Thursday, 14 May 2015

And now, the time is nigh...


It's mid-May and that tends to mean but one thing in our household - chase season is here. Helen and I will once again be heading off to the USA to pursue thunderstorms, as well as enjoying the hospitality of the Great Plains, and the food!

The season has been rather interesting to date - longer range climate models and analogues were suggested of a wet spring across the Plains, especially the southern Plains, as an emerging El Nino contributes to an active sub-tropical jetstream.

The lower latitude of this jet means that southern areas have seen the majority of what severe weather there has been thus far, but a combination of deep moisture and upper airflow patterns which are not always conducive to capping inversions has meant numerous thunderstorms on many days, perhaps limiting the overall severity (and chasibility) of the storms, but providing much needed rain across the region. Indeed, some areas have had flooding issues to deal with, and further rainfall is likely in the coming days.

Looking ahead to this weekend, another powerful Pacific upper storm system will move towards the Plains - abundant low-level moisture along with strong dynamics will yield further thunderstorms, some severe, and heavy rainfall. This trough looks like exiting early next week but a small short-wave trough may pass through around Tuesday/Wednesday. There are suggestions that shortwave ridging may develop mid-week - longer term model solutions indicate yet another upper low moving into the SW'ern USA late week or into the weekend - whilst this is a long way off, it seems that there may be several opportunities for thunderstorms through next week, especially across the western Plains.

As always, thunderstorms are the quarry but the overall experience of living like a nomad for a couple of weeks, never quite knowing where we'll be in a couple of days' time, is what makes it really special.

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