Sunday, September 17, 2017

Summer's last gasp... how long does it last?

I think we all got used to below normal temperatures from late July through August and into early September! In fact, according to our climate summary, August was the coolest in 13 years! However, summer decided to make one last stand once the remnants of Irma moved out earlier this week.

While temperatures the past few days are not that much above mid-September averages, the humidity factor has caught some folks off guard with the Muggy Meter registering dewpoint values not far off mid-summer norms.

While heat indices in the mid 90s wouldn't be considered awful in the dog days of summer, by mid-September, I think we're all pretty much over it...

Looking ahead, this warm pattern continues throughout the upcoming week, with only slight abatement in the high temperatures as we head towards next weekend. Rain chances increase a bit by mid-week due to a weakness in the upper level high pressure that is currently controlling our area, but no cold fronts are expected that would bring lasting relief from the heat.

Overall, it appears we may be stuck in a warmer than normal overall pattern (though not necessarily as warm as the next several days) right through the end of the month. The long-range upper level pattern favored by climate models indicate a return to cooler than average weather by around the first of October.

As the sticky-ness lingers and temperatures remain very warm, know that the end is in sight as autumn officially begins this Friday at 3:02pm! Pleasant fall days are not too far away, especially since we've gotten a sneak preview recently!

Erik Proseus
MWN Meteorologist

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August 2017 Climate Data for Memphis, TN

August Climate Recap

July temperatures were slightly above normal, but August returned to cooler than average weather for the third out of the previous four months. By the end of the month, only six of the previous 35 days had recorded an average temperature above normal, resulting in the coolest August in 13 years! I didn't hear any Mid-Southerners complaining about below average temperatures during the dog days of summer.

After running below normal for most of 2017, precipitation spiked above normal thanks mostly to the remnants of former Major Hurricane Harvey moving over the Mid-South on the 31st. Precipitation officially totaled 4.04" that day, which was the second wettest August day on record and also well over an inch more than Memphis typically averages for the entire month. Combined with previous heavy rain events that included three other days with more than an inch of rain, the month ended with over 9" of rain, the fourth wettest August on record. The remnants of Harvey resulted in areas of flash flooding, as well as many strong wind reports (including a severe wind gust of 60 mph at Memphis International Airport) and over 40,000 MLGW customers without power. Tornado Warnings were also issued mainly across the eastern metro as brief rotating cells resulted from Harvey. Tornadoes actually touched down well east of the metro (see map below). Additional scattered severe storms occurred on the 11th with a few reports of strong wind.

Severe weather reports across the region on August 31, associated with the remnants of Harvey. Thunderstorms in outer bands of the system resulted in tornadoes in northeast MS, northwest AL, and middle TN. Flash flooding reports were common closer to Memphis, as well as a handful of severe wind reports. (Graphic courtesy: Iowa State University).

Memphis International Airport, Memphis, TN

Average temperature: 79.4 degrees (2.6 degrees below average)
Average high temperature: 87.5 degrees (3.8 degrees below average)
Average low temperature: 71.3 degrees (1.4 degrees below average)
Warmest temperature: 95 degrees (20th, 21st)
Coolest temperature: 65 degrees (24th)
Heating Degrees Days: 0 (0 above average)
Cooling Degree Days: 455 (72 below average)
Records set or tied: None
Comments: Eight days recorded temperatures at or above 90 degrees, which is xxx less than an average July. Year to date, the average temperature of xx.x° remains the second warmest on record behind 2012.

Monthly total: 9.29" (6.41" above average)
Days with measurable precipitation: 13 (6.2 days above average)
Wettest 24-hour period: 4.04" (31st)
Snowfall: None
Records set or tied: Remnants of Major Hurricane Harvey resulted in a daily record rainfall total of 4.04" on August 31st. That day was also the second wettest August day on record.
Comments: Year to date, precipitation has totaled 36.66" or 104% of normal, the first time year-to-date precipitation has been above normal since early February.

Peak wind: North-northeast/60 mph (31st) (effects of Tropical Depression Harvey)
Average wind: 6.9 mph
Average relative humidity: 74%
Average sky cover: 60%

Click here for a daily statistical recap for Memphis International Airport.

