Soaring Guidance
Issued by NWS Pueblo, CO
Issued by NWS Pueblo, CO
678
UXUS97 KPUB 171221
SRGPUB
Soaring Forecast
National Weather Service Pueblo, Colorado
0621 MDT Saturday, May 17, 2025
This forecast is for Villa Grove, CO for Saturday, May 17, 2025:
If the trigger temperature of 52.3 F/11.3 C is reached...then
Thermal Soaring Index....................... Excellent
Maximum rate of lift........................ 1581 ft/min (8.0 m/s)
Maximum height of thermals.................. 26020 ft MSL (17027 ft AGL)
Forecast maximum temperature................... 70.0 F/21.6 C
Time of trigger temperature.................... 0845 MDT
Time of overdevelopment........................ None
Middle/high clouds during soaring window....... Overcast thin high
Surface winds during soaring window............ 20 mph or less
Height of the -3 thermal index................. 22618 ft MSL (13625 ft AGL)
Thermal soaring outlook for Sunday 05/18....... Excellent
Wave Soaring Index............................. Not available
Remarks...
Sunrise/Sunset.................... 05:50:22 / 20:09:39 MDT
Total possible sunshine........... 14 hr 19 min 17 sec (859 min 17 sec)
Altitude of sun at 13:00:00 MDT... 71.25 degrees
Upper air data from numerical model forecast valid on 05/17/2025 at 0600 MDT
Freezing level.................. 12685 ft MSL (3692 ft AGL)
Convective condensation level... 17147 ft MSL (8154 ft AGL)
Lifted condensation level....... 20822 ft MSL (11829 ft AGL)
Lifted index.................... -3.3
K index......................... +6.1
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 -58.7 -73.7 240 44 23 -0.1 -0.0 M M M M M
45000 -58.8 -73.8 240 49 25 0.1 0.1 M M M M M
40000 -58.7 -73.7 230 63 32 0.3 0.2 M M M M M
38000 -55.8 -68.4 230 61 31 6.3 3.4 M M M M M
36000 -52.0 -61.6 230 56 29 6.3 3.5 M M M M M
34000 -48.2 -54.8 230 49 25 6.8 3.7 M M M M M
32000 -44.1 -47.4 230 38 20 6.8 3.7 M M M M M
30000 -39.3 -38.7 230 31 16 7.6 4.2 24.7 76.5 2.8 M M
29000 -37.0 -34.6 235 30 16 7.6 4.2 23.8 74.9 2.2 M M
28000 -34.7 -30.5 240 30 15 7.6 4.2 23.1 73.6 1.6 M M
27000 -32.6 -26.7 240 30 16 6.7 3.7 22.2 72.0 0.9 M M
26000 -30.5 -22.9 240 31 16 6.8 3.7 21.1 69.9 -0.1 1674 8.5
25000 -28.5 -19.3 245 32 17 6.8 3.7 20.0 68.1 -1.0 1584 8.0
