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Soaring Guidance
Issued by NWS Pueblo, CO
Issued by NWS Pueblo, CO
000
UXUS97 KPUB 231157
SRGPUB
SOARING FORECAST
NATIONAL WEATHER SERVICE PUEBLO CO
557 AM MDT THU MAY 23 2013
EXPERIMENTAL PRODUCT
This forecast is for Thursday May 23, 2013:
If the trigger temperature of 62.1 F/16.7 C is reached...then
Thermal Soaring Index....................... Poor
Maximum rate of lift........................ 6 ft/min (0.0 m/s)
Maximum height of thermals.................. 12524 ft MSL (4862 ft AGL)
Forecast maximum temperature................... 65.0 F/18.8 C
Time of trigger temperature.................... 1115 MDT
Time of overdevelopment........................ None
Middle/high clouds during soaring window....... Broken/overcast opaque middle
Surface winds during soaring window............ Between 20 mph and 30 mph
Height of the -3 thermal index................. 11125 ft MSL (3463 ft AGL)
Thermal soaring outlook for Friday 05/24....... Excellent
Wave Soaring Index............................. Poor
Wave Soaring Index trend (to 1800 MDT)......... Poor
Height of stable layer (12-18K ft MSL)......... None
Weak PVA/NVA (through 1800 MDT)................ Weak PVA
Potential height of wave....................... 19201 ft MSL (11539 ft AGL)
Wave soaring outlook for Friday 05/24.......... Poor
Remarks...
Sunrise/Sunset.................... 05:40:21 / 20:11:36 MDT
Total possible sunshine........... 14 hr 31 min 15 sec (871 min 15 sec)
Altitude of sun at 12:56:10 MDT... 71.72 degrees
Upper air data from numerical model forecast valid on 05/23/2013 at 0600 MDT
Freezing level.................. 14140 ft MSL (6478 ft AGL)
Convective condensation level... 15367 ft MSL (7705 ft AGL)
Lifted condensation level....... 14861 ft MSL (7199 ft AGL)
Lifted index.................... -2.7
K index......................... +16.8
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 -60.5 -76.9 243 26 14 0.8 0.4 85.4 185.7 39.8 M M
45000 -59.6 -75.3 248 36 18 -1.4 -0.7 64.8 148.6 29.4 M M
40000 -61.8 -79.2 254 30 15 -1.5 -0.8 39.2 102.5 14.1 M M
38000 -58.4 -73.1 253 28 14 7.6 4.2 35.4 95.7 11.9 M M
36000 -53.3 -63.9 249 26 13 7.6 4.2 33.5 92.2 10.9 M M
34000 -48.5 -55.3 247 24 12 8.1 4.4 31.9 89.5 10.0 M M
32000 -43.7 -46.7 246 21 11 8.1 4.4 30.6 87.1 9.3 M M
30000 -38.8 -37.8 244 18 9 8.2 4.5 29.4 84.9 8.6 M M
29000 -36.4 -33.5 242 16 8 8.2 4.5 28.8 83.8 8.2 M M
28000 -33.9 -29.0 240 14 7 8.2 4.5 28.3 82.9 7.9 M M
27000 -31.6 -24.9 238 13 7 7.6 4.1 27.6 81.6 7.4 M M
