"Fall" and hurricane season end, so here's the winter outlook!

Meteorological Fall Comes to an End

As the calendar turns to December and minds collectively turn towards the end-of-year holiday season, meteorologists see a changing of the seasons. While the official start of winter is when the winter solstice occurs (December 21), "meteorological winter" for climate record-keeping purposes starts December 1 and runs through the end of February. That means the record books are closed on autumn. We'll have more detail in the November climate summary in a few days, but preliminary data indicates that the average temperature for fall this year was 65.1 degrees, which is above the long-term average of 64.4 degrees. Rainfall, however, was below normal, totaling 8.92" for September-November versus the average of 11.70". 

Winter 2021-2022 Outlook

So what does the crystal ball look like for winter, perhaps the most anticipated season of the year? Early prognostications are driven primarily by the state of El Nino-Southern Oscillation (ENSO), but there are many other factors that make it pretty unpredictable, especially in the south. What is likely is the current La Nina climate pattern - an oceanic pattern that features cooler than average waters in the central Pacific Ocean - will continue through the winter. In fact, it's a "double dip" La Nina after the pattern dominated last winter, receded this summer, but reappeared in the fall. The typical impacts from a La Nina pattern are shown below. The Mid-South tends to be in the battle zone between wetter conditions to our north and drier to our south, while temperatures tend to be above average.

Typical impacts over North America during a La Nina winter. (NOAA)

The official Winter Outlook from NOAA is very close to what we would expect from a La Nina pattern and is shown below. There is a 40-50% chance of temperatures averaging above normal and odds of wetter than average conditions dip as far south as west TN. 

The temperature outlook for December-February 2021 from NOAA.

The precipitation outlook for December-February 2021 from NOAA

Remember that these are predictions of average conditions over a three-month period. That means there can certainly be cold spells in an overall warm pattern, or rainy periods in a dry month. In fact, you will certainly remember the Arctic outbreak last February that occurred in a very similar overall pattern to this winter. Other factors and atmospheric patterns will dictate the day-to-day conditions.

Atlantic hurricane season also ends

The start of December also means that the Atlantic hurricane season has also come to an end. It also marks the first time that the pre-defined list of 21 storm names has been exhausted in consecutive years. The 2021 season featured exactly 21 named storms (the third most in a year), seven hurricanes (five of which classified as "rapidly intensifying" during their life cycle), four major hurricanes, and eight U.S. landfalls. It was also the sixth consecutive "above normal" season and seventh consecutive season in which a named storm formed before the official start of the season on June 1. (NOAA's outlook published in May called for 13-20 named storms, 6-10 hurricanes, and 3-5 major hurricanes.)

Erik Proseus

MWN Meteorologist

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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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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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Cool and wet for the first week of June, and Atlantic hurricane season begins!

Summer weather has held off for about as long as possible across the Mid-South. May temperatures finished off below average, coming on the heels of a cooler than average April. Overall, it was quite a nice spring across the Memphis area and for most of the Southeast! Rainfall was also a bit below normal, due to frequent cold fronts pushing Gulf moisture out of the area. We still have yet to hit 90 degrees this year, and are now almost a week behind the average first 90° reading of the year! 

Temperature departure from average for the month of May. Much of the country experienced cooler than typical weather. (WeatherBell)

Forecast overview - wet and cool

Now as we enter the month of June, another pattern shift will bring tropical moisture back into the region and set the stage for daily chances of showers and thunderstorms. Persistent lower pressure in the upper atmosphere over the central and eastern U.S., along with increased cloud cover from daily rain and storms will keep temperatures below average over the next week. We should finally be back in the 80s by Thursday, but temperatures will only slowly climb to the mid 80s as we enter this weekend and next week. Not an above average day in sight! 

We were a bit below average for rainfall in the month of May, but that trend looks to quickly be reversed as we enter the month of June. The Mid-South will be positioned between a ridge of high pressure to our east over the Atlantic and another large ridge over the western U.S., which is bringing very hot temperatures all the way into the Pacific Northwest. This pattern allows moisture to be pumped off the Gulf. When combined with a trough of low pressure over the area and repeated disturbances moving through the trough, we'll see daily chances of scattered to numerous showers and thunderstorms. 

