Soaring Guidance
Issued by NWS Grand Junction, CO
Issued by NWS Grand Junction, CO
989
UXUS97 KGJT 081306
SRGGJT
Soaring Forecast
National Weather Service Grand Junction, Colorado
606 AM MST Wednesday, January 8, 2025
This forecast is for Wednesday, January 8, 2025:
If the trigger temperature of 38.3 F/3.5 C is reached...then
Thermal Soaring Index....................... Fair
Maximum rate of lift........................ 279 ft/min (1.4 m/s)
Maximum height of thermals.................. 9048 ft MSL (4209 ft AGL)
Forecast maximum temperature................... 39.0 F/4.3 C
Time of trigger temperature.................... 1445 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................. 7131 ft MSL (2292 ft AGL)
Thermal soaring outlook for Thursday 01/09..... Good
Wave Soaring Index............................. Not available
Remarks...
Sunrise/Sunset.................... 07:33:23 / 17:08:43 MST
Total possible sunshine........... 9 hr 35 min 20 sec (575 min 20 sec)
Altitude of sun at 12:21:03 MST... 28.56 degrees
Upper air data from rawinsonde observation taken on 01/08/2025 at 0500 MST
Freezing level.................. Entire airmass below 32 F / 0 C
Convective condensation level... 15738 ft MSL (10899 ft AGL)
Lifted condensation level....... 11920 ft MSL (7080 ft AGL)
Lifted index.................... +16.8
K index......................... -23.0
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 -54.1 -65.4 350 20 11 0.6 0.3 113.6 236.4 62.1 M M
45000 -52.5 -62.5 030 25 13 2.0 1.1 90.0 194.1 52.3 M M
40000 -53.1 -63.6 015 45 23 -0.8 -0.4 65.7 150.3 40.2 M M
38000 -53.2 -63.8 025 59 31 2.5 1.4 56.7 134.1 35.2 M M
36000 -55.3 -67.5 040 65 33 0.4 0.2 45.0 113.0 28.1 M M
34000 -51.2 -60.2 050 72 37 9.7 5.3 42.4 108.4 27.1 M M
32000 -49.5 -57.1 050 89 46 7.8 4.3 35.6 96.1 23.0 M M
30000 -44.7 -48.5 055 85 44 8.4 4.6 34.1 93.5 22.5 M M
29000 -42.2 -44.0 055 78 40 7.4 4.1 33.6 92.4 22.3 M M
28000 -40.4 -40.7 050 68 35 5.7 3.1 32.1 89.8 21.5 M M
27000 -38.3 -36.9 045 71 37 7.6 4.2 31.1 88.0 21.0 M M
26000 -36.0 -32.8 045 73 38 7.6 4.2 30.3 86.5 20.6 M M
25000 -33.7 -28.7 050 68 35 8.8 4.8 29.5 85.2 20.3 M M
24000 -31.0 -23.8 055 62 32 8.7 4.8 29.1 84.5 20.2 M M
23000 -28.6 -19.5 050 64 33 9.4 5.2 28.6 83.5 20.0 M M
22000 -25.8 -14.4 050 64 33 9.2 5.0 28.4 83.1 20.1 M M
21000 -23.2 -9.8 050 66 34 7.6 4.2 27.9 82.3 20.0 M M
20000 -21.4 -6.5 060 58 30 5.2 2.9 26.7 80.0 19.1 M M
19500 -21.2 -6.2 050 43 22 -2.0 -1.1 25.2 77.3 18.0 M M
