National Weather Service Text Product
AFOS product SRGBOU
Dates interpreted at 00:00 UTCDisplaying AFOS PIL: SRGBOU
Product Timestamp: 2012-09-02 13:25 UTC
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022
UXUS97 KBOU 021325
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
725 AM MDT Sunday September 2, 2012
This forecast is for Sunday September 2, 2012:
If the trigger temperature of 80.5 F/26.9 C is reached...then
Thermal Soaring Index....................... Excellent
Maximum rate of lift........................ 818 ft/min (4.2 m/s)
Maximum height of thermals.................. 16766 ft MSL (11481 ft AGL)
Forecast maximum temperature................... 90.0 F/32.7 C
Time of trigger temperature.................... 1030 MDT
Time of overdevelopment........................ None
Middle/high clouds during soaring window....... Overcast opaque high
Surface winds during soaring window............ 20 mph or less
Height of the -3 thermal index................. 12117 ft MSL (6832 ft AGL)
Thermal soaring outlook for Monday 09/03....... Excellent
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)................ Neither
Potential height of wave....................... 19315 ft MSL (14030 ft AGL)
Wave soaring outlook for Monday 09/03.......... Poor
Remarks... Southwest flow aloft over colorado along the northern edge of a
strong upper level ridge centered over texas today.
Sunrise/Sunset.................... 06:28:53 / 19:29:43 MDT
Total possible sunshine........... 13 hr 0 min 50 sec (780 min 50 sec)
Altitude of sun at 12:58:51 MDT... 57.79 degrees
Upper air data from rawinsonde observation taken on 09/02/2012 at 0600 MDT
Freezing level.................. 15925 ft MSL (10640 ft AGL)
Convective condensation level... 15850 ft MSL (10565 ft AGL)
Lifted condensation level....... 16095 ft MSL (10809 ft AGL)
Lifted index.................... -1.0
K index......................... +23.6
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 -67.1 -88.8 240 48 25 4.7 2.6 80.1 176.1 27.9 M M
45000 -59.9 -75.8 245 70 36 7.1 3.9 66.3 151.4 21.4 M M
40000 -49.4 -56.9 250 74 38 6.0 3.3 60.4 140.6 18.9 M M
38000 -45.5 -49.9 250 67 35 5.4 3.0 57.4 135.3 17.3 M M
36000 -43.4 -46.1 250 60 31 8.3 4.6 52.1 125.7 14.0 M M
34000 -38.5 -37.3 244 52 27 8.3 4.5 50.7 123.3 13.4 M M
32000 -33.8 -28.8 236 44 23 7.2 3.9 49.3 120.7 12.6 M M
30000 -28.6 -19.5 235 44 22 7.5 4.1 47.5 117.5 11.6 M M
29000 -26.3 -15.3 236 41 21 7.7 4.2 46.6 115.9 11.0 M M
28000 -24.0 -11.2 238 38 19 7.7 4.2 45.7 114.3 10.5 M M
