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Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
000
UXUS97 KBOU 181334
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
733 AM MDT Saturday May 18, 2013
This forecast is for Saturday May 18, 2013:
If the trigger temperature of 74.0 F/23.3 C is reached...then
Thermal Soaring Index....................... Excellent
Maximum rate of lift........................ 1228 ft/min (6.2 m/s)
Maximum height of thermals.................. 19961 ft MSL (14676 ft AGL)
Forecast maximum temperature................... 82.0 F/28.2 C
Time of trigger temperature.................... 1015 MDT
Time of overdevelopment........................ 1500 MDT
Middle/high clouds during soaring window....... Overcast opaque high
Surface winds during soaring window............ 20 mph or less
Height of the -3 thermal index................. 10456 ft MSL (5171 ft AGL)
Thermal soaring outlook for Sunday 05/19....... Fair
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....................... 27482 ft MSL (22197 ft AGL)
Wave soaring outlook for Sunday 05/19.......... Poor
Remarks... None
Sunrise/Sunset.................... 05:42:09 / 20:09:32 MDT
Total possible sunshine........... 14 hr 27 min 23 sec (867 min 23 sec)
Altitude of sun at 12:56:02 MDT... 69.92 degrees
Upper air data from rawinsonde observation taken on 05/18/2013 at 0600 MDT
Freezing level.................. 13825 ft MSL (8540 ft AGL)
Convective condensation level... 23064 ft MSL (17779 ft AGL)
Lifted condensation level....... 22707 ft MSL (17421 ft AGL)
Lifted index.................... +0.9
K index......................... -3.2
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 -57.7 -71.9 244 25 13 -2.9 -1.6 100.4 212.8 41.9 M M
45000 -54.8 -66.6 225 20 10 1.2 0.7 80.8 177.4 32.7 M M
40000 -60.4 -76.7 211 49 25 -7.8 -4.3 48.9 120.0 14.0 M M
38000 -59.2 -74.6 207 49 25 8.2 4.5 41.7 107.0 9.4 M M
36000 -54.3 -65.7 199 46 24 8.2 4.5 40.2 104.4 8.7 M M
34000 -48.7 -55.7 192 44 23 7.3 4.0 39.1 102.3 8.1 M M
32000 -44.6 -48.3 187 44 23 8.9 4.9 36.6 97.9 6.5 M M
30000 -39.2 -38.6 190 45 23 8.9 4.9 36.1 97.0 6.3 M M
29000 -36.6 -33.9 192 45 23 8.9 4.9 35.5 96.0 5.9 M M
28000 -33.9 -29.0 194 45 23 8.9 4.9 35.1 95.2 5.7 M M
27000 -31.2 -24.2 196 45 23 8.9 4.9 34.8 94.7 5.5 M M
26000 -28.6 -19.5 198 45 23 8.7 4.8 34.6 94.4 5.4 M M
25000 -26.5 -15.7 199 45 23 0.8 0.4 33.6 92.4 4.6 M M
24000 -26.6 -15.9 200 42 21 5.3 2.9 29.9 85.8 1.7 M M
23000 -24.2 -11.6 201 40 21 8.0 4.4 29.3 84.8 1.2 M M
