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Soaring Guidance
Issued by NWS Grand Junction, CO
Issued by NWS Grand Junction, CO
147
UXUS97 KGJT 211216
SRGGJT
Soaring Forecast
National Weather Service Grand Junction, Colorado
0616 MDT Saturday, April 21, 2018
This forecast is for Saturday, April 21, 2018:
If the trigger temperature of 49.2 F/9.5 C is reached...then
Thermal Soaring Index....................... Good
Maximum rate of lift........................ 527 ft/min (2.7 m/s)
Maximum height of thermals.................. 14513 ft MSL (9674 ft AGL)
Forecast maximum temperature................... 63.0 F/17.7 C
Time of trigger temperature.................... 1045 MDT
Time of overdevelopment........................ None
Middle/high clouds during soaring window....... Broken/overcast thin middle
Surface winds during soaring window............ 20 mph or less
Height of the -3 thermal index................. 12197 ft MSL (7358 ft AGL)
Thermal soaring outlook for Sunday 04/22....... Good
Wave Soaring Index............................. Not available
Remarks...
Sunrise/Sunset.................... 06:28:50 / 19:56:32 MDT
Total possible sunshine........... 13 hr 27 min 41 sec (807 min 41 sec)
Altitude of sun at 13:12:50 MDT... 62.92 degrees
Upper air data from rawinsonde observation taken on 04/21/2018 at 0600 MDT
Freezing level.................. 7921 ft MSL (3082 ft AGL)
Convective condensation level... 8631 ft MSL (3792 ft AGL)
Lifted condensation level....... 11770 ft MSL (6931 ft AGL)
Lifted index.................... -0.8
K index......................... +21.0
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 -61.5 -78.7 345 30 15 8.3 4.5 97.3 207.1 45.8 M M
45000 -53.2 -63.8 340 39 20 1.6 0.9 85.4 185.7 41.8 M M
40000 -46.7 -52.1 345 69 36 -11.3 -6.2 72.7 162.9 36.4 M M
38000 -47.1 -52.8 345 68 35 -2.9 -1.6 63.3 145.9 31.0 M M
36000 -46.6 -51.9 345 67 35 4.4 2.4 55.4 131.7 26.3 M M
34000 -44.1 -47.4 350 66 34 1.9 1.0 50.7 123.2 23.7 M M
32000 -41.7 -43.1 355 62 32 0.1 0.1 44.9 112.8 20.1 M M
30000 -39.9 -39.8 010 72 37 -3.0 -1.7 39.3 102.8 16.5 M M
29000 -40.9 -41.6 010 68 35 1.3 0.7 34.2 93.6 12.8 M M
28000 -39.2 -38.6 005 64 33 5.6 3.1 32.4 90.3 11.6 M M
