Wednesday, June 21, 2017

Remnants of Cindy to pass over the Mid-South Friday

We've been keeping a close eye on (potential, then actual) Tropical Storm Cindy in the Gulf of Mexico the past few days. For the first time in several years, the remnants of a former tropical system are set to pass directly over the Mid-South. First, here are the latest forecast track and satellite view of Cindy (click any image on this page for a larger version):

Latest forecast track of Cindy from the National Hurricane Center.

Visible (infrared at night) satellite loop of Cindy. Click here if loop does not animate.

Forecast Path

As you can see from the graphic above, as of early Wednesday evening, Cindy is expected to make landfall early Thursday morning near Beaumont, TX, or along the TX/LA border. It will be a moderate tropical storm with maximum sustained wind near 45-50 mph when it makes landfall. From there, it heads north up the TX/LA border then begins a right turn Thursday night, heading into southern AR, That right turn continues, moving what will likely be Tropical Depression Cindy, over the Mid-South, if not Memphis proper, on Friday around mid-day. There are some model discrepancies on the exact track of the center of the low and the timing, but it will be during the day Friday.

Effects on the Mid-South

The effects here in the Mid-South will primarily be those that were problems to our south today - some gusty wind, not-insignificant rainfall which could lead to some flash flooding, and as with any landfalling/remnant tropical system, a few strong storms that could produce brief tornadoes. We'll take them one at a time.


Wind has not been a major factor even while Cindy was a tropical storm today. Strongest wind of up to 40-50 mph was primarily right near the center and in convective bands well removed east and north of the storm. Cindy will weaken after landfall, but we'll see breezy conditions (10-20 mph, some higher gusts) through Thursday night. On Friday, as the low approaches and depending on its exact track, some areas could see sustained wind of 20-30 mph with a few gusts to 40+ mph, mainly in convective (thunderstorm) bands and near the path of the low. By Friday evening, any strong wind will subside back to the baseline of 10-20 mph. Widespread power outages are not anticipated, but with a slightly weakened grid due to remaining tree limbs on lines, etc. from recent storms, sporadic or scattered outages are possible, mainly Friday.

Heavy rain and flooding

The primary threat from Cindy is, and will continue to be, periods of heavy rain and the potential for flash flooding. Timing of any "bands" or "slugs" of moisture is very difficult more than several hours out, so trying to pinpoint exact times of when they will occur is borderline futile. Suffice it to say, rain chances will be high from late tonight until the system passes late Friday, however it is not expected to rain hard the entire 2-day period.

For now, it appears showers will begin to overspread the area tonight with the first main band moving through early Thursday morning. After this round, there could be a lull during the mid-day hours tomorrow, although given the unstable and very moist atmosphere that is in place, scattered showers and thunderstorms are probably a decent bet. Another round could affect the metro late tomorrow into the early overnight Thursday night, though that may set up just to our north. (Again, this is not set in stone.) Then, indications are that we'll see one more period of rain, probably the heaviest, associated with the approach, passage, and departure of the low itself during the day Friday, quite possibly lasting into Friday evening. Again, this is HIGHLY subject to change. (If you have tickets to Live at the Garden Friday night or plan to attend a Levitt Shell concert, watch for information from those entities on their plans and stay tuned to the forecast. Even if it isn't raining during the concert times, conditions may be too wet leading up to the events to get them properly setup.)

Overall, rainfall totals could vary quite a bit from one place to another but are expected to generally fall in the 2-3" range between tonight and Saturday morning with some areas seeing up to 5". Flash flooding and urban ponding/flooding are possible. Flash Flood Watches are not currently in effect but I put odds at better than even that they will be before Friday. Our area is under a Moderate Risk of flash flooding for the Thursday night/Friday period, as shown below.