24000 -26.5 -15.7 245 33 17 7.1 3.9 19.1 66.3 -1.8 1493 7.6
23000 -24.4 -11.9 245 32 17 7.1 3.9 18.0 64.5 -2.7 1400 7.1
22000 -22.2 -8.0 250 31 16 7.1 3.9 17.1 62.8 -3.5 1307 6.6
21000 -20.2 -4.4 250 30 15 6.1 3.4 16.1 61.0 -4.4 1217 6.2
20000 -18.4 -1.1 250 29 15 6.2 3.4 14.9 58.8 -5.6 1132 5.8
19500 -17.5 0.5 250 28 15 6.2 3.4 14.3 57.7 -6.2 1090 5.5
19000 -16.6 2.1 245 28 14 6.2 3.4 13.7 56.7 -6.7 1048 5.3
18500 -15.6 3.9 250 27 14 6.9 3.8 13.2 55.8 -7.2 1005 5.1
18000 -14.6 5.7 250 27 14 7.0 3.8 12.7 54.9 -7.7 960 4.9
17500 -13.6 7.5 250 27 14 8.0 4.4 12.3 54.1 -8.2 915 4.6
17000 -12.3 9.9 250 26 13 9.1 5.0 12.2 53.9 -8.4 860 4.4
16500 -10.9 12.4 255 25 13 9.2 5.0 12.1 53.7 -8.6 805 4.1
16000 -9.5 14.9 255 24 12 9.6 5.3 12.0 53.6 -8.7 749 3.8
15500 -7.4 18.7 255 22 12 9.9 5.4 12.0 53.6 -8.8 662 3.4
15000 -5.8 21.6 255 21 11 10.5 5.7 12.1 53.8 -8.8 601 3.1
14500 -4.3 24.3 255 20 10 7.8 4.3 12.3 54.1 -8.7 539 2.7
14000 -3.1 26.4 255 18 9 10.0 5.5 11.9 53.4 -9.1 490 2.5
13500 -1.8 28.8 255 17 8 9.7 5.3 11.8 53.3 -9.2 435 2.2
13000 -0.5 31.1 250 14 7 7.2 4.0 11.6 52.9 -9.5 383 1.9
12500 0.6 33.1 240 12 6 7.8 4.3 11.3 52.3 -9.9 335 1.7
12000 1.6 34.9 230 11 5 6.7 3.7 10.9 51.7 -10.3 288 1.5
11750 2.1 35.8 225 10 5 6.5 3.6 10.7 51.2 -10.6 266 1.4
11500 2.6 36.7 220 9 5 6.5 3.6 10.4 50.8 -10.9 245 1.2
11250 3.1 37.6 215 9 5 6.8 3.7 10.2 50.3 -11.2 223 1.1
11000 3.6 38.5 210 8 4 7.5 4.1 10.0 50.0 -11.4 200 1.0
10750 4.2 39.6 210 8 4 7.1 3.9 9.8 49.7 -11.6 176 0.9
10500 4.7 40.5 205 8 4 7.3 4.0 9.6 49.3 -11.9 153 0.8
10250 5.2 41.4 200 7 4 5.1 2.8 9.4 48.9 -12.1 131 0.7
10000 5.4 41.7 200 7 4 1.1 0.6 8.8 47.9 -12.7 118 0.6
9750 5.4 41.7 195 6 3 -0.4 -0.2 8.1 46.6 -13.5 110 0.6
9500 5.3 41.5 195 6 3 -0.4 -0.2 7.4 45.2 -14.3 105 0.5
9250 5.1 41.2 195 5 2 -9.9 -5.4 6.4 43.5 -15.3 105 0.5
9000 2.7 36.9 245 2 1 -65.8 -36.1 3.2 37.8 -18.4 168 0.9
8750 M M M M M M M M M M M M
8500 M M M M M M M M M M M M
8250 M M M M M M M M M M M M
8000 M M M M M M M M M M M M
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
05/17/2025 at 0900 MDT | 05/17/2025 at 1200 MDT
|
CAPE... +4.5 LI... +0.6 | CAPE... +56.5 LI... -0.5
CINH... -24.1 K Index... +3.4 | CINH... 0.0 K Index... +12.6
|
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 -56.7 -70.1 235 44 23 0.3 0.1 | -56.1 -69.0 235 45 23 0.4 0.2
