gordon.dewis.ca - Random musings from Gordon


An active afternoon

May 29, 2012 @ 16:36 By: gordon Category: Weather

The thunderstorms arrived a bit ahead of schedule, but not excessively so:

SPECI CYOW 291837Z 24010G20KT 10SM TS BKN061CB 31/18 A2953 RMK CB7 CB SSW-N + E-SSE SLP000 DENSITY ALT 2700FT=

Basically, the TAF from this morning forecast their arrival as early as 3pm, but they arrived at 2:37pm — 23 minutes early. The SPECI observation reported the wind from the SW at 10 gusting 20 knots, 10 miles visibility, moderate thunderstorms, ceiling at 6100′ consisting of cumulonimbus clouds (CB). The remarks basically that that there were CBs pretty much surrounding the airport except to the south and northeast. The density altitude of 2700′ is pretty impressive given that the airport is at 374′ ASL, so the air pressure was very low — as evidenced by the altimeter setting of 29.53″ Hg (compared to the standard of 29.92″ Hg). Not too surprising given the temperature was 31C at the time.

I thought I’d take a look at the TAF to see if they had issued a new one from the one in my previous post and sure enough it was amended this afternoon:

TAF AMD CYOW 291842Z 2918/3018 24012G22KT P6SM BKN040
TEMPO 2918/3001 VRB20G35KT 1SM +TSRA BR BKN006 OVC030CB
FM300100 23008KT P6SM BKN140
BECMG 3002/3003 27008KT
FM300500 28005KT P6SM SKC
FM301500 29012KT P6SM FEW060

Previously, the thunderstorms were a 40% probability, but I guess when they actually happen it’s time to change that to TEMPO (occurences of less than an hour). 🙂

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