 -72.0 265 82 42 1.9 1.0
40000 -55.5 -67.9 281 100 52 0.9 0.5 | -55.0 -67.0 275 88 45 1.9 1.0
38000 -53.6 -64.5 280 99 51 3.9 2.1 | -52.8 -63.0 275 88 45 4.0 2.2
36000 -51.3 -60.3 278 95 49 3.9 2.1 | -50.5 -58.9 274 87 45 4.0 2.2
34000 -48.1 -54.6 275 91 47 7.8 4.3 | -47.2 -53.0 273 86 44 7.7 4.2
32000 -42.8 -45.0 273 88 45 7.8 4.3 | -42.1 -43.8 269 86 44 7.7 4.2
30000 -38.0 -36.4 271 85 44 8.4 4.6 | -37.3 -35.1 267 86 44 8.2 4.5
29000 -35.5 -31.9 271 84 43 8.4 4.6 | -34.9 -30.8 267 86 44 8.2 4.5
28000 -33.0 -27.4 270 83 43 8.4 4.6 | -32.4 -26.3 267 86 44 8.2 4.5
27000 -30.4 -22.7 270 82 42 8.8 4.8 | -29.9 -21.8 267 86 44 8.5 4.7
26000 -27.8 -18.0 271 81 42 8.8 4.8 | -27.4 -17.3 268 85 44 8.5 4.7
25000 -25.2 -13.4 271 81 42 8.8 4.8 | -24.8 -12.6 270 85 44 8.5 4.7
24000 -22.7 -8.9 272 79 41 6.2 3.4 | -22.5 -8.5 271 83 43 5.5 3.0
23000 -20.9 -5.6 273 75 38 5.8 3.2 | -20.9 -5.6 272 79 41 5.1 2.8
22000 -19.2 -2.6 274 70 36 5.8 3.2 | -19.4 -2.9 274 75 38 5.1 2.8
21000 -17.4 0.7 274 66 34 6.5 3.6 | -17.8 -0.0 274 70 36 6.6 3.6
20000 -15.5 4.1 273 62 32 6.5 3.5 | -15.8 3.6 273 66 34 6.5 3.6
19500 -14.5 5.9 272 61 31 6.5 3.5 | -14.9 5.2 272 64 33 6.5 3.6
19000 -13.5 7.7 271 59 31 6.5 3.5 | -13.9 7.0 272 61 32 6.5 3.6
18500 -12.6 9.3 270 58 30 6.4 3.5 | -12.9 8.8 271 59 30 6.4 3.5
18000 -11.6 11.1 269 55 28 6.4 3.5 | -12.0 10.4 269 55 28 6.3 3.5
17500 -10.7 12.7 269 53 27 6.2 3.4 | -11.0 12.2 268 52 27 6.1 3.3
17000 -9.7 14.5 270 49 25 4.2 2.3 | -10.0 14.0 267 47 24 4.5 2.5
16500 -9.0 15.8 271 46 24 4.1 2.2 | -9.3 15.3 267 45 23 4.3 2.4
16000 -8.5 16.7 272 44 22 3.6 2.0 | -8.8 16.2 267 43 22 3.9 2.1
15500 -8.0 17.6 272 41 21 3.5 1.9 | -8.2 17.2 268 42 21 3.9 2.1
15000 -7.4 18.7 273 37 19 5.1 2.8 | -7.6 18.3 269 39 20 5.4 2.9
14500 -6.7 19.9 272 34 17 4.9 2.7 | -6.9 19.6 270 36 18 5.2 2.8
14000 -5.9 21.4 271 30 16 6.4 3.5 | -6.1 21.0 271 32 17 6.5 3.5
13500 -4.9 23.2 271 27 14 6.6 3.6 | -5.1 22.8 273 29 15 6.6 3.6
13000 -3.9 25.0 271 24 12 7.0 3.9 | -4.1 24.6 274 26 14 6.8 3.7
12500 -2.9 26.8 271 22 11 7.2 4.0 | -3.1 26.4 275 23 12 6.8 3.7
12000 -1.9 28.6 272 19 10 6.4 3.5 | -2.1 28.2 275 20 10 6.6 3.6
11500 -1.0 30.2 273 17 9 5.9 3.2 | -1.2 29.8 276 18 9 6.4 3.5
11000 -0.2 31.6 275 15 8 5.5 3.0 | -0.3 31.5 276 15 8 6.4 3.5
10500 0.5 32.9 275 12 6 5.3 2.9 | 0.7 33.3 276 12 6 6.5 3.5
10250 0.9 33.6 275 11 6 5.3 2.9 | 1.1 34.0 275 11 6 6.5 3.6
10000 1.2 34.2 274 9 5 6.2 3.4 | 1.6 34.9 274 9 5 6.9 3.8