Rainfall projections from the NWS through Saturday morning show a band of 2-3" of rain expected across the metro. A few locations could see more, and possibly less, as these numbers are approximates. Memphis is just northeast of the 2-3" annotation in the center of the image. (NWS/WPC)

The Weather Prediction Center forecasts a Moderate Risk (10-15% chance) of flash flooding on Friday for the metro. (NOAA/WPC)

Brief tornadoes

Thunderstorms associated with remnant tropical systems build in highly-sheared environments where wind at various levels of the atmosphere is blowing briskly, and in varying directions. This can lead to the threat of spin-up tornadoes in some of these storms, even those that may not contain lightning or be severe by any other definition. (Storms from tropical systems tend to have much less lightning than a "normal" summertime thunderstorm and are also not as tall, but they can still pack a punch.) The greatest threat for any tornadoes will be to the right of the track of the storm. On Thursday, that threat will mainly be to the south of the metro in LA, southeast AR, and western MS where there is a Slight Risk of severe storms. The Memphis area is in a Marginal Risk on Thursday, meaning a few storms could contain brief damaging wind gusts or a spin-up tornado. (Hail is generally not a threat with tropical systems as their "core" is warm, not cold like classic low pressure systems.)

The Storm Prediction Center severe weather outlook for Thursday, showing the Slight Risk (where a tornado is most likely) south of the metro. (NOAA/SPC)
On Friday as the low passes near the metro moving northeast, the most favorable position for brief tornadoes will be in the southeast quadrant of the storm. If the low passes to our north, Memphis could be in that quadrant. If it passes just to the south or overhead, the favored area will be to our south. Currently, the Storm Prediction Center, based on the Hurricane Center track, places the Slight Risk south of Memphis with the metro in a Marginal Risk once again. That could change and will bear monitoring. Overall, the probability of tornadoes also will go down a bit from Thursday to Friday as the system weakens in general. As a last comment, the tornadoes associated with weak remnant systems in general are not the monsters we see in the Plains or Dixie Alley associated with supercells. They are more akin to the brief spin-up's that are possible with a squall line moving through, but we still need to prepare for the possibility that they could occur, and probably with little notice.

The Storm Prediction Center severe weather outlook for Thursday, showing the Slight Risk (where a tornado is most likely) southeast of the metro. (NOAA/SPC)

After the storm

By Friday night, it appears the worst will be over with perhaps a lingering shower that lasts until Saturday morning. Most of Saturday looks like it could be dry (though precipitation may hold back a little longer than current thinking) and Sunday introduces another conundrum, as computer models have fought like pre-teen siblings over whether an upper level system brings additional rain chances. Right now those chances appear fairly low. Stay tuned.

In the meantime, be sure to follow us on social media for the absolute latest on this dynamic weather situation; download the MWN app for radar, currents, the MWN Forecast, and our social feeds as well as StormWatch+ optional severe weather alerts; and check out the MWN Tropical page (optimized for desktop browsing) with more information on the current status and future of Cindy! All social and app links are listed below.

Erik Proseus
MWN Meteorologist

Follow MWN on Facebook, Twitter, and Google+
Visit on the web or on your mobile phone.
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

Saturday, June 17, 2017

Atlantic/Caribbean tropics getting started early

Atlantic hurricane season just started on June 1, but already things look to be "heating up" in the warm waters of the Caribbean and tropical Atlantic - about a month to six weeks earlier than average.

AL93 - Yucatan/Gulf of Mexico

Near the Yucatan Peninsula of Mexico in the southern Gulf of Mexico, home to resorts like Cancun and Cozumel, a large area of low pressure will move northwest across the peninsula with heavy rain and sub-tropical wind speeds this weekend before emerging into the southern Gulf early next week.  There is still a large disparity between various computer model solutions on where this system heads once it reaches the Gulf, ranging from the Rio Grande Valley of deep south Texas/northeastern Mexico to the central to northeastern Gulf coast of the United States (think of some of our favorite beaches along the AL/FL coastline or perhaps as far west as New Orleans).

