Soaring Guidance
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
572
UXUS97 KBOU 271319
SRGBOU
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
0719 MDT Saturday, April 27, 2024
This forecast is for Saturday, April 27, 2024:
If the trigger temperature of 51.9 F/11.1 C is reached...then
Thermal Soaring Index....................... Poor
Maximum rate of lift........................ 0 ft/min (0.0 m/s)
Maximum height of thermals.................. 5353 ft MSL (0 ft AGL)
Forecast maximum temperature................... 41.0 F/5.5 C
Time of trigger temperature.................... None
Time of overdevelopment........................ None
Middle/high clouds during soaring window....... Broken/overcast opaque middle
Surface winds during soaring window............ 20 mph or less
Height of the -3 thermal index................. None
Thermal soaring outlook for Sunday 04/28....... Poor
Wave Soaring Index............................. Poor
Wave Soaring Index trend (to 1800 MDT)......... No change
Height of stable layer (12-18K ft MSL)......... None
Weak PVA/NVA (through 1800 MDT)................ Neither
Potential height of wave....................... 21809 ft MSL (16456 ft AGL)
Wave soaring outlook for Sunday 04/28.......... Poor
Remarks...
Sunrise/Sunset.................... 06:03:53 / 19:50:07 MDT
Total possible sunshine........... 13 hr 46 min 15 sec (826 min 15 sec)
Altitude of sun at 12:57:00 MDT... 64.40 degrees
Upper air data from numerical model forecast valid on 04/27/2024 at 0600 MDT
Freezing level.................. 8645 ft MSL (3292 ft AGL)
Convective condensation level... 8389 ft MSL (3036 ft AGL)
Lifted condensation level....... 6614 ft MSL (1261 ft AGL)
Lifted index.................... +6.0
K index......................... +24.8
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 -51.7 -61.1 220 25 13 1.5 0.8 M M M M M
45000 -49.4 -56.9 215 26 13 0.9 0.5 M M M M M
40000 -48.9 -56.0 215 33 17 0.3 0.2 M M M M M
38000 -50.2 -58.4 210 33 17 -7.0 -3.8 M M M M M
36000 -54.4 -65.9 185 30 16 -7.1 -3.9 M M M M M
34000 -58.7 -73.7 165 33 17 -3.4 -1.9 M M M M M
32000 -52.6 -62.7 165 34 17 9.9 5.4 M M M M M
30000 -46.7 -52.1 160 34 18 9.2 5.0 28.4 83.1 17.6 M M
29000 -44.0 -47.2 160 33 17 9.1 5.0 28.0 82.4 17.5 M M
28000 -41.3 -42.3 160 32 16 9.1 5.0 27.7 81.9 17.5 M M
27000 -38.6 -37.5 160 30 16 9.2 5.0 27.6 81.7 17.6 M M
26000 -36.0 -32.8 160 29 15 8.3 4.6 27.1 80.8 17.4 M M
25000 -33.6 -28.5 155 27 14 8.4 4.6 26.5 79.7 17.2 M M
24000 -31.1 -24.0 155 26 13 8.4 4.6 26.1 78.9 17.0 M M
23000 -28.7 -19.7 150 24 12 8.0 4.4 25.5 77.8 16.7 M M