27000 -21.7 -7.1 240 35 18 7.8 4.3 45.0 113.0 10.0 M M
26000 -19.7 -3.5 242 32 16 2.4 1.3 44.0 111.2 9.2 M M
25000 -18.1 -0.6 245 29 15 8.7 4.8 42.4 108.2 7.9 M M
24000 -15.6 3.9 244 23 12 8.7 4.8 41.9 107.5 7.7 M M
23000 -13.0 8.6 233 22 12 8.7 4.8 41.5 106.6 7.4 M M
22000 -10.5 13.1 221 23 12 9.0 4.9 41.1 106.0 7.1 M M
21000 -9.7 14.5 210 24 12 -5.5 -3.0 38.7 101.7 5.0 M M
20000 -8.9 16.0 214 29 15 3.9 2.1 36.2 97.2 2.9 M M
19500 -8.4 16.9 215 31 16 4.5 2.5 35.2 95.4 2.0 M M
19000 -7.4 18.7 215 32 16 8.6 4.7 34.7 94.5 1.5 M M
18500 -6.2 20.8 215 31 16 8.3 4.6 34.5 94.1 1.3 M M
18000 -4.9 23.2 215 29 15 8.3 4.5 34.3 93.7 1.1 M M
17500 -3.8 25.2 215 27 14 7.1 3.9 33.9 93.0 0.7 M M
17000 -2.8 27.0 215 26 13 7.2 4.0 33.5 92.2 0.3 M M
16500 -1.8 28.8 215 24 12 7.9 4.3 33.1 91.5 -0.1 1003 5.1
16000 -0.5 31.1 215 22 12 8.3 4.5 32.8 91.1 -0.3 950 4.8
15500 0.8 33.4 215 20 10 8.3 4.6 32.6 90.7 -0.5 896 4.6
15000 2.7 36.9 215 16 8 8.2 4.5 32.2 90.0 -0.8 818 4.2
14500 3.9 39.0 215 14 7 8.2 4.5 32.0 89.5 -1.0 767 3.9
14000 5.0 41.0 214 11 6 8.2 4.5 31.7 89.1 -1.3 717 3.6
13500 6.2 43.2 212 9 5 8.5 4.7 31.5 88.6 -1.6 667 3.4
13000 7.1 44.8 209 6 3 5.1 2.8 31.0 87.8 -2.2 624 3.2
12500 8.0 46.4 201 4 2 6.9 3.8 30.4 86.8 -2.7 583 3.0
12000 9.1 48.4 195 2 1 6.8 3.7 30.0 85.9 -3.2 538 2.7
11500 10.1 50.2 267 4 2 6.8 3.7 29.5 85.1 -3.7 492 2.5
11000 11.1 52.0 280 8 4 6.8 3.7 29.0 84.2 -4.1 447 2.3
10500 12.1 53.8 284 12 6 7.9 4.3 28.6 83.5 -4.5 402 2.0
10250 12.7 54.9 285 12 6 8.6 4.7 28.5 83.3 -4.7 376 1.9
10000 13.3 55.9 286 12 6 8.3 4.6 28.4 83.1 -4.8 350 1.8
9750 14.0 57.2 299 12 6 8.4 4.6 28.3 82.9 -4.9 324 1.6
9500 14.6 58.3 311 13 6 8.4 4.6 28.2 82.7 -5.0 298 1.5
9250 15.2 59.4 322 14 7 8.4 4.6 28.1 82.6 -5.1 272 1.4
9000 15.8 60.4 329 15 8 8.4 4.6 28.0 82.4 -5.2 246 1.3
8750 16.4 61.5 328 14 7 8.4 4.6 27.9 82.2 -5.4 220 1.1
8500 17.1 62.8 327 13 7 8.4 4.6 27.8 82.0 -5.5 194 1.0
8250 17.7 63.9 326 13 7 8.4 4.6 27.7 81.8 -5.6 168 0.9
8000 18.3 64.9 324 12 6 8.3 4.6 27.6 81.6 -5.7 142 0.7
7750 18.9 66.0 317 13 6 8.6 4.7 27.5 81.4 -5.9 116 0.6
7500 19.5 67.1 311 13 7 7.4 4.1 27.4 81.2 -6.0 91 0.5
7250 20.0 68.0 305 14 7 4.7 2.6 27.1 80.7 -6.3 70 0.4
7000 20.2 68.4 300 15 8 4.0 2.2 26.6 80.0 -6.8 55 0.3
6750 20.5 68.9 295 13 7 4.1 2.2 26.2 79.2 -7.2 39 0.2
6500 20.8 69.4 289 11 6 4.5 2.5 25.8 78.4 -7.7 23 0.1
6250 21.1 70.0 280 9 5 2.6 1.4 25.4 77.7 -8.2 8 0.0
6000 21.0 69.8 266 7 4 -2.5 -1.4 24.6 76.3 -8.9 1 0.0
5750 20.7 69.3 264 6 3 -5.3 -2.9 23.6 74.5 -10.1 4 0.0
5500 20.2 68.4 262 4 2 -7.4 -4.1 22.4 72.3 -11.3 12 0.1
