Soaring Guidance
Issued by NWS Grand Junction, CO
Issued by NWS Grand Junction, CO
257
UXUS97 KGJT 211306
SRGGJT
Soaring Forecast
National Weather Service Grand Junction, Colorado
606 AM MST Friday, February 21, 2025
This forecast is for Friday, February 21, 2025:
If the trigger temperature of 42.5 F/5.8 C is reached...then
Thermal Soaring Index....................... Good
Maximum rate of lift........................ 675 ft/min (3.4 m/s)
Maximum height of thermals.................. 13262 ft MSL (8423 ft AGL)
Forecast maximum temperature................... 50.0 F/10.5 C
Time of trigger temperature.................... 1100 MST
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................. 9891 ft MSL (5052 ft AGL)
Thermal soaring outlook for Saturday 02/22..... Fair
Wave Soaring Index............................. Not available
Remarks...
Sunrise/Sunset.................... 06:57:07 / 17:58:13 MST
Total possible sunshine........... 11 hr 1 min 7 sec (661 min 7 sec)
Altitude of sun at 12:27:40 MST... 40.21 degrees
Upper air data from rawinsonde observation taken on 02/21/2025 at 0500 MST
Freezing level.................. 6097 ft MSL (1258 ft AGL)
Convective condensation level... 9242 ft MSL (4403 ft AGL)
Lifted condensation level....... 10860 ft MSL (6021 ft AGL)
Lifted index.................... +1.0
K index......................... +12.2
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 -56.7 -70.1 265 38 20 1.8 1.0 108.9 228.1 56.0 M M
45000 -52.6 -62.7 275 23 12 5.2 2.9 90.9 195.6 49.0 M M
40000 -50.4 -58.7 280 24 13 -1.3 -0.7 71.0 159.8 39.5 M M
38000 -49.5 -57.1 290 30 15 3.3 1.8 63.5 146.3 35.5 M M
36000 -50.2 -58.4 280 24 12 -2.4 -1.3 52.7 126.8 29.2 M M
34000 -48.9 -56.0 315 13 7 -2.1 -1.1 46.1 114.9 25.3 M M
32000 -48.7 -55.7 280 9 5 -1.2 -0.6 38.0 100.4 20.2 M M
30000 -48.5 -55.3 080 25 13 -1.0 -0.5 30.3 86.5 15.0 M M
29000 -49.3 -56.7 075 22 11 -0.3 -0.1 25.3 77.5 11.5 M M
28000 -48.1 -54.6 075 33 17 5.6 3.1 23.0 73.4 9.9 M M
27000 -45.9 -50.6 080 32 17 9.1 5.0 22.1 71.8 9.3 M M
26000 -43.1 -45.6 085 28 14 8.6 4.7 21.9 71.3 9.2 M M
25000 -40.9 -41.6 080 26 13 7.3 4.0 21.0 69.8 8.7 M M
24000 -38.7 -37.7 085 26 13 8.0 4.4 20.1 68.2 8.1 M M
23000 -36.6 -33.9 075 22 11 8.7 4.8 19.1 66.4 7.4 M M
22000 -34.0 -29.2 070 15 8 8.7 4.8 18.8 65.8 7.2 M M
