Issued by NWS Denver/Boulder, CO
000
UXUS97 KBOU 080011
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
611 PM MDT Thursday May 7, 2009
This forecast is for Friday May 8, 2009:
If the trigger temperature of 61.7 F/16.5 C is reached...then
Thermal Soaring Index....................... Fair
Maximum rate of lift........................ 203 ft/min (1.0 m/s)
Maximum height of thermals.................. 10664 ft MSL (5341 ft AGL)
Forecast maximum temperature................... 64.0 F/18.2 C
Time of trigger temperature.................... 1300 MDT
Time of overdevelopment........................ 1500 MDT
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................. 6754 ft MSL (1431 ft AGL)
Thermal soaring outlook for Saturday 05/09..... Poor
Wave Soaring Index............................. Fair
Wave Soaring Index trend (to 1800 MDT)......... No change
Height of stable layer (12-18K ft MSL)......... None
Weak PVA/NVA (through 1800 MDT)................ Neither
Potential height of wave....................... 39738 ft MSL (34415 ft AGL)
Wave soaring outlook for Saturday 05/09........ Good
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 numerical model forecast valid on 05/08/2009 at 0600 MDT
Freezing level.................. 11539 ft MSL (6216 ft AGL)
Convective condensation level... 13367 ft MSL (8044 ft AGL)
Lifted condensation level....... 12310 ft MSL (6987 ft AGL)
Lifted index.................... +5.2
K index......................... +4.2
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 -62.1 -79.8 271 58 30 1.7 0.9 91.6 196.9 42.7 M M
45000 -59.3 -74.7 271 83 43 2.7 1.5 72.2 161.9 33.7 M M
40000 -55.2 -67.4 278 95 49 2.7 1.5 56.0 132.8 25.3 M M
38000 -52.7 -62.9 279 95 49 4.4 2.4 50.7 123.2 22.4 M M
36000 -50.1 -58.2 280 93 48 4.4 2.4 46.1 115.0 19.8 M M
34000 -46.6 -51.9 280 90 46 7.6 4.2 42.8 109.1 18.0 M M
32000 -42.1 -43.8 278 83 43 7.6 4.1 41.0 105.7 17.0 M M
30000 -36.9 -34.4 277 78 40 8.0 4.4 39.2 102.6 16.2 M M
29000 -34.5 -30.1 277 77 40 8.0 4.4 38.5 101.3 15.9 M M
28000 -32.1 -25.8 278 77 39 8.0 4.4 37.9 100.2 15.6 M M
27000 -29.7 -21.5 278 75 39 8.4 4.6 37.3 99.2 15.3 M M
26000 -27.2 -17.0 279 73 38 8.3 4.6 36.7 98.1 15.0 M M
25000 -24.7 -12.5 279 71 36 8.4 4.6 36.2 97.2 14.8 M M
24000 -22.3 -8.1 280 69 35 6.1 3.4 35.6 96.1 14.4 M M
23000 -20.5 -4.9 281 68 35 6.1 3.3 34.1 93.5 13.4 M M
22000 -18.7 -1.7 282 66 34 6.1 3.3 32.8 91.1 12.5 M M
21000 -16.9 1.6 282 65 33 6.4 3.5 31.6 88.9 11.5 M M