Model tracks for AL93, which will cross the Yucatan this weekend then emerge into the Gulf early next week (WxBell)
In any scenario, it would be late next week before that occurs and none of the models turns "beast mode" on for AL93 (area of investigation #93), but it'll still bear watching! ANd it's also still much too soon to know if it will have any effect on local weather in the Mid-South. If a tropical storm forms from this system, it would likely be called Bret (see 2017 storm names), owing to the fact that premature Arlene formed in the vast reaches of the central Atlantic a couple of months prior to the official start of the season. Sea surface temperatures in the Gulf of Mexico are fairly close to average (within about 1° F, with actual water temperatures near 83° F), though they are warmer than average off the Texas coast.

This map from shows sea surface temperature anomalies in shades of red (warmer than average) and blue (cooler than average), as well as ocean currents. The Loop Current is well-established in the southeastern Gulf and the well-known Gulf Stream can also be seen flowing from the Loop Current up the east coast. The position of AL93 is shown and has near average water temperatures ahead of it, unless it heads towards the Lower TX coast.  

AL92 - Windward Islands and beyond?

If the Caribbean system isn't called Bret if/when it develops full tropical storm status, it'll only be because "AL92" in the south-central Atlantic beats it to the punch (see first graphic above)! Moving abeam the northern shores of South America in the next few days, this tropical disturbance seems to have less a chance of development in the long-run, but could be the earliest tropical developments in this part of the world on historical record! Check out the graphic below, which shows no previous development recorded in the central Atlantic during the middle part of June!
The early months of the Atlantic season are typically reserved for development in the Gulf of Mexico and Caribbean, while the long-haul trackers across the Atlantic that are born from storm systems in western Africa that take a drink in the eastern Atlantic don't start gearing up until well into the tropical season. Here are the potential tracks for AL92, which are fairly tightly clustered towards the Windward Islands in 3-4 days:

Model tracks for AL92 as it heads towards the Windward Islands in a few days (WxBell)

New for 2017

There are a couple of interesting items of note that are new for the 2017 hurricane season. First, the National Hurricane Center will have the option this year to issue advisories, watches, and warnings for disturbances that are not yet a tropical cyclone, but which pose the threat of bringing tropical storm or hurricane conditions to land areas within 48 hours.

Previously, a system must have attained tropical depression status for watches and warnings to be issued or NHC advisories to be initiated. Now, a "Potential Tropical Cyclone" can trigger advisories or watches/warnings for land prior to the storm actually officially "forming," thereby allowing more preparation time for those who might be affected in its path (but only if within 48 hours of potential impact to land).

In addition, this will be the first year that Storm Surge Watches and Warnings will be officially issued for tropical cyclones that pose a threat to U.S. soil. This additional warning type will help coastal communities to know about, and respond to, significant water rises above normal tidal levels, another step in alerting impacted communities to the various threats of hurricanes, separate from just the wind speeds expected. To learn more about these, and other new products and services that will be available from the Hurricane Center this year, check out this link.

A potential storm surge flooding map for a sample hurricane making landfall along the upper Texas coast. This is just an example of the types of maps that will be available for any U.S. land-falling tropical system this year, developed by the Storm Surge unit of the National Hurricane Center. (NOAA/NHC)
For additional resources during the 2017 hurricane season, be sure to check out MWN's Tropical Page, which we do our best to keep up-to-date throughout the season! Also, StormWatch+ is being updated to include push alerts for Storm Surge Watches and Warnings for coastal areas (remember StormWatch+ works nationwide!), so you can rest assured that if you visit your favorite beach this year, you will receive all of the pertinent alerts from the Hurricane Center and local National Weather Service office while you are there (as long as you program the alerts for your vacation destination)!

