Saturday, August 28, 2021

Hurricane Ida to pummel the LA coast, then head into the Mid-South: what to expect locally

All eyes are on the Gulf of Mexico, as this morning Hurricane Ida is poised to go through what meteorologists call "rapid intensification," and what those in the path must call terrifying. 

Saturday morning "sandwich" RGB satellite imagery of Hurricane Ida in the central Gulf (COD)

16 years to the day after Hurricane Katrina barreled into southeast Louisiana, Ida is poised to do the same with forecasts of 130 mph maximum sustained wind and 10-15 FEET of storm surge are expected along coastal southeast LA on Sunday evening. Local officials are urging all in the path in Louisiana to finalize preparations, and leave if necessary, today before wind and rain picks up Sunday morning. New Orleans, in the right front quadrant of the storm, is bracing for high impacts, including flooding rain, hurricane force wind, and a few feet of surge even in Lake Pontchartrain. Hopefully this time the levees hold.

The latest forecast track from the National Hurricane Center (NHC) has been remarkably consistent as forecast models have a strong lock on the path of the storm, at least until after landfall. The path thereafter, as the storm takes a turn to the north and northeast into Mississippi, has also been fairly steady the past 24-36 hours with only minor adjustments east and west on Monday and Tuesday. Once again, models are fairly consistent in their guidance.

What does that mean for Memphis? 

Ida is a relatively slow-mover into early next week. This means a couple of things. First, that considerable weakening of the storm over land will take place before it gets into north MS. And second, when it does pass by, heavy rain will be the primary threat due to the proximity to Memphis and duration of its passage across north MS. Let's dig into the details...

Heavy rain

The flooding threat will likely be moderate for the Memphis area and points south and east. Models bring anywhere from 2-6" of rain to the general area over a roughly 24-hour window, starting as light showers Monday (mainly afternoon) and picking up overnight in Tuesday morning as the center of T.D. Ida passes by roughly 40-50 miles to our southeast on the current track. Rain should let up as it pulls away Tuesday afternoon and evening. Most of the urban area can handle that amount of rain in 24 hours, but if there are squalls of heavier rain, maybe an inch or an hour or two, the impervious surfaces in the city could see low lying flooding. We'll be keeping a close eye on this threat, particularly if forecast totals rise above 4".

The National Blend of Models (NBM) shows roughly 2-4" of rain for the larger area around Memphis, roughly 3" in the city, in approximately 24 hours from late Monday through late Tuesday.

Strong wind

The probability of tropical storm force wind (sustained at 39+ mph) graphic tells the wind story for us, which is that damaging wind is unlikely. The chance of occurrence is less than 20%, according to NHC (below).

Probability of tropical storm force wind (sustained at 39 mph or higher) from Ida. Memphis' chance is near 10%, although gusts could be strong at times. (NHC)

However, that doesn't mean it won't be breezy or even windy for a time Monday afternoon through Tuesday morning in particular. Wind will be from the east Monday night, shifting to the north on Tuesday as the circulation around the center of Ida moves by to our southeast. Early estimates are that sustained wind could reach 20-30 mph with wind gusts possibly into the 40s ,though 30s is a more realistic guess.

The GFS model prediction of maximum wind gusts from Ida. For Memphis, that number is 40 mph and actually occurs Monday evening. (Not shown: the latest European model puts our max wind gust closer to 60 mph. I just don't believe that at this point.) (WeatherBell)

The good news is that the center is passing closest to us early Tuesday in a weakening state and the wind field around tropical remnants tends to "contract" towards the center of the storm with fewer gusts during the coolest part of the day with gusts picking back up as heating from the sun occurs during the day. So, plan to secure loose outdoor objects and other potential airborne projectiles (and small pets!) by Monday afternoon and keep them secure through Tuesday. No sense giving your neighbor a free patio umbrella or trampoline!