19000 -21.2 -6.2 045 32 17 0.3 0.1 23.4 74.2 16.6 M M
18500 -21.6 -6.9 045 31 16 -3.6 -2.0 21.2 70.2 14.8 M M
18000 -22.3 -8.1 045 26 13 -1.5 -0.8 18.7 65.6 12.7 M M
17500 -21.7 -7.1 030 14 7 2.9 1.6 16.8 62.3 11.2 M M
17000 -21.2 -6.2 005 8 4 5.1 2.8 15.8 60.4 10.3 M M
16500 -20.2 -4.4 005 8 4 6.2 3.4 15.2 59.3 9.9 M M
16000 -19.3 -2.7 010 8 4 6.3 3.5 14.6 58.2 9.4 M M
15500 -18.3 -0.9 015 8 4 6.5 3.6 14.0 57.2 9.0 M M
15000 -17.4 0.7 010 8 4 6.5 3.6 13.5 56.2 8.5 M M
14500 -16.4 2.5 340 7 4 6.5 3.6 12.9 55.3 8.1 M M
14000 -15.4 4.3 345 6 3 6.5 3.6 12.4 54.3 7.7 M M
13500 -14.5 5.9 360 4 2 6.8 3.7 11.8 53.3 7.2 M M
13000 -13.6 7.5 015 4 2 5.2 2.9 11.2 52.1 6.6 M M
12500 -13.3 8.1 005 6 3 -3.4 -1.9 10.0 49.9 5.5 M M
12000 -13.3 8.1 345 8 4 7.1 3.9 8.3 47.0 4.0 M M
11500 -12.2 10.0 340 5 2 6.4 3.5 8.0 46.4 3.7 M M
11000 -11.3 11.7 320 2 1 6.4 3.5 7.5 45.5 3.2 M M
10500 -10.4 13.3 285 1 0 6.2 3.4 7.0 44.5 2.7 M M
10250 -10.0 14.0 195 3 1 5.9 3.2 6.6 44.0 2.3 M M
10000 -9.5 14.9 195 3 2 5.2 2.9 6.3 43.4 2.0 M M
9750 -9.2 15.4 225 5 2 3.5 1.9 5.9 42.6 1.6 M M
9500 -9.0 15.8 195 5 3 2.5 1.4 5.4 41.6 1.1 M M
9250 -8.9 16.0 175 6 3 1.9 1.1 4.8 40.6 0.5 M M
9000 -8.7 16.3 160 7 4 3.1 1.7 4.2 39.5 -0.1 277 1.4
8750 -8.4 16.9 155 6 3 4.5 2.4 3.7 38.7 -0.5 261 1.3
8500 -8.1 17.4 150 5 3 4.5 2.5 3.3 38.0 -0.9 243 1.2
8250 -7.7 18.1 125 5 3 4.5 2.5 2.9 37.2 -1.2 225 1.1
8000 -7.4 18.7 105 6 3 4.5 2.5 2.5 36.5 -1.6 207 1.1
7750 -7.0 19.4 100 6 3 4.5 2.5 2.1 35.8 -2.0 189 1.0
7500 -6.7 19.9 095 6 3 4.4 2.4 1.7 35.0 -2.4 171 0.9
7250 -6.3 20.7 085 6 3 5.0 2.8 1.3 34.3 -2.8 153 0.8
7000 -5.9 21.4 075 7 4 5.7 3.2 1.0 33.7 -3.1 133 0.7
6750 -5.5 22.1 080 7 3 5.6 3.1 0.6 33.2 -3.4 113 0.6
6500 -5.1 22.8 085 6 3 5.6 3.1 0.3 32.6 -3.7 93 0.5
6250 -4.6 23.7 075 6 3 5.6 3.1 0.0 32.0 -4.1 73 0.4
6000 -4.2 24.4 080 4 2 5.7 3.1 -0.3 31.5 -4.4 53 0.3
5750 -3.8 25.2 075 4 2 5.5 3.0 -0.6 30.9 -4.7 33 0.2
5500 -3.4 25.9 060 5 2 6.3 3.4 -0.9 30.3 -5.0 13 0.1
5250 -3.0 26.6 045 6 3 1.1 0.6 -1.3 29.7 -5.4 M M
5000 -3.5 25.7 040 7 4 -15.7 -8.6 -2.5 27.5 -6.7 3 0.0
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
01/08/2025 at 0800 MST | 01/08/2025 at 1100 MST
|
CAPE... 0.0 LI... +13.6 | CAPE... 0.0 LI... +14.1
CINH... -0.2 K Index... -30.1 | CINH... -0.1 K Index... -31.1
|
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 -68.4 360 21 11 1.4 0.7 | -56.4 -69.5 355 22 11 2.1 1.1
45000 -53.8 -64.8 015 23 12 -1.2 -0.6 | -53.5 -64.3 355 28 15 -1.7 -0.9