Erik Proseus
MWN Meteorologist

Follow MWN on Facebook, Twitter, and Google+
Visit on the web or on your mobile phone.
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

Wednesday, June 14, 2017

A summer pattern yields chances of strong storms Thursday

Summer is here! I've seen several references the past couple of days to "sweating as soon as I step outside" and "rain falling while the sun is shining." Both are clearly indications that it is summer in the city! Here's another good sign of the same:

Visible satellite imagery at mid-day Wednesday, described below. (SSEC/RealEarth - data is preliminary and non-operational) Click here if image does not loop.
Visible satellite loops this afternoon from our amazing new GOES-16 satellite, which produces a high-resolution picture every 5 minutes, clearly shows abundant moisture in place (evidenced by a widespread cumulus cloud field across the region) and small showers popping up seemingly at random (the brighter, more "agitated" clouds). It looks a lot like a tropical airmass. These small downpours have been popping up the past 3 days as temperatures have reached near or just above 90° each day. In fact, combined with increasing humidity, today is the first day this year that the heat index has reached 100° and it was also the warmest day of the year at 92°! Hopefully those of you working outside have been taking it easy, with frequent breaks and plenty of water.


The scenario changes a bit tomorrow as storms will upstream of the Mid-South start infringing on the northern periphery of the high pressure system dominating our area tonight. As they do, outflow boundaries from said storm systems work their way south and encounter our warm, moist airmass. I expect that by Thursday morning we'll start seeing increasing thunderstorm chances. I currently have a 50/50 chance of storms in the Thursday forecast, including during the morning hours. Scattered storms could continue into the afternoon unless a more organized complex happens to move through during the morning, in which case it could scrub the instability from the atmosphere long enough to put a damper on afternoon storms. In any case, be prepared for more thunderstorms tomorrow than we have see previously this week.

The late afternoon run of the HRRR high-resolution model, showing "future radar" through 11am Thursday. It indicates the possibility of a few t'storms overnight (which I'm not sure will actually happen) and more organized chances by mid-morning. The HRRR can be a bit aggressive in its handling of precipitation, but gives us an idea of what to watch out for! (WxBell - click here if image does not loop)

Severe weather chances

As for severe weather, the Storm Prediction Center says we have a Slight Risk (category 2 of 5) of damaging wind in storms on Thursday. Any storms will also be capable of very heavy rain thanks to humidity thick enough to slice with a knife, and perhaps some small hail.

A Slight Risk (category 2/5) of severe weather is forecast Thursday by the Storm Prediction Center (SPC). 
The good news is that it appears that by Thursday evening most of the storm chances will have moved east and south of the metro, leaving humid but likely dry conditions in place for outdoor activities like Levitt Shell and the Memphis Redbirds.

This weekend

Heading into the weekend, I expect conditions not unlike what we've experienced to start the week. Hot and humid with a few afternoon and evening showers or thunderstorms. By Sunday evening, a "for real" cold front looks to make a run at us and move through overnight. This front will bring increased chances of rain and thunder late Sunday into early Monday, but then drier and less humid weather to start next week. Let's hope!

As always, get the latest weather information for Memphis via our social media feeds and MWN Forecast, which you can find online and in our apps. Also in the apps, local radar and current conditions, as well as our Twitter feed for the most recent updates. Be sure to check it out!

Erik Proseus
MWN Meteorologist

Follow MWN on Facebook, Twitter, and Google+
Visit on the web or on your mobile phone.
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

Saturday, June 10, 2017

Summer returns this week - heat, humidity, and PM rain chances

Following an early week cold front, an upper level trough over the eastern U.S. and high pressure at the surface provided for some very pleasant early-June conditions! Low dewpoints provided for cool mornings, warm but not humid afternoons and very pleasant evenings this week.

The upper level pattern on Thursday evening shows the reason for pleasant weather locally - a large trough that brought cooler conditions to the eastern U.S. However, a large ridge to the west was lurking. (PivotalWx.)

One by-product of the stable conditions provided by surface high pressure late this week has been a buildup of ozone at the low levels. While ozone high in the atmosphere is a good thing, near the surface, it means difficulty breathing for those with asthma and other lung-related diseases, as well as the very young and old, and those who do strenuous work outdoors during peak heating hours. The ozone buildup resulted in the Shelby County Health Department issuing a "Code Orange" advisory for Friday and Saturday, indicating that the air was unhealthy to breathe for the sensitive groups listed above. In addition, ozone rose to a high enough level that a "Code Red" advisory (one higher than Code Orange) was issued for a few hours late Friday afternoon and evening, indicating that the ozone levels could cause difficulty breathing for all groups of people. You can monitor air quality status by visiting or the MWN Air Quality/UV Forecast page.