21000 -31.3 -24.3 050 17 9 8.7 4.8 18.4 65.0 6.9 M M
20000 -28.7 -19.7 040 18 9 8.6 4.7 17.9 64.3 6.6 M M
19500 -27.1 -16.8 040 17 9 7.0 3.8 17.3 63.1 6.1 M M
19000 -26.1 -15.0 040 18 9 7.0 3.9 16.8 62.2 5.8 M M
18500 -25.0 -13.0 040 18 9 7.6 4.2 16.3 61.3 5.3 M M
18000 -23.7 -10.7 045 17 9 8.6 4.7 16.1 61.0 5.2 M M
17500 -22.5 -8.5 050 16 8 8.6 4.7 15.8 60.4 5.0 M M
17000 -21.5 -6.7 055 13 7 5.3 2.9 15.4 59.6 4.6 M M
16500 -20.6 -5.1 045 7 4 5.6 3.0 14.7 58.4 4.0 M M
16000 -19.8 -3.6 045 9 5 5.6 3.1 14.0 57.1 3.4 M M
15500 -19.0 -2.2 050 9 5 5.6 3.1 13.3 55.9 2.8 M M
15000 -18.1 -0.6 005 10 5 5.6 3.1 12.6 54.7 2.2 M M
14500 -17.3 0.9 345 10 5 5.7 3.1 11.9 53.4 1.6 M M
14000 -16.5 2.3 330 10 5 5.7 3.1 11.2 52.2 0.9 M M
13500 -15.7 3.7 330 9 5 5.7 3.1 10.5 50.9 0.3 M M
13000 -14.8 5.4 330 8 4 5.8 3.2 9.8 49.7 -0.4 651 3.3
12500 -14.0 6.8 325 6 3 6.5 3.6 9.2 48.5 -1.0 612 3.1
12000 -12.9 8.8 355 7 4 7.8 4.3 8.8 47.9 -1.4 564 2.9
11500 -11.8 10.8 010 7 4 7.2 4.0 8.5 47.3 -1.7 515 2.6
11000 -10.7 12.7 360 6 3 7.2 3.9 8.1 46.5 -2.1 468 2.4
10500 -9.6 14.7 360 11 6 7.5 4.1 7.7 45.8 -2.5 422 2.1
10250 -9.0 15.8 360 12 6 8.5 4.6 7.5 45.5 -2.7 396 2.0
10000 -8.4 16.9 360 14 7 6.9 3.8 7.4 45.3 -2.8 371 1.9
9750 -8.0 17.6 360 12 6 5.6 3.1 7.1 44.7 -3.2 351 1.8
9500 -7.6 18.3 360 10 5 5.6 3.1 6.7 44.1 -3.5 331 1.7
9250 -7.2 19.0 005 7 4 6.9 3.8 6.4 43.6 -3.8 312 1.6
9000 -6.6 20.1 010 4 2 8.8 4.8 6.3 43.4 -3.9 286 1.5
8750 -5.9 21.4 010 4 2 8.8 4.8 6.3 43.3 -4.0 259 1.3
8500 -5.3 22.5 010 5 2 8.8 4.9 6.2 43.1 -4.1 232 1.2
8250 -4.6 23.7 015 5 3 8.8 4.8 6.1 43.0 -4.2 205 1.0
8000 -4.0 24.8 025 5 2 8.9 4.9 6.0 42.9 -4.3 178 0.9
7750 -3.3 26.1 020 4 2 8.8 4.8 6.0 42.8 -4.4 151 0.8
7500 -2.7 27.1 005 3 1 9.1 5.0 5.9 42.6 -4.5 124 0.6
7250 -2.0 28.4 345 3 2 8.0 4.4 5.8 42.5 -4.6 97 0.5
7000 -1.5 29.3 345 6 3 8.3 4.5 5.7 42.2 -4.8 73 0.4
6750 -0.9 30.4 335 7 3 3.7 2.0 5.5 41.8 -5.0 50 0.3
6500 -0.9 30.4 330 8 4 1.4 0.8 4.8 40.6 -5.7 41 0.2
6250 -0.6 30.9 320 8 4 7.4 4.0 4.4 39.9 -6.1 24 0.1
6000 0.1 32.2 310 9 5 8.8 4.8 4.3 39.7 -6.2 M M
5750 0.7 33.3 310 9 4 8.3 4.6 4.2 39.6 -6.4 M M
5500 1.3 34.3 315 8 4 8.8 4.8 4.1 39.4 -6.5 M M
5250 1.9 35.4 320 10 5 7.3 4.0 4.0 39.2 -6.6 M M
5000 2.3 36.1 330 11 6 3.9 2.1 3.7 38.6 -7.0 M M
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
02/21/2025 at 0800 MST | 02/21/2025 at 1100 MST