27000 -37.5 -35.5 005 61 31 5.6 3.1 30.7 87.3 10.5 M M
26000 -35.9 -32.6 360 57 30 5.7 3.1 29.2 84.6 9.4 M M
25000 -33.7 -28.7 360 54 28 9.1 5.0 28.3 83.0 8.8 M M
24000 -31.2 -24.2 360 55 28 7.9 4.3 27.8 82.0 8.5 M M
23000 -29.2 -20.6 360 54 28 7.5 4.1 26.7 80.1 7.7 M M
22000 -26.9 -16.4 355 54 28 9.3 5.1 26.0 78.7 7.1 M M
21000 -24.1 -11.4 355 51 26 12.3 6.7 25.9 78.7 7.1 M M
20000 -22.5 -8.5 360 48 25 6.9 3.8 24.4 75.9 5.9 M M
19500 -21.4 -6.5 360 47 24 7.3 4.0 23.9 75.1 5.5 M M
19000 -20.4 -4.7 360 46 24 7.3 4.0 23.5 74.3 5.2 M M
18500 -19.3 -2.7 360 45 23 7.4 4.1 23.1 73.6 4.9 M M
18000 -18.2 -0.8 360 45 23 7.5 4.1 22.7 72.9 4.5 M M
17500 -16.5 2.3 360 46 24 6.5 3.6 22.1 71.8 4.0 M M
17000 -15.7 3.7 360 45 23 5.7 3.1 21.4 70.5 3.4 M M
16500 -14.9 5.2 010 40 20 5.6 3.1 20.7 69.2 2.8 M M
16000 -14.1 6.6 015 36 18 5.2 2.9 20.0 68.0 2.1 M M
15500 -13.4 7.9 020 35 18 4.9 2.7 19.2 66.5 1.4 M M
15000 -12.7 9.1 020 33 17 4.9 2.7 18.3 65.0 0.6 M M
14500 -11.9 10.6 015 30 15 5.6 3.1 17.5 63.5 -0.1 721 3.7
14000 -11.0 12.2 015 27 14 6.5 3.6 17.0 62.5 -0.6 678 3.4
13500 -10.0 14.0 015 27 14 6.6 3.6 16.4 61.6 -1.2 634 3.2
13000 -9.1 15.6 015 27 14 4.9 2.7 15.8 60.5 -1.7 593 3.0
12500 -8.5 16.7 015 27 14 4.5 2.5 14.9 58.9 -2.6 559 2.8
12000 -7.8 18.0 015 27 14 4.5 2.5 14.1 57.4 -3.4 525 2.7
11500 -7.2 19.0 010 26 13 4.5 2.5 13.2 55.8 -4.2 490 2.5
11000 -6.5 20.3 005 24 13 4.6 2.5 12.4 54.3 -5.1 456 2.3
10500 -5.7 21.7 360 24 12 6.9 3.8 11.8 53.2 -5.7 416 2.1
10250 -5.2 22.6 355 23 12 6.6 3.6 11.5 52.8 -6.0 394 2.0
10000 -4.7 23.5 355 22 12 6.8 3.7 11.3 52.3 -6.2 372 1.9
9750 -4.2 24.4 355 21 11 6.8 3.7 11.1 51.9 -6.5 350 1.8
9500 -3.7 25.3 360 19 10 6.8 3.8 10.8 51.5 -6.7 327 1.7
9250 -3.2 26.2 360 18 9 6.7 3.7 10.6 51.1 -7.0 305 1.6
9000 -2.7 27.1 005 16 8 7.1 3.9 10.4 50.7 -7.2 283 1.4
8750 -2.2 28.0 005 15 8 8.3 4.5 10.2 50.4 -7.4 259 1.3
8500 -1.6 29.1 005 15 8 8.7 4.8 10.1 50.2 -7.5 232 1.2
8250 -0.9 30.4 360 14 7 8.6 4.7 10.1 50.1 -7.6 206 1.0
8000 -0.3 31.5 360 13 7 8.6 4.7 10.0 50.0 -7.7 180 0.9
7750 0.3 32.5 355 12 6 8.6 4.7 9.9 49.8 -7.9 154 0.8
7500 1.0 33.8 350 12 6 8.6 4.7 9.8 49.6 -8.0 127 0.6
7250 1.6 34.9 345 11 6 8.6 4.7 9.7 49.5 -8.1 101 0.5