As we head deeper into the weekend, the trough over the east is being replaced by a very strong upper level ridge, which extends south into the Mid-South. This will mean much warmer temperatures (records in fact) for the next few days over the Midwest and into the Northeast, while we start to see warmer temperatures and increasing humidity thanks to high pressure over the southeast U.S. that is bringing more moisture from the Gulf. While the weather remains dry and partly cloudy, southerly wind and the building high aloft will push temperatures into the upper 80s to near 90 this weekend. Sunday in particular will see dewpoints rise well into the 60s, which will make it feel more muggy.

By this weekend, the ridge described above has shifted east, bringing with it hot air and high pressure. Under the ridge, a developing upper level low in east TX will trigger this week's heating-of -the-day thunderstorm chances. (PivotalWx) 

For next week, unfortunately, an unsettled pattern will be in place, promoting daily chances of showers and thunderstorms, particularly in the afternoon and evening when heating is at a maximum. With the high pressure ridge aloft in place to our northeast, surface high pressure over the southeast, and an upper level low over Texas, temperatures will be in the upper 80s to near 90 during the afternoon when scattered showers and thunderstorms are expected and lows will remain above 70 degrees, making for muggy and warm mornings. The pattern looks to let up, if not break, by late in the week to early next weekend when a weak cold front moves into the region. Until then, plan to keep an umbrella handy each day and prepare for downpours where slow-moving cells form. Severe weather threats appear minimal as wind energy and upper level dynamics remains weak.

The MWN app featuring the human-generated Memphis forecast and our social media feeds will keep you on top of the latest on what areas can expect to be affected by storms on a daily basis! Pertinent links can be found below.

Erik Proseus
MWN Meteorologist

Follow MWN on Facebook, Twitter, and Google+
Visit on the web or on your mobile phone.
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

Wednesday, June 7, 2017

May 2017 Climate Data for Memphis, TN

May Recap

For the first time in a calendar year, May was actually cooler than average in Memphis, the first below normal monthly average since last May. The average first 90° day in Memphis is May 24, but the month came and went with the highest temperature being 89° reached twice at the end of the month. (Subsequently, Memphis reached 90° for the first time in 2017 on June 6.) High temperatures were just below average, but low temperatures were cooler than normal by almost 2 degrees, which included a couple days in the first week of the month that dropped into the mid 40s.

Precipitation-wise, May was overall drier than average with rainy systems moving through about once a week and dry periods between. Nearly half of the month's total precipitation fell in the last week or so, including heavy rain and severe thunderstorms on Memorial Day weekend (more below).

Despite the rainfall deficit, May saw a couple of episodes of severe weather. The first were reports of sporadic wind damage on May 5. The last, and much more significant, was a bow echo/derecho that moved through the metro during the late evening on May 27. This storm, which resulted in widespread wind damage and peak wind that topped out above 100 mph in a microburst downburst near Frayser and 60-80 mph over a large part of the Shelby and DeSoto County, resulted in the second largest loss of utility power by customers in MLGW history (188,000 customers, or 45% of the customer base of the utility). It took 10 days to fully restore all power with approximately 100 utility crews, sourced locally and hundreds of miles away, working 16 hour days.

May also marked the end of meteorological spring, the period from March through May, averaging 64.7° (1.8° above normal) with precipitation totaling 13.19", or 2.72" below average.

Memphis International Airport, Memphis, TN

Average temperature: 70.7 degrees (1.0 degrees below average)
Average high temperature: 80.8 degrees (0.4 degrees below average)
Average low temperature: 60.5 degrees (1.7 degrees below average)
Warmest temperature: 89 degrees (27th, 31st)
Coolest temperature: 47 degrees (4th, 6th)
Heating Degrees Days: 23 (4 above average)
Cooling Degree Days: 206 (20 below average)
Records set or tied: None
Comments: Year to date, the average temperature of 59.6° is 4.5° above normal and second warmest on record (2012).

