Module f14

Step 5. Data Available before Landing

Soundings

Aside:
To better synchronize weather observations around the world, meteorologists use Coordinated Universal Time (UTC). This corresponds to the time in Greenwich, England. The letter designation for this time zone is "Z", which pilots and controllers call "zulu" using the phonetic alphabet.

In the eastern time zone (where this aircraft is being flown) , 0000 UTC corresponds to a local time 8 PM.

The 00 UTC sounding below was observed roughly 4 hours your arrival time, at Buffalo, New York. This was the sounding station that was closest to Toronto. You did not have access to this info while approaching Toronto airport. However, the Environment Canada forecasters had access to similar sounding forecasts, which they had used to create their Graphic Area Forecasts (GAFs) and Terminal Area Forecasts (TAFs) that was available before you arrived at Toronto.

sounding at Buffalo, NY

CAPE = 2057 J/kg.
K index = 34.5 .

Interpretation hints:

The atmosphere is unstable, which means that it will develop strong up- and down-drafts in "deep convection".
"Deep convection" means that tall cumuliform clouds could form (cumulus congestus and thunderstorms).
If thunderstorms form, their cloud base would be at about 1000 m altitude.
K index suggests that ordinary thunderstorms are possible, with a chance they could be supercells.
CAPE value is large, suggesting that supercells could be violent, and perhaps have tornadoes.
If thunderstorms form, their tops will be at the tropopause, roughly 12.5 km altitude on this day.

X-info. Extra info for experts. (Not needed to pass the course.)
The sounding data above plotted on a skew-T diagram, along with all the stability indices.

Soundings courtesy of the University of Wyoming. http://weather.uwyo.edu/upperair/sounding.html

UBC ATSC 113 Weather for Sailing, Flying & Snow Sports

Last modification: May 2017