22000 -21.6 -6.9 202 39 20 8.9 4.9 28.9 84.1 0.8 M M
21000 -18.8 -1.8 203 38 20 10.4 5.7 28.8 83.8 0.7 M M
20000 -16.5 2.3 204 37 19 7.8 4.3 28.1 82.6 0.1 M M
19500 -15.3 4.5 203 37 19 8.4 4.6 27.8 82.1 -0.2 1388 7.1
19000 -14.1 6.6 201 36 19 8.1 4.4 27.6 81.7 -0.4 1337 6.8
18500 -12.8 9.0 200 36 18 8.7 4.8 27.3 81.2 -0.6 1284 6.5
18000 -11.5 11.3 202 35 18 8.7 4.8 27.1 80.8 -0.8 1230 6.2
17500 -10.2 13.6 203 34 17 8.7 4.8 26.9 80.5 -1.0 1176 6.0
17000 -8.2 17.2 206 32 17 8.7 4.8 26.7 80.0 -1.2 1095 5.6
16500 -6.9 19.6 208 32 16 8.7 4.8 26.5 79.8 -1.3 1040 5.3
16000 -5.6 21.9 210 31 16 8.7 4.8 26.4 79.5 -1.4 986 5.0
15500 -4.3 24.3 213 29 15 8.7 4.8 26.2 79.1 -1.6 932 4.7
15000 -3.0 26.6 217 28 14 8.8 4.8 26.0 78.8 -1.8 878 4.5
14500 -1.6 29.1 221 27 14 9.0 5.0 25.9 78.6 -1.9 823 4.2
14000 -0.3 31.5 225 26 13 9.1 5.0 25.8 78.4 -2.0 767 3.9
13500 1.1 34.0 227 25 13 9.1 5.0 25.7 78.2 -2.1 711 3.6
13000 2.5 36.5 229 24 12 9.1 5.0 25.5 78.0 -2.2 655 3.3
12500 3.8 38.8 232 23 12 9.1 5.0 25.4 77.8 -2.3 599 3.0
12000 5.2 41.4 235 22 11 9.1 5.0 25.4 77.6 -2.4 544 2.8
11500 6.6 43.9 235 19 10 9.1 5.0 25.2 77.4 -2.6 488 2.5
11000 7.9 46.2 237 17 9 9.2 5.1 25.1 77.1 -2.7 432 2.2
10500 9.1 48.4 238 15 8 5.3 2.9 24.8 76.6 -3.0 381 1.9
10250 9.5 49.1 239 14 7 4.8 2.6 24.4 75.9 -3.4 364 1.9
10000 9.9 49.8 242 12 6 6.8 3.7 24.1 75.3 -3.7 344 1.7
9750 10.4 50.7 248 11 6 7.3 4.0 23.9 75.0 -3.9 320 1.6
9500 11.0 51.8 255 10 5 7.1 3.9 23.7 74.6 -4.1 297 1.5
9250 11.5 52.7 264 9 4 7.2 3.9 23.5 74.2 -4.3 273 1.4
9000 12.0 53.6 275 8 4 7.2 3.9 23.3 73.9 -4.5 250 1.3
8750 12.6 54.7 278 8 4 7.2 3.9 23.1 73.5 -4.7 226 1.2
8500 13.1 55.6 282 8 4 7.2 4.0 22.9 73.2 -4.9 203 1.0
8250 13.7 56.7 286 8 4 7.0 3.8 22.7 72.8 -5.2 179 0.9
8000 14.2 57.6 290 8 4 7.8 4.3 22.5 72.5 -5.4 156 0.8
7750 14.8 58.6 295 7 4 8.7 4.8 22.4 72.3 -5.5 129 0.7
7500 15.5 59.9 302 7 3 8.5 4.7 22.3 72.1 -5.6 103 0.5
7250 16.1 61.0 310 6 3 8.5 4.7 22.2 71.9 -5.7 77 0.4
7000 16.7 62.1 319 6 3 8.6 4.7 22.1 71.8 -5.8 50 0.3
6750 17.4 63.3 309 6 3 8.1 4.5 22.0 71.6 -5.9 24 0.1
6500 18.0 64.4 298 6 3 10.0 5.5 21.9 71.4 -6.0 M M
6250 18.6 65.5 286 6 3 3.1 1.7 21.8 71.3 -6.1 M M
6000 18.4 65.1 276 6 3 -3.7 -2.0 20.9 69.6 -7.1 M M
5750 17.9 64.2 275 4 2 -13.8 -7.6 19.7 67.5 -8.3 M M
5500 15.8 60.4 275 2 1 -39.8 -21.8 17.0 62.5 -11.2 32 0.2
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
05/18/2013 at 0900 MDT | 05/18/2013 at 1200 MDT
|
K index... +9.8 | K index... +10.3
|