22000 -26.3 -15.3 150 23 12 8.0 4.4 24.8 76.6 16.3 M M
21000 -23.9 -11.0 145 21 11 8.0 4.4 24.2 75.6 16.0 M M
20000 -21.7 -7.1 145 19 10 7.6 4.2 23.4 74.2 15.5 M M
19500 -20.5 -4.9 145 19 10 7.6 4.2 23.1 73.5 15.2 M M
19000 -19.4 -2.9 140 18 9 7.6 4.2 22.7 72.8 15.0 M M
18500 -18.3 -0.9 140 17 9 7.7 4.2 22.3 72.2 14.7 M M
18000 -16.8 1.8 140 15 8 6.7 3.7 21.7 71.0 14.2 M M
17500 -15.8 3.6 135 14 7 6.7 3.7 21.1 70.1 13.8 M M
17000 -14.8 5.4 135 13 7 6.9 3.8 20.6 69.2 13.5 M M
16500 -13.8 7.2 130 12 6 6.9 3.8 20.2 68.3 13.1 M M
16000 -12.7 9.1 130 11 6 6.8 3.7 19.7 67.5 12.7 M M
15500 -11.8 10.8 125 10 5 6.7 3.7 19.2 66.5 12.3 M M
15000 -10.8 12.6 125 10 5 6.7 3.7 18.7 65.6 11.9 M M
14500 -9.8 14.4 120 9 5 6.6 3.6 18.1 64.6 11.4 M M
14000 -8.9 16.0 120 9 4 6.6 3.6 17.6 63.7 11.0 M M
13500 -7.9 17.8 115 8 4 6.3 3.5 17.1 62.7 10.5 M M
13000 -7.0 19.4 115 8 4 6.4 3.5 16.5 61.7 10.1 M M
12500 -6.1 21.0 110 8 4 6.2 3.4 16.0 60.7 9.6 M M
12000 -5.2 22.6 105 8 4 6.2 3.4 15.4 59.7 9.0 M M
11500 -4.4 24.1 100 8 4 6.1 3.3 14.8 58.7 8.5 M M
11000 -3.5 25.7 090 9 4 6.2 3.4 14.2 57.6 8.0 M M
10500 -2.6 27.3 085 10 5 5.4 3.0 13.6 56.5 7.4 M M
10250 -2.3 27.9 080 10 5 5.4 2.9 13.3 55.9 7.1 M M
10000 -1.9 28.6 075 11 5 5.7 3.1 12.9 55.3 6.8 M M
9750 -1.5 29.3 070 10 5 5.3 2.9 12.6 54.7 6.5 M M
9500 -1.1 30.0 070 11 5 4.5 2.5 12.2 54.0 6.1 M M
9250 -0.8 30.6 065 11 6 5.0 2.7 11.8 53.3 5.7 M M
9000 -0.4 31.3 065 11 6 4.0 2.2 11.4 52.6 5.3 M M
8750 -0.2 31.6 065 10 5 3.8 2.1 10.9 51.7 4.9 M M
8500 0.1 32.2 065 10 5 4.6 2.5 10.5 51.0 4.5 M M
8250 0.5 32.9 065 10 5 4.5 2.5 10.1 50.2 4.1 M M
8000 0.8 33.4 065 10 5 4.3 2.4 9.7 49.5 3.7 M M
7750 1.1 34.0 065 11 6 4.9 2.7 9.3 48.8 3.3 M M
7500 1.5 34.7 065 10 5 5.5 3.0 9.0 48.2 3.0 M M
7250 1.9 35.4 065 9 5 5.5 3.0 8.6 47.6 2.6 M M
7000 2.2 36.0 065 9 5 4.7 2.6 8.3 47.0 2.3 M M
6750 2.6 36.7 060 9 5 6.4 3.5 7.9 46.3 1.9 M M
6500 3.2 37.8 055 8 4 8.5 4.6 7.8 46.1 1.8 M M
6250 3.7 38.7 055 6 3 8.0 4.4 7.7 45.8 1.6 M M
6000 4.3 39.7 050 6 3 8.5 4.6 7.6 45.6 1.5 M M
5750 4.9 40.8 045 6 3 8.2 4.5 7.5 45.5 1.4 M M
5500 5.5 41.9 045 5 2 9.4 5.1 7.4 45.3 1.2 M M
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
04/27/2024 at 0900 MDT | 04/27/2024 at 1200 MDT
|
CAPE... +3.4 LI... +1.5 | CAPE... +6.9 LI... +1.2
CINH... -0.1 K Index... +23.1 | CINH... -0.1 K Index... +22.6
|
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 -51.3 -60.3 210 24 12 1.5 0.8 | -51.6 -60.9 215 26 13 1.5 0.8
45000 -48.9 -56.0 200 25 13 1.0 0.6 | -49.2 -56.6 200 31 16 1.0 0.5
40000 -48.2 -54.8 210 29 15 0.5 0.3 | -48.8 -55.8 210 29 15 0.2 0.1