The upcoming pattern (as depicted by this upper level forecast chart for Wednesday night) features a trough of low pressure in the middle of the country and ridges of high pressure to the east and west. This pattern is very favorable for showers and storms, as well as cooler than normal temperatures. (WeatherBell)

Rain chances and amounts

Tonight and Wednesday look to have an almost guaranteed chance of rain across the area as a disturbance moves through the Mid-South. Rain chances diminish a bit Thursday through Saturday, but there will still be a chance for widely scattered to scattered afternoon showers and storms. By the latter half of the weekend and into the beginning of next week, another disturbance is poised to move through the area, once again bringing more widespread coverage of showers and thunderstorms. 

Over the next week, models are showing most of us picking up a healthy dose of rain - around 1.5 to 2.5 inches by next Tuesday. However, it is important to note that this time of year, storms can be fairly random, and it can rain 2 inches on one side of town but be completely dry on the other. Forecasting exactly where and who will get a storm is nearly impossible with pop-up storms, but just know there will be at least  a chance nearly every day. Severe weather doesn’t look to be a threat, but any storm could have lightning, torrential rain, and gusty wind. Just because it isn’t warned doesn’t mean you shouldn’t be careful, especially if lightning is present.

The European model forecast of rainfall over the Mid-South through next Tuesday morning. Due to the random nature of storms, a wide range of rainfall accumulation is likely across the area. (WeatherBell)

Atlantic hurricane season begins

Something else of note as we enter the month of June - today is the first day of the 2021 Atlantic hurricane season! While we may be a few hundred miles away from the coast, tropical cyclones can still have a significant impact in Memphis, with flooding rains and the potential for spin-up tornadoes. Nothing is on the radar in the Atlantic at the moment, but just something to keep in the back of your mind, especially if you are planning on a beach vacation later in the summer.  NOAA's prediction for this year is a 60% chance of above normal activity with 13-20 named storms. (We've already had Tropical Storm Ana - another early-bird that formed in May - that affected Bermuda!)

NOAA's prediction for the 2021 hurricane season.

Overall, as long as you don’t mind some rain and humidity, the pattern is not looking bad for us. We have really lucked out on missing any big-time heat so far this season, and that trend looks to continue for at least the next week. However we know our luck can’t last forever, and 90 degree days are probably lurking just around the corner. Stay tuned, and enjoy this first week of meteorological summer! 

Christian Bridges
MWN Social Media Intern

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Rain and wind on the way for Memphis thanks to Hurricane Delta

The latest of Hurricane Delta

As of mid afternoon, Hurricane Delta is closing in on the Louisiana coastline and is expected to make landfall near Cameron, Louisiana early this evening.  Hurricane-force winds, life-threatening storm surge and flash flooding is expected along southern Louisiana this afternoon and evening.  Delta will move northeast into northeastern Louisiana overnight into Saturday morning, weakening to a tropical storm tonight after landfall.  By Saturday morning, Delta will be moving into southeast Arkansas as it continues to weaken to a tropical depression, then continues northeast into northwestern Mississippi Saturday evening.  By Sunday morning, what's left of the storm will be located over the Tennessee Valley and will cease to be a tropical system by Sunday evening.

National Hurricane Center forecast for Hurricane Delta as of 1pm Friday

Impacts on Memphis this weekend

For Memphis, expect light rain showers this evening, with heavier showers moving in early Saturday morning.  Winds should be from the east at 12mph tonight, increasing to 20mph with gusts to 30mph on Saturday. Combined with the rain, it will make for a pretty ugly day for anything outdoors! Temperatures will remain in the 70-75° range from early morning through the day. Saturday night, winds should begin to shift out of the north and diminish, with showers also decreasing.  Scattered showers will be possible on Sunday though much less coverage than Saturday with only a 30% chance of rain. Temperatures rebound to the upper 70s but tropical humidity sticks around! Total rainfall amounts from this storm through Sunday look to be right at 2 inches for Memphis, with anywhere from 1 to 3 inches across the Mid-South, and up to 3 to 5 inches to our southwest across the (Mississippi/Arkansas) Delta. At least it isn't the 6 to 8 inches of rain that is likely for parts of Louisiana! 

Minor flooding is possible on Saturday in low-lying areas and urban ponding is also possible in heavier rounds of rainfall. Thunder is expected to be minimal in the metro, though a few tropical thunderstorms are possible not too far to our south and east. A few of these in eastern MS and AL may even produce isolated tornadoes. Wind gusts in the Memphis area will likely not be strong enough to do any widespread damage, though some tree debris is possible as the day goes on.

