Soaring Guidance
Issued by NWS Grand Junction, CO
Issued by NWS Grand Junction, CO
818
UXUS97 KGJT 301306
SRGGJT
Soaring Forecast
National Weather Service Grand Junction, Colorado
606 AM MST Thursday, January 30, 2025
This forecast is for Thursday, January 30, 2025:
If the trigger temperature of 43.0 F/6.1 C is reached...then
Thermal Soaring Index....................... Fair
Maximum rate of lift........................ 345 ft/min (1.8 m/s)
Maximum height of thermals.................. 10176 ft MSL (5337 ft AGL)
Forecast maximum temperature................... 48.0 F/9.3 C
Time of trigger temperature.................... 1145 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................. 8106 ft MSL (3266 ft AGL)
Thermal soaring outlook for Friday 01/31....... Fair
Wave Soaring Index............................. Not available
Remarks...
Sunrise/Sunset.................... 07:22:02 / 17:32:59 MST
Total possible sunshine........... 10 hr 10 min 58 sec (610 min 58 sec)
Altitude of sun at 12:27:30 MST... 33.09 degrees
Upper air data from rawinsonde observation taken on 01/30/2025 at 0500 MST
Freezing level.................. 5290 ft MSL (451 ft AGL)
Additional freezing level....... 6237 ft MSL (1398 ft AGL)
Convective condensation level... 16371 ft MSL (11532 ft AGL)
Lifted condensation level....... 13386 ft MSL (8546 ft AGL)
Lifted index.................... +10.6
K index......................... -9.2
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 -55.2 -67.4 265 21 11 1.2 0.6 109.6 229.2 57.3 M M
45000 -51.5 -60.7 345 11 6 4.0 2.2 90.9 195.7 50.0 M M
40000 -49.7 -57.5 015 19 10 0.6 0.3 70.6 159.1 40.1 M M
38000 -47.3 -53.1 005 23 12 1.2 0.7 64.2 147.5 37.0 M M
36000 -52.7 -62.9 020 45 23 -13.3 -7.3 47.6 117.7 26.6 M M
34000 -52.5 -62.5 035 58 30 3.3 1.8 39.5 103.0 21.6 M M
32000 -50.3 -58.5 040 65 33 5.6 3.1 34.3 93.7 18.4 M M
30000 -45.4 -49.7 040 69 36 6.3 3.5 33.0 91.4 17.9 M M
29000 -43.5 -46.3 030 66 34 6.6 3.6 31.6 88.8 17.1 M M
28000 -41.6 -42.9 030 64 33 6.5 3.6 30.3 86.5 16.3 M M
27000 -39.4 -38.9 030 63 32 7.3 4.0 29.2 84.6 15.7 M M
26000 -37.2 -35.0 030 65 33 7.3 4.0 28.3 82.9 15.2 M M
25000 -34.9 -30.8 035 58 30 8.1 4.4 27.5 81.6 14.8 M M
24000 -32.5 -26.5 035 58 30 8.1 4.4 26.9 80.4 14.4 M M
23000 -30.1 -22.2 040 54 28 8.0 4.4 26.3 79.3 14.1 M M
22000 -28.0 -18.4 040 49 25 7.5 4.1 25.2 77.3 13.4 M M
21000 -25.8 -14.4 035 49 25 8.7 4.8 24.4 75.9 12.9 M M
20000 -22.6 -8.7 035 47 24 8.4 4.6 23.9 75.0 12.6 M M
19500 -21.5 -6.7 030 45 23 6.0 3.3 23.4 74.1 12.3 M M