20000 -15.0 5.0 281 62 32 6.3 3.5 30.3 86.6 10.6 M M
19500 -14.0 6.8 280 61 32 6.3 3.5 29.7 85.5 10.2 M M
19000 -13.1 8.4 280 60 31 6.4 3.5 29.2 84.5 9.7 M M
18500 -12.2 10.0 279 59 30 5.6 3.0 28.6 83.5 9.3 M M
18000 -11.4 11.5 279 58 30 5.4 2.9 27.8 82.1 8.6 M M
17500 -10.6 12.9 279 56 29 5.2 2.9 27.1 80.7 8.0 M M
17000 -9.9 14.2 279 55 28 4.4 2.4 26.2 79.2 7.3 M M
16500 -8.9 16.0 278 52 27 4.8 2.6 24.9 76.8 6.2 M M
16000 -8.1 17.4 278 49 25 5.6 3.1 24.1 75.4 5.5 M M
15500 -7.3 18.9 277 46 24 5.6 3.1 23.5 74.2 4.9 M M
15000 -6.4 20.5 277 43 22 6.3 3.5 22.8 73.1 4.4 M M
14500 -5.5 22.1 277 39 20 6.3 3.4 22.2 72.0 3.8 M M
14000 -4.6 23.7 276 35 18 6.5 3.6 21.7 71.0 3.3 M M
13500 -3.7 25.3 276 31 16 6.6 3.6 21.2 70.1 2.8 M M
13000 -2.7 27.1 275 28 14 6.8 3.7 20.7 69.2 2.2 M M
12500 -1.8 28.8 273 25 13 6.8 3.8 20.2 68.3 1.7 M M
12000 -0.8 30.6 269 22 11 6.8 3.7 19.7 67.5 1.3 M M
11500 0.1 32.2 263 18 9 6.7 3.7 19.2 66.6 0.8 M M
11000 1.1 34.0 255 15 8 6.8 3.7 18.8 65.8 0.3 M M
10500 2.1 35.8 246 12 6 6.9 3.8 18.3 64.9 -0.2 386 2.0
10250 2.6 36.7 239 10 5 6.9 3.8 18.1 64.5 -0.4 364 1.8
10000 3.1 37.6 232 9 5 7.0 3.8 17.8 64.1 -0.6 341 1.7
9750 3.6 38.5 229 7 4 7.1 3.9 17.6 63.7 -0.8 319 1.6
9500 4.1 39.4 224 5 3 7.1 3.9 17.4 63.4 -1.1 296 1.5
9250 4.6 40.3 213 4 2 7.3 4.0 17.2 63.0 -1.3 274 1.4
9000 5.2 41.4 196 2 1 7.9 4.3 17.0 62.7 -1.5 250 1.3
8750 5.8 42.4 166 1 1 8.2 4.5 16.9 62.5 -1.7 226 1.1
8500 6.3 43.3 104 1 1 8.1 4.4 16.8 62.2 -1.8 201 1.0
8250 6.9 44.4 074 2 1 8.2 4.5 16.7 62.0 -2.0 176 0.9
8000 7.5 45.5 063 3 2 8.4 4.6 16.6 61.8 -2.1 151 0.8
7750 8.1 46.6 055 4 2 8.4 4.6 16.5 61.6 -2.2 125 0.6
7500 8.7 47.7 049 4 2 8.6 4.7 16.4 61.5 -2.3 99 0.5
7250 9.3 48.7 045 5 2 7.2 4.0 16.3 61.3 -2.5 74 0.4
7000 9.8 49.6 041 5 3 5.7 3.1 16.0 60.7 -2.7 52 0.3
6750 10.3 50.5 038 6 3 6.8 3.7 15.7 60.3 -3.0 30 0.2
6500 10.8 51.4 035 7 3 4.0 2.2 15.4 59.8 -3.2 8 0.0
6250 10.9 51.6 031 7 3 -2.3 -1.2 14.7 58.5 -3.9 M M
6000 10.6 51.1 024 6 3 -4.1 -2.2 13.7 56.7 -4.9 M M
5750 10.3 50.5 015 5 3 -3.6 -2.0 12.7 54.9 -5.9 M M
5500 9.9 49.8 005 5 2 -9.8 -5.4 11.5 52.8 -7.1 6 0.0
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
05/08/2009 at 0900 MDT | 05/08/2009 at 1200 MDT
|
K index... +4.8 | K index... +13.9
|
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 -61.5 -78.7 266 56 29 1.3 0.7 | -61.8 -79.2 263 64 33 1.5 0.8
45000 -59.2 -74.6 272 81 42 2.6 1.4 | -59.6 -75.3 271 84 43 1.4 0.7