Monthly total: 4.22" (1.03" below average)
Days with measurable precipitation: 13 (2.7 days above average)
Wettest 24-hour period: 1.17" (28th)
Snowfall: None
Records set or tied: None
Comments: Year to date, precipitation has totaled 18.85" or 78% of normal.

Peak wind: West/66 mph (27th)
Average wind: 8.6 mph
Average relative humidity: 68%
Average sky cover: 50%

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

Cirrus Weather Solutions /, Bartlett, TN

Average temperature: 72.1 degrees
Average high temperature: 82.7 degrees
Average low temperature: 60.7 degrees
Warmest temperature: 89.1 degrees (30th)
Coolest temperature: 47.9 degrees (7th)
Comments: Data only covers the period May 6-31.

Monthly total: 5.71" (automated rain gauge after May 5, prior rainfall recorded via manual gauge), 5.84" (manual CoCoRaHS rain gauge)
Days with measurable precipitation: 10
Wettest date: 1.11" (28th) (via automated gauge)
Snowfall: None
Comments: None

Peak wind: West/38 mph (27th)
Average relative humidity: 72%
Average barometric pressure: 29.92 in. Hg
Comments: Data only covers the period May 6-31.

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

MWN Forecast Accuracy

MWN average temperature error: 1.95 degrees
MWN forecast temperatures within 2 degrees of actual: 70%
MWN average dewpoint error: 2.65 degrees
MWN forecast dewpoints within 2 degrees of actual: 55%

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, Twitter, and Google+
Visit on the web or on your mobile phone.
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

Saturday, June 3, 2017

Unsettled weather through Monday, then June perfection!

The summer-like humidity has made a return to the metro the past few days along with a smattering of showers and thunderstorms. However the additional cloud cover has extended our streak without 90-degree temperatures and it appears that will continue for the foreseeable future! A cold front ushers in pleasant temperatures and much lower humidity for a good part of the upcoming work week.

Starting with the next couple of days, the very moist atmosphere from the surface up, along with a fairly non-descript upper level pattern and lack of meaningful surface fronts, means we'll be dealing with hit and miss showers and thunderstorms through the evening and into early Sunday. The lack of wind aloft means the severe threat is low, but also means that anything that forms won't move very fast, so some spots could get decent rain totals from any shower or thunderstorm the next day or so.

The surface map at mid-day Sunday shows a stalled out weak front south of the area with high rain chances covering the metro, and large parts of the southeast in fact. (NOAA)

As we head into the day Sunday, rain chances increase as even more moisture moves north into the region and an upper level trough approaches from the west. All outdoor activities on Sunday need to have a rain plan. I don't expect a washout all day, but there is currently no "window" when rain is not possible.

The trend continues into Sunday night, though with the setting sun, coverage of showers and storms will be a bit less, but still scattered activity is worth keeping in the forecast. Finally, by Monday, a cold front pushes into the region from the northwest as the upper trough also begins to shift east. Look for continued rain and thunderstorm chances until probably late afternoon when the front moves through. By the evening, well be drying out though it will take until Tuesday to begin feeling the drier, less humid air.

By Monday evening, a pre-frontal trough should push rain chances to our south as the front ushering in drier air moves in from the north, leaving pleasant conditions in it's wake for the mid/end of the week. (NOAA)

Tuesday through Friday looks very nice with abundant sunshine, low humidity on north wind through at least Thursday, and temperatures below normal. A great week to be playing in the FedEx St. Jude Golf tournament if you're a golfer not used to southern humidity! Look for highs in the lower to mid 80s, lows in the lower 60s to maybe the upper 50s in rural areas by mid-week, and dewpoints in the 50s. Perfection for June!

By next weekend, southerly wind returns so humidity and temperatures will return to near normal, but dry weather looks to continue to end out the week. Early indications point to above normal temperatures returning by the second week of June, so perhaps we'll see the 90s that week! Click here for the complete forecast.