45000 -56.5 -69.7 230 51 26 -1.3 -0.7 | -55.5 -67.9 235 55 28 -1.2 -0.6
40000 -58.4 -73.1 230 47 24 -1.2 -0.7 | -57.8 -72.0 235 41 21 -1.4 -0.8
38000 -56.7 -70.1 225 44 23 4.7 2.6 | -56.7 -70.1 235 36 19 3.6 2.0
36000 -53.9 -65.0 225 41 21 4.7 2.6 | -54.5 -66.1 235 31 16 3.6 2.0
34000 -50.4 -58.7 225 38 20 7.9 4.3 | -51.6 -60.9 235 28 14 7.8 4.3
32000 -45.7 -50.3 225 38 19 7.9 4.3 | -46.9 -52.4 240 29 15 7.8 4.3
30000 -41.0 -41.8 225 36 19 8.0 4.4 | -41.5 -42.7 240 30 15 8.3 4.5
29000 -38.0 -36.4 225 35 18 8.0 4.4 | -39.0 -38.2 240 29 15 8.3 4.5
28000 -35.6 -32.1 225 33 17 8.0 4.4 | -36.5 -33.7 240 29 15 8.3 4.5
27000 -33.3 -27.9 225 32 16 7.6 4.2 | -34.1 -29.4 240 28 15 7.5 4.1
26000 -31.0 -23.8 230 31 16 7.6 4.2 | -31.8 -25.2 240 28 14 7.6 4.1
25000 -28.7 -19.7 235 30 15 7.7 4.2 | -29.6 -21.3 235 27 14 7.6 4.1
24000 -26.4 -15.5 235 29 15 7.6 4.2 | -27.3 -17.1 235 27 14 7.3 4.0
23000 -24.1 -11.4 240 28 14 7.6 4.2 | -25.2 -13.4 235 27 14 7.3 4.0
22000 -21.8 -7.2 240 26 14 7.6 4.2 | -23.0 -9.4 240 28 14 7.3 4.0
21000 -19.8 -3.6 245 26 13 5.0 2.8 | -20.9 -5.6 240 27 14 6.4 3.5
20000 -18.2 -0.8 245 27 14 5.3 2.9 | -18.9 -2.0 245 26 13 6.6 3.6
19500 -17.5 0.5 250 27 14 5.3 2.9 | -18.0 -0.4 245 25 13 6.7 3.7
19000 -16.7 1.9 250 28 14 5.2 2.9 | -17.0 1.4 245 24 12 6.7 3.7
18500 -15.9 3.4 250 27 14 6.5 3.5 | -16.0 3.2 245 23 12 8.0 4.4
18000 -14.9 5.2 250 25 13 6.6 3.6 | -14.8 5.4 245 21 11 8.0 4.4
17500 -14.0 6.8 250 24 12 7.8 4.3 | -13.6 7.5 240 19 10 8.3 4.6
17000 -12.7 9.1 250 22 12 9.2 5.0 | -12.4 9.7 235 18 9 8.7 4.8
16500 -11.3 11.7 250 21 11 9.3 5.1 | -11.1 12.0 230 18 9 8.7 4.8
16000 -9.9 14.2 255 21 11 9.9 5.4 | -9.7 14.5 230 17 9 9.7 5.3
15500 -8.4 16.9 255 20 10 9.8 5.4 | -7.6 18.3 225 17 9 9.9 5.4
15000 -6.9 19.6 255 20 10 10.7 5.9 | -6.0 21.2 225 17 9 11.0 6.0
14500 -4.5 23.9 250 19 10 8.0 4.4 | -4.4 24.1 220 17 9 7.1 3.9
14000 -3.3 26.1 250 18 9 10.0 5.5 | -3.2 26.2 220 17 9 10.8 5.9
13500 -1.9 28.6 250 17 9 9.3 5.1 | -1.8 28.8 220 17 9 10.2 5.6
13000 -0.5 31.1 245 17 9 9.4 5.1 | -0.3 31.5 220 17 9 9.4 5.1
12500 0.8 33.4 245 17 9 9.1 5.0 | 1.2 34.2 220 17 9 10.0 5.5
12000 1.9 35.4 240 17 9 5.2 2.8 | 2.6 36.7 215 16 8 9.5 5.2
11750 2.3 36.1 235 16 8 5.8 3.2 | 3.3 37.9 215 16 8 10.1 5.6