Tornado threat

Regarding wind of the spinning variety, remnant low pressure systems with tropical origins tend to sometimes be spin-up tornado producers. This phenomena is most likely to the RIGHT of the track of the center and during the daytime hours. Thus, we judge the metro tornado threat to be very low, as we'll be on the left side of the track and mainly during the cooler hours of the day. Northeast MS might see a brief twister or two on Monday afternoon or evening, so be aware if that includes you.

Day 3 (Monday) severe weather threat is currently forecast as "Marginal" for a possible brief spin-up tornado in north MS south of the metro. (SPC)

The calm after the storm

The good news is that once all of this leaves, which I expect by Wednesday morning, a drier and a bit cooler airmass moves over the area and likely stays with us into early Labor Day weekend! Dewpoints should drop into the 60s with abundant sunshine, highs in the mid 80s, and pleasant mornings. On the "12 Seasons Scale," I label this #FalseFall. Real fall night be still a little ways out as we can get some hot days in September, and I wouldn't really call mid 80s high temperatures true fall weather, but we're getting closer!

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

Saturday, August 21, 2021

One more storm chance, then hot and humid + a note on Henri

Some of us have gotten some beneficial rainfall this past week! Others (I'm looking at you eastern Shelby County) have had more than your fair share, while others could definitely use some more. Such is the nature of summertime convection, even when it is more organized than a typical summer day.

Radar-estimated rainfall over the past 72 hours indicates northwest Shelby and Tipton Counties with less than an inch, while the eastern metro and points east received 2-4"! (MRMS data via NOAA)

Today: last rain chance for a while

The "wet" pattern is transitioning to the "hot" pattern via the "humid" route this weekend. Today is the last decent chance of thunderstorms in the Mid-South until later next week as a large ridge of high pressure aloft begins to squash rain chances as it builds east from the southern plains. Today's rain chances are driven primarily by a couple of outflows moving through unstable and very moist air. 

The first outflow, which is now to our south, has sparked scattered showers south of Memphis. The next outflow from storms in Missouri earlier this morning will arrive early this evening and encounter more unstable air, as temperatures reach the 90 degree mark. Precipitable water  (PW) values, which measure total moisture in the air (not just the humidity we feel at the ground) are very high for August - above 2". This combination will likely spark scattered storms around the early-dinner hour and into the evening. High-res models expect those to form somewhere close by and then drop south into north MS. So the best chances will be south of I-40, basically increasing from very low just north of the metro, to likely in north MS. 

The 9am run of the HRRR model predicts initial showers to drop to our south this morning, a lull in activity, then additional storms to form, mainly in north MS, early this evening (after 5-6pm). The loop runs through midnight. Remember, model ≠ gospel. (WeatheBell)

Threats with Saturday storms

Whoever gets some of these storms will be visited by very heavy rain (owing to the high PW values) and some gusty wind, as downbursts are likely in these summer storms and outflows will be prevalent.  Our area is under a Marginal Risk (level 1) of severe weather today, so a few gusts could reach 40-50 mph in spots. In addition, we are in a level 2 Slight Risk of excessive rainfall, so storms could quickly drop a couple inches of rain and cause some flooding issues.

A Marginal Risk (level 1) of a few scattered severe storms exists today, mainly bringing a gusty wind and heavy rain threat.

A Slight Risk of excessive rainfall (level 2) is forecast for most of the metro today. (NWS)

Sunday-Wednesday: hot and humid

Once we are on the backside of this rain chance, he building ridge aloft and high pressure at the surface will result in dry but very humid, weather Sunday into the first half of next week. Highs will climb to the mid 90s by Monday. Combined with dewpoints in the mid 70s (which borders on insufferable), heat indices will easily reach the danger level of 105 degrees and could go above 110. Heat Advisories are a sure bet, and so is heat illness if you aren't avoiding long stretches out in it without hydrating properly and taking frequent breaks. This pattern continues through about Wednesday.