Be sure to download the mobile app to keep an eye over the horizon the next few days, so you aren't caught in a sudden rain storm, as well as get the latest forecast information!

Erik Proseus
MWN Meteorologist

Follow MWN on Facebook, Twitter, and Google+
Visit on the web or on your mobile phone.
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

Friday, June 2, 2017

Behind-the-scenes: providing weather support to Memphis in May was proud to be the official weather partner of Memphis in May for the third consecutive year! That means that we had a presence on-site anytime the gates were open to the public, as well as provided ancillary forecasting services leading up to all events. It's time-consuming, but very rewarding to be part of an awesome team of staff and volunteers that make Memphis in May a huge success year in and year out! While on-site, our job is to keep a close eye on both current weather conditions and the short-term forecast for the park and the area surrounding it and advise festival officials on any potentially hazardous conditions. These include moderate to heavy rain, lightning, strong wind, hail, and even heat indices and river levels! Communication is accomplished by two-way radio, text message or phone call, and of course face-to-face briefings.

Weather is always tricky for outdoor festivals. If you haven't been in the Memphis area long, May is peak severe weather season in the Mid-South, a fairly wet month in general, and can also feature spells of hot and humid conditions as summer draws closer. This year, we were actually very fortunate in most respects down on the river. Beale Street Music Fest saw rain early on the first day (Friday), but dry conditions by the time gates opened and a pleasant weekend. Strong wind was an issue on Friday and it remained breezy Saturday, otherwise a nice weekend!

Looking north over Tom Lee Park towards downtown from Ashburn-Coppick Park.
The World Championship Barbecue Cooking Contest overall was not bad weather-wise either. Despite seasonally warm and humid conditions, Wednesday night and Thursday were dry. Unfortunately, luck would run out on Friday afternoon as our forecast called for scattered thunderstorms across the metro, which materialized as expected. Out of an abundance of caution and for everyone's safety, the park was evacuated once lightning entered the established safety zone around the park. With roughly 250 metal structures in Tom Lee Park, the area is basically packed with lightning rods.

As storms repeatedly fired just down river from the park and move towards downtown, the park remained closed until the threat diminished, despite no lightning or heavy rain in the park itself. Saturday's forecast looked just as foreboding as Friday, however the barbecue gods smiled down in the form of an early morning outflow boundary that brought morning showers (which settled the dust nicely) and cooler, stable air that resulted in ideal conditions for the afternoon and evening hours. Certainly, the best possible option considering the bad news that computer models were painting for the day!

901Fest featured a great day on the river with luck again on the side of the festival as a severe wind storm that was forecast to arrive that evening hit about an hour after gates closed after a spectacular fireworks display. We are all familiar with the effects of that storm, which produced wind estimated at 70 mph at Tom Lee Park.

The memorial obelisk toppled and shattered by severe wind Saturday night, May 27, just an hour after Tom Lee Park closed following 901Fest. (Photo credit: Joe Birch)
Despite rain and thunder continuing much of the night, the rain let up around the start time for the Great American River Race. The race was delayed for a short time due to overnight cleanup efforts that were required, but despite some early showers, weather cooperated for the majority of the event. Fortunately, the major storms snuck in between 901Fest and the race the next morning! Another stroke of luck.

Having worked "behind-the-scenes" for three Memphis in May festivals now, I have to say that the festival staff is unbelievably great to work with. They are a professional, hard-working, and dedicated group of people whose main goals are the safety and comfort of patrons and ensuring that everything operationally flows as smoothly as possible. They want everyone to have a great time and remain safe - the only way that the festival can remain successful each year. All decisions are made with that in mind. The logistics involved are mind-boggling and knowing that a lot of the 'hands-on' work is done by a small army of dedicated volunteers is even more impressive.

The setup for the official meteorologist of Memphis in May. 
Park evacuations are not taken lightly and only occur when the safety of the patrons, volunteers, and others in the park is threatened. Just because "it isn't even raining at the park" doesn't mean that there is not a threat to safety (i.e., lightning doesn't just occur where rain is falling). It's also a significant challenge on many fronts to clear the park of patrons. Doing so multiple times in a short span is even more complicating. It just makes common sense that the "compliance rate" on subsequent evacuations would drop, thereby raising the risk level for everyone.