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
09/02/2012 at 0900 MDT | 09/02/2012 at 1200 MDT
|
K index... +29.3 | K index... +25.8
|
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 -66.7 -88.1 247 45 23 3.6 2.0 | -66.5 -87.7 246 48 25 3.7 2.0
45000 -58.9 -74.0 248 64 33 7.5 4.1 | -58.7 -73.7 250 64 33 7.2 3.9
40000 -48.2 -54.8 248 72 37 5.4 3.0 | -48.4 -55.1 250 73 38 5.3 2.9
38000 -44.9 -48.8 250 67 35 5.4 3.0 | -45.2 -49.4 249 69 36 5.3 2.9
36000 -41.6 -42.9 253 63 32 5.5 3.0 | -42.1 -43.8 248 65 33 5.5 3.0
34000 -37.9 -36.2 252 58 30 6.4 3.5 | -38.0 -36.4 246 61 32 7.0 3.8
32000 -34.1 -29.4 249 53 27 6.3 3.5 | -33.4 -28.1 243 57 29 7.3 4.0
30000 -29.0 -20.2 249 47 24 7.8 4.3 | -28.7 -19.7 244 50 26 7.9 4.3
29000 -26.7 -16.1 249 44 23 7.9 4.3 | -26.4 -15.5 244 47 24 7.9 4.3
28000 -24.5 -12.1 250 41 21 6.2 3.4 | -24.1 -11.4 244 44 23 6.9 3.8
27000 -22.6 -8.7 251 38 20 6.3 3.5 | -22.0 -7.6 246 43 22 7.0 3.8
26000 -20.7 -5.3 252 35 18 6.3 3.5 | -20.0 -4.0 247 41 21 7.0 3.8
25000 -18.9 -2.0 253 32 16 6.6 3.6 | -17.9 -0.2 248 40 20 6.4 3.5
24000 -16.9 1.6 252 30 15 6.9 3.8 | -16.2 2.8 251 36 18 5.5 3.0
23000 -14.8 5.4 251 28 14 7.0 3.8 | -14.6 5.7 254 32 17 5.5 3.0
22000 -12.8 9.0 250 26 13 6.4 3.5 | -12.9 8.8 258 29 15 6.2 3.4
21000 -11.1 12.0 250 24 12 5.7 3.2 | -10.8 12.6 256 26 13 6.9 3.8
20000 -9.5 14.9 250 22 11 5.8 3.2 | -8.8 16.2 253 23 12 7.0 3.8
19500 -8.6 16.5 250 21 11 5.8 3.2 | -7.8 18.0 251 22 11 7.0 3.8
19000 -7.8 18.0 248 20 10 6.2 3.4 | -6.8 19.8 250 21 11 6.2 3.4
18500 -6.9 19.6 245 19 10 6.2 3.4 | -5.9 21.4 248 21 11 6.3 3.5
18000 -6.0 21.2 241 18 9 6.7 3.7 | -5.0 23.0 247 20 10 6.4 3.5
17500 -4.9 23.2 236 18 9 7.1 3.9 | -4.1 24.6 245 20 10 6.4 3.5
17000 -3.4 25.9 228 18 9 8.3 4.5 | -2.7 27.1 242 19 10 7.0 3.9
16500 -2.0 28.4 224 18 9 8.9 4.9 | -1.6 29.1 241 18 9 7.4 4.1
16000 -0.7 30.7 220 18 9 8.9 4.9 | -0.6 30.9 239 17 9 7.4 4.1
15500 0.5 32.9 220 17 9 8.2 4.5 | 0.5 32.9 237 16 8 7.5 4.1
15000 1.7 35.1 220 16 8 8.3 4.6 | 1.6 34.9 235 15 8 7.5 4.1
14500 2.9 37.2 221 14 7 7.3 4.0 | 2.7 36.9 233 14 7 8.0 4.4
14000 4.0 39.2 223 12 6 7.4 4.0 | 3.9 39.0 231 12 6 8.0 4.4
13500 5.1 41.2 226 10 5 8.1 4.4 | 5.0 41.0 230 10 5 8.2 4.5
13000 6.3 43.3 230 8 4 8.3 4.5 | 6.2 43.2 231 9 5 8.3 4.6
12500 7.5 45.5 237 7 3 8.8 4.8 | 7.4 45.3 233 7 4 8.5 4.7
12000 8.8 47.8 256 7 4 9.1 5.0 | 8.7 47.7 238 7 3 8.6 4.7
11500 10.2 50.4 270 9 4 8.7 4.7 | 9.9 49.8 244 6 3 8.3 4.6
11000 11.3 52.3 279 10 5 8.1 4.5 | 11.0 51.8 255 4 2 8.0 4.4
10500 12.5 54.5 287 12 6 8.4 4.6 | 12.1 53.8 280 3 1 8.4 4.6