11500 2.7 36.9 235 16 8 6.2 3.4 | 4.1 39.4 215 16 8 10.0 5.5
11250 3.1 37.6 230 15 8 5.5 3.0 | 4.8 40.6 215 16 8 10.2 5.6
11000 3.5 38.3 225 15 8 3.5 1.9 | 5.6 42.1 215 16 8 10.8 5.9
10750 3.7 38.7 220 14 7 4.9 2.7 | 6.4 43.5 215 16 8 10.7 5.9
10500 4.2 39.6 215 12 6 6.7 3.7 | 7.2 45.0 215 16 8 10.3 5.6
10250 4.6 40.3 210 11 6 7.4 4.0 | 8.0 46.4 215 16 8 10.5 5.8
10000 5.2 41.4 205 10 5 9.1 5.0 | 8.8 47.8 215 16 8 10.7 5.9
9750 5.9 42.6 205 9 5 9.9 5.4 | 9.6 49.3 215 15 8 11.6 6.3
9500 6.7 44.1 200 8 4 10.6 5.8 | 10.5 50.9 210 15 8 11.3 6.2
9250 7.6 45.7 200 7 4 16.4 9.0 | 11.5 52.7 210 14 7 19.5 10.7
9000 9.7 49.5 195 6 3 45.2 24.8 | 14.6 58.3 210 12 6 78.4 43.0
8750 M M M M M M M | M M M M M M M
8500 M M M M M M M | M M M M M M M
8250 M M M M M M M | M M M M M M M
8000 M M M M M M M | M M M M M M M
05/17/2025 at 1500 MDT | 05/17/2025 at 1800 MDT
|
CAPE... +90.0 LI... -0.1 | CAPE... +47.6 LI... 0.0
CINH... -0.2 K Index... +14.5 | CINH... -4.0 K Index... +14.9
|
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 -55.6 -68.1 245 42 22 1.1 0.6 | -56.6 -69.9 245 46 24 0.6 0.4
45000 -54.3 -65.7 245 55 28 -3.1 -1.7 | -55.9 -68.6 250 54 28 -1.5 -0.8
40000 -58.7 -73.7 250 44 23 -2.9 -1.6 | -58.0 -72.4 250 53 28 -1.4 -0.8
38000 -57.6 -71.7 255 39 20 4.6 2.5 | -56.9 -70.4 250 52 27 3.6 2.0
36000 -54.9 -66.8 260 33 17 4.6 2.5 | -54.7 -66.5 250 49 25 3.6 2.0
34000 -51.5 -60.7 265 29 15 8.0 4.4 | -51.7 -61.1 250 44 23 8.5 4.6
32000 -46.7 -52.1 265 27 14 8.1 4.4 | -46.6 -51.9 250 36 19 8.5 4.7
30000 -41.1 -42.0 260 26 13 8.3 4.6 | -40.7 -41.3 250 28 14 9.1 5.0
29000 -38.6 -37.5 255 26 13 8.3 4.6 | -37.9 -36.2 250 24 12 9.1 5.0
28000 -36.1 -33.0 250 26 13 8.3 4.6 | -35.2 -31.4 255 21 11 9.1 5.0
27000 -33.8 -28.8 250 27 14 6.5 3.6 | -32.8 -27.0 260 20 10 5.5 3.0
26000 -31.8 -25.2 245 30 15 6.7 3.7 | -31.1 -24.0 255 24 12 5.8 3.2
25000 -29.8 -21.6 245 32 17 6.7 3.7 | -29.4 -20.9 250 28 14 5.8 3.2
24000 -27.8 -18.0 245 34 17 7.2 4.0 | -27.6 -17.7 250 31 16 7.5 4.1
23000 -25.6 -14.1 245 31 16 7.3 4.0 | -25.3 -13.5 250 28 15 7.7 4.2
22000 -23.4 -10.1 245 29 15 7.3 4.0 | -23.0 -9.4 245 26 13 7.7 4.2
21000 -21.2 -6.2 245 26 14 8.6 4.7 | -20.6 -5.1 245 25 13 8.5 4.7
20000 -18.7 -1.7 240 24 13 8.5 4.7 | -18.1 -0.6 240 24 12 8.5 4.7
