I recently sat CPL Met Exam and got a question and KDR in regards to a Microburst (Thunderstorms & Microbursts Part 61 MOS Unit 1.8.3 CMTC, 2.8.1viii)

I cannot remember the exact wording of the question however it was specifically asking what kind of air you could expect within a microburst and was a two part question i.e cold moist, warm dry (which was the answer I chose if I can remember correctly). Could anyone please shed some light on how to approach this question and what CASA could potentially be asking?

Another KDR I received was in regards to Wind variations. It was asking what happens to the surface wind speed and direction if a pressure system (high or low) were to remain stationary over an inland area for an extended period of time. The answers were in terms of backing and veering, and increasing or decreasing speed. To my knowledge the wind speed veers 30 degrees over land and decreases speed by 2/3's. I chose that it decreases speed and veered however got it incorrect. Does a stationary pressure system over an extended period of time affect the wind speed and direction in a different manner?

If anyone has any idea on how to approach these questions/topics that would be greatly appreciated,

Cheers,
Jeremy

The air in a microburst is colder that the environment air, that is why it is descending. The answer to pick would have been cold/moist.

The question on the high pressure system would probably have been asking for diurnal variation of surface wind. Since diurnal means throughout the day, the surface wind would have veered during the night as surface friction would have slowed it down giving the pressure gradient more time to act on it and push it out of the system. By early morning, the surface wind will be almost stationary and so will have veered by the greatest amount. As temperature increases after sunrise, convection mixes the surface wind with the faster wind above so the average speed of the surface wind increases. That means that is is 'less veered' during the day-especially by mid afternoon. Since in is 'most veered' a dawn and 'less veered' during the day, the surface wind in the afternoon would have backed with respect to the surface wind in the early morning and its speed would have increased with respect to the surface wind in the early morning.

Hi Bob,

Thanks for the fast response explanation. Just in regards to the microburst question, it was a two part answer. For example cold moist, warm dry. So i was unable to only choose cold moist.

My logic for choosing cold moist, warm dry was that the air descending down is initially cold and moist but as it is accelerated toward the ground it loses its moisture and heats up, becoming warm and dry. However i got this question incorrect.

Is there potentially different scenarios where the air around/within a microburst may change?

Cheers,
Jeremy

Without seeing the actual wording of the question I must admit I'm at a loss to understand how you can describe a region of air to be cold and moist and warm and dry at the same time. So I can't give much advice on that one. It leaves me baffled.

No worries, ive got to resit the exam on the 31st of August so if i get the question ill be sure to send it through!