19000 -20.6 -5.1 035 43 22 5.9 3.3 22.8 73.0 11.8 M M
18500 -19.5 -3.1 035 46 24 8.5 4.7 22.3 72.2 11.5 M M
18000 -18.3 -0.9 040 40 21 8.9 4.9 22.1 71.7 11.4 M M
17500 -18.1 -0.6 040 40 21 -5.4 -3.0 20.6 69.1 10.1 M M
17000 -18.8 -1.8 040 38 19 -1.7 -0.9 18.2 64.8 8.0 M M
16500 -18.1 -0.6 035 35 18 8.7 4.8 17.3 63.2 7.3 M M
16000 -16.7 1.9 030 32 16 9.2 5.1 17.3 63.1 7.3 M M
15500 -15.3 4.5 030 35 18 9.3 5.1 17.2 63.0 7.3 M M
15000 -13.9 7.0 025 33 17 9.3 5.1 17.2 62.9 7.3 M M
14500 -12.5 9.5 025 35 18 9.3 5.1 17.1 62.7 7.3 M M
14000 -11.1 12.0 030 37 19 9.3 5.1 17.0 62.6 7.3 M M
13500 -9.7 14.5 025 35 18 9.3 5.1 16.9 62.4 7.2 M M
13000 -8.3 17.1 025 40 21 9.3 5.1 16.8 62.3 7.2 M M
12500 -6.9 19.6 025 42 21 9.8 5.4 16.7 62.1 7.1 M M
12000 -5.8 21.6 020 33 17 2.6 1.4 16.2 61.2 6.7 M M
11500 -5.5 22.1 020 33 17 -0.4 -0.2 15.0 59.0 5.6 M M
11000 -5.5 22.1 020 31 16 4.9 2.7 13.5 56.3 4.2 M M
10500 -6.2 20.8 015 34 17 -13.2 -7.2 11.2 52.1 2.0 M M
10250 -7.1 19.2 015 33 17 -8.9 -4.9 9.5 49.2 0.4 M M
10000 -7.5 18.5 010 29 15 -0.6 -0.3 8.3 47.0 -0.8 349 1.8
9750 -7.2 19.0 010 26 13 6.7 3.7 7.9 46.1 -1.2 333 1.7
9500 -6.7 19.9 010 23 12 7.1 3.9 7.6 45.8 -1.4 310 1.6
9250 -6.3 20.7 005 20 10 4.2 2.3 7.3 45.2 -1.7 289 1.5
9000 -6.1 21.0 355 13 7 1.8 1.0 6.8 44.2 -2.3 276 1.4
8750 -5.8 21.6 355 11 6 6.2 3.4 6.3 43.3 -2.8 262 1.3
8500 -5.2 22.6 345 10 5 9.6 5.3 6.2 43.1 -2.9 235 1.2
8250 -4.5 23.9 335 9 5 8.7 4.8 6.1 43.0 -2.9 208 1.1
8000 -3.9 25.0 320 9 5 8.9 4.9 6.1 42.9 -3.0 180 0.9
7750 -3.2 26.2 315 10 5 8.9 4.9 6.0 42.8 -3.1 153 0.8
7500 -2.5 27.5 305 11 6 8.8 4.9 5.9 42.7 -3.2 126 0.6
7250 -1.9 28.6 295 12 6 9.1 5.0 5.9 42.5 -3.3 99 0.5
7000 -1.2 29.8 285 11 6 6.6 3.6 5.7 42.3 -3.4 73 0.4
6750 -0.9 30.4 295 8 4 4.5 2.5 5.4 41.7 -3.8 54 0.3
6500 -0.5 31.1 310 9 4 5.0 2.8 5.0 41.0 -4.1 35 0.2
6250 -0.1 31.8 325 10 5 4.9 2.7 4.6 40.3 -4.5 17 0.1
6000 0.3 32.5 340 12 6 4.9 2.7 4.3 39.7 -4.9 M M
5750 0.7 33.3 340 13 7 9.1 5.0 4.0 39.2 -5.2 M M
5500 1.2 34.2 340 12 6 -1.0 -0.5 3.8 38.8 -5.4 M M
5250 0.3 32.5 340 9 4 -20.5 -11.3 2.1 35.8 -7.1 M M
5000 -1.4 29.5 335 5 3 -21.4 -11.7 -0.3 31.4 -9.5 18 0.1
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
01/30/2025 at 0800 MST | 01/30/2025 at 1100 MST
|
CAPE... 0.0 LI... +6.7 | CAPE... 0.0 LI... +5.9
CINH... -0.2 K Index... -10.2 | CINH... 0.0 K Index... -2.7
|
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 -55.3 -67.5 280 18 9 2.2 1.2 | -55.2 -67.4 270 19 10 2.2 1.2
45000 -52.1 -61.8 295 16 8 1.8 1.0 | -51.9 -61.4 305 17 9 1.7 1.0