40000 -55.3 -67.5 276 93 48 2.5 1.4 | -57.4 -71.3 278 88 45 1.2 0.7
38000 -53.0 -63.4 277 92 47 4.3 2.4 | -54.5 -66.1 277 87 45 5.7 3.1
36000 -50.4 -58.7 279 90 46 4.3 2.4 | -51.1 -60.0 276 87 45 5.7 3.1
34000 -47.0 -52.6 279 87 45 7.5 4.1 | -47.2 -53.0 275 86 44 7.7 4.2
32000 -42.5 -44.5 276 84 43 7.5 4.1 | -42.6 -44.7 272 86 44 7.7 4.2
30000 -37.2 -35.0 275 82 42 8.5 4.7 | -37.2 -35.0 270 85 44 8.4 4.6
29000 -34.6 -30.3 276 82 42 8.5 4.7 | -34.7 -30.5 270 84 43 8.4 4.6
28000 -32.1 -25.8 276 82 42 8.5 4.7 | -32.2 -26.0 271 83 43 8.4 4.6
27000 -29.6 -21.3 277 80 41 8.5 4.6 | -29.6 -21.3 271 81 42 8.9 4.9
26000 -27.0 -16.6 278 78 40 8.5 4.6 | -27.0 -16.6 270 78 40 8.9 4.9
25000 -24.5 -12.1 278 75 39 8.5 4.7 | -24.3 -11.7 270 75 38 8.9 4.9
24000 -22.1 -7.8 278 73 37 6.1 3.4 | -21.9 -7.4 271 72 37 5.4 2.9
23000 -20.3 -4.5 278 71 37 6.0 3.3 | -20.3 -4.5 271 73 37 5.4 3.0
22000 -18.5 -1.3 278 69 36 6.0 3.3 | -18.7 -1.7 272 73 38 5.4 3.0
21000 -16.7 1.9 277 67 35 6.0 3.3 | -17.0 1.4 273 72 37 5.6 3.1
20000 -14.9 5.2 277 65 33 6.0 3.3 | -15.4 4.3 273 70 36 5.6 3.1
19500 -14.1 6.6 277 63 33 6.0 3.3 | -14.5 5.9 273 68 35 5.6 3.1
19000 -13.2 8.2 277 62 32 6.0 3.3 | -13.7 7.3 273 67 34 5.7 3.1
18500 -12.3 9.9 276 60 31 4.5 2.4 | -13.0 8.6 273 65 33 3.9 2.1
18000 -11.7 10.9 276 57 29 4.0 2.2 | -12.4 9.7 273 62 32 3.6 2.0
17500 -11.2 11.8 276 54 28 4.0 2.2 | -11.9 10.6 273 60 31 3.6 2.0
17000 -10.2 13.6 274 49 25 4.3 2.4 | -11.4 11.5 272 56 29 3.5 1.9
16500 -9.6 14.7 272 45 23 4.5 2.5 | -10.9 12.4 272 52 27 3.3 1.8
16000 -8.8 16.2 271 41 21 5.1 2.8 | -9.8 14.4 271 47 24 6.1 3.3
15500 -8.1 17.4 269 37 19 5.0 2.7 | -9.0 15.8 269 42 22 6.1 3.3
15000 -7.2 19.0 268 34 18 6.5 3.6 | -7.9 17.8 269 39 20 8.0 4.4
14500 -6.3 20.7 268 32 16 6.4 3.5 | -6.8 19.8 268 35 18 7.8 4.3
14000 -5.4 22.3 268 30 15 6.9 3.8 | -5.6 21.9 268 32 17 8.0 4.4
13500 -4.4 24.1 270 28 14 6.9 3.8 | -4.5 23.9 268 29 15 8.0 4.4
13000 -3.3 26.1 271 27 14 7.2 3.9 | -3.3 26.1 268 26 13 7.7 4.2
12500 -2.3 27.9 273 26 13 7.3 4.0 | -2.2 28.0 269 24 12 7.7 4.2
12000 -1.2 29.8 275 25 13 7.2 4.0 | -1.1 30.0 270 21 11 6.8 3.7
11500 -0.2 31.6 276 24 12 7.2 4.0 | -0.2 31.6 269 17 9 6.5 3.6
11000 0.9 33.6 276 23 12 6.6 3.6 | 0.7 33.3 269 14 7 5.3 2.9
10500 1.7 35.1 274 19 10 6.3 3.5 | 1.3 34.3 266 9 5 4.8 2.6
10250 2.1 35.8 273 17 9 6.3 3.5 | 1.7 35.1 264 6 3 5.0 2.7
10000 2.6 36.7 271 15 8 6.2 3.4 | 2.1 35.8 259 4 2 5.9 3.3
9750 3.0 37.4 268 13 7 6.1 3.4 | 2.5 36.5 240 2 1 6.5 3.6