Forecast rainfall amounts from Delta (NOAA/WPC)

The latest Memphis forecast can be found on our website or on the MWN app using the links below.

Richard Hoseney

MWN Meteorologist

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August 2020 Climate Data for Memphis, TN

August Climate Recap

After a July that featured persistent heat - in which every day featured high temperatures of at least 89 degrees and lows were in the 70s every day - August cooled off relative to normal. The signal emerged on the first day of the month with a high of just 79 degrees and the first week of the month averaging five degrees below normal. From there, temperatures warmed above average for week 2 but then cooled for the second half of the month. Overall, the average temperature was 1.3 degrees below normal with several mornings dropping into the upper 60s. 

Precipitation for August, a typically dry month, was a marked departure from a dry July and ended up 12th wettest on record. Multiple systems brought areas of heavy rain, including the remnants of Major Hurricane Laura that made landfall in southwest LA near the end of the month and then re-curved to pass by to our north. Tropical Depression Laura also brought our windiest day of the month with wind gusts into the 30s to mid 40s mph on the 27th-28th. 

Severe weather was nearly negligible during the month of August, with the exception of a few Tornado Warnings spawned by the remnants of Laura on the evening of the 27th in northwest MS. These storms did not produce tornadoes, although there were a few weak tornadoes in northeast AR and far northwest TN from Laura. Scattered tree and power pole damage was observed in Tunica County on the 28th from Laura's remnants. Finally, flash flooding occurred in eastern Tipton County on the early morning of the 30th. Flash Flood Warnings were issued on multiple slow moving storms throughout the month with heavy downpours common.

NWS-Memphis map of tornadoes produced by the remnants of Hurricane Laura. 

Memphis International Airport, Memphis, TN

Temperature 

Average temperature: 80.7 degrees (1.3 degrees below average) 

Average high temperature: 89.6 degrees (1.7 degrees below average) 

Average low temperature: 71.7 degrees (1.0 degrees below average) 

Warmest temperature: 97 degrees (9th, 10th, 11th) 

Coolest temperature: 65 degrees (5th) 

Heating Degrees Days: 0

Cooling Degree Days: 492 (35 below average) 

Records set or tied: None 

Comments: None

Precipitation 

Monthly total: 6.47" (3.59" above average) 

Days with measurable precipitation: 13 (6.2 days above average) 

Wettest 24-hour period: 1.93" (13th) 

Snowfall: None 

Records set or tied: None 

Comments: This month was the 12th wettest August on record.

Miscellaneous 

Peak wind: South/46 mph (28th) 

Average wind: 6.7 mph 

Average relative humidity: 69% 

Average sky cover: 50% 

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

 

Cirrus Weather Solutions / MemphisWeather.net, Bartlett, TN

Temperature 

Average temperature: 77.6 degrees 

Average high temperature: 88.8 degrees 

Average low temperature: 68.8 degrees 

Warmest temperature: 98.4 degrees (10th) 

Coolest temperature: 59.6 degrees (5th) 

Comments: None 

Precipitation 

Monthly total: 6.87" (automated rain gauge), 7.45" (manual CoCoRaHS rain gauge) 

Days with measurable precipitation: 12 

Wettest date: 2.06" (28th) (via automated gauge) 

Snowfall: None 

Comments: None 

Miscellaneous 

Peak wind: South/30 mph (28th)

Average relative humidity: 83% 

Average barometric pressure: 29.93 in. Hg

Comments: None

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

 

MWN Forecast Accuracy

MWN average temperature error: 1.76 degrees 

MWN forecast temperatures within 2 degrees of actual: 74% 

MWN average dewpoint error: 1.72 degrees 

MWN forecast dewpoints within 2 degrees of actual: 80% 

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

 

Climate Outlook - September 2020

The September climate outlook for the United States from the Climate Prediction Center is shown below. Above average temperatures are again forecast for areas in and west of the Rocky Mountains, as well as the Florida peninsula. Cooler than average temperatures are forecast for the eastern Plains into the Midwest and Ohio Valley and sections of the Mid-South. Odds slightly favor below average temperatures for Memphis (35%) versus only a 32% chance of above average temperatures. Memphis' average temperatures for September is 75.2 degrees.