26000 -29.3 -20.7 238 13 7 7.5 4.1 26.7 80.0 6.8 M M
25000 -27.1 -16.8 237 13 7 7.5 4.1 25.9 78.6 6.2 M M
24000 -24.9 -12.8 237 14 7 7.2 4.0 25.1 77.2 5.7 M M
23000 -22.2 -8.0 240 18 10 7.2 4.0 23.9 75.1 4.7 M M
22000 -20.0 -4.0 242 22 11 7.2 4.0 23.1 73.6 4.1 M M
21000 -17.8 -0.0 242 25 13 7.6 4.2 22.3 72.2 3.4 M M
20000 -15.6 3.9 242 28 14 7.7 4.2 21.6 70.8 2.7 M M
19500 -14.4 6.1 241 29 15 7.7 4.3 21.3 70.3 2.4 M M
19000 -13.3 8.1 241 30 15 8.3 4.6 21.0 69.8 2.1 M M
18500 -12.0 10.4 242 29 15 8.8 4.8 20.8 69.4 1.9 M M
18000 -10.8 12.6 242 27 14 8.8 4.8 20.6 69.2 1.8 M M
17500 -9.4 15.1 243 26 13 9.6 5.3 20.6 69.0 1.7 M M
17000 -8.0 17.6 244 25 13 9.5 5.2 20.5 68.9 1.6 M M
16500 -6.6 20.1 244 24 12 9.4 5.2 20.5 68.9 1.6 M M
16000 -5.2 22.6 244 22 11 9.4 5.2 20.4 68.7 1.6 M M
15500 -3.8 25.2 243 21 11 9.3 5.1 20.4 68.7 1.5 M M
15000 -2.4 27.7 241 20 10 9.2 5.0 20.3 68.5 1.4 M M
14500 -1.0 30.2 238 19 10 9.2 5.1 20.2 68.3 1.3 M M
14000 0.2 32.4 234 18 9 8.1 4.4 20.0 68.0 1.2 M M
13500 1.4 34.5 231 17 9 8.4 4.6 19.8 67.6 0.9 M M
13000 2.6 36.7 226 16 8 6.4 3.5 19.4 66.9 0.6 M M
12500 3.5 38.3 219 15 8 6.5 3.6 18.9 66.0 0.1 M M
12000 4.3 39.7 212 14 7 3.7 2.0 18.2 64.8 -0.6 372 1.9
11750 4.4 39.9 209 14 7 2.8 1.5 17.7 63.8 -1.2 359 1.8
11500 4.6 40.3 207 14 7 3.4 1.9 17.2 62.9 -1.7 346 1.8
11250 4.8 40.6 204 14 7 2.1 1.2 16.6 62.0 -2.3 333 1.7
11000 4.7 40.5 200 15 7 -4.2 -2.3 15.8 60.5 -3.1 329 1.7
10750 4.1 39.4 196 16 8 -7.5 -4.1 14.5 58.2 -4.4 338 1.7
10500 3.6 38.5 192 17 9 -6.8 -3.8 13.3 55.9 -5.7 348 1.8
10250 3.0 37.4 188 18 9 -5.9 -3.3 12.0 53.6 -7.0 358 1.8
10000 2.6 36.7 184 19 10 -1.6 -0.9 10.9 51.7 -8.1 361 1.8
9750 2.6 36.7 178 21 11 0.5 0.3 10.2 50.3 -8.9 355 1.8
9500 2.5 36.5 168 23 12 1.3 0.7 8.7 47.7 -10.5 342 1.7
9250 2.7 36.9 166 23 12 4.3 2.4 8.2 46.7 -11.1 329 1.7
9000 3.1 37.6 164 21 11 5.2 2.8 7.8 46.1 -11.5 311 1.6
8750 3.4 38.1 161 19 10 4.4 2.4 7.5 45.4 -11.9 293 1.5
8500 3.8 38.8 158 17 9 6.6 3.6 7.1 44.8 -12.3 275 1.4
8250 4.4 39.9 161 13 7 9.3 5.1 7.0 44.6 -12.4 249 1.3
8000 5.0 41.0 167 9 5 7.5 4.1 6.9 44.5 -12.5 223 1.1
7750 5.7 42.3 181 6 3 12.6 6.9 6.8 44.3 -12.7 197 1.0
7500 M M M M M M M M M M M M
7250 M M M M M M M M M M M M
7000 M M M M M M M M M M M M
6750 M M M M M M M M M M M M
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
05/23/2013 at 0900 MDT | 05/23/2013 at 1200 MDT
|
K index... +11.6 | K index... +4.5
|
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 -61.1 -78.0 247 30 15 1.2 0.7 | -61.0 -77.8 247 31 16 0.8 0.4
45000 -59.6 -75.3 245 42 22 -1.1 -0.6 | -60.1 -76.2 254 43 22 -0.8 -0.4