9500 3.4 38.1 265 11 6 6.2 3.4 | 3.0 37.4 124 1 1 6.1 3.4
9250 3.8 38.8 259 9 4 6.2 3.4 | 3.5 38.3 102 4 2 7.1 3.9
9000 4.3 39.7 252 7 3 6.0 3.3 | 4.1 39.4 099 5 3 8.8 4.8
8750 4.7 40.5 243 5 2 5.8 3.2 | 4.7 40.5 097 5 3 9.3 5.1
8500 5.2 41.4 225 3 2 6.0 3.3 | 5.4 41.7 095 6 3 9.0 5.0
8250 5.6 42.1 185 2 1 5.6 3.1 | 6.1 43.0 094 6 3 9.6 5.2
8000 6.0 42.8 142 2 1 5.1 2.8 | 6.8 44.2 093 6 3 10.1 5.5
7750 6.4 43.5 113 3 2 5.1 2.8 | 7.6 45.7 092 6 3 10.0 5.5
7500 6.8 44.2 099 5 2 5.1 2.8 | 8.3 46.9 091 6 3 10.0 5.5
7250 7.2 45.0 091 6 3 5.3 2.9 | 9.1 48.4 090 6 3 9.9 5.5
7000 7.6 45.7 087 6 3 5.5 3.0 | 9.8 49.6 090 6 3 9.9 5.4
6750 8.0 46.4 082 7 3 5.0 2.7 | 10.6 51.1 089 6 3 9.8 5.4
6500 8.4 47.1 079 7 4 6.9 3.8 | 11.3 52.3 089 6 3 10.3 5.7
6250 9.0 48.2 078 7 4 10.2 5.6 | 12.1 53.8 088 6 3 11.3 6.2
6000 9.8 49.6 078 7 3 10.2 5.6 | 12.9 55.2 087 6 3 10.6 5.8
5750 10.5 50.9 078 7 3 11.4 6.2 | 13.8 56.8 086 6 3 13.1 7.2
5500 11.6 52.9 076 6 3 18.5 10.2 | 15.1 59.2 084 6 3 24.5 13.4
05/08/2009 at 1500 MDT | 05/08/2009 at 1800 MDT
|
K index... +19.6 | K index... +22.3
|
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 -61.9 -79.4 264 60 31 1.0 0.6 | -61.4 -78.5 272 53 27 1.3 0.7
45000 -60.3 -76.5 271 91 47 1.5 0.8 | -59.5 -75.1 274 90 47 1.2 0.6
40000 -58.1 -72.6 273 94 49 1.6 0.9 | -57.6 -71.7 274 96 50 1.3 0.7
38000 -54.7 -66.5 274 94 48 6.2 3.4 | -54.7 -66.5 274 97 50 6.0 3.3
36000 -51.0 -59.8 274 93 48 6.2 3.4 | -51.1 -60.0 274 96 50 6.0 3.3
34000 -46.9 -52.4 273 92 47 7.6 4.2 | -47.2 -53.0 273 96 49 7.5 4.1
32000 -42.3 -44.1 270 91 47 7.6 4.2 | -42.7 -44.9 273 94 48 7.5 4.1
30000 -37.6 -35.7 267 90 46 8.1 4.4 | -37.5 -35.5 271 91 47 8.0 4.4
29000 -35.2 -31.4 267 89 46 8.1 4.4 | -35.1 -31.2 270 89 46 8.0 4.4
28000 -32.8 -27.0 266 88 45 8.1 4.4 | -32.8 -27.0 269 87 45 8.0 4.4
27000 -30.4 -22.7 265 86 44 7.5 4.1 | -30.5 -22.9 268 85 44 6.3 3.5
26000 -28.2 -18.8 266 85 44 7.5 4.1 | -28.6 -19.5 267 83 43 6.5 3.6
25000 -25.9 -14.6 267 84 43 7.6 4.1 | -26.7 -16.1 267 82 42 6.5 3.6
24000 -23.7 -10.7 267 83 43 6.0 3.3 | -24.8 -12.6 266 81 42 5.9 3.3
23000 -22.1 -7.8 268 80 41 5.3 2.9 | -23.1 -9.6 268 79 41 5.8 3.2
22000 -20.5 -4.9 268 77 40 5.3 2.9 | -21.3 -6.3 269 78 40 5.8 3.2
21000 -19.0 -2.2 269 74 38 4.9 2.7 | -19.7 -3.5 270 75 39 5.1 2.8
20000 -17.5 0.5 270 69 36 4.9 2.7 | -18.1 -0.6 271 68 35 5.2 2.9
19500 -16.4 2.5 271 66 34 4.9 2.7 | -17.4 0.7 271 64 33 5.2 2.9
19000 -15.7 3.7 271 63 32 4.9 2.7 | -16.6 2.1 272 61 31 5.1 2.8