10250 13.1 55.6 289 12 6 8.9 4.9 | 12.8 55.0 290 2 1 8.8 4.8
10000 13.8 56.8 292 11 6 8.8 4.8 | 13.4 56.1 302 2 1 8.8 4.8
9750 14.4 57.9 295 11 6 8.8 4.9 | 14.0 57.2 315 2 1 8.7 4.8
9500 15.1 59.2 298 11 6 8.8 4.8 | 14.6 58.3 330 2 1 9.2 5.0
9250 15.7 60.3 300 11 6 8.8 4.8 | 15.4 59.7 333 2 1 9.7 5.3
9000 16.4 61.5 302 11 6 8.8 4.8 | 16.1 61.0 335 2 1 9.5 5.2
8750 17.0 62.6 304 11 6 8.9 4.9 | 16.8 62.2 338 2 1 9.6 5.3
8500 17.7 63.9 306 11 6 8.3 4.5 | 17.5 63.5 340 2 1 9.7 5.3
8250 18.2 64.8 308 11 6 7.8 4.3 | 18.2 64.8 340 2 1 9.7 5.3
8000 18.8 65.8 309 11 6 7.9 4.3 | 18.9 66.0 340 2 1 9.7 5.3
7750 19.4 66.9 311 12 6 7.8 4.3 | 19.7 67.5 340 2 1 9.8 5.4
7500 20.0 68.0 313 12 6 7.6 4.2 | 20.4 68.7 340 2 1 10.1 5.5
7250 20.5 68.9 316 12 6 7.4 4.1 | 21.2 70.2 340 3 1 10.2 5.6
7000 21.1 70.0 318 12 6 7.6 4.2 | 21.9 71.4 339 3 1 10.2 5.6
6750 21.6 70.9 321 12 6 7.0 3.8 | 22.7 72.9 339 3 1 10.2 5.6
6500 22.1 71.8 320 10 5 6.1 3.3 | 23.4 74.1 338 3 1 10.2 5.6
6250 22.5 72.5 317 8 4 6.1 3.3 | 24.2 75.6 338 3 1 10.2 5.6
6000 23.0 73.4 311 6 3 5.8 3.2 | 25.0 77.0 337 3 1 10.0 5.5
5750 23.6 74.5 303 4 2 12.0 6.6 | 25.8 78.4 337 3 1 15.8 8.7
5500 24.9 76.8 302 4 2 23.1 12.7 | 27.4 81.3 339 2 1 26.0 14.3
09/02/2012 at 1500 MDT | 09/02/2012 at 1800 MDT
|
K index... +29.4 | K index... +29.3
|
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 -66.4 -87.5 246 50 26 4.0 2.2 | -65.9 -86.6 249 52 27 4.0 2.2
45000 -58.5 -73.3 249 64 33 6.8 3.7 | -58.3 -72.9 249 66 34 6.3 3.5
40000 -48.7 -55.7 250 73 38 5.3 2.9 | -49.0 -56.2 249 73 38 5.4 2.9
38000 -45.5 -49.9 250 70 36 5.3 2.9 | -45.8 -50.4 250 69 35 5.4 2.9
36000 -42.3 -44.1 249 66 34 5.7 3.1 | -42.6 -44.7 251 65 33 5.7 3.1
34000 -38.0 -36.4 246 63 32 7.4 4.0 | -38.0 -36.4 247 57 29 7.8 4.3
32000 -33.6 -28.5 243 60 31 7.3 4.0 | -33.4 -28.1 240 49 25 7.8 4.3
30000 -28.2 -18.8 241 51 26 8.3 4.5 | -28.3 -18.9 240 45 23 7.7 4.2
29000 -25.7 -14.3 240 46 24 8.3 4.6 | -26.0 -14.8 241 43 22 7.8 4.3
28000 -23.5 -10.3 240 42 22 5.1 2.8 | -23.8 -10.8 243 41 21 6.6 3.6
27000 -21.9 -7.4 243 40 21 5.4 3.0 | -21.8 -7.2 245 37 19 6.7 3.7
26000 -20.3 -4.5 247 38 20 5.4 3.0 | -19.8 -3.6 249 32 17 6.7 3.7
25000 -18.7 -1.7 251 36 19 6.2 3.4 | -17.9 -0.2 253 28 14 6.3 3.5
24000 -16.4 2.5 254 34 17 7.5 4.1 | -16.2 2.8 259 24 13 5.6 3.1
23000 -14.1 6.6 258 32 16 7.5 4.1 | -14.6 5.7 265 21 11 5.6 3.1
22000 -11.9 10.6 262 30 15 6.5 3.6 | -12.9 8.8 275 19 10 5.9 3.2
21000 -10.3 13.5 263 26 13 5.4 2.9 | -11.1 12.0 272 15 8 6.3 3.5
20000 -8.6 16.5 263 21 11 5.3 2.9 | -9.3 15.3 268 12 6 6.3 3.5