Sprawling high pressure aloft (a "ridge") encompasses a large portion of the U.S. as shown by the European model valid Tuesday night. The ridge results in hot weather and diminished rain chances. (WeatherBell)

Later in the week: minor relief

As we reach mid-week, the ridge will start to weaken a bit and afternoon rain chances start to tick up a bit. This will help to lower high temperatures slightly, back to the lower 90s or maybe near 90 by next weekend. Overnight lows will remain rather uncomfortable. In all, summer looks to continue through the end of August!

A note on Hurricane Henri

First, this isn't Derrick Henry of the Titans, it's pronounced "ahn-REE" (pretend you are a French chef when you say it). Hurricane Henri is beating a path towards southern New England with category 1 wind, a large storm surge, and very heavy rain. Landfall is forecast on Long Island east of New York City Sunday afternoon, then it will slow down and take it's time exiting New England. 

Forecast track for Hurricane Henri as of Saturday morning.

Henri will likely be the most significant storm to hit this area since at least Sandy in 2012 and perhaps Hurricane Bob in 1981. Expect to see footage of trees and power poles down, excessive flooding, coastal erosion, and the like. Officials are bracing for power outages that could last for many days. Not really what that area wants to be dealing with right now.

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, August 13, 2021

Summer heat abates as rain chances return, the tropics come to life, and transition on #TeamMWN

The first week of August seemed a bit surreal with below average temperatures and drier than average humidity. Mother Nature made up for that this past week as the blast furnace was cranked up, highs reached the mid 90s each day, lows barely dropped below 80, and rain-free weather continued. As we hit mid-month, we are looking at yet another pattern, one with slightly cooler but not abnormal temperatures and daily rain chances. 

Recent dry spell

The rain is welcome after a 16-day spell with no recorded rainfall at Memphis International. As of Thursday, portions of Shelby and Tipton Counties officially moved into D0 "abnormally dry" status on the National Drought Monitor (if you have been watering daily, you would not be surprised to hear that!). In fact, the 12 dry days to start the month has only been matched three times on record, the last in 1989. That all ended today as storms deluged portions of the city with 2-3"+ and the airport officially recorded just over an inch of rain.

The Drought Monitor for the Mid-South on Thursday shows abnormally dry conditions across east AR into the Delta and western sections of  the metro due to a lack of recent rainfall. (UNL)

The forecast

Looking towards the weekend, a cold front will seep into the area, providing potential for daily showers and thunderstorms, though not high chances, and additional cloud cover. That will serve to keep temperatures down a bit - near 90 Saturday and mid to upper 80s Sunday. The front will stall over the area, resulting in light north wind for a couple of days, but it won't move far enough south to drop the humidity much. Fortunately, midsummer dewpoints in the low 70s won't be paired with mid 90s temps!

The European model's forecast of mid-level (18,000') pressure values (black lines) and anomaly (colors) for the next week depicts below average pressure (blues) to start the week, which results in slightly cooler temperatures, then building pressure as the week goes on, thus a period of warming. If you look close you can spot a couple of tropical systems, one in the Gulf of Mexico (Fred) and one in the eastern Pacific (blue circles of small areas of low pressure). (WeatherBell)

Heading into next week, we'll see high pressure begin to build aloft a bit, slowly causing temperatures to return to the low 90s.With dewpoints remaining in the 70s, it'll be quite muggy, but there will also be daily thunderstorm chances continuing right through the week, most likely in the afternoons. Another front looks to make a run at us late next weekend. We'll see how far it gets! For the complete MWN forecast, updated daily, search out our app or visit on the web.

Tropical Update

The Atlantic and Gulf tropics are starting to pick up as well, though no direct impacts are expected in the Mid-South at this point. Tropical Depression Fred is likely to skirt the west coast of Florida this weekend and make landfall in the panhandle as a moderate tropical storm early Monday before turning north and east away from our area. Tropical Depression 7 will become Grace as it races west on nearly the same track Fred took across the Caribbean. It's too early to know for sure where it is headed after about the middle of next week. Forecast tracks on both storms from the National Hurricane Center are below.

