Saturday, September 23, 2023

Recent and forecast weather trends as autumn officially begins

A pretty wild and stormy summer has transitioned to much drier conditions of late, with temperatures generally near to slightly below average over the past month or so. Comparing the departure from normal precipitation for the past 90 days (in the first image below) to the past 30 days (second image) really shows how the northern metro received plentiful precipitation earlier this summer, but more recently, most of the area has dried up. 

Precipitation departure from average for the past 90 days shows the effect of summertime storms across west TN and northeast AR from late June through July. Most of those missed the Mississippi Delta, setting the stage for drought later in the summer. (NWS/WPC)

Precipitation departure from average for the past month is evidence of much drier conditions for the Mid-South once the summer storm track moved north. The only areas with above average precipitation are in far northwest MS and Crittenden Co, due mainly to storms earlier this week. (NWS/WPC)

We also see drought conditions expanding in north Mississippi in the past 30 days, since that area started the summer with much less rainfall than west TN.

Drought Index for the Mid-South as of this week. The Mississippi Delta is running well below normal for precipitation this summer. (U.S. Drought Monitor)

As summer officially turns to fall today (at 1:50am this morning), we're starting pumpkin spice season off with above average temperatures. Afternoon temperatures will flirt with the 90 degree mark, which is not completely unusual since our typical last 90 degree day is September 19. (And recall clast year, when mid-September featured multiple 100 degree days!) But it doesn't FEEL much like fall out there! Thank goodness for humidity levels that are early-autumn-like.

A frontal system will approach the area on Sunday, bringing more clouds which will temper the warmth. It will also introduce scattered shower and thunderstorm chances, especially Sunday afternoon and night into Monday morning. However, the HRRR model (below) is more bullish on storms in Arkansas than areas east of the Mississippi River, thanks to high pressure to our east causing precipitation to fall apart as it approaches.

Once we get past Monday, another dry spell sets up for the rest of the week it appears, with temperatures just slightly above normal. It'll be a rinse-and-repeat pattern with partly cloudy to mostly sunny skies, high temperatures in the mid 80s and morning lows in the mid 60s. Normal highs this time of year run about 82-84 degrees. 

If you are waiting for visible signs of fall (not Starbucks advertising signs for PSL's!), fall colors are still about a month off in the Mid-South. Any leaves changing color at this point are more likely due to trauma from lack of precipitation than true fall color setting in! 

Erik Proseus
MWN Meteorologist

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

Friday, September 8, 2023

August 2023 Climate Report for Memphis, TN

August Climate Recap

The month of August generally saw temperatures waver every few days from slightly above to slightly below normal. The exception was a string of hot days in the third week of the month, which resulted in four days hitting the century mark and nearly a week of average temperatures 5-10 degrees above normal. Multiple warm temperature records were also set during that late summer heat wave and a string of four consecutive days with temperatures no lower than 80 degrees (August 22-26) tied for fifth longest on record and is the latest (in the year) occurrence of a streak of three or more such days on record. The periodically cooler weather tempered the overall average for the month, which ended slightly above normal. An interesting note though was that that average was driven almost entirely by the overnight lows, which were more than a degree above normal. Average high temperatures for the month were right at average for August. For the period of meteorological summer (June-August), the average temperature for the three-month period of 81.4 degrees ended in the top 25% of all years (period of record: 149 years).

A wet summer to date continued for portions of the Memphis area as multiple rounds of heavy rain tracked across the northern metro during the month, resulting in over eight inches of precipitation in Bartlett. However, southern Shelby County and north MS missed out on much of this, with the airport recording just under three inches of rain for the month (much of that falling during storms on the 9th and 10th). The dry weather in the MS Delta region during both July and August resulted in drought conditions setting in mid-month in those agricultural areas. For the period of meteorological summer (June-August), total precipitation of 16.84" ended in the top 10% of all years (period of record: 152 years).

Departure from average rainfall for the Mid-South in August 2023. The precipitation disparity between northern and southern areas of the metro was stark, as evidenced by 8"+ of rainfall in Bartlett and less than 3" at Memphis Int'l in south Memphis. By the middle of the month, drought conditions had developed in the Mississippi Delta. (NOAA)

An active summer severe weather pattern continued into early August with severe thunderstorms resulting in wind damage on afternoon of the 5th, followed by another round of midday storms on the 9th that brought large hail, damaging wind, and areas of flash flooding in Shelby County. A few strong storms also occurred mainly in Crittenden County on the evening of the 26th as the heat wave was broken by a cold front. 

Memphis International Airport, Memphis, TN

Average temperature: 82.6 degrees (0.5 degrees above average) 
Average high temperature: 91.4 degrees (0.1 degrees below average) 
Average low temperature: 73.8 degrees (1.2 degrees above average) 
Warmest temperature: 102 degrees (25th, 26th) 
Coolest temperature: 63 degrees (31st) 
Heating Degrees Days: 0
Cooling Degree Days: 553 (25 above  average) 
Records set or tiedAugust 22, (80°, tied record warm low), August 23, (81°, set record warm low), August 24 (100°, tied record high), August 25 (102°, set record high; 80°, set record warm low), August 26 (80°, set record warm low). 
Comments: 18 days reached 90°, which is 2.2 days below average for the month of August

Monthly total: 2.82" (0.55" below average) 
Days with measurable precipitation: 8 (0.4 days above average) 
Wettest 24-hour period: 2.17" (9th-10th) 
Snowfall: None
Records set or tied: N/A
Comments: More than three-fourths of the total rain for the month fell in a 24-hour period over the 9th-10th. 

Peak wind: North-northwest/51 mph (9th) 
Average wind: 6.8 mph 
Average relative humidity: 69%
Average sky cover: 42%

 Click here for a daily statistical recap for Memphis International Airport. Headquarters, Bartlett, TN

Average temperature: 79.6 degrees 
Average high temperature: 90.5 degrees 
Average low temperature: 70.8 degrees 
Warmest temperature: 99.8 degrees (5th) 
Coolest temperature: 58.8 degrees (31st) 
Comments: None 

Monthly total: 8.20" (automated rain gauge), 8.09" (CoCoRaHS rain gauge) 
Days with measurable precipitation: 8
Wettest date: 3.33" (9th) (via automated gauge) 
Snowfall: None
Comments: Bartlett received over five inches more rain than fell at the airport, or almost 300% of the airport total. In fact, more rain fell on August 9 in Bartlett than the airport received for the entire month. The July-August total for Bartlett was well over 16 inches.

Peak wind: Southwest/28 mph (5th)
Average relative humidity: 79% 
Average barometric pressure: 29.95 in. Hg
Comments: None

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

MWN Forecast Accuracy

MWN average temperature error: 1.99 degrees 
MWN forecast temperatures within 2 degrees of actual: 76% 
MWN average dewpoint error: 1.70 degrees 
MWN forecast dewpoints within 2 degrees of actual: 72% 

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

Follow MWN on Facebook and Twitter for routine updates and the latest info!
Complete MWN Forecast: on the mobile web or via the MWN mobile app
Download our iPhone or Android apps, featuring StormWatch+ severe weather alerts!
MWN is a NOAA Weather Ready Nation Ambassador Meteorologist Erik Proseus is an NWA Digital Seal Holder