9750 1.7 35.1 271 7 4 6.8 3.7 | 2.1 35.8 270 8 4 7.1 3.9
9500 2.1 35.8 265 5 3 6.7 3.7 | 2.6 36.7 264 7 4 7.1 3.9
9250 2.6 36.7 253 3 2 6.8 3.7 | 3.1 37.6 256 6 3 6.9 3.8
9000 3.1 37.6 224 2 1 6.8 3.7 | 3.5 38.3 246 4 2 6.3 3.4
8750 3.5 38.3 166 2 1 6.9 3.8 | 4.0 39.2 223 2 1 6.1 3.4
8500 4.0 39.2 130 3 1 6.9 3.8 | 4.4 39.9 148 2 1 5.9 3.2
8250 4.4 39.9 118 5 2 7.0 3.8 | 4.8 40.6 111 4 2 7.1 3.9
8000 4.9 40.8 113 5 3 7.1 3.9 | 5.4 41.7 101 5 2 8.6 4.7
7750 5.4 41.7 109 6 3 7.2 3.9 | 6.0 42.8 094 6 3 8.6 4.7
7500 5.9 42.6 107 7 4 7.2 3.9 | 6.7 44.1 090 7 4 8.6 4.7
7250 6.5 43.7 105 8 4 7.5 4.1 | 7.3 45.1 087 8 4 9.5 5.2
7000 7.0 44.6 102 7 4 7.8 4.3 | 8.1 46.6 087 8 4 10.1 5.5
6750 7.5 45.5 099 7 4 7.5 4.1 | 8.8 47.8 086 8 4 9.8 5.4
6500 8.1 46.6 095 6 3 8.6 4.7 | 9.6 49.3 085 8 4 10.3 5.6
6250 8.8 47.8 093 6 3 10.4 5.7 | 10.4 50.7 084 8 4 11.1 6.1
6000 9.5 49.1 091 6 3 10.3 5.6 | 11.2 52.2 083 8 4 10.5 5.8
5750 10.3 50.5 090 6 3 11.3 6.2 | 12.0 53.6 082 8 4 12.8 7.0
5500 11.3 52.3 087 6 3 17.1 9.4 | 13.3 55.9 082 8 4 23.6 13.0
05/08/2009 at 1500 MDT | 05/08/2009 at 1800 MDT
|
K index... +22.0 | K index... +22.2
|
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 -62.1 -79.8 268 57 29 1.7 0.9 | -60.7 -77.3 267 52 27 1.0 0.6
45000 -59.5 -75.1 271 86 44 2.5 1.4 | -59.0 -74.2 273 85 44 1.9 1.0
40000 -55.6 -68.1 275 91 47 2.4 1.3 | -56.1 -69.0 276 94 48 2.0 1.1
38000 -53.0 -63.4 274 91 47 4.8 2.6 | -53.4 -64.1 275 96 49 5.5 3.0
36000 -50.1 -58.2 273 92 47 4.8 2.6 | -50.1 -58.2 274 96 50 5.5 3.0
34000 -46.6 -51.9 272 91 47 7.7 4.2 | -46.4 -51.5 274 96 49 7.4 4.0
32000 -42.1 -43.8 270 90 47 7.6 4.2 | -41.4 -42.5 274 94 49 7.3 4.0
30000 -36.9 -34.4 269 89 46 7.7 4.2 | -37.2 -35.0 274 92 47 6.6 3.6
29000 -34.6 -30.3 269 88 45 7.7 4.2 | -35.3 -31.5 274 91 47 6.6 3.6
28000 -32.3 -26.1 268 88 45 7.7 4.2 | -33.3 -27.9 274 89 46 6.6 3.6
27000 -30.0 -22.0 269 86 45 7.8 4.3 | -31.2 -24.2 273 87 45 8.1 4.5
26000 -27.6 -17.7 270 85 44 7.8 4.3 | -28.8 -19.8 273 85 44 8.0 4.4
25000 -25.3 -13.5 270 84 43 7.9 4.3 | -26.4 -15.5 273 84 43 8.0 4.4
24000 -23.1 -9.6 271 82 42 5.3 2.9 | -24.1 -11.4 273 82 42 5.6 3.1
23000 -21.6 -6.9 272 79 41 4.9 2.7 | -22.7 -8.9 273 80 41 4.9 2.7
22000 -20.1 -4.2 273 77 39 4.9 2.7 | -21.2 -6.2 272 79 40 5.0 2.7
21000 -18.7 -1.7 274 73 38 5.0 2.8 | -19.8 -3.6 273 75 39 5.0 2.8
20000 -17.2 1.0 274 69 36 5.1 2.8 | -18.3 -0.9 275 67 34 5.1 2.8
19500 -16.4 2.5 274 67 34 5.1 2.8 | -17.6 0.3 276 62 32 5.1 2.8