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 -56.9 -70.4 240 18 9 2.3 1.3 | -56.2 -69.2 242 14 7 2.1 1.2
45000 -54.2 -65.6 229 28 14 -3.1 -1.7 | -53.6 -64.5 234 19 10 -2.6 -1.4
40000 -59.0 -74.2 205 51 26 -3.0 -1.7 | -57.5 -71.5 205 48 25 -2.6 -1.4
38000 -57.1 -70.8 201 55 28 6.0 3.3 | -56.3 -69.3 201 54 28 4.4 2.4
36000 -53.0 -63.4 198 56 29 6.0 3.3 | -53.4 -64.1 197 59 30 4.4 2.4
34000 -48.9 -56.0 196 55 28 7.6 4.2 | -49.8 -57.6 195 60 31 8.3 4.5
32000 -44.4 -47.9 195 53 27 7.7 4.2 | -44.8 -48.6 197 57 30 8.3 4.5
30000 -39.9 -39.8 195 51 26 7.2 4.0 | -40.0 -40.0 198 55 28 7.8 4.3
29000 -37.7 -35.9 195 51 26 7.2 4.0 | -37.6 -35.7 199 53 27 7.8 4.3
28000 -35.5 -31.9 195 50 26 7.2 4.0 | -35.3 -31.5 200 51 26 7.8 4.3
27000 -33.4 -28.1 195 49 25 7.3 4.0 | -33.1 -27.6 199 50 26 6.0 3.3
26000 -31.2 -24.2 196 47 24 7.3 4.0 | -31.3 -24.3 197 48 25 6.1 3.4
25000 -29.0 -20.2 198 45 23 7.3 4.0 | -29.5 -21.1 195 47 24 6.1 3.4
24000 -26.8 -16.2 199 44 23 8.1 4.4 | -27.6 -17.7 193 45 23 7.5 4.1
23000 -24.4 -11.9 198 44 22 8.1 4.4 | -25.3 -13.5 192 41 21 7.7 4.2
22000 -22.0 -7.6 197 43 22 8.2 4.5 | -23.0 -9.4 192 37 19 7.7 4.2
21000 -19.6 -3.3 197 42 22 8.3 4.5 | -20.6 -5.1 192 34 18 8.8 4.8
20000 -17.2 1.0 197 39 20 8.3 4.6 | -18.1 -0.6 190 33 17 8.7 4.8
19500 -15.9 3.4 197 37 19 8.3 4.6 | -16.1 3.0 189 32 17 8.7 4.8
19000 -14.1 6.6 197 34 18 8.1 4.4 | -14.8 5.4 188 31 16 8.8 4.8
18500 -12.9 8.8 198 33 17 7.8 4.3 | -13.5 7.7 188 30 16 8.8 4.8
18000 -11.8 10.8 198 32 16 7.7 4.2 | -12.2 10.0 187 29 15 8.8 4.8
17500 -10.6 12.9 199 31 16 8.6 4.7 | -10.9 12.4 186 27 14 8.2 4.5
17000 -9.3 15.3 201 30 15 8.6 4.7 | -9.7 14.5 186 25 13 8.2 4.5
16500 -7.9 17.8 203 29 15 8.7 4.8 | -8.5 16.7 187 23 12 8.2 4.5
16000 -6.6 20.1 205 28 14 8.8 4.8 | -7.2 19.0 191 21 11 8.2 4.5
15500 -5.3 22.5 207 26 14 8.6 4.7 | -6.0 21.2 196 20 10 8.2 4.5
15000 -4.1 24.6 209 24 12 7.6 4.2 | -4.7 23.5 201 19 10 8.3 4.5
14500 -2.9 26.8 212 22 11 7.6 4.2 | -3.5 25.7 206 19 10 8.2 4.5
14000 -1.8 28.8 214 19 10 7.6 4.2 | -2.3 27.9 210 19 10 8.6 4.7
13500 -0.6 30.9 215 17 8 7.5 4.1 | -1.0 30.2 214 19 10 8.6 4.7
13000 0.6 33.1 216 15 8 9.3 5.1 | 0.2 32.4 217 19 10 8.4 4.6
12500 2.0 35.6 216 14 7 9.4 5.1 | 1.5 34.7 217 18 9 8.4 4.6
12000 3.3 37.9 215 12 6 8.4 4.6 | 2.7 36.9 218 17 9 8.0 4.4
11500 4.6 40.3 209 10 5 8.3 4.5 | 3.9 39.0 219 14 7 7.9 4.3
11000 5.8 42.4 203 7 4 8.7 4.8 | 5.1 41.2 219 12 6 8.7 4.7
10500 7.1 44.8 210 6 3 8.8 4.8 | 6.4 43.5 218 10 5 8.9 4.9
10250 7.8 46.0 215 6 3 8.6 4.7 | 7.1 44.8 216 9 5 8.9 4.9
10000 8.4 47.1 227 5 3 8.1 4.4 | 7.7 45.9 217 8 4 8.8 4.9