19500 -17.4 0.7 240 23 12 8.5 4.7 | -16.9 1.6 235 24 12 8.5 4.7
19000 -16.2 2.8 235 22 12 8.5 4.7 | -15.6 3.9 235 24 12 8.5 4.7
18500 -14.9 5.2 235 22 11 8.5 4.7 | -14.4 6.1 235 23 12 8.5 4.7
18000 -13.7 7.3 230 22 11 8.5 4.7 | -13.1 8.4 230 23 12 8.5 4.7
17500 -12.4 9.7 225 22 11 8.6 4.7 | -11.8 10.8 230 23 12 8.7 4.8
17000 -11.1 12.0 220 22 11 8.8 4.8 | -10.5 13.1 230 22 12 9.0 5.0
16500 -9.8 14.4 220 22 11 8.7 4.8 | -9.2 15.4 230 22 11 9.0 4.9
16000 -8.4 16.9 215 22 11 9.9 5.4 | -7.1 19.2 230 22 11 9.4 5.1
15500 -6.9 19.6 215 22 11 9.8 5.4 | -5.7 21.7 225 22 11 9.6 5.3
15000 -4.6 23.7 215 22 11 11.5 6.3 | -4.0 24.8 225 21 11 12.6 6.9
14500 -3.0 26.6 215 22 11 7.3 4.0 | -2.4 27.7 225 21 11 6.3 3.4
14000 -1.8 28.8 215 22 11 10.8 5.9 | -1.3 29.7 225 21 11 10.7 5.9
13500 -0.3 31.5 215 21 11 10.5 5.7 | 0.2 32.4 225 21 11 10.4 5.7
13000 1.1 34.0 210 21 11 9.0 5.0 | 1.6 34.9 225 21 11 8.8 4.8
12500 2.6 36.7 210 21 11 10.2 5.6 | 3.0 37.4 225 21 11 10.0 5.5
12000 4.0 39.2 210 21 11 9.4 5.1 | 4.4 39.9 225 20 10 9.2 5.1
11750 4.8 40.6 210 21 11 10.6 5.8 | 5.2 41.4 225 20 10 10.3 5.6
11500 5.6 42.1 210 21 11 10.3 5.7 | 5.9 42.6 225 20 10 10.0 5.5
11250 6.3 43.3 210 21 11 10.4 5.7 | 6.7 44.1 225 20 10 10.0 5.5
11000 7.1 44.8 210 21 11 9.8 5.4 | 7.4 45.3 225 20 10 10.5 5.7
10750 7.8 46.0 210 21 11 10.2 5.6 | 8.2 46.8 225 20 10 10.2 5.6
10500 8.6 47.5 210 21 11 10.8 5.9 | 9.0 48.2 225 20 10 9.7 5.3
10250 9.4 48.9 210 20 10 10.7 5.9 | 9.7 49.5 225 19 10 9.7 5.3
10000 10.2 50.4 210 20 10 10.9 6.0 | 10.4 50.7 225 19 10 10.7 5.9
9750 11.1 52.0 210 20 10 11.6 6.4 | 11.3 52.3 225 18 9 11.6 6.4
9500 11.9 53.4 210 19 10 10.2 5.6 | 12.1 53.8 225 18 9 9.6 5.3
9250 12.8 55.0 210 18 9 17.3 9.5 | 12.8 55.0 225 17 9 12.0 6.6
9000 15.8 60.4 210 15 8 78.4 43.0 | 14.5 58.1 225 12 6 41.6 22.8
8750 M M M M M M M | M M M M M M M
8500 M M M M M M M | M M M M M M M
8250 M M M M M M M | M M M M M M M
8000 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). 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 Villa Grove, Colorado at:
North Latitude: 38 deg 16 min 03 sec
West Longitude: 105 deg 53 min 37 sec
Elevation: 7986 feet (2434 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.
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