What Makes Rain Speed Up And Slow Down At Times?

Question

Why Can It Start Pouring Then Immediatly Slow Down Then Speed Up Again?

Star Please.

Answer 1

wind speed is my guess

Answer 2

Storms (especially convective storms like thunderstorms and cold fronts) are made from small cells, that feed into updrafts and downdrafts.  I think the time scale of the variations that you're seeing is on the order of the diameter of one of those cells divided by how fast the storm is moving.  Individual storm cells may move at 50 miles per hour or more (especially in the spring months) so you can get pretty fast variations in rain intensity.

On the other hand, if you're underneath a slow moving warm front, the rain's going to be pretty steady, without much variation in intensity.

Answer 3

The actual rain drops fall at the same velocity but the number of drops per second can increase or decrease depending on what is causing the rain.  The only thing that would affect a rain drop speed is wind.  For instance, a downdraft from a thunderstorm.  But that is usually a short burst.  

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Answer 4

Several factors may be at work but the most likely reasons would be the strength of the thunderstorm's updrafts and the amount of moisture in the air.

Since you stated that the rain goes from torrential to light then back to torrential again, I would suspect that very strong updrafts in the thunderstorm are the cause.  Thunderstorm updrafts are often strong enough to suspend raindrops in them, and even lift them up so high that they freeze and finally fall as hail stones.

As with any wind, it is not steady, so when the updraft subsides, the rain falls freely, then slows down again with the next strong updraft.  This phenomenon would be more likely in a developing storm rather than a mature or dying storm, where the heaviest rains usually occur.