38000 -49.3 -56.7 205 27 14 -6.1 -3.3 | -49.4 -56.9 205 26 13 -3.1 -1.7
36000 -52.9 -63.2 180 23 12 -6.1 -3.4 | -51.2 -60.2 180 20 10 -3.2 -1.7
34000 -56.6 -69.9 150 25 13 -4.5 -2.5 | -53.1 -63.6 145 20 11 -3.1 -1.7
32000 -52.1 -61.8 130 23 12 7.6 4.1 | -50.6 -59.1 105 23 12 4.4 2.4
30000 -47.5 -53.5 120 22 11 9.1 5.0 | -47.8 -54.0 085 31 16 8.0 4.4
29000 -44.8 -48.6 120 22 11 9.0 4.9 | -45.2 -49.4 085 28 15 8.6 4.7
28000 -42.2 -44.0 120 22 11 9.0 4.9 | -42.6 -44.7 090 26 13 8.6 4.7
27000 -39.5 -39.1 120 21 11 9.1 5.0 | -40.1 -40.2 095 24 12 8.6 4.7
26000 -36.9 -34.4 125 21 11 8.6 4.7 | -37.5 -35.5 105 22 11 8.5 4.6
25000 -34.3 -29.7 125 21 11 8.6 4.7 | -35.0 -31.0 110 20 10 8.5 4.6
24000 -31.7 -25.1 125 20 11 8.7 4.8 | -32.5 -26.5 120 18 9 8.5 4.7
23000 -29.3 -20.7 130 20 10 8.0 4.4 | -30.0 -22.0 125 18 9 8.2 4.5
22000 -26.9 -16.4 130 20 10 8.0 4.4 | -27.6 -17.7 135 18 9 8.2 4.5
21000 -24.5 -12.1 130 20 10 8.1 4.4 | -25.2 -13.4 145 18 9 8.4 4.6
20000 -22.2 -8.0 135 20 10 7.5 4.1 | -23.0 -9.4 145 18 9 6.8 3.7
19500 -21.1 -6.0 135 19 10 7.5 4.1 | -22.0 -7.6 150 18 9 6.8 3.8
19000 -20.0 -4.0 135 19 10 7.5 4.1 | -21.0 -5.8 150 18 9 6.9 3.8
18500 -18.4 -1.1 135 19 10 7.4 4.1 | -20.0 -4.0 155 17 9 6.8 3.8
18000 -17.3 0.9 135 19 10 7.3 4.0 | -19.0 -2.2 155 17 9 7.2 3.9
17500 -16.2 2.8 130 18 9 7.3 4.0 | -17.9 -0.2 150 17 9 7.2 4.0
17000 -15.2 4.6 130 18 9 6.9 3.8 | -16.3 2.7 150 16 8 7.2 4.0
16500 -14.2 6.4 130 18 9 6.9 3.8 | -15.3 4.5 145 15 8 7.2 4.0
16000 -13.2 8.2 130 17 9 6.7 3.7 | -14.2 6.4 140 15 8 6.8 3.7
15500 -12.2 10.0 130 17 9 6.6 3.6 | -13.3 8.1 140 14 7 6.5 3.6
15000 -11.3 11.7 125 16 8 6.5 3.6 | -12.3 9.9 130 13 7 6.4 3.5
14500 -10.3 13.5 125 16 8 6.2 3.4 | -11.4 11.5 130 12 6 6.0 3.3
14000 -9.4 15.1 125 15 8 6.3 3.4 | -10.5 13.1 125 12 6 6.0 3.3
13500 -8.5 16.7 125 14 7 6.0 3.3 | -9.6 14.7 120 11 6 6.4 3.5
13000 -7.7 18.1 125 14 7 6.0 3.3 | -8.7 16.3 115 11 6 6.5 3.5
12500 -6.8 19.8 120 13 7 5.5 3.0 | -7.8 18.0 105 11 6 6.0 3.3
12000 -6.0 21.2 120 12 6 5.6 3.1 | -6.9 19.6 100 11 6 6.1 3.3
11500 -5.2 22.6 115 12 6 5.4 3.0 | -6.0 21.2 095 11 6 6.2 3.4
11000 -4.4 24.1 110 11 6 5.5 3.0 | -5.1 22.8 090 12 6 6.4 3.5
10500 -3.7 25.3 110 10 5 4.9 2.7 | -4.3 24.3 085 12 6 4.9 2.7
10250 -3.3 26.1 110 10 5 4.5 2.5 | -4.0 24.8 080 12 6 4.9 2.7
10000 -3.0 26.6 105 9 5 6.3 3.5 | -3.6 25.5 075 12 6 5.6 3.1
9750 -2.5 27.5 100 9 5 6.5 3.6 | -3.2 26.2 070 13 7 5.1 2.8
9500 -2.1 28.2 100 8 4 4.9 2.7 | -2.9 26.8 065 14 7 4.0 2.2
9250 -1.7 28.9 100 8 4 5.3 2.9 | -2.6 27.3 060 14 7 4.3 2.4
