#Reigate Post-Jonas storm brings mild side to UK

January 25, 2016 — Leave a comment

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Jonas to UK this week

The phenomenal winter storm Jonas brought NE USA to a standstill over the weekend as more than 20 inches of snow fell on Washington and New York.   Jonas was a truly massive storm and broke regional snowfall records with up to a metre of snow in places, and brought a record storm surge of 9.27 feet on the Delaware coast with significant coastal flooding (beating Super Storm Sandy surge in places*). Weather Underground reported…

This nor’easter, dubbed Winter Storm Jonas, was one for the ages–among the most powerful and far-reaching in regional history.  Jeff Masters Weather Underground

Jonas threw blizzards, storm surge, heavy snow, icy rain and thundersnow at the US over the weekend.  Here is a brief outline of the storm and a look at where it is headed next.  It is worth noting that potentially another Nor-Easter snow storm is possible for this part of the USA later this week, although less likely to be as powerful.

New York had it’s heaviest daily snowfall total on record on Saturday courtesy of Jonas. Forecasters started warnings several days out and the National Weather Service made people aware of the seriousness of this storm in the lead up.

Jonas was a classic and historic “Nor-Easter” storm albeit with the potential added spark of warmer than usual Gulf Stream temperatures.  The system was well forecasted by the NWP models from several days out.  An insignificant low pressure disturbance entered the NW Pacific coast of the North America earlier last week, traversed the continent and emerged out of the SE dragging cold continental air to interact with warm Gulf moisture.

This explosive mix was exacerbated because both the Gulf of Mexico and Gulf Stream sea surface temperatures were anomalously high adding to the moisture and energy available for this storm.

“Take unusually warm Atlantic ocean surface temperatures (temperatures are in the 70s off the coast of Virginia), add a cold Arctic outbreak (something we’ll continue to get even as global warming proceeds), mix them together and you get huge amounts of energy and moisture, and monster snowfalls, like we’re about to see here” Michael Mann, climate researcher who directs Penn State University’s earth systems science center.

The storm got hooked up by a strong jetstream and traveled rapidly north over Friday 22 Jan, hugging the east coast and intensifying as pressure fell into Saturday 23 Jan and leaving the coast by Sunday 24 Jan.

The chart below shows the jet during the lead up to the storm on Tuesday 19 Jan.  Spot the LOW mid-west, this was Jonas in the making.

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jetstream emerging out of Gulf of Mexico… perfect Nor-Easter set up, spot LOW Jonas over MidWest

Another important element making this one of the top two most intense Nor-Easter winter storms on record was HIGH pressure lodged over NE Canada which intensified the pressure gradient and increasing those north-easterly wind speeds.  These strong winds drove ice and snow across a vast swathe of the NE and dumped 2 feet of snow as far north as New York city.

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In addition to large snowfalls the low pressure and strong on-shore winds also created a storm surge risk on high tides.  The coastal impact was recorded by a series of video cameras placed along the New Jersey coast by Hurricane Track’s Mark Sudduth.

Jonas is now forecast to track across the Atlantic, riding the jetstream and deepening on approach to the UK by Tuesday.

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Jonas GEFS tracks set to cross near NW Scotland

Through Tuesday and Wednesday Jonas will bring some stormy and wet but mild conditions especially to the NW of the UK.  Nevertheless potentially 70mph gusts are forecast for parts NW Britain.  Gusty conditions on associated fronts are likely at times here in the SE as well, but nothing like the intensity or disruption of the US version.

Further ahead, at least this week, the NAO and AO are both trending positive and this is set to bring further unsettled conditions across the Atlantic separated by drier periods of higher pressure, but mostly staying a good deal milder than average.

The pressure over the Poles has weakened and the Icelandic low has deepend, both indicating a lack of sustained cold potential in the near future for the UK.  Nevertheless, action in the stratosphere is hotting up with a forecast sudden stratospheric warming afoot.  Sudden warming events in the stratosphere can build pressure over the Poles and increase the chance of sustained cold weather, sometimes, over Europe.  This occurs several weeks after an SSW and the forecast SSW, if it occurs, is still at the end of model runs so… any chance of sustained cold risk can most likely be reserved for several weeks ahead as things stand. The temperature and pressure anomaly scene in the Post – Jonas world looks like this: a warm NW Europe, warm Pole and cold NE USA.

 

Winter storm Jonas References

http://www.wunderground.com/blog/JeffMasters/colossal-noreaster-dumps-record-snow-from-maryland-to-new-york

http://www.realclimate.org/index.php?p=19070

http://mashable.com/2016/01/22/causes-of-east-coast-blizzard-global-warming/#ZQIP9mQOOmqb

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