#TeamMWN Update

Finally, we end with a farewell. #TeamMWN intern Ajay Kanteti joined our little junket in January, graduated in May from Mississippi State with his Bachelor's Degree in Meteorology and now is heading to the University of Wisconsin to pursue a Master's Degree. Below are Ajay's parting words:

I have greatly appreciated the chance to serve the Memphis metro area & gotten to know some great people in my time working at MemphisWeather.Net! I hope that my future career might give me an opportunity to return to the Memphis area & serve the people of the Memphis metro again. Meanwhile, you are being left in very capable hands with my co-interns and of course Erik!

I am so appreciative of Ajay's willingness to share his knowledge of weather with our Memphis-based audience and for his dedication to the team the past eight months, not to mention staying on through the summer to help me in the transition! We wish him all the best as he pursues another degree and ultimately a career using his passion for weather to serve. All the best, Ajay!

While Ajay moves on, I am happy to announce that #TeamMWN is actually growing! Joining the team of interns for this coming year are sophomore Dylan Hudler and seniors Natalie Naquin and Sami Deffenbaugh! All are meteorology majors at Mississippi State and are looking forward to honing their skills in the weather and communication on our MWN social media channels! Welcome aboard and #HailState!

Erik Proseus
MWN Meteorologist

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Complete MWN Forecast: on the mobile web or via the MWN mobile app
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MWN is a NOAA Weather Ready Nation Ambassador Meteorologist Erik Proseus is an NWA Digital Seal Holder

Monday, August 9, 2021

July 2021 Climate Report for Memphis, TN

July Climate Recap

Temperature trends from the previous few months continued in July with nearly every day in the first three weeks averaging cooler than normal. In fact, the typically hot July 4th weekend featured morning lows in the mid 60s and highs in the mid 80s. The cool pattern changed heading into the last week of the month as hot, dry and humid summer weather finally arrived. The result was an average temperatures that was a little more than a degree below average for the month. The number of 90 degree days ended 5 days below normal at 17 days. 

Precipitation ended the month almost an inch above average at 5.73", with most of it falling prior to the heat arriving in the last third of the month. The only severe weather of the month occurred  around mid-day on the 9th as very heavy rain trained along the TN/MS state line, prompting Flash Flood  and Severe Thunderstorm Warnings and reports of flooding in DeSoto and northwest Marshall Counties. Isolated flash flooding also occurred on the late afternoon of the 1st in western Shelby County. Severe Thunderstorm Warnings also were issued in the metro on the 10th and 11th with no severe weather reports. 

Memphis International Airport, Memphis, TN

Average temperature: 81.6 degrees (1.2 degrees below average) 
Average high temperature: 89.6 degrees (2.3 degrees below average) 
Average low temperature: 73.6 degrees (0.0 degrees below average) 
Warmest temperature: 96 degrees (28th, 30th, 31st) 
Coolest temperature: 65 degrees (4th) 
Heating Degrees Days: 0 (0 above average)
Cooling Degree Days: 525 (25 below average) 
Records set or tied: None
Comments: There were 17 days with high temperatures above 90 degrees, which is 5 days below average for July.

Monthly total: 5.73" (0.91" above average) 
Days with measurable precipitation: 13 (3.5 days above average) 
Wettest 24-hour period: 1.89" (9th) 
Snowfall: 0.0"
Records set or tied: Daily record on July 9th (1.89")
Comments: Five days recorded precipitation of more than an one-half inch, while July averages 3.3 days.

Peak wind: East/51 mph (18th) 
Average wind: 6.7 mph 
Average relative humidity: 73% 
Average sky cover: 51% 

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

Cirrus Weather Solutions /, Bartlett, TN

Average temperature: 80.2 degrees 
Average high temperature: 90.5 degrees 
Average low temperature: 71.6 degrees 
Warmest temperature: 98.7 degrees (31st) 
Coolest temperature: 60.0 degrees (4th) 
Comments: None 

Monthly total: 5.05" (automated rain gauge), 5.24"(manual CoCoRaHS rain gauge) 
Days with measurable precipitation: 9
Wettest date: 2.83" (11th) (via automated gauge) 
Snowfall: 0.0"
Comments: None