9750 9.0 48.2 246 6 3 7.9 4.3 | 8.4 47.1 222 7 4 8.8 4.9
9500 9.6 49.3 262 7 4 7.9 4.3 | 9.0 48.2 229 6 3 8.8 4.8
9250 10.2 50.4 272 8 4 8.0 4.4 | 9.7 49.5 240 5 2 8.9 4.9
9000 10.8 51.4 278 9 5 8.2 4.5 | 10.3 50.5 252 4 2 9.2 5.0
8750 11.4 52.5 282 9 5 8.2 4.5 | 11.0 51.8 266 4 2 9.3 5.1
8500 12.0 53.6 285 10 5 8.3 4.5 | 11.7 53.1 280 4 2 9.2 5.0
8250 12.6 54.7 288 11 5 8.2 4.5 | 12.4 54.3 293 4 2 9.5 5.2
8000 13.2 55.8 291 11 5 8.1 4.4 | 13.1 55.6 296 4 2 9.9 5.4
7750 13.8 56.8 293 11 5 8.1 4.4 | 13.8 56.8 297 4 2 9.9 5.4
7500 14.4 57.9 296 11 5 8.1 4.4 | 14.6 58.3 298 4 2 9.9 5.4
7250 14.9 58.8 298 11 6 5.8 3.2 | 15.3 59.5 299 4 2 10.0 5.5
7000 15.2 59.4 297 12 6 4.0 2.2 | 16.0 60.8 299 4 2 10.1 5.5
6750 15.6 60.1 297 12 6 4.6 2.5 | 16.8 62.2 299 4 2 10.0 5.5
6500 15.9 60.6 296 13 7 4.1 2.3 | 17.6 63.7 300 4 2 10.3 5.6
6250 16.1 61.0 293 12 6 3.6 2.0 | 18.3 64.9 300 4 2 10.7 5.9
6000 16.3 61.3 285 9 5 3.4 1.9 | 19.2 66.6 301 4 2 11.1 6.1
5750 16.5 61.7 270 7 3 4.0 2.2 | 20.0 68.0 302 4 2 10.4 5.7
5500 17.0 62.6 248 5 3 10.9 6.0 | 20.9 69.6 302 4 2 16.6 9.1
05/18/2013 at 1500 MDT | 05/18/2013 at 1800 MDT
|
K index... +21.7 | K index... +20.8
|
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 -55.8 -68.4 243 10 5 2.5 1.4 | -55.3 -67.5 251 11 6 3.3 1.8
45000 -52.5 -62.5 227 12 6 -1.3 -0.7 | -50.9 -59.6 233 13 7 -1.2 -0.7
40000 -54.3 -65.7 206 40 21 -1.1 -0.6 | -52.4 -62.3 217 28 14 -1.0 -0.5
38000 -53.8 -64.8 202 47 24 1.5 0.8 | -52.4 -62.3 208 35 18 0.5 0.3
36000 -52.9 -63.2 198 52 27 1.5 0.8 | -52.1 -61.8 200 43 22 0.5 0.3
34000 -50.9 -59.6 196 56 29 7.3 4.0 | -50.8 -59.4 197 48 25 5.9 3.2
32000 -46.5 -51.7 196 56 29 7.4 4.0 | -47.3 -53.1 198 46 24 6.0 3.3
30000 -42.0 -43.6 198 54 28 8.0 4.4 | -42.6 -44.7 202 43 22 8.5 4.7
29000 -39.0 -38.2 202 52 27 8.0 4.4 | -40.1 -40.2 205 40 21 8.5 4.7
28000 -36.6 -33.9 205 49 25 8.0 4.4 | -37.5 -35.5 209 37 19 8.5 4.7
27000 -34.2 -29.6 207 47 24 8.1 4.4 | -35.0 -31.0 212 34 18 8.0 4.4
26000 -31.8 -25.2 209 44 23 8.1 4.4 | -32.7 -26.9 213 31 16 8.1 4.4
25000 -29.4 -20.9 211 41 21 8.1 4.4 | -30.3 -22.5 213 27 14 8.1 4.4
24000 -27.0 -16.6 212 38 19 7.7 4.2 | -27.9 -18.2 214 24 12 7.9 4.3
23000 -24.7 -12.5 210 35 18 7.7 4.2 | -25.5 -13.9 212 23 12 7.9 4.3
22000 -22.5 -8.5 208 33 17 7.7 4.2 | -23.2 -9.8 209 22 11 7.9 4.4
21000 -20.2 -4.4 204 31 16 7.6 4.2 | -20.8 -5.4 206 22 11 8.2 4.5
20000 -17.9 -0.2 199 30 15 7.6 4.2 | -18.4 -1.1 201 22 11 8.2 4.5
19500 -16.8 1.8 196 29 15 7.6 4.2 | -17.2 1.0 199 23 12 8.2 4.5