|
CAPE... +0.2 LI... +4.4 | CAPE... +10.4 LI... +4.3
CINH... -0.1 K Index... +12.4 | CINH... -0.0 K Index... +11.0
|
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 -56.0 -68.8 280 23 12 2.0 1.1 | -55.9 -68.6 275 21 11 2.0 1.1
45000 -53.0 -63.4 275 26 14 2.0 1.1 | -53.0 -63.4 275 28 15 2.0 1.1
40000 -50.3 -58.5 290 20 10 1.7 0.9 | -51.8 -61.2 280 22 11 0.6 0.4
38000 -49.8 -57.6 300 17 9 -0.8 -0.4 | -51.7 -61.1 290 17 9 -0.5 -0.3
36000 -50.3 -58.5 320 14 7 -0.8 -0.4 | -51.9 -61.4 330 10 5 -0.5 -0.3
34000 -50.8 -59.4 340 14 7 -0.8 -0.4 | -52.2 -62.0 025 13 7 -0.0 -0.0
32000 -50.7 -59.3 050 18 9 0.2 0.1 | -51.3 -60.3 060 21 11 1.7 0.9
30000 -50.6 -59.1 075 34 18 1.2 0.7 | -50.2 -58.4 070 32 17 3.7 2.0
29000 -49.0 -56.2 075 34 17 6.2 3.4 | -48.3 -54.9 070 31 16 6.8 3.8
28000 -47.2 -53.0 070 32 16 6.2 3.4 | -46.2 -51.2 070 30 15 6.9 3.8
27000 -45.3 -49.5 065 30 15 6.2 3.4 | -44.1 -47.4 065 28 15 6.9 3.8
26000 -43.2 -45.8 065 27 14 8.0 4.4 | -41.9 -43.4 060 26 13 7.7 4.2
25000 -40.8 -41.4 060 24 13 8.1 4.4 | -39.1 -38.4 050 22 11 7.7 4.2
24000 -37.8 -36.0 050 21 11 8.0 4.4 | -36.7 -34.1 040 19 10 7.7 4.2
23000 -35.3 -31.5 040 20 10 8.4 4.6 | -34.3 -29.7 035 18 9 8.2 4.5
22000 -32.8 -27.0 035 19 10 8.4 4.6 | -31.9 -25.4 025 19 10 8.2 4.5
21000 -30.3 -22.5 030 19 10 8.4 4.6 | -29.5 -21.1 020 19 10 8.2 4.5
20000 -27.8 -18.0 030 18 9 8.4 4.6 | -27.0 -16.6 020 18 9 8.2 4.5
19500 -26.5 -15.7 030 18 9 8.4 4.6 | -25.8 -14.4 020 18 9 8.2 4.5
19000 -25.3 -13.5 030 18 9 8.4 4.6 | -24.6 -12.3 015 18 9 8.2 4.5
18500 -24.0 -11.2 025 18 9 8.2 4.5 | -23.3 -9.9 015 18 9 8.2 4.5
18000 -22.9 -9.2 025 17 9 7.8 4.3 | -22.1 -7.8 015 17 9 8.0 4.4
17500 -21.7 -7.1 030 17 9 7.8 4.3 | -20.9 -5.6 015 16 8 8.1 4.4
17000 -20.6 -5.1 030 16 8 7.0 3.9 | -19.8 -3.6 015 14 7 7.1 3.9
16500 -19.5 -3.1 030 15 8 7.1 3.9 | -18.7 -1.7 010 13 7 7.2 3.9
16000 -18.5 -1.3 030 14 7 6.7 3.7 | -17.7 0.1 010 12 6 6.7 3.7
15500 -17.5 0.5 025 13 7 6.5 3.6 | -16.7 1.9 010 11 6 6.6 3.6
15000 -16.6 2.1 025 12 6 6.1 3.3 | -15.7 3.7 005 11 5 6.3 3.5
14500 -15.8 3.6 025 11 6 5.5 3.0 | -14.9 5.2 005 10 5 6.0 3.3
14000 -14.9 5.2 025 10 5 5.3 2.9 | -14.0 6.8 005 9 5 5.8 3.2
13500 -14.2 6.4 025 9 5 4.6 2.5 | -13.2 8.2 005 8 4 5.3 2.9
13000 -13.6 7.5 020 8 4 4.7 2.6 | -12.4 9.7 010 8 4 5.2 2.9
12500 -12.9 8.8 020 8 4 4.8 2.6 | -11.7 10.9 010 7 4 4.7 2.6