40000 -57.0 -70.6 025 48 25 -2.1 -1.2 | -56.9 -70.4 015 39 20 -2.3 -1.2
38000 -56.7 -70.1 030 55 28 3.3 1.8 | -56.8 -70.2 020 42 21 2.8 1.6
36000 -54.8 -66.6 035 58 30 3.3 1.8 | -54.8 -66.6 025 41 21 2.9 1.6
34000 -52.0 -61.6 040 61 31 6.9 3.8 | -52.3 -62.1 030 40 21 7.8 4.3
32000 -47.9 -54.2 045 61 31 7.0 3.8 | -47.6 -53.7 035 39 20 7.9 4.3
30000 -43.5 -46.3 045 60 31 8.0 4.4 | -42.9 -45.2 040 39 20 7.8 4.3
29000 -41.1 -42.0 045 59 30 8.1 4.4 | -40.6 -41.1 040 39 20 7.8 4.3
28000 -38.7 -37.7 040 58 30 8.1 4.4 | -38.2 -36.8 040 39 20 7.8 4.3
27000 -36.3 -33.3 040 57 29 8.0 4.4 | -35.9 -32.6 040 40 21 7.7 4.2
26000 -33.9 -29.0 040 56 29 7.9 4.3 | -33.6 -28.5 040 39 20 7.6 4.2
25000 -31.6 -24.9 040 55 28 7.9 4.3 | -31.4 -24.5 040 38 20 7.6 4.2
24000 -29.2 -20.6 040 54 28 7.9 4.3 | -29.1 -20.4 040 37 19 7.5 4.1
23000 -27.0 -16.6 045 52 27 7.3 4.0 | -27.0 -16.6 045 35 18 7.0 3.8
22000 -24.8 -12.6 050 50 26 7.3 4.0 | -24.4 -11.9 045 33 17 7.0 3.8
21000 -22.2 -8.0 050 47 24 5.6 3.1 | -22.3 -8.1 045 31 16 6.7 3.7
20000 -20.5 -4.9 055 43 22 5.7 3.1 | -20.3 -4.5 045 29 15 6.7 3.7
19500 -19.6 -3.3 055 41 21 5.7 3.2 | -19.3 -2.7 045 28 14 6.7 3.7
19000 -18.8 -1.8 055 39 20 5.9 3.2 | -18.3 -0.9 045 27 14 6.8 3.7
18500 -18.0 -0.4 055 36 19 3.0 1.6 | -17.3 0.9 045 26 13 5.5 3.0
18000 -17.7 0.1 055 33 17 2.3 1.3 | -16.5 2.3 040 25 13 5.4 3.0
17500 -17.3 0.9 050 29 15 2.0 1.1 | -15.7 3.7 040 25 13 5.0 2.8
17000 -17.1 1.2 045 26 13 1.0 0.5 | -15.0 5.0 035 24 13 4.3 2.4
16500 -17.0 1.4 040 23 12 0.9 0.5 | -14.3 6.3 030 24 13 4.4 2.4
16000 -16.8 1.8 035 20 10 1.9 1.1 | -13.8 7.2 030 24 12 2.9 1.6
15500 -16.5 2.3 025 18 9 1.8 1.0 | -13.4 7.9 025 24 12 3.1 1.7
15000 -16.1 3.0 015 17 9 3.7 2.0 | -13.0 8.6 025 23 12 1.9 1.0
14500 -15.5 4.1 010 15 8 4.1 2.3 | -12.7 9.1 025 21 11 1.7 0.9
14000 -14.9 5.2 360 15 7 4.7 2.6 | -12.5 9.5 020 19 10 1.9 1.0
13500 -14.1 6.6 355 14 7 5.0 2.7 | -12.2 10.0 015 17 9 2.0 1.1
13000 -13.4 7.9 350 13 7 5.0 2.7 | -11.9 10.6 010 15 8 2.5 1.3
12500 -12.7 9.1 345 12 6 4.9 2.7 | -11.4 11.5 005 13 7 2.8 1.5
12000 -12.0 10.4 345 11 6 4.5 2.5 | -11.0 12.2 360 11 6 3.0 1.6
11500 -11.4 11.5 340 10 5 4.2 2.3 | -10.6 12.9 350 10 5 3.1 1.7
11000 -10.8 12.6 340 9 4 3.9 2.1 | -10.1 13.8 345 8 4 3.1 1.7
10500 -10.3 13.5 340 7 4 3.8 2.1 | -9.7 14.5 340 7 3 3.1 1.7
10250 -10.0 14.0 340 6 3 3.8 2.1 | -9.5 14.9 335 6 3 3.3 1.8
10000 -9.8 14.4 340 5 3 3.6 2.0 | -9.2 15.4 335 5 3 3.8 2.1
9750 -9.5 14.9 345 5 2 4.0 2.2 | -9.0 15.8 330 4 2 3.5 1.9
9500 -9.2 15.4 350 4 2 4.2 2.3 | -8.8 16.2 330 3 2 2.8 1.6