Precipitation is expected to be above normal in the southeast U.S. with a strong signal for anomalously wet conditions in portions of the south-central Plains east into the middle Mississippi Valley. Drier than average weather is forecast for much of the Great Plains into the western U.S. For Memphis, odds favor above average rainfall (a 52% chance) versus only a 15% chance of below average rainfall. Precipitation historically averages only 3.09 inches in September. 

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Complete MWN Forecast: MemphisWeather.net on the mobile web or via the MWN mobile app 

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Hurricane Laura strengthens; remnants to impact the Mid-South

Laura became a hurricane in the southeastern Gulf of Mexico this morning about 7am and has intensified only slightly since that time as it churns northwestward towards the central Gulf Coast. However, more rapid intensification is expected over the next 24 hours as it nears the coast, ultimately reaching major hurricane (category 3) status by the time it reaches the coast near the TX/LA border overnight Wednesday night. Here's a look at the visible satellite imagery of an organizing Laura the last couple of hours before sunset Tuesday:

The track provided by the National Hurricane Center at 4pm Tuesday (below) shows the turn from the west to north tonight and tomorrow and landfall around midnight Wednesday night with maximum sustained wind of 115 mph and gusts to 140 mph! It should be noted that there is still some discrepancy between the models, and it is entirely possible that it could be a bit stronger than that. In addition, the Hurricane Warning extends as far west as Galveston Bay (Houston) and the storm could still shift a bit more to the west towards the greater Houston metro. Needless to say, a strong category 3 storm sideswiping a massive American city like Houston during a pandemic could be devastating (2020, it that you?), but no matter where the center hits (Beaumont, Lake Charles, or vicinity), the results will be simply awful.

After landfall, Laura will take a path north along the TX/LA border into Arkansas by Thursday evening, still as a tropical storm. By Thursday night, Tropical Storm Laura is near Little Rock and starting to take a turn to the east as it gets caught up in strong westerly wind flow. The center of the remnants should be north of Jonesboro near the AR/MO line by Friday afternoon then swiftly move by to our north and across KY through mid-day Saturday.

As for Mid-South impacts, we will know it passed nearby. We'll see chances of showers and thunderstorms for the next couple of days leading up to its approach, but our best chance for impact-ful weather from Laura will be late Thursday through Friday night. This is when we could see wind gusts close to 40 mph (particularly daytime Friday) with sustained wind to 20-30 mph. In addition, periods of heavy rain are likely Friday into Friday night, though heavy downpours could be scattered about or in bands Thursday afternoon as well. In addition, tropical remnants are occasionally known to throw out (typically weak) tornadoes, and we'll be on the right side of the storm track for those to possibly occur, again most likely Friday when temperatures are warmest and instability highest.

The main threat though, besides some trash can throwing wind gusts, will be heavy rain. The Weather Prediction Center currently has much of AR right up to the Mississippi River in a Moderate Risk for excessive rainfall capable of producing flash flooding Thursday into Friday morning, though I expect a similar threat to be extended in to Friday. For now, west TN and northwest MS are in a Slight Risk, but that may be higher on Friday as the storm passes to our north. Current rainfall projections from the NWS are between 4-5" for the metro through Sunday evening. This does include additional showers and scattered thunderstorms this weekend after the storm passes as well.

My suggestions for preparation on Wednesday and Thursday:

• Tie down or bring inside any loose outdoor objects, including patio seat cushions!
• Make sure gutters and storm drains are clear of debris and ready to accept heavy rain.
• Know where you'll go and have your safe place ready just in case a Tornado Warning is issued
• If out in heavy rain, avoid swollen waterways (and watch your kids closely too) and don't drive into areas where water covers the road.

Scattered showers and thunderstorms unfortunately remain in the forecast for several days after Laura's remnants pass, so remember that after heavy rain has saturated the ground from Laura, additional rainfall is more likely to run off and result in flooding in low-lying areas more easily. There are early hints of a potential pattern shift as we hit the first of September. Let's get through this week first though!

Stay safe and follow us on social media for the latest information!

Erik Proseus
MWN Meteorologist

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Follow MWN on Facebook and Twitter for routine updates and the latest info!
Complete MWN Forecast: MemphisWeather.net on the mobile web or via the MWN mobile app
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Meteorologist Erik Proseus is an NWA Digital Seal Holder

It's still 2020! TWO hurricanes in the Gulf of Mexico this week?