9000 -1.4 29.5 100 7 4 5.4 3.0 | -2.3 27.9 055 15 8 4.2 2.3
8750 -1.0 30.2 090 7 4 4.3 2.3 | -2.0 28.4 050 16 8 3.2 1.7
8500 -0.7 30.7 090 7 4 3.2 1.8 | -1.8 28.8 045 16 8 2.4 1.3
8250 -0.5 31.1 085 6 3 3.5 1.9 | -1.6 29.1 045 17 9 2.5 1.4
8000 -0.2 31.6 085 6 3 3.3 1.8 | -1.4 29.5 040 18 9 2.9 1.6
7750 -0.0 32.0 100 4 2 1.9 1.1 | -1.2 29.8 035 18 9 2.8 1.5
7500 0.0 32.0 095 3 2 1.1 0.6 | -1.0 30.2 030 18 9 2.4 1.3
7250 0.1 32.2 085 3 2 1.3 0.7 | -0.8 30.6 025 17 9 2.4 1.3
7000 0.2 32.4 085 2 1 1.2 0.7 | -0.7 30.7 020 17 9 0.5 0.3
6750 0.3 32.5 160 1 1 1.4 0.8 | -0.7 30.7 015 17 9 2.2 1.2
6500 0.4 32.7 190 1 1 1.3 0.7 | -0.4 31.3 010 16 8 4.7 2.6
6250 0.6 33.1 220 1 1 2.1 1.1 | -0.1 31.8 005 15 8 4.6 2.5
6000 0.7 33.3 225 2 1 2.5 1.4 | 0.3 32.5 360 14 7 4.7 2.6
5750 1.0 33.8 225 3 1 4.3 2.4 | 0.7 33.3 355 13 7 6.2 3.4
5500 1.5 34.7 235 2 1 10.4 5.7 | 1.3 34.3 355 11 6 12.4 6.8
04/27/2024 at 1500 MDT | 04/27/2024 at 1800 MDT
|
CAPE... +13.8 LI... +2.3 | CAPE... +18.8 LI... +2.3
CINH... 0.0 K Index... +21.4 | CINH... -0.2 K Index... +19.4
|
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 -51.8 -61.2 215 24 12 1.4 0.8 | -52.4 -62.3 220 22 11 1.9 1.0
45000 -49.5 -57.1 210 31 16 1.0 0.5 | -49.5 -57.1 210 26 13 1.1 0.6
40000 -48.9 -56.0 210 26 13 0.4 0.2 | -49.1 -56.4 215 18 9 0.3 0.1
38000 -49.1 -56.4 210 23 12 -1.6 -0.9 | -49.3 -56.7 215 16 8 -1.7 -1.0
36000 -50.1 -58.2 195 18 9 -1.7 -0.9 | -50.4 -58.7 210 13 7 -1.7 -1.0
34000 -51.1 -60.0 180 15 8 -1.5 -0.8 | -51.4 -60.5 200 10 5 -1.1 -0.6
32000 -49.6 -57.3 085 16 8 2.5 1.4 | -49.6 -57.3 125 8 4 3.1 1.7
30000 -47.9 -54.2 060 33 17 6.8 3.7 | -47.5 -53.5 090 14 7 7.2 3.9
29000 -45.6 -50.1 060 26 14 7.9 4.3 | -45.2 -49.4 090 12 6 7.7 4.2
28000 -43.2 -45.8 065 20 10 7.9 4.3 | -42.9 -45.2 090 10 5 7.7 4.2
27000 -40.9 -41.6 070 14 7 7.8 4.3 | -40.6 -41.1 090 8 4 7.6 4.2
26000 -38.3 -36.9 075 11 5 8.9 4.9 | -38.1 -36.6 080 6 3 8.6 4.7
25000 -35.7 -32.3 085 10 5 8.9 4.9 | -35.5 -31.9 070 5 3 8.6 4.7
24000 -33.0 -27.4 095 9 4 8.9 4.9 | -32.9 -27.2 045 4 2 8.7 4.8
23000 -30.5 -22.9 105 8 4 8.3 4.6 | -30.4 -22.7 035 4 2 8.4 4.6
22000 -28.0 -18.4 115 8 4 8.3 4.6 | -27.9 -18.2 030 4 2 8.4 4.6
21000 -25.5 -13.9 130 9 4 8.4 4.6 | -25.4 -13.7 020 4 2 8.4 4.6
20000 -23.2 -9.8 135 9 5 7.6 4.2 | -23.1 -9.6 020 3 2 7.7 4.2
19500 -22.1 -7.8 135 9 5 7.6 4.2 | -22.0 -7.6 015 2 1 7.7 4.2
19000 -21.0 -5.8 135 9 5 7.6 4.2 | -20.8 -5.4 010 2 1 7.7 4.2
18500 -19.8 -3.6 135 10 5 7.7 4.2 | -19.7 -3.5 005 1 1 7.7 4.2
18000 -18.7 -1.7 135 10 5 7.1 3.9 | -18.6 -1.5 345 1 0 7.6 4.2
17500 -17.2 1.0 135 10 5 7.1 3.9 | -16.9 1.6 270 1 0 7.7 4.2