Cirrus Weather Solutions /, Bartlett, TN

Average temperature: 77.1 degrees
Average high temperature: 87.7 degrees
Average low temperature: 68.4 degrees
Warmest temperature: 95.2 degrees (20th)
Coolest temperature: 58.2 degrees (24th)
Comments: None

Monthly total: 7.13" (automated rain gauge), 7.79" (manual CoCoRaHS rain gauge)
Days with measurable precipitation: 9
Wettest date: 4.19" (31st) (via automated gauge)
Snowfall: None
Comments: No measurable rain fell from the 18th-30th, a span of nearly two weeks.

Peak wind: North/30 mph (31st)
Average relative humidity: 83%
Average barometric pressure: 29.99 in. Hg
Comments: None

Click here for a daily statistical recap for Bartlett, TN.

MWN Forecast Accuracy

MWN average temperature error: 1.48 degrees
MWN forecast temperatures within 2 degrees of actual: 82%
MWN average dewpoint error: 2.04 degrees
MWN forecast dewpoints within 2 degrees of actual: 70%

MWN's forecasts extend out five periods (2.5 days, or roughly 60 hours). Historical accuracy statistics can be found here.

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MWN is a NOAA Weather Ready Nation Ambassador Meteorologist Erik Proseus is an NWA Digital Seal Holder

Sunday, September 10, 2017

More tropical remnants will pay a visit to the Mid-South

Following a frontal system that moved through Tuesday, the week has been phenomenal with well below average temperatures, sunny skies, and low humidity. Since July 27, we have had only 6 days with a daily average temperature above normal, so the summer has definitely ended in a cool way! I'm glad to have fall weather in the Mid-South - probably my favorite season!

Looking ahead to this week, it appears that the second consecutive major U.S. hurricane to make landfall, Harvey then Irma, will have remnants that affect the Mid-South. While Monday looks decent with still a good deal of sunshine and temperatures that peak in the upper 70s, the wind will be a more breezy at 10-20 mph with gusts as high as 30 mph.

As the remnants of Irma move into eastern Alabama on Monday night as a tropical storm, clouds and rain chances increase in the Mid-South, as does the wind. Rain becomes likely after midnight Monday night and continues Tuesday. The strongest wind will likely occur early Tuesday as we feel sustained north wind of up to 20 mph and gusts of 30 mph as Irma runs into high pressure to our north, increasing the pressure gradient and resulting in gusty wind. During the day, as the remnants move closer in tropical depression form, wind could actually lessen a bit as the storm itself weakens further and the center draws closer and the influence of the high to our north weakens a bit. As the ultimate track, and decay rate, of Irma becomes a little more clear Monday, the forecast may need adjusting a bit. It's possible that we could see a bit stronger wind, but overall I do not expect the rain rates or the wind produced by Harvey a couple weeks earlier. Tuesday's temperatures are likely to remain in the 60s, so it'll be a cool, wet, breezy day.

The latest forecast track from the National Hurricane Center for Irma.

Wednesday will see Irma's remnants dying out, but lingering showers in the area and less wind. It will also be another fairly cool day as temperatures likely only make it to about 70 degrees with cloud cover lingering. Rainfall totals in the Memphis area currently look to be in the 1.5-3" range (starting before sunrise Tuesday through the Wednesday showers).

Forecast rainfall amounts as of early Sunday afternoon from Irma's remnants. 2-3" of rain could fall between early Tuesday and Wednesday afternoon in the Mid-South.

Conditions improve heading towards the weekend as what's left of Irma's remnant low move east of the area, some sunshine returns and temperatures rebound back to 80+. Slight rain chances Thursday and Friday can't be ruled out. It appears that decent weather will occur for Friday night football, Cooper Young Fest, and Live at the Garden's closing concert, as well as Saturday's Memphis-UCLA football game - finally one not affected by a tropical cyclone!

We'll post the latest on Hurricane Irma and the effects on the southeast U.S. and Memphis area on our social media feeds. Also stay up to date with local conditions and forecast information via the MWN mobile app, available in your app store. All links are below.

Erik Proseus
MWN Meteorologist

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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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MWN is a NOAA Weather Ready Nation Ambassador Meteorologist Erik Proseus is an NWA Digital Seal Holder