19000 -15.7 3.7 275 65 33 5.1 2.8 | -16.8 1.8 277 58 30 5.0 2.8
18500 -14.9 5.2 275 62 32 5.3 2.9 | -16.0 3.2 279 54 28 6.7 3.7
18000 -14.2 6.4 274 57 30 5.4 3.0 | -15.0 5.0 279 49 25 7.3 4.0
17500 -13.4 7.9 273 53 27 5.7 3.1 | -13.9 7.0 278 43 22 7.5 4.1
17000 -12.5 9.5 272 48 25 6.9 3.8 | -12.2 10.0 278 38 19 8.1 4.5
16500 -11.5 11.3 271 44 23 6.9 3.8 | -11.0 12.2 278 34 18 7.9 4.3
16000 -9.9 14.2 270 38 19 7.3 4.0 | -9.9 14.2 279 31 16 7.3 4.0
15500 -8.9 16.0 269 33 17 7.3 4.0 | -8.8 16.2 280 28 14 7.4 4.0
15000 -7.8 18.0 269 30 15 6.9 3.8 | -7.8 18.0 281 25 13 6.7 3.7
14500 -6.8 19.8 270 27 14 7.0 3.8 | -6.8 19.8 283 22 11 6.8 3.8
14000 -5.9 21.4 271 24 12 6.4 3.5 | -5.8 21.6 285 19 10 6.5 3.5
13500 -4.9 23.2 273 20 11 6.4 3.5 | -4.9 23.2 288 16 8 6.5 3.6
13000 -4.0 24.8 275 17 9 5.7 3.2 | -3.9 25.0 292 13 7 6.3 3.5
12500 -3.2 26.2 276 13 7 5.6 3.1 | -3.0 26.6 296 10 5 6.3 3.4
12000 -2.4 27.7 276 9 4 6.2 3.4 | -2.1 28.2 303 7 3 6.6 3.6
11500 -1.5 29.3 260 4 2 6.5 3.6 | -1.1 30.0 312 4 2 6.8 3.7
11000 -0.5 31.1 154 2 1 8.8 4.8 | -0.1 31.8 343 2 1 7.5 4.1
10500 0.9 33.6 137 3 2 9.6 5.3 | 1.0 33.8 052 2 1 7.7 4.2
10250 1.6 34.9 132 4 2 9.7 5.3 | 1.6 34.9 073 2 1 8.0 4.4
10000 2.3 36.1 129 4 2 9.7 5.3 | 2.2 36.0 082 3 1 9.2 5.0
9750 3.0 37.4 129 4 2 9.7 5.3 | 2.9 37.2 087 3 2 9.8 5.4
9500 3.7 38.7 129 5 2 9.6 5.3 | 3.6 38.5 090 4 2 9.6 5.3
9250 4.4 39.9 129 5 2 9.8 5.4 | 4.3 39.7 093 4 2 9.7 5.3
9000 5.2 41.4 128 5 3 10.2 5.6 | 5.0 41.0 096 4 2 9.6 5.3
8750 5.9 42.6 128 5 3 10.3 5.6 | 5.7 42.3 100 4 2 9.6 5.2
8500 6.7 44.1 127 5 3 10.3 5.6 | 6.4 43.5 102 5 2 9.6 5.3
8250 7.5 45.5 127 6 3 10.2 5.6 | 7.1 44.8 105 5 3 9.5 5.2
8000 8.2 46.8 127 6 3 10.0 5.5 | 7.8 46.0 110 6 3 9.3 5.1
7750 9.0 48.2 127 6 3 10.0 5.5 | 8.5 47.3 115 7 3 9.4 5.1
7500 9.7 49.5 127 6 3 10.0 5.5 | 9.1 48.4 118 7 4 9.4 5.1
7250 10.4 50.7 126 6 3 9.9 5.4 | 9.8 49.6 121 8 4 9.6 5.3
7000 11.2 52.2 126 6 3 9.9 5.4 | 10.5 50.9 123 8 4 9.7 5.3
6750 11.9 53.4 126 6 3 9.8 5.4 | 11.2 52.2 124 9 5 9.7 5.3
6500 12.6 54.7 125 6 3 10.1 5.5 | 11.9 53.4 126 9 5 9.8 5.4
6250 13.4 56.1 125 6 3 10.7 5.9 | 12.6 54.7 126 9 5 9.9 5.4
6000 14.2 57.6 124 6 3 10.3 5.7 | 13.4 56.1 126 9 5 9.8 5.4
5750 15.0 59.0 124 6 3 11.9 6.5 | 14.1 57.4 127 9 5 10.2 5.6
5500 16.2 61.2 124 6 3 21.6 11.9 | 14.9 58.8 128 9 5 12.3 6.7
________________________________________________________________________________
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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