Diadem wrote: ↑Fri Jan 12, 2018 9:03 pm
There was vertical low-level wind shear concentrated exactly at the centre of the runway, that had no effect on the wind detection equipment at the airport ...
Just saying that if concentrated "at the center" (unobstructed infield) no detection necessarily at 10 Meters elev down in the retreating cooler air ... esp slower moving among buildings/trees outside the airport perimeter where the station is. A reading at CWMM (among the factory buildings) might not properly produce an extra "V"eering reading even if existed (45deg clockwise shift in less than 15min ). The "V" value (example 110V180) is indicative of potential Vertical llws on/above a runway, but not available where the station is not able to read exactly or not set up to do so.
Warm air advection at CYXX (18nm SE/ upwind) ... the TCUs before / after, on both 2-pm & 3pm Metar Nov 23/2017 (a source of Vertical LLWS). Private surface wx station records southwest of the runway also briefly show drier/warmer(14-15C) Southerly 10kts ahead-of "2:45PM" (IBCSURRE6 at 98Meters elev, IBRITISH438 96Meters, IBCSURRE21 82Meters, IDelta3 91Meters, IBRITISH292 79Meters).
EDIT (Monday Jan 15):
CYVR has Towering Cumulus 1pm/2pm and CYXX 2pm/3pm ... where CWMM is between (and that indicates the line seems to move East right past the incident area). The stations show daytime heating just before. Would a disruption be expected beneath/around this warming air that is advecting into more-isolated Towering Cumulus if passing by YPK's wide open area ? .. if the drier air there produces less cloud ? I hope this suffices as " a sketch" GyvAir.
A burst of tailquartering warmer air mid takeoff would increase DA while decaying airpseed, which might also destabilize at high GS and highspeed rollout when choosing to abort.
When in an accident it's wiser not to speak out about it too quick, alone for the reason you yourself are unaware of ALL the factors involved. PDW
( edited out as much "jiberrish" as I could)