40000 -61.3 -78.3 240 29 15 -1.2 -0.7 | -61.4 -78.5 263 32 17 -1.1 -0.6
38000 -58.3 -72.9 236 27 14 6.9 3.8 | -58.1 -72.6 257 30 15 7.1 3.9
36000 -53.7 -64.7 231 25 13 6.9 3.8 | -53.3 -63.9 247 29 15 7.1 3.9
34000 -49.2 -56.6 231 25 13 8.1 4.4 | -48.8 -55.8 243 29 15 7.7 4.2
32000 -44.3 -47.7 235 27 14 8.1 4.4 | -44.2 -47.6 243 29 15 7.7 4.2
30000 -39.4 -38.9 236 26 13 8.4 4.6 | -39.4 -38.9 244 31 16 8.4 4.6
29000 -36.9 -34.4 235 25 13 8.4 4.6 | -36.9 -34.4 245 32 17 8.4 4.6
28000 -34.4 -29.9 234 24 12 8.4 4.6 | -34.4 -29.9 245 34 17 8.4 4.6
27000 -31.9 -25.4 235 23 12 8.1 4.4 | -31.9 -25.4 245 34 17 8.2 4.5
26000 -29.5 -21.1 238 23 12 8.0 4.4 | -29.5 -21.1 242 32 17 8.2 4.5
25000 -27.1 -16.8 241 23 12 8.0 4.4 | -27.0 -16.6 240 31 16 8.2 4.5
24000 -24.8 -12.6 243 23 12 7.4 4.0 | -24.6 -12.3 238 30 15 7.9 4.3
23000 -22.0 -7.6 244 24 12 7.4 4.1 | -21.7 -7.1 239 30 15 7.9 4.3
22000 -19.8 -3.6 245 25 13 7.4 4.1 | -19.3 -2.7 240 29 15 7.9 4.3
21000 -17.5 0.5 242 26 13 8.1 4.4 | -16.9 1.6 239 30 15 8.5 4.6
20000 -15.1 4.8 237 27 14 8.1 4.5 | -14.4 6.1 239 30 16 8.5 4.7
19500 -13.9 7.0 235 28 14 8.2 4.5 | -13.1 8.4 238 31 16 8.5 4.7
19000 -12.7 9.1 233 28 15 8.3 4.6 | -11.9 10.6 238 31 16 8.2 4.5
18500 -11.5 11.3 229 27 14 8.4 4.6 | -10.6 12.9 239 31 16 8.0 4.4
18000 -10.2 13.6 226 26 13 8.4 4.6 | -9.4 15.1 240 31 16 8.0 4.4
17500 -9.0 15.8 224 25 13 7.5 4.1 | -8.3 17.1 241 31 16 7.6 4.2
17000 -7.9 17.8 223 23 12 7.6 4.2 | -7.1 19.2 244 31 16 7.7 4.2
16500 -6.8 19.8 221 21 11 8.9 4.9 | -6.0 21.2 245 32 16 8.1 4.5
16000 -5.4 22.3 219 20 10 9.3 5.1 | -4.8 23.4 245 32 16 8.2 4.5
15500 -4.0 24.8 216 19 10 9.4 5.1 | -3.5 25.7 245 32 17 8.2 4.5
15000 -2.6 27.3 214 18 9 9.4 5.2 | -2.3 27.9 244 31 16 8.2 4.5
14500 -1.2 29.8 210 18 9 9.4 5.2 | -1.1 30.0 243 30 15 8.3 4.5
14000 0.1 32.2 208 17 9 9.0 4.9 | 0.2 32.4 242 29 15 9.6 5.2
13500 1.4 34.5 205 18 9 9.1 5.0 | 1.6 34.9 241 29 15 9.6 5.3
13000 2.7 36.9 203 18 9 8.2 4.5 | 3.0 37.4 240 28 14 8.4 4.6
12500 4.0 39.2 201 17 9 8.3 4.6 | 4.2 39.6 238 26 13 8.5 4.7
12000 5.1 41.2 199 17 9 7.3 4.0 | 5.4 41.7 235 24 12 8.4 4.6
11750 5.6 42.1 199 16 8 7.0 3.8 | 6.1 43.0 234 23 12 8.4 4.6
11500 6.2 43.2 199 15 8 7.3 4.0 | 6.7 44.1 232 22 11 8.5 4.6
11250 6.7 44.1 200 15 8 6.4 3.5 | 7.3 45.1 230 20 11 8.2 4.5
11000 7.0 44.6 200 15 7 3.4 1.9 | 7.8 46.0 228 19 10 7.6 4.2
10750 7.1 44.8 199 14 7 1.9 1.0 | 8.3 46.9 227 18 9 7.2 4.0
10500 7.3 45.1 199 14 7 3.1 1.7 | 8.9 48.0 226 17 9 8.1 4.5
10250 7.4 45.3 199 14 7 0.1 0.1 | 9.4 48.9 224 16 8 5.2 2.9