19000 -15.7 3.7 193 29 15 7.6 4.2 | -15.9 3.4 197 23 12 8.2 4.5
18500 -14.6 5.7 191 28 14 7.7 4.2 | -14.7 5.5 196 23 12 8.2 4.5
18000 -13.4 7.9 190 26 14 7.7 4.2 | -13.5 7.7 196 22 12 8.2 4.5
17500 -12.3 9.9 188 25 13 7.5 4.1 | -12.3 9.9 196 22 11 8.4 4.6
17000 -11.2 11.8 188 23 12 7.3 4.0 | -11.1 12.0 197 21 11 8.7 4.7
16500 -10.2 13.6 188 21 11 7.2 4.0 | -9.1 15.6 199 19 10 8.5 4.7
16000 -8.4 16.9 190 20 10 8.3 4.6 | -7.9 17.8 199 18 9 8.3 4.6
15500 -7.1 19.2 193 19 10 8.5 4.7 | -6.7 19.9 199 18 9 8.4 4.6
15000 -5.8 21.6 194 19 10 9.3 5.1 | -5.4 22.3 198 17 9 8.6 4.7
14500 -4.4 24.1 196 19 10 9.2 5.1 | -4.2 24.4 197 16 8 8.5 4.7
14000 -3.0 26.6 197 19 10 9.9 5.4 | -2.8 27.0 197 16 8 9.6 5.3
13500 -1.6 29.1 198 18 9 9.9 5.4 | -1.4 29.5 198 15 8 9.5 5.2
13000 -0.1 31.8 200 17 9 9.5 5.2 | 0.0 32.0 199 15 8 9.6 5.3
12500 1.3 34.3 202 16 8 9.5 5.2 | 1.4 34.5 201 14 7 9.6 5.3
12000 2.7 36.9 205 15 8 9.2 5.1 | 2.9 37.2 203 14 7 9.5 5.2
11500 4.1 39.4 208 12 6 9.2 5.1 | 4.3 39.7 206 13 7 9.4 5.2
11000 5.4 41.7 212 10 5 8.6 4.7 | 5.7 42.3 209 12 6 9.4 5.1
10500 6.6 43.9 221 8 4 8.4 4.6 | 7.1 44.8 212 11 6 9.3 5.1
10250 7.2 45.0 228 7 3 8.6 4.7 | 7.8 46.0 214 10 5 9.3 5.1
10000 7.9 46.2 234 6 3 9.3 5.1 | 8.4 47.1 216 10 5 8.8 4.8
9750 8.6 47.5 238 6 3 9.6 5.3 | 9.1 48.4 219 9 4 8.5 4.6
9500 9.3 48.7 241 5 3 9.5 5.2 | 9.7 49.5 222 8 4 8.6 4.7
9250 10.0 50.0 245 5 3 9.6 5.3 | 10.3 50.5 225 7 3 8.4 4.6
9000 10.7 51.3 248 5 3 9.8 5.4 | 10.9 51.6 233 6 3 7.5 4.1
8750 11.5 52.7 250 5 3 9.8 5.4 | 11.4 52.5 251 4 2 7.2 4.0
8500 12.2 54.0 252 5 3 9.8 5.4 | 11.9 53.4 276 4 2 7.1 3.9
8250 12.9 55.2 253 5 3 9.8 5.4 | 12.5 54.5 302 4 2 8.0 4.4
8000 13.6 56.5 255 5 3 9.7 5.3 | 13.1 55.6 313 5 2 9.6 5.3
7750 14.4 57.9 257 5 3 9.7 5.3 | 13.8 56.8 316 5 3 9.9 5.4
7500 15.1 59.2 259 5 3 9.7 5.3 | 14.6 58.3 320 6 3 9.8 5.4
7250 15.8 60.4 260 5 3 9.9 5.4 | 15.3 59.5 322 6 3 9.8 5.4
7000 16.6 61.9 261 5 3 10.1 5.5 | 16.0 60.8 323 6 3 9.8 5.4
6750 17.3 63.1 262 5 3 10.0 5.5 | 16.8 62.2 323 6 3 9.8 5.4
6500 18.1 64.6 263 6 3 10.1 5.6 | 17.5 63.5 324 6 3 9.9 5.4
6250 18.8 65.8 264 6 3 10.2 5.6 | 18.2 64.8 324 7 3 10.2 5.6
6000 19.6 67.3 266 6 3 10.6 5.8 | 19.0 66.2 325 7 3 10.5 5.8
5750 20.4 68.7 267 6 3 9.4 5.2 | 19.8 67.6 325 6 3 9.8 5.4
5500 21.1 70.0 268 6 3 13.7 7.5 | 20.5 68.9 325 6 3 12.4 6.8
________________________________________________________________________________
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.
071806
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