17000 -16.1 3.0 135 10 5 7.1 3.9 | -15.8 3.6 235 1 1 6.8 3.8
16500 -15.1 4.8 130 10 5 7.1 3.9 | -14.8 5.4 220 2 1 6.9 3.8
16000 -14.0 6.8 130 10 5 6.9 3.8 | -13.8 7.2 215 3 1 6.3 3.4
15500 -13.0 8.6 125 11 6 6.8 3.7 | -12.9 8.8 210 3 2 6.0 3.3
15000 -12.0 10.4 125 11 6 6.6 3.6 | -12.1 10.2 205 4 2 6.1 3.4
14500 -11.1 12.0 120 11 6 6.1 3.4 | -11.2 11.8 190 3 2 6.4 3.5
14000 -10.2 13.6 115 12 6 6.1 3.4 | -10.2 13.6 170 3 2 6.4 3.5
13500 -9.4 15.1 110 12 6 5.6 3.1 | -9.3 15.3 145 3 2 6.0 3.3
13000 -8.6 16.5 105 12 6 5.7 3.1 | -8.5 16.7 120 4 2 6.1 3.3
12500 -7.8 18.0 100 12 6 5.2 2.8 | -7.7 18.1 100 5 3 4.9 2.7
12000 -7.0 19.4 090 13 7 5.3 2.9 | -7.0 19.4 085 7 4 5.1 2.8
11500 -6.3 20.7 080 13 7 4.6 2.5 | -6.3 20.7 070 9 4 3.7 2.1
11000 -5.6 21.9 070 14 7 4.8 2.6 | -5.8 21.6 055 10 5 3.9 2.1
10500 -5.0 23.0 065 15 8 3.6 2.0 | -5.2 22.6 045 12 6 4.0 2.2
10250 -4.8 23.4 055 15 8 3.0 1.7 | -4.9 23.2 040 12 6 3.0 1.6
10000 -4.5 23.9 050 16 8 5.7 3.1 | -4.6 23.7 035 13 6 7.0 3.8
9750 -4.0 24.8 050 16 8 6.4 3.5 | -4.0 24.8 030 13 7 7.8 4.3
9500 -3.7 25.3 045 16 8 4.2 2.3 | -3.6 25.5 030 13 7 4.2 2.3
9250 -3.3 26.1 040 17 9 4.9 2.7 | -3.3 26.1 025 14 7 5.3 2.9
9000 -3.0 26.6 040 17 9 4.1 2.2 | -2.9 26.8 025 15 8 4.5 2.5
8750 -2.7 27.1 035 18 9 4.4 2.4 | -2.6 27.3 020 16 8 5.2 2.9
8500 -2.3 27.9 030 18 9 5.2 2.9 | -2.1 28.2 020 16 8 6.1 3.3
8250 -2.0 28.4 025 18 9 5.3 2.9 | -1.7 28.9 020 16 8 6.4 3.5
8000 -1.6 29.1 020 18 9 4.1 2.2 | -1.3 29.7 015 16 8 4.2 2.3
7750 -1.4 29.5 015 18 9 3.6 2.0 | -1.1 30.0 015 17 9 4.0 2.2
7500 -1.0 30.2 010 17 9 4.7 2.6 | -0.7 30.7 010 17 9 6.3 3.5
7250 -0.7 30.7 005 17 9 4.2 2.3 | -0.2 31.6 010 16 8 5.1 2.8
7000 -0.5 31.1 360 17 9 2.4 1.3 | 0.1 32.2 005 16 8 2.6 1.4
6750 -0.3 31.5 350 16 8 3.8 2.1 | 0.2 32.4 360 16 8 4.1 2.2
6500 0.1 32.2 350 15 8 6.2 3.4 | 0.7 33.3 355 15 8 6.4 3.5
6250 0.5 32.9 345 15 7 5.3 2.9 | 1.1 34.0 350 14 7 6.3 3.5
6000 0.9 33.6 340 13 7 4.8 2.6 | 1.6 34.9 350 13 7 6.7 3.7
5750 1.2 34.2 330 12 6 5.7 3.1 | 2.1 35.8 350 12 6 7.1 3.9
5500 1.8 35.2 330 10 5 9.8 5.4 | 2.7 36.9 345 10 5 10.1 5.6
________________________________________________________________________________
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 near the old Stapleton
Airport site in Denver, Colorado at
North Latitude: 39 deg 46 min 5.016 sec
West Longitude: 104 deg 52 min 9.984 sec
Elevation: 5285 feet (1611 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.
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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