7000 2.2 36.0 335 11 6 8.6 4.7 9.6 49.3 -8.2 75 0.4
6750 2.9 37.2 330 12 6 8.6 4.7 9.5 49.2 -8.3 48 0.2
6500 3.5 38.3 320 12 6 8.6 4.7 9.4 49.0 -8.5 22 0.1
6250 4.1 39.4 315 13 7 8.5 4.7 9.3 48.8 -8.6 M M
6000 4.7 40.5 310 15 8 5.4 3.0 9.2 48.5 -8.8 M M
5750 4.9 40.8 310 13 7 2.6 1.4 8.7 47.7 -9.3 M M
5500 5.1 41.2 310 11 6 5.3 2.9 8.2 46.8 -9.8 M M
5250 5.4 41.7 310 9 4 -2.5 -1.4 7.8 46.0 -10.3 M M
5000 4.6 40.3 315 6 3 -13.1 -7.2 6.3 43.4 -11.8 M M
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
04/21/2018 at 0900 MDT | 04/21/2018 at 1200 MDT
|
K index... +9.7 LI... +6.1 | K index... +13.3 LI... +5.1
CAPE... +1.3 CIN... -0.3 | CAPE... 0.0 CIN... 0.0
|
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 -60.5 -76.9 345 27 14 4.2 2.3 | -62.5 -80.5 335 22 12 3.1 1.7
45000 -54.3 -65.7 355 45 23 3.9 2.1 | -57.2 -71.0 335 34 18 6.2 3.4
40000 -48.5 -55.3 360 57 29 3.8 2.1 | -47.8 -54.0 345 47 24 6.1 3.4
38000 -47.2 -53.0 360 61 32 1.3 0.7 | -47.1 -52.8 350 53 27 -0.3 -0.2
36000 -46.4 -51.5 360 66 34 1.3 0.7 | -47.2 -53.0 350 58 30 -0.3 -0.2
34000 -45.2 -49.4 360 69 35 4.0 2.2 | -45.8 -50.4 355 62 32 5.8 3.2
32000 -42.5 -44.5 005 69 35 4.1 2.2 | -42.3 -44.1 355 62 32 5.8 3.2
30000 -39.9 -39.8 005 66 34 4.7 2.6 | -38.6 -37.5 360 61 31 6.6 3.6
29000 -38.5 -37.3 010 61 31 4.7 2.6 | -36.6 -33.9 360 59 30 6.6 3.6
28000 -37.1 -34.8 010 57 29 4.7 2.6 | -34.6 -30.3 360 58 30 6.6 3.6
27000 -35.5 -31.9 015 52 27 7.3 4.0 | -32.7 -26.9 360 55 28 5.8 3.2
26000 -33.3 -27.9 015 49 25 7.6 4.2 | -30.9 -23.6 360 47 24 5.9 3.2
25000 -31.0 -23.8 020 46 24 7.6 4.2 | -29.1 -20.4 360 39 20 5.9 3.2
24000 -28.7 -19.7 020 43 22 8.0 4.4 | -27.3 -17.1 355 32 17 8.3 4.5
23000 -26.2 -15.2 030 37 19 8.3 4.5 | -24.6 -12.3 355 31 16 8.7 4.8
22000 -23.7 -10.7 035 32 16 8.3 4.5 | -22.0 -7.6 350 30 15 8.8 4.8
21000 -21.3 -6.3 040 28 14 6.9 3.8 | -19.6 -3.3 350 29 15 5.9 3.2
20000 -19.3 -2.7 035 25 13 6.8 3.7 | -17.7 0.1 350 28 14 6.2 3.4
19500 -18.2 -0.8 030 24 12 6.8 3.7 | -16.8 1.8 350 27 14 6.2 3.4
19000 -17.2 1.0 020 23 12 6.8 3.7 | -15.9 3.4 350 27 14 6.3 3.4
18500 -16.2 2.8 015 22 11 6.6 3.6 | -15.0 5.0 350 27 14 5.4 3.0