18500 -15.0 5.0 271 59 30 4.9 2.7 | -15.8 3.6 272 57 29 6.6 3.6
18000 -14.3 6.3 271 54 28 4.9 2.7 | -14.8 5.4 270 53 27 7.0 3.8
17500 -13.5 7.7 270 49 25 7.1 3.9 | -13.7 7.3 268 48 25 7.2 3.9
17000 -12.3 9.9 269 46 23 7.9 4.3 | -12.6 9.3 266 45 23 7.9 4.3
16500 -11.2 11.8 268 42 22 8.0 4.4 | -10.9 12.4 263 40 21 7.7 4.2
16000 -10.0 14.0 267 39 20 8.0 4.4 | -9.8 14.4 262 38 19 7.4 4.0
15500 -8.8 16.2 265 36 19 8.0 4.4 | -8.8 16.2 260 36 18 7.4 4.1
15000 -7.6 18.3 264 33 17 7.9 4.3 | -7.8 18.0 258 33 17 7.0 3.8
14500 -6.5 20.3 263 30 16 8.0 4.4 | -6.8 19.8 256 30 16 7.0 3.9
14000 -5.4 22.3 261 27 14 6.6 3.6 | -5.8 21.6 253 28 14 6.9 3.8
13500 -4.5 23.9 259 23 12 6.6 3.6 | -4.8 23.4 249 25 13 6.9 3.8
13000 -3.6 25.5 254 18 10 4.9 2.7 | -3.8 25.2 244 22 11 6.9 3.8
12500 -3.0 26.6 246 13 6 4.4 2.4 | -2.8 27.0 239 19 10 6.9 3.8
12000 -2.4 27.7 228 7 4 6.2 3.4 | -1.8 28.8 231 16 8 7.2 4.0
11500 -1.3 29.7 196 4 2 7.1 3.9 | -0.7 30.7 224 13 7 7.3 4.0
11000 -0.2 31.6 127 4 2 8.8 4.8 | 0.4 32.7 212 11 5 6.8 3.8
10500 1.2 34.2 112 4 2 9.6 5.3 | 1.4 34.5 194 8 4 6.7 3.7
10250 1.9 35.4 106 5 2 9.7 5.3 | 1.9 35.4 180 7 4 6.6 3.6
10000 2.7 36.9 102 5 2 9.7 5.3 | 2.4 36.3 162 6 3 6.1 3.3
9750 3.4 38.1 100 5 3 9.8 5.4 | 2.8 37.0 141 6 3 5.9 3.2
9500 4.1 39.4 098 5 3 9.7 5.3 | 3.3 37.9 122 7 4 5.9 3.2
9250 4.9 40.8 096 5 3 9.8 5.4 | 3.7 38.7 109 9 4 6.1 3.4
9000 5.6 42.1 095 5 3 9.9 5.4 | 4.2 39.6 098 10 5 6.7 3.7
8750 6.3 43.3 093 5 3 9.9 5.4 | 4.7 40.5 090 11 6 6.9 3.8
8500 7.1 44.8 092 6 3 9.9 5.4 | 5.2 41.4 084 13 7 6.5 3.6
8250 7.8 46.0 091 6 3 10.0 5.5 | 5.7 42.3 079 15 8 8.0 4.4
8000 8.6 47.5 089 6 3 10.2 5.6 | 6.4 43.5 077 15 8 9.8 5.4
7750 9.3 48.7 088 6 3 10.2 5.6 | 7.1 44.8 075 16 8 9.5 5.2
7500 10.1 50.2 087 6 3 10.2 5.6 | 7.8 46.0 073 16 8 9.6 5.3
7250 10.8 51.4 086 6 3 10.1 5.5 | 8.5 47.3 072 16 8 9.8 5.4
7000 11.6 52.9 085 6 3 10.1 5.5 | 9.3 48.7 071 16 8 9.9 5.4
6750 12.4 54.3 084 6 3 10.0 5.5 | 10.0 50.0 071 16 8 9.8 5.4
6500 13.1 55.6 083 6 3 10.3 5.7 | 10.8 51.4 070 17 9 10.0 5.5
6250 13.9 57.0 082 6 3 11.0 6.0 | 11.5 52.7 069 16 8 10.4 5.7
6000 14.7 58.5 081 6 3 10.6 5.8 | 12.3 54.1 068 16 8 10.0 5.5
5750 15.5 59.9 080 6 3 12.1 6.7 | 13.0 55.4 067 16 8 11.4 6.3
5500 16.7 62.1 078 6 3 22.2 12.2 | 14.1 57.4 066 15 8 17.5 9.6
________________________________________________________________________________
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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