12000 -12.2 10.0 020 7 4 4.7 2.6 | -11.0 12.2 010 6 3 4.7 2.6
11500 -11.5 11.3 020 7 4 4.5 2.5 | -10.3 13.5 010 6 3 4.6 2.5
11000 -10.9 12.4 020 7 3 5.1 2.8 | -9.6 14.7 015 6 3 4.8 2.6
10500 -9.9 14.2 020 7 3 7.0 3.8 | -8.9 16.0 020 6 3 5.2 2.9
10250 -9.4 15.1 025 7 3 7.0 3.8 | -8.5 16.7 020 6 3 4.9 2.7
10000 -8.9 16.0 025 7 3 6.6 3.6 | -8.1 17.4 025 5 3 6.0 3.3
9750 -8.4 16.9 025 7 3 7.0 3.8 | -7.6 18.3 025 6 3 6.5 3.5
9500 -7.9 17.8 025 7 4 7.7 4.2 | -7.2 19.0 030 6 3 5.7 3.1
9250 -7.3 18.9 030 7 4 7.5 4.1 | -6.8 19.8 030 5 3 6.2 3.4
9000 -6.8 19.8 030 7 4 8.7 4.8 | -6.3 20.7 035 5 3 8.4 4.6
8750 -5.7 21.7 030 7 4 5.1 2.8 | -5.2 22.6 035 5 3 5.0 2.7
8500 -5.3 22.5 030 7 4 6.0 3.3 | -4.8 23.4 035 5 3 6.3 3.5
8250 -4.9 23.2 025 7 4 6.2 3.4 | -4.3 24.3 035 5 3 6.9 3.8
8000 -4.4 24.1 025 8 4 6.6 3.6 | -3.8 25.2 035 5 3 7.7 4.2
7750 -3.9 25.0 025 7 4 6.7 3.7 | -3.2 26.2 035 5 3 8.2 4.5
7500 -3.4 25.9 020 7 3 5.6 3.1 | -2.7 27.1 035 5 2 6.9 3.8
7250 -3.1 26.4 020 6 3 4.4 2.4 | -2.2 28.0 035 4 2 5.5 3.0
7000 -2.7 27.1 015 5 3 5.9 3.2 | -1.8 28.8 035 3 2 8.6 4.7
6750 -2.3 27.9 010 4 2 6.6 3.6 | -1.0 30.2 030 3 2 10.9 6.0
6500 -1.8 28.8 005 4 2 5.8 3.2 | -0.2 31.6 035 3 1 9.9 5.5
6250 -1.4 29.5 360 3 2 6.3 3.4 | 0.5 32.9 035 3 1 9.7 5.3
6000 -0.9 30.4 355 3 1 4.9 2.7 | 1.3 34.3 040 2 1 11.6 6.4
5750 -0.7 30.7 350 2 1 2.8 1.5 | 2.3 36.1 035 2 1 17.9 9.8
5500 -0.2 31.6 340 2 1 14.7 8.0 | 3.7 38.7 040 2 1 14.3 7.9
5250 M M M M M M M | M M M M M M M
5000 M M M M M M M | M M M M M M M
02/21/2025 at 1400 MST | 02/21/2025 at 1700 MST
|
CAPE... +7.4 LI... +4.1 | CAPE... +0.2 LI... +5.3
CINH... -1.0 K Index... +9.2 | CINH... -0.2 K Index... +4.0
|
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 -56.4 -69.5 275 23 12 1.3 0.7 | -56.7 -70.1 280 26 13 1.6 0.9
45000 -54.4 -65.9 280 28 15 1.4 0.7 | -54.3 -65.7 295 28 14 1.7 0.9
40000 -52.8 -63.0 295 27 14 1.0 0.5 | -54.3 -65.7 310 19 10 -0.1 -0.1
38000 -52.7 -62.9 305 21 11 -0.9 -0.5 | -54.7 -66.5 335 15 8 -1.2 -0.6
36000 -53.2 -63.8 350 12 6 -0.9 -0.5 | -55.4 -67.7 030 19 10 -1.2 -0.6
34000 -53.8 -64.8 050 17 9 0.9 0.5 | -55.9 -68.6 050 32 16 3.6 2.0
32000 -51.7 -61.1 060 26 13 3.5 1.9 | -52.1 -61.8 055 33 17 6.3 3.4
30000 -49.6 -57.3 070 35 18 6.0 3.3 | -48.3 -54.9 060 35 18 7.5 4.1
29000 -47.3 -53.1 070 34 17 7.6 4.2 | -46.0 -50.8 060 34 18 7.6 4.2