18000 -15.2 4.6 015 24 12 6.6 3.6 | -14.2 6.4 355 28 14 5.3 2.9
17500 -14.3 6.3 010 26 13 6.5 3.6 | -13.4 7.9 360 29 15 5.4 3.0
17000 -13.4 7.9 010 28 14 5.6 3.0 | -12.6 9.3 005 30 16 5.6 3.1
16500 -12.6 9.3 010 30 15 5.7 3.1 | -11.8 10.8 005 31 16 5.8 3.2
16000 -11.8 10.8 010 32 16 5.0 2.7 | -11.1 12.0 005 32 16 5.1 2.8
15500 -11.1 12.0 010 32 17 5.0 2.7 | -9.9 14.2 005 31 16 5.3 2.9
15000 -10.0 14.0 010 32 17 5.2 2.8 | -9.1 15.6 005 30 16 5.5 3.0
14500 -9.3 15.3 010 31 16 5.2 2.9 | -8.3 17.1 005 30 15 5.4 3.0
14000 -8.5 16.7 010 30 15 4.8 2.6 | -7.5 18.5 005 29 15 6.7 3.6
13500 -7.8 18.0 010 28 15 4.8 2.6 | -6.5 20.3 005 29 15 6.6 3.6
13000 -7.1 19.2 010 27 14 5.0 2.7 | -5.6 21.9 005 29 15 5.7 3.1
12500 -6.4 20.5 010 26 13 5.0 2.7 | -4.8 23.4 005 29 15 5.9 3.2
12000 -5.6 21.9 010 25 13 5.1 2.8 | -4.0 24.8 005 29 15 4.3 2.4
11500 -4.9 23.2 010 24 12 5.2 2.8 | -3.4 25.9 005 28 14 4.3 2.4
11000 -4.1 24.6 015 23 12 5.3 2.9 | -2.8 27.0 010 27 14 4.3 2.3
10500 -3.3 26.1 015 22 11 5.9 3.2 | -2.2 28.0 015 24 13 4.8 2.6
10250 -3.0 26.6 015 22 11 3.0 1.7 | -1.9 28.6 015 23 12 2.1 1.1
10000 -2.8 27.0 015 21 11 3.5 1.9 | -1.8 28.8 015 21 11 1.8 1.0
9750 -2.4 27.7 015 21 11 6.5 3.5 | -1.6 29.1 015 18 9 4.3 2.4
9500 -2.0 28.4 015 20 10 6.4 3.5 | -1.3 29.7 015 15 8 3.8 2.1
9250 -1.6 29.1 015 19 10 3.7 2.0 | -1.0 30.2 015 13 6 3.8 2.1
9000 -1.5 29.3 020 18 9 1.5 0.8 | -0.7 30.7 015 11 6 5.6 3.1
8750 -1.3 29.7 020 18 9 3.1 1.7 | -0.2 31.6 010 10 5 7.4 4.1
8500 -1.1 30.0 020 17 9 3.5 1.9 | 0.3 32.5 010 9 5 7.8 4.3
8250 -0.8 30.6 020 16 8 5.5 3.0 | 0.9 33.6 010 9 4 9.0 4.9
8000 -0.3 31.5 020 14 7 6.6 3.6 | 1.6 34.9 010 8 4 9.6 5.3
7750 0.1 32.2 020 13 7 6.1 3.3 | 2.3 36.1 005 8 4 10.1 5.5
7500 0.5 32.9 020 11 6 6.6 3.6 | 3.1 37.6 010 8 4 10.3 5.6
7250 1.0 33.8 020 9 5 7.1 3.9 | 3.9 39.0 005 7 4 10.4 5.7
7000 1.6 34.9 020 8 4 7.1 3.9 | 4.7 40.5 005 7 4 9.8 5.4
6750 2.1 35.8 020 6 3 7.7 4.2 | 5.4 41.7 005 7 4 9.6 5.3
6500 2.7 36.9 015 5 3 8.1 4.4 | 6.1 43.0 005 7 3 10.9 6.0
6250 3.3 37.9 015 4 2 8.5 4.6 | 7.0 44.6 005 6 3 12.2 6.7
6000 3.9 39.0 015 4 2 7.1 3.9 | 7.9 46.2 005 6 3 9.8 5.4
5750 4.4 39.9 015 3 2 8.9 4.9 | 8.6 47.5 005 6 3 12.6 6.9
5500 5.2 41.4 010 3 2 12.4 6.8 | 9.8 49.6 005 6 3 18.0 9.9
