Meteorology question

[Asbo Zaprudder]

I would post this query in Science and Technology except it's mostly tumbleweed and low footfall in there nowadays.

In part one of a BBC 4 documentary "Wild Weather" shown yesterday evening, Richard "The Hamster" Hammond claimed that you can forecast oncoming weather trends with some degree of accuacy by standing with your back to the surface wind and observing the direction that higher-level clouds are moving as compared to lower-level ones:

• If same direction, likely no change
• If left to right, weather will likely take a turn for the worse
• If right to left, weather will likely improve

Reverse the second and third bullet-point directions for the southern hemisphere (explain that, flat earthers). Of course, if you can only see stratus-type cloud, the advice is pretty useless as the fronts are probably already passing over you.

Anyway, while his advice fits for an approaching low pressure (cyclonic) frontal system, where wind shear turns near-ground winds away from the Coriolis effect imposed tendency to follow the isobars and instead makes them tend to head towards the centre of the system (observable as an apparent clockwise turning of higher-level clouds' velocity vectors with respect to those of lower level clouds - anticlockwise in southern hemisphere), I don't see that it works as he describes after the fronts have passed over you and you're still in the low-pressure system (the velocity vectors tend to align again but don't reverse rotation).

His advice also probably works even less well for high pressure (anticyclonic) systems. These can occasionally be associated with persistent stratus or stratocumulus clouds (so-called "anticyclonic gloom") - in maritime Europe for moist, tropical air at least. The velocity vectors would rotate anticlockwise and back again to alignment (clockwise for southern hemisphere). However, I expect there are usually very few clouds to observe at different levels and often there are almost no visible clouds at all in anticyclonic systems.

Anyway, can anyone more versed in meteorological study comment on Hammond's suggested forecasting system?

The whole series is worth watching anyway as there's a lot more interesting stuff on show. The section I'm rattling on about starts at about t=10 minutes.

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[UncleRogi]

I think there's an algorithm describing just that, over at Cornell University. Didn't go looking
though.

EDIT: went and asked those folk here at Dartmouth, and they said talk to Cornell

 

[Asbo Zaprudder]

I expect anything coming out of Cornell will be a lot more sophisticated than Hammond's method. He's essentially only a journalist and perhaps he takes whatever information the BBC researchers feed him on trust.

 

[StarCruiser]

Not sure if that's actually reliable of itself but, there is that ol' sailors thing:

Red sky at night, sailors' delight.
Red sky at morning, sailors take warning

That is, of course, based on centuries of observation that storms (northern hemisphere again, I believe):
https://en.wikipedia.org/wiki/Red_sky_at_morning

 

[Gary7]

It's an extreme generalization. Not much different than someone with a bum knee who can predict the weather by pressure change. If you know what to look for in the sky, you can tell a lot simply by the type and extent of clouds. But ultimately all of that will have mediocre accuracy. The only thing that makes weather forecasting more accurate is more data. Thus, with a sufficient dispersal of sensors and data collection system, you can get pretty accurate for small regions. Airport weather forecasting is more critical and accurate than regional forecasts. When you extend to a region, it's more difficult because you're applying a generalized description of the weather over a larger area. That difficulty will vary a lot based on the locale. Some places are inherently more unstable with weather than others... like comparing NYC to Los Angeles.