Peak wind: North/19mph (27th)
Average relative humidity: 81% 
Average barometric pressure: 29.97in. Hg
Comments: None

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

MWN Forecast Accuracy

MWN average temperature error: 1.54 degrees 
MWN forecast temperatures within 2 degrees of actual: 84% 
MWN average dewpoint error: 1.24 degrees 
MWN forecast dewpoints within 2 degrees of actual: 88% 

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

Climate Outlook - August 2021

The August climate outlook for the United States from the Climate Prediction Center is shown below. Above average temperatures are forecast for the western U.S. across the northern tier into the Northeast with highest odds across the Northern Plains. Below average temperatures are forecast in the Southern Plains to Lower Mississippi Valley. Odds favor very near average temperatures for Memphis with a 35% chance of below average temperatures and a 32% chance of above average conditions. The average temperature for August is 82.1 degrees, just slightly below the July average.

Precipitation is expected to be above normal for much of the southeastern U.S. east into the Mid-Atlantic and north into the Ohio Valley, with highest odds in the eastern Carolinas. Additional above average precipitation is forecast for the Desert Southwest. Below average precipitation is forecast for the Northern Plains. For Memphis, odds are slightly in favor of above average precipitation (36%) versus a 31% chance of below average precipitation. Rainfall historically averages only 3.37 inches.

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

Sunday, August 1, 2021

A reprieve from mid-summer heat and humidity this week

The first three weeks of July featured temperatures largely below average, but the past week made up for that, reminding us just what Memphis summers typically feel like! The daily temperatures for the past eight days averaged nearly 4 degrees above normal with high temperatures consistently in the mid 90s and feels like temperatures reaching heat advisory criteria (105°+) on multiple days - a few even topping 110°! So what does the next week hold? A nice break from the heat!

Overall pattern

The upper level atmospheric weather pattern over the past week featured a large ridge of high pressure that built over the region, resulting in those above average temperatures. However, with the passage of last night's surface cold front, the upper level pattern also shifts. A trough of low pressure over the northeastern quarter of the nation dips south, then into the week lingers over the Ohio and Tennessee Valleys before finally weakening and lifting out by the end of the week. 

Lower pressure aloft typically means cooler temperatures at the surface. Coupled with the passage of a series of upper level disturbances rotating through the upper level trough that result in periods of cloud cover, temperatures will be well below average for much of the upcoming week. 

The European model ensemble of upper level height anomalies for the coming week. In short, lower than average pressure aloft is shown in blue and higher than average is in yellow. The blue colors that move over the Mid-South  mean low pressure aloft, which translates to cooler than average temperatures. (WxBell)

Early-week cool temps

In the wake of Sunday's cold front and arrival of the upper level trough, we'll see a fair amount of cloud cover Sunday night into Monday, then partly cloudy skies on Tuesday. A north to northeast wind, dry conditions, and dewpoints falling into the low to mid 60s will set the stage for very pleasant conditions for early August with highs in the mid 80s and lows dropping to around 70 Monday morning and the mid 60s Tuesday morning.

Mid-week persistence

We'll see more sunshine on Wednesday with just partly cloudy skies as highs remain in the mid 80s. Morning lows start in the mid 60s in the city but could drop a few degrees cooler in outlying areas. A bit of warming occurs Thursday with highs in the upper 80s, but with humidity still remaining below average, there still won't be much to complain about!

More warming into the weekend

By the end of the week, temperatures start to climb further as the upper level trough pulls out and higher pressure aloft results in warmer temps below. A passing upper disturbance could mean a few showers Friday, but that is still too far out for anything conclusive. Highs will be at or just above 90. Sunshine returns Saturday with highs back near average in the low 90s and lows returning to the low 70s. Sunday into the following week (as schools return for many students) could be back above normal with highs in the mid 90s, so enjoy this coming week while we have it!

Forecast temperatures for the next 10 days from the NWS model blend. (WeatherModels)

Erik Proseus
MWN Meteorologist

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