9250 -8.9 16.0 355 3 2 4.4 2.4 | -8.6 16.5 325 2 1 4.1 2.2
9000 -8.5 16.7 005 3 2 5.2 2.8 | -8.2 17.2 320 2 1 6.0 3.3
8750 -8.2 17.2 015 3 1 4.2 2.3 | -7.8 18.0 310 1 1 4.3 2.3
8500 -7.9 17.8 030 3 1 3.4 1.8 | -7.6 18.3 300 1 0 2.8 1.5
8250 -7.6 18.3 045 3 1 4.2 2.3 | -7.0 19.4 000 0 0 4.9 2.7
8000 -6.9 19.6 060 3 2 3.5 1.9 | -6.6 20.1 150 1 0 4.2 2.3
7750 -6.7 19.9 065 3 2 3.2 1.8 | -6.3 20.7 130 1 1 4.1 2.2
7500 -6.4 20.5 070 4 2 4.4 2.4 | -6.0 21.2 125 1 1 4.9 2.7
7250 -6.1 21.0 080 4 2 4.7 2.6 | -5.6 21.9 120 1 1 4.0 2.2
7000 -5.8 21.6 085 4 2 2.7 1.5 | -5.3 22.5 115 1 1 6.9 3.8
6750 -5.7 21.7 075 4 2 2.4 1.3 | -4.6 23.7 105 1 1 8.8 4.8
6500 -5.4 22.3 080 4 2 3.6 2.0 | -4.1 24.6 100 1 1 7.4 4.1
6250 -5.1 22.8 080 3 2 5.0 2.8 | -3.5 25.7 095 1 1 7.3 4.0
6000 -4.8 23.4 085 4 2 0.7 0.4 | -2.9 26.8 095 2 1 10.8 5.9
5750 -5.3 22.5 090 3 2 -13.0 -7.1 | -1.8 28.8 090 2 1 18.9 10.3
5500 -5.8 21.6 095 2 1 9.0 4.9 | -0.6 30.9 085 2 1 5.5 3.0
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
01/08/2025 at 1400 MST | 01/08/2025 at 1700 MST
|
CAPE... 0.0 LI... +13.2 | CAPE... 0.0 LI... +11.6
CINH... -0.1 K Index... -25.6 | CINH... -0.0 K Index... -18.4
|
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 -56.6 -69.9 350 20 10 1.6 0.9 | -56.1 -69.0 345 21 11 2.5 1.4
45000 -54.3 -65.7 360 27 14 -0.5 -0.3 | -52.5 -62.5 360 26 13 -0.6 -0.3
40000 -55.6 -68.1 360 36 19 -0.8 -0.5 | -53.9 -65.0 355 46 24 -0.9 -0.5
38000 -55.5 -67.9 355 36 19 1.3 0.7 | -54.0 -65.2 355 53 27 0.6 0.3
36000 -54.6 -66.3 350 32 17 1.3 0.7 | -53.6 -64.5 355 61 32 0.6 0.3
34000 -52.7 -62.9 350 29 15 8.2 4.5 | -52.2 -62.0 355 65 34 7.7 4.2
32000 -47.6 -53.7 355 26 14 8.5 4.6 | -47.5 -53.5 355 60 31 7.9 4.3
30000 -42.7 -44.9 355 24 12 7.7 4.2 | -42.9 -45.2 350 51 26 7.3 4.0
29000 -40.4 -40.7 360 24 12 7.6 4.2 | -40.7 -41.3 345 42 22 7.3 4.0
28000 -38.1 -36.6 360 23 12 7.7 4.2 | -38.5 -37.3 335 34 17 7.3 4.0
27000 -35.8 -32.4 005 23 12 7.8 4.3 | -36.3 -33.3 320 27 14 7.5 4.1
26000 -33.5 -28.3 010 23 12 7.9 4.3 | -34.0 -29.2 320 26 13 7.7 4.2
25000 -31.1 -24.0 010 22 12 7.9 4.3 | -31.7 -25.1 320 26 13 7.7 4.2
24000 -28.8 -19.8 010 22 11 7.7 4.2 | -29.4 -20.9 325 25 13 7.6 4.2
23000 -26.6 -15.9 015 21 11 7.0 3.8 | -27.2 -17.0 325 24 13 7.3 4.0
22000 -24.0 -11.2 020 19 10 7.0 3.9 | -24.5 -12.1 325 24 12 7.3 4.0
21000 -22.0 -7.6 020 18 9 6.6 3.6 | -22.4 -8.3 330 23 12 7.1 3.9
20000 -20.0 -4.0 015 17 9 6.7 3.7 | -20.2 -4.4 330 23 12 7.1 3.9
