Sunday, May 29, 2016

This week's weather & Atlantic hurricane season

MWN in May

It's been a crazy, busy month at so I apologize for few blog posts than normal, but I'm grateful for the opportunities that seem to all come together in May! The primary activity for MWN this month has been Memphis in May. A big thank you to CEO Mr. Jim Holt and the operations staff for seeing the wisdom in having a meteorologist on-site when tends of thousands of people are packed into multiple outdoor events during the rain and storm season in Memphis! This was the 2nd year we've partnered and it was again a pleasure to work with great folks who put on a heck of a series in Tom Lee Park each year! They work their tails off literally around-the-clock for the benefit of the visitors. Somehow, despite a very wet month, the weather turned out pretty decent nearly every time the gates opened at the park, if you ignored the mud!

In addition, the Memphis Redbirds are well into their 2016 season and MWN is proud to once again be their Official Weather Partner, providing weather updates to operations staff throughout the season. We also officially signed on as Official Weather Partner for Levitt Shell for this year's Orion Free Summer Concert Series and will serve in an advisory and consulting capacity. I'm also proud to recognize Levitt Shell as the first sponsor of the brand-new MWN StormView Radar that was launched this month! If you haven't checked it out yet, please do! There is even a video tutorial on how to use the new features. Thanks Levitt Shell! And be on the lookout for StormView Radar on the video boards at the Shell if inclement weather threatens a concert!

Now on to the weather

An early summer pattern has set in as light southerly flow wraps around high pressure in the southeastern U.S. This results in humid and unstable air over the region, susceptible to passing upper level disturbances producing widely scattered thunderstorms. For most, today will be dry, though there is a small threat of a few showers late this evening as one of these disturbances moves across AR, producing a cluster of thunderstorms that weakens as it nears the metro after dark.

For Memorial Day, weak high pressure builds closer to the region from the north and a weak cold front slides to our east. As wind shifts to light northerly, slightly drier (less humid) air works its way into the region by afternoon and thunderstorm chances diminish even further. Temperatures should climb near the 90° mark under partly cloudy skies, making for great pool weather.

Precipitable water values (PW) show the amount of total moisture in the air over a particular location. Lower PW values (drier air, in green) will work their way into the Mid-South by Monday afternoon, pushing more humid air (purples) west.

Tuesday will be much the same with slightly less humid air, weak flow at the surface, and similar temperatures and sky condition to Monday with a very small afternoon thunderstorm chance. As a cold front moving out of the Plains gets a bit closer to the region on Wednesday, southerly flow is re-established and the air becomes more unstable and humid again. A few more thunderstorms are possible Wednesday, especially in the afternoon and west of the metro, though chances remain only near 30%.

Total precipitation projected by the GFS (American medium-range) model between 7am-7pm on Wednesday. An approaching frontal system will cause increased rain chances mainly to our west, though a few showers or thunderstorms will be possible in the Mid-South by Wednesday afternoon.

By Thursday, the cold front moves into the Mid-South. Scattered thunderstorms are expected as the front interacts with an unstable airmass. With a bit more wind support at the upper levels, a few storms could become strong to severe with high wind at the surface and perhaps some hail the main threats, in addition to heavy rain. The front creeps south into Friday, so rain and thunderstorm chances remain in the region to end the week. The elevated rain chances will also serve to keep afternoon highs in check with low to mid 80s expected Thursday and Friday.

Total precipitation projected by the GFS (American medium-range) model between 7pm Wednesday and 7pm Friday. As the cold front slowly inches through the Mid-South, scattered to widespread showers and thunderstorms will be possible Thursday and Friday. Rainfall totals will likely be higher over western sections of the region.

The cold front stalls not far to our south next weekend it appears, so rain chances diminish but could still be possible, especially across north MS. Cooler air also filters into the region with highs next weekend in the lower 80s at best. It appears the below average temperatures (normal is 86-87° in early June) could continue into early the following week with a drier pattern setting up as well.

Surface temperatures at 7pm Saturday as projected by the GFS model. Note the cooler air (60s and 70s) over the eastern U.S. At this time, we are expecting highs near 80 on Saturday with mid-evening temperatures, as shown here, in the mid 70s.

A word on the tropics

Atlantic hurricane season officially starts on Wednesday, but Mother Nature again showed how the calendar means little. By the time June 1 rolls around, the next named storm will start with the letter "C" thanks to a surprise appearance by a very rare January hurricane in the eastern Atlantic (Alex) and an early bloomer in disorganized Bonnie, which made landfall today on the SC coast as a tropical depression (but received the name Bonnie on Friday as it reached tropical storm strength).

Late Sunday morning update on Tropical Depression Bonnie, after landfall on the central SC coast earlier in the day. Bonnie will slowly re-curve up the Carolina coastline for the next few days with heavy rain being the primary threat.

Officially, NOAA and the NWS predict a season "near normal" in the Atlantic Basin after a quieter than average last 3 years. The official prediction is shown below, which has a 70% likelihood of occuring. El Nino is dissipating and La Nina is becoming more likely during the peak of hurricane season, which tends to favor elevated Atlantic activity, though it is unknown how strong La Nina will get during hurricane season.

With an unprecedented 10 years (3,870 days to be exact) having gone by since the last major hurricane to make landfall in the U.S. (Wilma in late 2005), the NWS is preaching "It Only Takes One" to drive home the point that no matter how many storms are named, one landfall can cause a significant impact.

A lot has changed on the U.S. coastlines since 2005, including burgeoning populations and a new generation of residents and retirees that have never experienced a hurricane. Think about it - when Wilma made landfall in southwest Florida in October 2005, the iPhone and Twitter had not been invented and Facebook was less than 2 years old!

There is some concern this year that, due to warmer than average sea surface temperatures near coastal areas, any system that has favorable atmospheric conditions could strengthen as it approaches landfall, and indeed may form closer to land, providing for less lead time as residents and businesses in harm's way prepare. It will be an interesting season to watch play out.

Erik Proseus
MWN Meteorologist

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