40000 -52.0 -61.6 010 24 12 0.0 0.0 | -51.9 -61.4 345 19 10 -0.0 -0.0
38000 -52.1 -61.8 020 32 17 -0.9 -0.5 | -52.2 -62.0 360 25 13 -1.3 -0.7
36000 -52.7 -62.9 025 43 22 -0.9 -0.5 | -53.0 -63.4 005 35 18 -1.3 -0.7
34000 -53.1 -63.6 025 52 27 4.6 2.6 | -53.4 -64.1 010 44 23 5.8 3.2
32000 -49.1 -56.4 025 57 29 6.6 3.6 | -49.0 -56.2 005 49 25 7.4 4.0
30000 -45.1 -49.2 020 61 32 7.9 4.3 | -44.6 -48.3 005 54 28 7.9 4.4
29000 -42.6 -44.7 020 62 32 8.1 4.4 | -42.2 -44.0 005 53 27 7.9 4.4
28000 -40.2 -40.4 020 62 32 8.1 4.4 | -39.8 -39.6 005 53 27 7.9 4.4
27000 -37.8 -36.0 020 62 32 8.2 4.5 | -37.4 -35.3 005 53 27 8.1 4.4
26000 -35.6 -32.1 020 61 32 6.7 3.6 | -35.4 -31.7 005 52 27 6.0 3.3
25000 -33.7 -28.7 020 59 31 6.6 3.6 | -33.7 -28.7 010 51 26 6.0 3.3
24000 -31.7 -25.1 020 57 30 6.6 3.6 | -31.9 -25.4 010 49 25 6.0 3.3
23000 -29.7 -21.5 025 55 29 6.5 3.6 | -29.6 -21.3 010 48 24 6.2 3.4
22000 -27.3 -17.1 025 53 27 6.5 3.6 | -27.8 -18.0 010 46 24 6.2 3.4
21000 -25.4 -13.7 025 52 27 6.6 3.6 | -25.9 -14.6 010 44 23 6.8 3.7
20000 -23.4 -10.1 025 51 26 6.7 3.7 | -23.7 -10.7 015 43 22 7.5 4.1
19500 -22.4 -8.3 025 51 26 6.7 3.7 | -22.6 -8.7 015 43 22 7.5 4.1
19000 -21.4 -6.5 030 51 26 6.7 3.7 | -21.5 -6.7 015 43 22 7.5 4.1
18500 -20.4 -4.7 030 51 26 6.8 3.7 | -20.3 -4.5 015 42 22 7.5 4.1
18000 -19.4 -2.9 030 50 26 7.1 3.9 | -19.2 -2.6 015 42 22 7.4 4.1
17500 -18.3 -0.9 030 49 25 7.1 3.9 | -18.1 -0.6 015 41 21 7.4 4.1
17000 -17.2 1.0 030 47 24 6.8 3.8 | -17.0 1.4 020 41 21 7.6 4.1
16500 -16.2 2.8 030 46 23 6.8 3.7 | -15.9 3.4 020 41 21 7.6 4.1
16000 -15.2 4.6 030 44 22 6.8 3.8 | -14.7 5.5 020 40 21 7.5 4.1
15500 -14.1 6.6 030 42 22 6.9 3.8 | -13.6 7.5 020 39 20 7.4 4.1
15000 -13.1 8.4 030 40 21 6.9 3.8 | -12.5 9.5 020 39 20 7.3 4.0
14500 -12.0 10.4 030 38 20 7.1 3.9 | -11.4 11.5 025 38 20 7.1 3.9
14000 -11.0 12.2 030 37 19 7.2 3.9 | -10.4 13.3 025 37 19 7.1 3.9
13500 -9.9 14.2 025 36 18 6.7 3.7 | -9.3 15.3 025 36 18 7.0 3.8
13000 -8.9 16.0 025 35 18 6.9 3.8 | -8.3 17.1 025 34 18 7.1 3.9
12500 -8.0 17.6 025 34 17 5.4 2.9 | -7.3 18.9 025 33 17 5.9 3.3
12000 -7.2 19.0 025 33 17 5.6 3.1 | -6.4 20.5 020 31 16 6.3 3.5
11500 -6.5 20.3 020 32 16 3.5 1.9 | -5.6 21.9 020 30 15 3.6 2.0
11000 -6.0 21.2 020 30 16 3.7 2.0 | -5.1 22.8 020 28 14 4.1 2.3
10500 -5.7 21.7 015 29 15 1.0 0.6 | -4.7 23.5 020 26 13 1.0 0.6
10250 -5.6 21.9 015 28 14 0.7 0.4 | -4.6 23.7 015 25 13 1.2 0.7
10000 -5.6 21.9 015 27 14 2.2 1.2 | -4.6 23.7 015 25 13 2.0 1.1
9750 -5.4 22.3 010 24 13 1.9 1.0 | -4.4 24.1 015 22 11 1.2 0.7
