Hello!
Well, we're well into mid-May now and that can mean but one things - storm chasing!
Fairly soon we'll be heading out to the USA so what does the crystal ball say? This season has been mediocre as far as storm chasing chances have been concerned - yes, there have been a few gems but they've often been hard-won by the chasers. Now, a synoptically-evident outbreak of severe storms may give us the best chance of seeing a tornado, but it also attracts a large number of other chasers out. Less obvious set-ups, especially across the western High Plains can yield some great chase action, with not so many people around.
Of course, this kind of talk is something we all like to say when it looks pretty quiet, but truly it is great to be on the vast western prairie with a lone storm and not many people about - last year, on May 27th, we got just that and saw an amazing supercell. Granted, no tornado, but tornadoes are hard to come by anyway, so one should never go out expecting to see one.
Anyway, back to this year. The pattern has been dominated by 'blocking' the atmosphere - that is, large, slow-moving areas of high pressure with the jet stream splitting around them - rather than a more mobile pattern where trough push into the western USA, encourage moisture-laden air to surge northwards from the Gulf of Mexico, and help outbreaks of severe storms to form. Much more modest mid-level flow has been present, but, at times, steep lapse have overspread reasonable moisture and given some good supercells, and one or two tornadoes.
Chasers over the next couple of days will have a trough in the sub-tropical jet moving into the Plains, so some severe storms, and perhaps a few tornadoes, will be possible - but they will have to work for them.
Early next week, modest ridging will move over the western Plains before a weak upper trough moves NE through the Great Basin, potentially bringing enough mid-level flow to the High Plains to induce lee troughing, thunderstorms development, and perhaps isolated supercells. So there should be storms to chase through part of next week at least.
Later in the week and into the following weekend it becomes much more difficult to find a consistent signal in the models - they don't do well with blocky patterns. It looks like a trough will approach the Pacific Northwest but if recent weeks are anything to go by, it will split from the jet and throw some kind of ridge across central parts of the US, but the southern branch of the jet could well still affect the central/southern Plains. A few runs of ensembles have tried to make it more into a deeper trough out west, but we'll see! Another possibility is that a deeper trough runs ESE across Canada, inducing more of a NW flow into the Plains, with a ridge out west.
Whatever happens we'll enjoy the nomadic lifestyle, the food, and simply being out in the vastness of the Plains!