10000 7.0 44.6 198 14 7 -10.0 -5.5 | 9.4 48.9 221 15 8 -3.1 -1.7
9750 5.9 42.6 197 15 7 -14.0 -7.7 | 8.8 47.8 217 14 7 -5.9 -3.2
9500 3.8 38.8 194 16 8 -8.4 -4.6 | 7.8 46.0 208 14 7 -2.1 -1.2
9250 3.6 38.5 191 16 8 4.0 2.2 | 7.9 46.2 200 13 7 5.2 2.9
9000 4.0 39.2 187 16 8 7.3 4.0 | 8.4 47.1 191 13 7 7.5 4.1
8750 4.5 40.1 184 16 8 5.0 2.7 | 8.8 47.8 182 14 7 4.9 2.7
8500 4.9 40.8 180 15 8 11.0 6.0 | 9.3 48.7 173 14 7 13.1 7.2
8250 6.1 43.0 177 14 7 18.5 10.2 | 10.8 51.4 169 14 7 24.5 13.4
8000 7.3 45.1 174 12 6 14.0 7.7 | 12.5 54.5 166 13 7 19.2 10.5
7750 8.5 47.3 169 10 5 27.1 14.9 | 14.2 57.6 162 12 6 35.9 19.7
7500 M M M M M M M | M M M M M M M
7250 M M M M M M M | M M M M M M M
7000 M M M M M M M | M M M M M M M
6750 M M M M M M M | M M M M M M M
05/23/2013 at 1500 MDT | 05/23/2013 at 1800 MDT
|
K index... +13.0 | K index... +19.8
|
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 -61.0 -77.8 251 29 15 -0.2 -0.1 | -61.6 -78.9 256 23 12 -0.4 -0.2
45000 -61.3 -78.3 265 40 21 -0.1 -0.1 | -62.0 -79.6 276 25 13 0.7 0.4
40000 -61.5 -78.7 264 46 23 -0.6 -0.4 | -60.9 -77.6 267 42 22 0.2 0.1
38000 -57.8 -72.0 263 42 22 7.5 4.1 | -56.7 -70.1 264 39 20 7.1 3.9
36000 -52.7 -62.9 262 37 19 7.5 4.1 | -52.5 -62.5 261 35 18 7.0 3.9
34000 -48.1 -54.6 261 33 17 7.9 4.3 | -47.8 -54.0 259 31 16 8.4 4.6
32000 -43.4 -46.1 260 29 15 7.9 4.3 | -42.8 -45.0 260 29 15 8.4 4.6
30000 -38.5 -37.3 263 27 14 8.3 4.5 | -37.8 -36.0 260 29 15 8.2 4.5
29000 -36.1 -33.0 265 28 14 8.3 4.5 | -35.4 -31.7 261 30 16 8.2 4.5
28000 -33.6 -28.5 267 28 14 8.3 4.6 | -32.9 -27.2 262 32 16 8.2 4.5
27000 -31.3 -24.3 266 29 15 7.4 4.0 | -30.5 -22.9 261 33 17 7.8 4.3
26000 -29.1 -20.4 262 31 16 7.4 4.0 | -28.2 -18.8 259 35 18 7.8 4.3
25000 -26.9 -16.4 259 34 17 7.4 4.0 | -25.9 -14.6 257 38 19 7.8 4.3
24000 -24.6 -12.3 256 36 18 8.0 4.4 | -23.0 -9.4 253 41 21 7.4 4.1
23000 -21.7 -7.1 253 38 20 8.0 4.4 | -20.8 -5.4 250 45 23 7.5 4.1
22000 -19.3 -2.7 251 40 21 7.9 4.3 | -18.6 -1.5 247 48 25 7.3 4.0
21000 -16.8 1.8 249 38 20 8.6 4.7 | -16.2 2.8 244 48 25 8.4 4.6
20000 -14.2 6.4 248 35 18 8.6 4.7 | -13.7 7.3 241 47 24 8.5 4.7
19500 -13.0 8.6 247 34 17 8.6 4.7 | -12.4 9.7 239 46 24 8.5 4.7
19000 -11.7 10.9 246 32 17 9.2 5.0 | -11.2 11.8 238 45 23 8.8 4.8
18500 -10.3 13.5 244 32 17 9.3 5.1 | -9.9 14.2 236 43 22 8.9 4.9
18000 -8.9 16.0 243 33 17 9.3 5.1 | -8.6 16.5 234 41 21 8.9 4.9
17500 -7.6 18.3 242 34 18 8.5 4.7 | -7.4 18.7 232 39 20 8.4 4.6
17000 -6.3 20.7 241 36 19 8.6 4.7 | -6.1 21.0 230 38 19 8.4 4.6