28000 -45.0 -49.0 065 32 17 7.6 4.2 | -43.7 -46.7 060 33 17 7.6 4.2
27000 -42.7 -44.9 065 31 16 7.6 4.2 | -41.4 -42.5 060 33 17 7.6 4.2
26000 -40.4 -40.7 065 28 15 7.6 4.1 | -38.5 -37.3 060 31 16 7.9 4.3
25000 -37.6 -35.7 055 25 13 7.6 4.1 | -36.1 -33.0 060 29 15 7.9 4.3
24000 -35.3 -31.5 050 22 11 7.6 4.2 | -33.7 -28.7 060 27 14 7.9 4.3
23000 -33.0 -27.4 045 21 11 7.9 4.3 | -31.4 -24.5 055 24 13 7.7 4.2
22000 -30.6 -23.1 040 20 10 7.9 4.3 | -29.1 -20.4 050 23 12 7.7 4.2
21000 -28.2 -18.8 030 19 10 7.6 4.2 | -26.8 -16.2 040 21 11 7.8 4.3
20000 -26.0 -14.8 030 18 9 7.5 4.1 | -24.4 -11.9 035 20 10 7.9 4.3
19500 -24.9 -12.8 025 17 9 7.5 4.1 | -23.2 -9.8 035 20 10 7.9 4.3
19000 -23.8 -10.8 025 16 8 7.6 4.2 | -22.0 -7.6 035 19 10 7.9 4.3
18500 -22.6 -8.7 020 16 8 7.9 4.4 | -20.9 -5.6 030 19 10 7.3 4.0
18000 -21.4 -6.5 020 15 8 8.2 4.5 | -19.8 -3.6 030 17 9 6.9 3.8
17500 -20.2 -4.4 015 14 7 8.3 4.5 | -18.8 -1.8 030 16 8 6.8 3.8
17000 -19.0 -2.2 010 13 7 7.4 4.1 | -17.8 -0.0 025 15 8 6.4 3.5
16500 -17.9 -0.2 005 12 6 7.5 4.1 | -16.9 1.6 020 13 7 6.5 3.6
16000 -16.9 1.6 360 12 6 6.6 3.6 | -15.9 3.4 015 12 6 6.2 3.4
15500 -15.9 3.4 355 11 6 6.5 3.6 | -15.0 5.0 010 11 6 6.2 3.4
15000 -15.0 5.0 350 10 5 6.1 3.4 | -14.1 6.6 360 11 5 5.9 3.2
14500 -14.1 6.6 350 9 5 5.9 3.3 | -13.3 8.1 360 10 5 5.7 3.1
14000 -13.2 8.2 350 9 5 5.5 3.0 | -12.5 9.5 355 10 5 5.4 3.0
13500 -12.5 9.5 350 8 4 4.9 2.7 | -11.7 10.9 355 9 4 5.1 2.8
13000 -11.8 10.8 355 7 4 4.8 2.6 | -11.0 12.2 350 8 4 5.1 2.8
12500 -11.1 12.0 360 6 3 4.6 2.5 | -10.2 13.6 355 6 3 5.0 2.8
12000 -10.4 13.3 360 5 3 4.8 2.7 | -9.5 14.9 355 5 3 5.1 2.8
11500 -9.7 14.5 005 5 3 5.3 2.9 | -8.7 16.3 360 5 2 5.4 2.9
11000 -8.9 16.0 010 5 2 5.5 3.0 | -8.0 17.6 005 4 2 5.6 3.1
10500 -8.0 17.6 010 5 3 6.0 3.3 | -7.1 19.2 010 4 2 5.9 3.3
10250 -7.6 18.3 010 5 3 5.8 3.2 | -6.7 19.9 010 4 2 6.0 3.3
10000 -7.2 19.0 010 5 3 7.3 4.0 | -6.2 20.8 010 5 2 6.7 3.7
9750 -6.6 20.1 010 5 2 7.4 4.0 | -5.7 21.7 010 4 2 6.9 3.8
9500 -6.1 21.0 015 5 2 5.9 3.2 | -5.2 22.6 010 4 2 6.4 3.5
9250 -5.6 21.9 015 5 2 6.8 3.8 | -4.7 23.5 015 4 2 7.3 4.0
9000 -4.4 24.1 015 4 2 7.8 4.3 | -4.1 24.6 015 4 2 9.1 5.0
8750 -4.0 24.8 015 4 2 6.0 3.3 | -3.5 25.7 010 4 2 7.7 4.2
8500 -3.5 25.7 015 4 2 7.2 3.9 | -2.6 27.3 015 3 2 7.2 4.0