19500 -19.0 -2.2 015 17 9 6.7 3.7 | -19.2 -2.6 330 23 12 7.1 3.9
19000 -18.0 -0.4 015 17 9 6.7 3.7 | -18.1 -0.6 330 23 12 7.2 3.9
18500 -17.0 1.4 010 17 9 6.9 3.8 | -17.1 1.2 335 23 12 6.7 3.7
18000 -15.9 3.4 010 18 9 6.9 3.8 | -16.1 3.0 335 23 12 6.7 3.6
17500 -14.9 5.2 010 19 10 6.6 3.6 | -15.1 4.8 335 23 12 6.5 3.6
17000 -14.0 6.8 010 20 10 5.9 3.3 | -14.2 6.4 340 23 12 6.0 3.3
16500 -13.1 8.4 010 21 11 6.1 3.4 | -13.3 8.1 340 23 12 6.1 3.3
16000 -12.3 9.9 010 21 11 4.4 2.4 | -12.4 9.7 340 23 12 5.2 2.9
15500 -11.6 11.1 015 21 11 4.6 2.5 | -11.6 11.1 345 22 11 5.3 2.9
15000 -11.0 12.2 015 21 11 3.3 1.8 | -10.9 12.4 345 22 11 4.7 2.6
14500 -10.5 13.1 015 20 10 3.0 1.6 | -10.2 13.6 345 21 11 4.4 2.4
14000 -10.1 13.8 020 19 10 1.9 1.1 | -9.5 14.9 345 20 10 3.8 2.1
13500 -9.9 14.2 020 17 9 1.1 0.6 | -9.1 15.6 345 18 9 3.0 1.7
13000 -9.8 14.4 015 15 8 1.1 0.6 | -8.6 16.5 340 17 9 2.7 1.5
12500 -9.6 14.7 015 12 6 1.2 0.6 | -8.3 17.1 340 15 8 1.9 1.1
12000 -9.4 15.1 010 10 5 1.5 0.8 | -8.0 17.6 335 13 7 1.9 1.1
11500 -9.1 15.6 360 8 4 2.0 1.1 | -7.7 18.1 335 11 6 1.8 1.0
11000 -8.8 16.2 350 6 3 2.1 1.2 | -7.4 18.7 330 9 5 1.9 1.0
10500 -8.5 16.7 340 5 2 2.3 1.3 | -7.1 19.2 320 8 4 2.0 1.1
10250 -8.3 17.1 335 4 2 2.5 1.3 | -7.0 19.4 320 7 4 1.9 1.1
10000 -8.1 17.4 325 4 2 4.0 2.2 | -6.8 19.8 315 6 3 2.2 1.2
9750 -7.8 18.0 320 3 2 3.7 2.0 | -6.6 20.1 310 6 3 2.4 1.3
9500 -7.6 18.3 315 3 1 2.1 1.2 | -6.5 20.3 305 5 3 2.2 1.2
9250 -7.4 18.7 300 2 1 3.6 2.0 | -6.3 20.7 300 4 2 2.5 1.4
9000 -7.1 19.2 295 2 1 6.5 3.6 | -6.1 21.0 295 4 2 4.6 2.5
8750 -6.6 20.1 295 2 1 5.0 2.8 | -5.7 21.7 285 3 2 4.2 2.3
8500 -6.2 20.8 270 1 1 4.9 2.7 | -5.5 22.1 280 3 1 2.3 1.2
8250 -5.7 21.7 270 1 1 6.9 3.8 | -5.3 22.5 275 2 1 3.9 2.1
8000 -5.2 22.6 270 1 0 6.1 3.4 | -4.6 23.7 265 2 1 5.4 3.0
7750 -4.8 23.4 000 0 0 6.2 3.4 | -4.2 24.4 250 1 1 5.5 3.0
7500 -4.3 24.3 000 0 0 7.0 3.8 | -3.8 25.2 235 1 0 6.2 3.4
7250 -3.8 25.2 000 0 0 6.5 3.6 | -3.3 26.1 220 1 0 6.3 3.4
7000 -3.3 26.1 000 0 0 8.7 4.8 | -2.8 27.0 200 1 0 7.0 3.9
6750 -2.5 27.5 000 0 0 10.1 5.5 | -2.2 28.0 170 1 0 8.3 4.5
6500 -1.8 28.8 000 0 0 9.1 5.0 | -1.6 29.1 000 0 0 7.9 4.3
6250 -1.2 29.8 000 0 0 8.5 4.7 | -1.0 30.2 000 0 0 9.0 4.9
6000 -0.5 31.1 000 0 0 11.9 6.5 | -0.4 31.3 000 0 0 5.0 2.7
5750 0.7 33.3 010 1 0 20.2 11.1 | -0.5 31.1 000 0 0 -4.6 -2.5
5500 1.9 35.4 010 1 0 3.8 2.1 | -0.4 31.3 000 0 0 14.6 8.0
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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