9500 -5.4 22.3 010 23 12 -0.0 -0.0 | -4.4 24.1 010 21 11 -0.2 -0.1
9250 -5.4 22.3 005 21 11 0.7 0.4 | -4.4 24.1 010 19 10 0.3 0.2
9000 -5.3 22.5 005 19 10 -0.4 -0.2 | -4.4 24.1 010 18 9 -0.3 -0.2
8750 -5.4 22.3 005 19 10 0.4 0.2 | -4.5 23.9 010 18 9 -0.1 -0.1
8500 -5.3 22.5 005 17 9 1.9 1.1 | -4.4 24.1 005 16 8 0.4 0.2
8250 -5.2 22.6 360 15 8 1.7 1.0 | -4.4 24.1 005 14 7 0.4 0.2
8000 -5.0 23.0 355 12 6 2.0 1.1 | -4.4 24.1 360 11 6 2.4 1.3
7750 -4.7 23.5 355 10 5 3.7 2.0 | -4.1 24.6 360 9 5 4.5 2.5
7500 -4.5 23.9 350 8 4 3.4 1.9 | -3.8 25.2 360 7 4 3.8 2.1
7250 -4.2 24.4 350 7 4 3.8 2.1 | -3.5 25.7 355 6 3 1.5 0.8
7000 -3.9 25.0 345 7 3 4.5 2.5 | -3.4 25.9 350 5 2 5.9 3.2
6750 -3.6 25.5 345 5 3 5.1 2.8 | -2.6 27.3 350 4 2 11.6 6.4
6500 -3.2 26.2 345 4 2 4.8 2.6 | -1.9 28.6 345 3 2 9.2 5.1
6250 -2.8 27.0 345 4 2 4.2 2.3 | -1.2 29.8 340 3 2 8.2 4.5
6000 -2.5 27.5 345 3 2 5.2 2.8 | -0.6 30.9 335 3 1 8.8 4.8
5750 -2.3 27.9 345 2 1 -2.1 -1.1 | 0.2 32.4 340 3 1 13.4 7.4
5500 -3.9 25.0 005 2 1 -52.6 -28.9 | 1.8 35.2 330 2 1 34.7 19.0
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
01/30/2025 at 1400 MST | 01/30/2025 at 1700 MST
|
CAPE... 0.0 LI... +5.8 | CAPE... 0.0 LI... +6.3
CINH... -0.0 K Index... -6.7 | CINH... -0.1 K Index... -11.9
|
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 -55.8 -68.4 275 21 11 2.2 1.2 | -56.2 -69.2 285 24 13 2.5 1.4
45000 -52.5 -62.5 305 23 12 1.5 0.8 | -52.4 -62.3 300 24 12 1.6 0.9
40000 -53.7 -64.7 325 27 14 -0.9 -0.5 | -54.3 -65.7 330 29 15 -1.3 -0.7
38000 -53.9 -65.0 330 30 15 0.8 0.4 | -54.4 -65.9 335 33 17 1.4 0.8
36000 -53.4 -64.1 340 33 17 0.8 0.4 | -53.6 -64.5 335 38 20 1.4 0.8
34000 -52.7 -62.9 345 37 19 6.2 3.4 | -52.4 -62.3 340 42 22 6.3 3.5
32000 -48.6 -55.5 345 42 21 6.7 3.7 | -48.7 -55.7 345 41 21 6.3 3.4
30000 -44.6 -48.3 350 46 24 7.4 4.1 | -44.9 -48.8 350 40 21 7.0 3.9
29000 -42.4 -44.3 350 46 24 7.4 4.1 | -42.8 -45.0 350 40 21 7.0 3.8
28000 -40.1 -40.2 350 46 24 7.4 4.1 | -40.7 -41.3 350 41 21 7.0 3.8
27000 -37.9 -36.2 350 46 23 7.4 4.1 | -38.6 -37.5 355 41 21 6.9 3.8
26000 -35.8 -32.4 350 45 23 7.1 3.9 | -36.4 -33.5 355 41 21 7.5 4.1
25000 -33.6 -28.5 355 44 23 7.1 3.9 | -34.1 -29.4 355 41 21 7.5 4.1
24000 -31.5 -24.7 355 43 22 7.1 3.9 | -31.3 -24.3 355 41 21 7.4 4.1
23000 -29.1 -20.4 360 42 21 6.1 3.3 | -29.2 -20.6 355 41 21 7.3 4.0
22000 -27.3 -17.1 360 40 21 6.1 3.4 | -27.0 -16.6 355 40 21 7.3 4.0
21000 -25.4 -13.7 360 39 20 6.6 3.6 | -24.8 -12.6 355 39 20 6.8 3.8
20000 -23.3 -9.9 360 38 19 7.1 3.9 | -22.8 -9.0 355 37 19 6.6 3.6