5250 6.1 43.0 010 4 2 9.7 5.3 | 11.0 51.8 005 6 3 13.7 7.5
5000 M M M M M M M | M M M M M M M
04/21/2018 at 1500 MDT | 04/21/2018 at 1800 MDT
|
K index... +8.7 LI... +4.4 | K index... -4.9 LI... +3.7
CAPE... 0.0 CIN... 0.0 | CAPE... +2.0 CIN... -2.1
|
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 -63.0 -81.4 305 11 6 3.1 1.7 | -63.1 -81.6 265 19 10 3.6 2.0
45000 -58.0 -72.4 315 16 8 4.7 2.6 | -57.8 -72.0 275 26 13 3.2 1.8
40000 -50.7 -59.3 330 38 20 4.9 2.7 | -52.7 -62.9 285 32 17 3.2 1.8
38000 -49.4 -56.9 330 45 23 1.8 1.0 | -50.7 -59.3 300 37 19 3.5 1.9
36000 -48.3 -54.9 335 51 26 1.8 1.0 | -48.6 -55.5 315 44 22 3.5 1.9
34000 -46.0 -50.8 335 53 27 6.5 3.6 | -45.7 -50.3 320 46 24 6.3 3.5
32000 -42.1 -43.8 340 49 25 6.5 3.6 | -41.9 -43.4 320 44 22 6.3 3.5
30000 -38.2 -36.8 345 47 24 6.6 3.6 | -37.8 -36.0 320 41 21 7.5 4.1
29000 -36.2 -33.2 345 46 24 6.6 3.6 | -35.6 -32.1 320 40 21 7.5 4.1
28000 -34.2 -29.6 345 45 23 6.6 3.6 | -33.3 -27.9 325 39 20 7.5 4.1
27000 -32.2 -26.0 350 44 23 8.2 4.5 | -31.1 -24.0 325 38 19 7.0 3.8
26000 -29.2 -20.6 350 44 22 8.0 4.4 | -28.5 -19.3 330 35 18 7.0 3.9
25000 -26.8 -16.2 355 43 22 8.0 4.4 | -26.4 -15.5 330 32 17 7.0 3.9
24000 -24.5 -12.1 355 42 22 6.9 3.8 | -24.2 -11.6 335 31 16 8.0 4.4
23000 -22.4 -8.3 355 40 20 7.0 3.8 | -21.8 -7.2 340 30 15 8.0 4.4
22000 -20.3 -4.5 355 37 19 7.0 3.8 | -19.4 -2.9 345 29 15 7.9 4.3
21000 -18.3 -0.9 360 35 18 6.1 3.3 | -17.3 0.9 345 29 15 6.0 3.3
20000 -16.5 2.3 355 33 17 6.1 3.4 | -15.5 4.1 345 29 15 6.0 3.3
19500 -15.6 3.9 355 33 17 6.1 3.4 | -14.6 5.7 350 29 15 6.0 3.3
19000 -14.7 5.5 355 32 16 6.2 3.4 | -13.7 7.3 350 29 15 6.0 3.3
18500 -13.8 7.2 355 31 16 5.7 3.1 | -12.9 8.8 350 29 15 5.5 3.0
18000 -13.0 8.6 355 31 16 5.8 3.2 | -12.1 10.2 350 29 15 5.6 3.0
17500 -12.1 10.2 355 30 15 5.9 3.2 | -11.2 11.8 350 29 15 6.0 3.3
17000 -11.3 11.7 360 29 15 6.0 3.3 | -10.3 13.5 355 28 14 6.1 3.4
16500 -10.4 13.3 360 29 15 5.9 3.3 | -9.4 15.1 355 27 14 6.0 3.3
16000 -9.5 14.9 360 29 15 5.6 3.1 | -8.5 16.7 355 27 14 5.4 3.0
15500 -8.7 16.3 005 28 15 5.7 3.2 | -7.7 18.1 360 26 13 5.6 3.0
15000 -7.9 17.8 005 28 15 5.0 2.7 | -7.0 19.4 360 26 13 4.6 2.5
