Monday, September 4, 2017

Our first autumn cold front nears, plus a look at Irma's potential track

Have you grown tired of the off and on summertime heat across the Mid-South? Are you ready for the fall-like weather to return to the Memphis area for September? If so, then we have some great news. Mother Nature is listening to your complaints. Fall will be back for the area this week.

The Trough of Change

As many head out to celebrate the Labor Day holiday, the weather is setting up for a big change in the next 48 hours. An upper level trough digging in from the Rocky Mountains will bring in rain and cooler air, beginning with a chance of a few showers on Monday afternoon. Those showers become more numerous heading into Tuesday, as the cold front associated with this trough pushes closer to Memphis. Highs on Labor Day will hit the upper 80s, with lows on Monday night dropping to the low 70s.

The trough moving in from the Rocky Mountains will help shove the cold front south into the Memphis area, bringing rain and cooler temperatures with it. (NOAA/NWS)
Tuesday marks the beginning of the cooler temperatures, with plenty of clouds and rain and a few thunderstorms likely. Definitely have your rain jacket and umbrella ready when heading to work or back to school, with highs only reaching the upper 70s. This comes as the cold front bringing all the rain pushes through the region early on Tuesday. Showers will begin to decrease Tuesday evening as the front digs deeper into Mississippi, with lows Wednesday morning in the upper 50s (yes, you read that right).

Throwing It Back to the 70s

It may feel like it's been a while since we've talked about highs only hitting the 70s in the Mid-South, but September feels like the right time for some summertime relief! Once the cold front pushes out of our area on Tuesday night and the upper level trough moves over the area, conditions will clear out with cooler temperatures too. Wednesday begins the new cool trend, with mostly sunny skies and highs only reaching the mid 70s. Lows will drop down to the mid 50s.

Friday's high temperatures will be in the mid 70s across the Mid-South, closer to our lows this past week than our recent highs.
The cooler trend continues into the late week, as Thursday and Friday continue with sunny skies and highs in the mid 70s. Lows once again drop into the 50s, something we haven't seen in several months! Temperatures will begin to warm a bit by the weekend as the upper trough lifts out, however highs will still be comfortable on Saturday (in the upper 70s) and Sunday (near 80). Sunny skies will continue too.

Could fall finally be here? Or will summer crank back up one last time in September? Keep checking our MWN human-powered forecast for the latest weather around the Memphis area, which you can also find on our MWN Weather App. Be sure to also follow us on Facebook and Twitter for all the great weather updates and fun facts.

Alex Herbst, Meteorologist
MWN Social Media Intern

Checking in on Irma

After one major U.S. landfall with Harvey ended the 12-year drought of U.S. major landfalls, it is becoming increasingly possible that we could have two of these in a month. Hurricane Irma is a category 3 major storm as it approaches the Caribbean Islands. Over the course of the next few days, it will take on a west-northwest track, likely moving it just north of the main island chain in the Caribbean, including Puerto Rico and Hispaniola. All of the islands in that chain could see tropical storm to hurricane conditions as Irma actually strengthens more.

The latest official track for Hurricane Irma. The MWN Tropical Page has the latest details.

The end of the week into the weekend is the tricky part of the forecast, though we’re getting within range of making some predictions that could be considered educated and distinctly possible, rather than just guesses or “hype-casts.” Irma is expected to remain a major (category 3+) hurricane until it makes landfall. Where that landfall happens is still TBD.

At the risk of getting “weather nerdy” on you, there is a major trough (that Alex talked about above) that will move into the northeast U.S. and have a direct influence on the track of Irma. At some point, Irma is likely to make a right (northward) turn towards that trough. Earlier it appeared that that might occur before it reached the Florida peninsula, pulling Irma north along the east coast. It now appears that the trough could lift north before Irma is able to start turning towards it, resulting in a later turn and a northward motion that could take it directly into south Florida. If it turns even later, it could go up the west side of Florida in the Gulf.

Multiple computer models provide a fairly consistent track for Irma until it nears Florida. However.... (see below)

...the American GFS computer model's ensemble system (basically, the model being run multiple times with different initial and forecast parameters) shows the true picture. There are potentially many options yet for Irma including landfalls from the Carolinas to the Florida panhandle. The European model (not shown) still also shows the potential for a narrow miss of the east coast with an earlier turn north. (WxBell)

We don’t know yet when that will happen, but NOAA and the NWS are starting a massive atmospheric data gathering surge to try and sample the upper levels as best as possible to help the forecasters, and computer models, more accurately predict Irma’s motion. If you have friends or family in Florida or along the southeast U.S. coast up to the Carolinas, they need to start preparing now for the possibility of a strong storm this weekend as forecasters work to more accurately predict the eventual track.

You’ll find much more information on the tropics on the MWN Tropical Page.

Erik Proseus, Meteorologist

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