19500 -22.3 -8.1 360 37 19 7.1 3.9 | -21.8 -7.2 355 36 19 6.6 3.6
19000 -21.2 -6.2 360 37 19 7.1 3.9 | -20.8 -5.4 355 36 18 6.6 3.6
18500 -20.2 -4.4 360 36 19 7.2 4.0 | -19.9 -3.8 355 35 18 6.7 3.7
18000 -19.1 -2.4 360 36 19 7.5 4.1 | -18.9 -2.0 355 34 17 6.7 3.7
17500 -17.9 -0.2 360 36 19 7.5 4.1 | -17.9 -0.2 360 33 17 6.7 3.7
17000 -16.8 1.8 360 36 19 7.3 4.0 | -16.8 1.8 360 32 17 7.1 3.9
16500 -15.7 3.7 360 36 18 7.3 4.0 | -15.8 3.6 360 31 16 7.1 3.9
16000 -14.6 5.7 360 36 18 7.4 4.1 | -14.7 5.5 005 31 16 7.4 4.1
15500 -13.5 7.7 005 35 18 7.4 4.1 | -13.6 7.5 005 30 16 7.5 4.1
15000 -12.4 9.7 005 35 18 7.3 4.0 | -12.5 9.5 005 30 15 7.4 4.1
14500 -11.4 11.5 010 34 18 7.0 3.8 | -11.4 11.5 010 29 15 7.3 4.0
14000 -10.3 13.5 010 33 17 6.9 3.8 | -10.3 13.5 010 28 15 7.2 3.9
13500 -9.3 15.3 015 32 17 6.5 3.6 | -9.2 15.4 010 28 14 6.8 3.7
13000 -8.3 17.1 015 32 16 6.5 3.6 | -8.2 17.2 010 27 14 6.7 3.7
12500 -7.4 18.7 015 31 16 6.7 3.6 | -7.3 18.9 010 27 14 5.8 3.2
12000 -6.4 20.5 020 29 15 6.7 3.7 | -6.4 20.5 010 26 13 5.9 3.2
11500 -5.5 22.1 020 28 14 5.3 2.9 | -5.6 21.9 010 25 13 5.3 2.9
11000 -4.7 23.5 020 26 13 5.7 3.1 | -4.8 23.4 010 23 12 5.2 2.9
10500 -4.1 24.6 020 24 13 2.1 1.2 | -4.2 24.4 010 22 11 3.7 2.0
10250 -4.0 24.8 015 24 12 2.1 1.2 | -4.0 24.8 005 21 11 3.1 1.7
10000 -3.8 25.2 015 23 12 3.7 2.0 | -3.7 25.3 005 20 10 6.1 3.3
9750 -3.5 25.7 015 20 11 3.2 1.7 | -3.2 26.2 005 18 10 5.9 3.2
9500 -3.4 25.9 010 19 10 0.9 0.5 | -2.9 26.8 005 17 9 2.7 1.5
9250 -3.3 26.1 010 18 9 1.9 1.1 | -2.7 27.1 360 16 8 3.5 1.9
9000 -3.2 26.2 005 16 8 0.2 0.1 | -2.4 27.7 360 15 8 3.6 2.0
8750 -3.2 26.2 005 15 8 0.8 0.4 | -1.9 28.6 355 12 6 3.6 2.0
8500 -3.1 26.4 360 13 7 2.7 1.5 | -1.7 28.9 350 11 6 3.5 1.9
8250 -2.8 27.0 355 9 5 1.9 1.0 | -1.4 29.5 350 10 5 6.1 3.3
8000 -2.6 27.3 345 8 4 5.0 2.7 | -0.8 30.6 345 8 4 6.2 3.4
7750 -2.0 28.4 345 7 3 7.8 4.3 | -0.5 31.1 340 7 4 4.0 2.2
7500 -1.5 29.3 340 6 3 7.1 3.9 | -0.2 31.6 340 6 3 5.6 3.1
7250 -1.0 30.2 335 5 3 6.2 3.4 | 0.3 32.5 335 5 3 7.3 4.0
7000 -0.5 31.1 325 5 2 8.9 4.9 | 0.9 33.6 325 5 2 7.1 3.9
6750 0.4 32.7 330 4 2 12.0 6.6 | 1.4 34.5 325 4 2 7.0 3.9
6500 1.2 34.2 330 4 2 10.2 5.6 | 2.0 35.6 320 3 2 8.9 4.9
6250 1.9 35.4 320 4 2 10.2 5.6 | 2.7 36.9 310 3 1 10.8 5.9
6000 2.7 36.9 315 4 2 8.7 4.8 | 3.5 38.3 300 2 1 7.7 4.2
5750 3.3 37.9 325 3 2 10.7 5.9 | 3.8 38.8 305 2 1 0.0 0.0
5500 5.2 41.4 315 3 2 48.3 26.5 | 3.7 38.7 290 1 1 3.6 2.0
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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