14500 -7.2 19.0 005 28 15 5.0 2.7 | -6.3 20.7 360 25 13 4.8 2.6
14000 -6.5 20.3 005 28 14 4.8 2.7 | -5.7 21.7 360 24 13 3.9 2.2
13500 -5.8 21.6 010 28 14 4.8 2.6 | -5.2 22.6 005 23 12 3.9 2.2
13000 -4.7 23.5 010 28 14 5.3 2.9 | -4.3 24.3 005 20 10 6.1 3.4
12500 -3.9 25.0 010 27 14 5.2 2.9 | -3.5 25.7 005 18 9 5.9 3.3
12000 -3.2 26.2 010 25 13 5.7 3.1 | -2.5 27.5 005 16 8 8.7 4.8
11500 -2.4 27.7 010 22 12 5.8 3.2 | -1.3 29.7 005 14 7 8.6 4.7
11000 -1.6 29.1 010 19 10 5.7 3.1 | -0.1 31.8 010 12 6 7.9 4.3
10500 -0.9 30.4 010 14 7 5.5 3.0 | 1.1 34.0 010 10 5 7.2 3.9
10250 -0.5 31.1 010 12 6 4.6 2.5 | 1.5 34.7 015 9 4 5.8 3.2
10000 -0.1 31.8 010 12 6 7.4 4.1 | 2.0 35.6 015 8 4 8.3 4.5
9750 0.6 33.1 010 11 6 9.9 5.4 | 2.7 36.9 020 7 4 10.2 5.6
9500 1.3 34.3 010 10 5 9.1 5.0 | 3.5 38.3 020 6 3 9.3 5.1
9250 1.9 35.4 010 10 5 7.8 4.3 | 4.1 39.4 025 5 3 7.2 3.9
9000 2.5 36.5 010 9 5 9.0 4.9 | 4.6 40.3 025 5 2 7.8 4.3
8750 3.3 37.9 010 9 5 10.9 6.0 | 5.3 41.5 030 4 2 9.5 5.2
8500 4.0 39.2 010 9 5 10.3 5.7 | 6.0 42.8 035 4 2 9.0 5.0
8250 4.8 40.6 010 9 4 10.4 5.7 | 6.6 43.9 040 3 2 9.1 5.0
8000 5.6 42.1 010 8 4 9.9 5.4 | 7.3 45.1 040 3 1 9.3 5.1
7750 6.3 43.3 010 8 4 9.0 4.9 | 8.0 46.4 045 3 1 9.6 5.3
7500 7.0 44.6 010 8 4 9.9 5.4 | 8.7 47.7 055 2 1 9.7 5.3
7250 7.7 45.9 010 8 4 10.8 5.9 | 9.5 49.1 055 2 1 10.0 5.5
7000 8.5 47.3 015 7 4 10.3 5.6 | 10.2 50.4 060 2 1 9.4 5.2
6750 9.3 48.7 015 7 4 10.2 5.6 | 10.9 51.6 065 2 1 9.3 5.1
6500 10.1 50.2 015 7 4 10.8 5.9 | 11.6 52.9 075 2 1 10.4 5.7
6250 10.9 51.6 015 7 3 11.5 6.3 | 12.4 54.3 080 2 1 11.2 6.2
6000 11.7 53.1 015 6 3 10.0 5.5 | 13.2 55.8 085 1 1 9.8 5.4
5750 12.5 54.5 015 6 3 13.2 7.2 | 13.9 57.0 095 1 1 9.7 5.3
5500 13.7 56.7 015 6 3 17.8 9.7 | 14.7 58.5 085 1 1 11.2 6.1
5250 14.9 58.8 010 6 3 14.2 7.8 | 15.5 59.9 075 1 1 10.0 5.5
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.
CIN (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.
042613
- National Weather Service
- Grand Junction, CO Weather Forecast Office
- 2844 Aviators Way
- Grand Junction, CO 81506-8644
- 970-243-7007
- Page Author: GJT Webmaster
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- Page last modified: Mar 8th, 2018 20:36 UTC