Many of you are aware, perhaps from hype articles/videos shared by unscrupulous (or perhaps just naive) sources on social media, that the Gulf of Mexico will be visited by two tropical systems this week. Typically, I devote space on this blog to weather that has impacts to the Memphis area. 

Since it is appearing possible that we could get some tropical remnants later next week, which I will get into in a minute, I'm going to entertain the discussion/bust myths of merging tropical systems, the possibility of a mega-super-duper-storm, and the "new term" Fujiwhara effect. 

Forecast tracks of Marco and Laura

As of 4pm Saturday, the National Hurricane Center forecasts for Marco (currently passing between Cuba and the Yucatan peninsula of Mexico) and Laura (sliding west of Puerto Rico towards Hispaniola) are now presenting the very real possibility not only of two hurricanes in the Gulf at the same time, but a double-landfall within 48 hours of each other on the Gulf Coast, perhaps affecting the same area twice. 

If two storms of at least tropical storm strength are in the Gulf at the same time, which looks likely for a short time late on Monday, it will be only the third time on record. If two hurricanes are in the Gulf at the same time, also possible, it will be the first time on record. (Of course, it's #2020.) Here are the forecasts as of 4pm CDT Saturday:

There are still a lot of uncertainties on both systems, which I will not delve into here, but it's good to remember that these forecasts can be fairly uncertain multiple days out despite advances in forecast techniques. You'll notice though that Marco now appears to be headed for the central Gulf Coast with landfall projected Monday afternoon in southeast Louisiana as a hurricane (perhaps a very strong tropical storm). Just two days later, Wednesday afternoon, Laura heads for the same approximate area as a hurricane and likely stronger than Marco. Again, lots can change - and has just in the past 24 hours. However, a double-landfall in the same general area could be devastating for said area in terms of flooding, storm surge, and strong wind that could be dealt a powerful blow by a second storm after being weakened by the first. Let's hope and pray not.

Dualing tropical systems and the Fujiwhara Effect

As for the interaction of the two, it appears right now that this is fairly unlikely given that Laura is forecast to be just entering the southern Gulf as Marco makes landfall in the northern Gulf. But let's talk for a second about the Fujiwhara Effect - a term that is indeed NOT new (just like Polar Vortex and bombogenesis), but new to us because it doesn't happen often, and rarely in the Atlantic/Gulf of Mexico basin. It is more common, though still somewhat rare, in the western Pacific where there tend to be more tropical systems. 

The AMS Glossary of Meteorology defines it as "the tendency of two nearby tropical cyclones to rotate cyclonically about each other as a result of their circulations' mutual advection." Notice it does not say "merge into a megastorm and result in massive death and destruction." In fact, the forces acting on and around a tropical system that cause it to maintain itself would be destructive to another system that approaches it. I think the best way I have seen it described in a visual fashion is through the animation in this really cool tweet:

A lot needs to happen before recent #Fujiwhara headlines come true, but here's what it looks like in a high-res simulation.

Background rotation is turned up beyond real-Earth values to fit a bunch of tiny TCs. No other forcing, so they're allowed to purely interact on their own. pic.twitter.com/rAZMM4LU8A

— Jake Carstens (@JakeCarstens) August 21, 2020

Mesmerizing isn't it? Go ahead, watch it again.

Notice that as these "tropical storms in a virtual lab" approach each other, they tend to either repel or weaken one another, with the weaker of the two typically falling apart, sometimes with the remnants being absorbed by the larger one. So, while it doesn't appear Laura and Marco will have much influence on each other this week, if they were, it would likely just be a minor deflection of one or the other system or a further weakening of the "weakest link," not a massive COVID-cane named "Laurco."

Effects on the Mid-South

Looking out a bit further, most models that agree with the NHC assessment of the forecast tracks right now bring the remnants of Laura into the Mid-South later next week. We'll definitely be watching this as it could mean a healthy dose of precipitation - perhaps a couple of inches - and some gusty wind. Further forecasts will refine that, but for now, the Weather Prediction Center of the NWS provides the precipitation forecast for the upcoming week below, which presumes some tropical moisture moving across the Mid-South about Thursday or Friday. It's got the Memphis area solidly in the 2"+ range.

The Weather Prediction Center forecast for rainfall over the coming week. The influence of two tropical systems on the Gulf coast is easy to pick out with remnants moving north through the lower Mississippi Valley late in the week. (WPC via Pivotal Weather)

Erik Proseus
MWN Meteorologist

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