16500 -5.0 23.0 240 38 19 8.5 4.6 | -4.9 23.2 228 36 18 9.0 4.9
16000 -3.8 25.2 238 38 19 8.5 4.6 | -3.5 25.7 225 34 18 9.1 5.0
15500 -2.6 27.3 237 38 20 8.7 4.8 | -2.2 28.0 222 32 17 9.2 5.1
15000 -1.3 29.7 235 38 19 9.1 5.0 | -0.8 30.6 222 30 15 9.4 5.2
14500 0.1 32.2 233 37 19 9.1 5.0 | 0.6 33.1 221 28 14 9.4 5.2
14000 1.3 34.3 231 36 18 8.5 4.7 | 1.9 35.4 218 26 14 8.2 4.5
13500 2.6 36.7 228 34 18 8.6 4.7 | 3.1 37.6 213 26 14 8.4 4.6
13000 3.8 38.8 225 32 17 8.1 4.5 | 4.2 39.6 208 27 14 6.7 3.7
12500 5.0 41.0 221 30 15 8.3 4.5 | 5.2 41.4 203 28 14 6.9 3.8
12000 6.1 43.0 216 27 14 6.9 3.8 | 6.1 43.0 199 29 15 4.8 2.6
11750 6.6 43.9 214 27 14 6.7 3.7 | 6.4 43.5 197 30 15 4.3 2.4
11500 7.1 44.8 211 26 14 6.8 3.7 | 6.7 44.1 196 30 16 4.7 2.6
11250 7.6 45.7 208 26 13 6.7 3.7 | 7.0 44.6 194 31 16 3.7 2.0
11000 8.1 46.6 206 25 13 6.3 3.5 | 7.1 44.8 192 31 16 0.6 0.3
10750 8.5 47.3 204 24 13 6.0 3.3 | 7.0 44.6 189 30 16 -0.7 -0.4
10500 8.9 48.0 202 24 12 6.5 3.6 | 6.9 44.4 186 30 15 -0.5 -0.3
10250 9.3 48.7 199 23 12 4.9 2.7 | 6.8 44.2 183 29 15 0.3 0.2
10000 9.4 48.9 196 22 12 -0.4 -0.2 | 6.9 44.4 179 29 15 2.9 1.6
9750 9.2 48.6 190 22 11 -2.3 -1.3 | 7.3 45.1 173 28 14 3.4 1.8
9500 8.7 47.7 179 22 11 0.7 0.4 | 7.6 45.7 170 27 14 5.5 3.0
9250 9.0 48.2 175 22 11 7.8 4.3 | 8.1 46.6 168 27 14 9.5 5.2
9000 9.7 49.5 172 22 11 10.1 5.6 | 8.9 48.0 167 27 14 10.7 5.9
8750 10.4 50.7 169 22 11 8.0 4.4 | 9.6 49.3 167 26 14 9.5 5.2
8500 11.1 52.0 167 22 11 14.2 7.8 | 10.4 50.7 166 26 14 13.1 7.2
8250 12.5 54.5 164 20 11 23.3 12.8 | 11.6 52.9 165 24 12 18.1 10.0
8000 14.2 57.6 162 19 10 20.2 11.1 | 12.9 55.2 163 21 11 16.0 8.8
7750 15.9 60.6 159 17 9 31.1 17.1 | 14.2 57.6 161 18 9 22.9 12.6
7500 M M M M M M M | M M M M M M M
7250 M M M M M M M | M M M M M M M
7000 M M M M M M M | M M M M M M M
6750 M M M M M M M | M M M M M M M
________________________________________________________________________________
This product is issued one per day by approximately 0630 MST/0730 MDT
(1330 UTC). It is not continuously monitored nor updated after its initial
issuance.
The information contained herein is based on numerical weather prediction
model data taken near the Air Force Academy in Colorado Springs, Colorado
at
North Latitude: 38 deg 58 min 48.000 sec
West Longitude: 104 deg 49 min 12.000 sec
Elevation: 6572 feet (2003 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.
At this time, the output from this considered experimental.
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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