8250 -2.9 26.8 015 4 2 7.7 4.2 | -2.0 28.4 015 3 2 8.1 4.5
8000 -2.4 27.7 015 3 2 8.9 4.9 | -1.4 29.5 010 3 1 8.6 4.7
7750 -1.6 29.1 015 3 2 9.8 5.4 | -0.7 30.7 010 3 1 9.0 5.0
7500 -1.0 30.2 015 3 2 9.1 5.0 | -0.1 31.8 015 3 1 8.5 4.7
7250 -0.3 31.5 015 3 2 8.2 4.5 | 0.6 33.1 010 3 1 7.7 4.2
7000 0.3 32.5 015 3 2 10.5 5.8 | 1.2 34.2 010 3 1 10.1 5.5
6750 1.2 34.2 015 3 2 11.6 6.4 | 2.0 35.6 015 3 1 11.4 6.3
6500 2.0 35.6 015 3 2 10.3 5.6 | 2.8 37.0 010 2 1 10.0 5.5
6250 2.8 37.0 015 3 2 10.3 5.7 | 3.6 38.5 010 2 1 10.5 5.8
6000 3.6 38.5 010 3 2 11.5 6.3 | 4.4 39.9 010 2 1 9.7 5.3
5750 4.6 40.3 010 3 2 17.0 9.3 | 5.0 41.0 010 2 1 9.9 5.4
5500 6.1 43.0 010 3 2 22.3 12.2 | 6.1 43.0 010 2 1 20.5 11.2
5250 M M M M M M M | M M M M M M M
5000 M M M M M M M | M M M M M M M
________________________________________________________________________________
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 at Walker Field in Grand
Junction, Colorado at
North Latitude: 39 deg 07 min 00.001 sec
West Longitude: 108 deg 31 min 59.998 sec
Elevation: 4839 feet (1475 meters)
and may not be representative of other areas along the Western Slope of
Colorado. 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:
CAPE (Convective Available Potential Energy) - An integrated measure of the
energy available for convective development, also known as the positive
area on a thermodynamic diagram. Units are Joules per kilogram. Larger
values are indicative of greater instability and the possibility of
stronger convective activity, including thunderstorms. Values around or
greater than 1000 suggest the possibility of severe weather should
convective activity develop.
CINH (Convective Inhibition) - An integrated measure of the amount of energy
needed to initiate convective activity, also known as the negative area on
a thermodynamic diagram. Units are Joules per kilogram. The more negative
this number, the more energy is required to initiate convection. This
inhibitive energy can be overcome through surface heating, cooling aloft,
lifting mechanisms (orographic, frontal, gravity waves, etc.)
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 (LI) - 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, cirrostratus, 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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