19500 -7.8 18.0 263 19 10 5.3 2.9 | -8.4 16.9 265 10 5 6.3 3.5
19000 -7.0 19.4 264 18 9 6.7 3.7 | -7.5 18.5 263 9 5 6.3 3.5
18500 -6.0 21.2 265 18 9 6.7 3.7 | -6.5 20.3 263 9 4 6.3 3.5
18000 -5.1 22.8 267 18 9 7.0 3.8 | -5.6 21.9 263 8 4 6.4 3.5
17500 -4.1 24.6 268 17 9 7.4 4.1 | -4.7 23.5 257 8 4 6.5 3.6
17000 -3.1 26.4 269 17 9 7.6 4.2 | -3.7 25.3 251 8 4 6.5 3.5
16500 -1.5 29.3 269 15 8 7.7 4.2 | -2.1 28.2 246 8 4 7.9 4.3
16000 -0.4 31.3 267 14 7 7.8 4.3 | -0.9 30.4 244 9 4 8.0 4.4
15500 0.7 33.3 264 12 6 8.0 4.4 | 0.3 32.5 238 9 5 8.4 4.6
15000 1.8 35.2 258 10 5 8.0 4.4 | 1.5 34.7 232 10 5 8.3 4.6
14500 3.0 37.4 249 9 5 8.0 4.4 | 2.7 36.9 226 11 6 8.8 4.9
14000 4.2 39.6 237 8 4 8.0 4.4 | 4.0 39.2 219 12 6 8.8 4.8
13500 5.3 41.5 221 7 3 8.5 4.6 | 5.3 41.5 214 13 7 9.6 5.3
13000 6.6 43.9 206 7 3 8.6 4.7 | 6.8 44.2 214 13 7 9.8 5.4
12500 7.8 46.0 191 7 4 8.8 4.8 | 8.2 46.8 213 13 7 9.7 5.3
12000 9.1 48.4 183 7 4 8.9 4.9 | 9.6 49.3 213 13 6 9.5 5.2
11500 10.4 50.7 176 7 4 8.9 4.9 | 11.0 51.8 213 12 6 9.4 5.1
11000 11.7 53.1 174 7 4 8.9 4.9 | 12.4 54.3 212 12 6 9.2 5.0
10500 13.0 55.4 172 7 4 9.3 5.1 | 13.7 56.7 211 11 6 9.4 5.1
10250 13.7 56.7 171 7 4 9.9 5.4 | 14.4 57.9 211 11 6 9.8 5.4
10000 14.4 57.9 171 7 4 9.9 5.4 | 15.2 59.4 211 11 6 9.7 5.3
9750 15.2 59.4 171 7 4 9.9 5.4 | 15.9 60.6 211 11 5 9.8 5.4
9500 15.9 60.6 170 7 3 9.8 5.4 | 16.6 61.9 211 10 5 9.6 5.3
9250 16.6 61.9 170 7 3 9.8 5.4 | 17.3 63.1 211 10 5 9.3 5.1
9000 17.4 63.3 171 7 3 9.8 5.4 | 18.0 64.4 211 10 5 9.4 5.1
8750 18.1 64.6 171 7 3 9.8 5.4 | 18.7 65.7 211 10 5 9.3 5.1
8500 18.8 65.8 171 7 3 9.8 5.4 | 19.4 66.9 211 9 5 9.5 5.2
8250 19.6 67.3 171 7 3 9.9 5.4 | 20.1 68.2 211 9 5 9.7 5.3
8000 20.3 68.5 171 7 3 9.9 5.4 | 20.8 69.4 212 9 4 9.6 5.3
7750 21.1 70.0 171 6 3 9.9 5.4 | 21.5 70.7 212 8 4 9.6 5.3
7500 21.8 71.2 172 6 3 10.1 5.5 | 22.2 72.0 212 8 4 9.6 5.3
7250 22.6 72.7 172 6 3 10.3 5.6 | 22.9 73.2 213 8 4 9.6 5.3
7000 23.3 73.9 172 6 3 10.2 5.6 | 23.7 74.7 213 8 4 9.6 5.3
6750 24.1 75.4 173 6 3 10.4 5.7 | 24.4 75.9 214 8 4 9.7 5.3
6500 24.9 76.8 173 6 3 10.7 5.9 | 25.1 77.2 215 8 4 9.9 5.4
6250 25.7 78.3 173 6 3 11.3 6.2 | 25.9 78.6 216 7 4 10.1 5.5
6000 26.5 79.7 173 6 3 9.5 5.2 | 26.6 79.9 217 7 4 9.7 5.3
5750 27.3 81.1 173 6 3 16.1 8.8 | 27.3 81.1 218 7 4 10.9 6.0
5500 29.1 84.4 173 6 3 32.3 17.7 | 28.2 82.8 219 6 3 13.8 7.6
________________________________________________________________________________
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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