Serving as the staff meteorologist means that I provide the weather-related data necessary to allow festival staff to make an informed decision on how to respond. As mentioned, the decisions are not made lightly and all factors are considered. The situation is re-evaluated routinely so as to allow normal operations to resume as soon as the threat has abated. I am honored to be a part of the Memphis in May team and strive to provide the most accurate current weather information and forecasts possible so that the best decisions can be made in line with the goals stated above.

Erik Proseus
MWN Meteorologist

Follow MWN on Facebook, Twitter, and Google+
Visit on the web or on your mobile phone.
Download our iPhone or Android apps, featuring StormWatch+ severe weather alerts!

In charge of an outdoor event and interested in having a dedicated meteorologist monitoring the weather specifically for your event? Contact us!
MWN is a NOAA Weather Ready Nation Ambassador Meteorologist Erik Proseus is an NWA Digital Seal Holder

Monday, May 29, 2017

Memphis in May-hem: 105 mph microburst damage in Frayser

WOW, that was quite a storm!

Memphis Light Gas and Water reports that, at peak, 188,000 customers were without power at some point after the monstrosity hit on Saturday night, darkening large portions of Shelby County. High wind also affected portions of Tipton and DeSoto Counties.

There will be more time to recap the entire event later, but in this post I'd like to focus on one particular area of damage where the highest wind likely occurred. The damage occurred at and around the Memphis Police Department Training Academy near the intersection of Highway 51 and North Watkins in Frayser. This is where the severe storm moving southeast intersected an outflow boundary moving southwest from storms that were occurring north of the metro.

It is typical for colliding outflow boundaries in an unstable airmass to produce new storms. We see it all the time. In this case, when pre-existing storms along one outflow boundary encountered the other outflow, mayhem resulted. What would have been a more "typical" severe wind event became a more rare one when explosive development produced a very strong microburst that landed on the area in question and spread out to the east and south, pushed by storms moving at near highway speeds. It is estimated from these damage photos, particularly the swath of trees that collapsed or were uprooted in the first image below, that wind speeds were near or exceeded 100 mph. This is corroborated by radar data that indicates wind of more than 100 mph just 1000' above ground in the hardest hit areas, which was likely forced to the ground by the microburst near the MPD Training Academy.

Wind that spread out from that area across north Memphis and south into downtown and midtown was likely in the 60-80 mph range. Aerial photo and radar documentation is shown below.

Aerial photo showing the classic ground signature of a very strong microburst, with a stand of trees collapsing under the weight of approximately 100 mph wind. You'll notice they all fell in roughly the same direction. Photo taken over US 51, northeast of  North Watkins.

Another angle on the above photo, annotated to show the path of the wind as it blew from northwest to southeast, fanning out slightly from a point where the wind came crashing down from above and spreading out in the path the storm was taking.

An aerial shot of part of the MPD Training Academy showing damage to structures and uprooting of large trees.

Additional damage from overhead in the area of US 51 and North Watkins.

Another view of the same damage shown in the image above.

One more photo, taken west of the MPD Academy showing trees uprooted and additional damage.

Wind velocity data from the Terminal Doppler Weather Radar (TDWR) south of Memphis International Airport detected wind speeds greater than 100 mph just under 1,000' above the US 51/Watkins area at 10:51pm. A rush of air loaded with very heavy precipitation likely resulted in that wind being forced to the surface in the form of a microburst, causing the damage seen above. Image credit: Kevin Terry, who was thinking fast enough to archive the event as it was occurring!
Full credit and many thanks to Casey Kirby of Memphis Police Department's Air Support Division for providing the full set of aerial photos exclusively to MWN!

The National Weather Service in Memphis has posted this preliminary assessment of the storm:

I'd also like to use this venue to re-post what I wrote on Facebook Sunday night after having a chance to wrap my head around the events of the night before:

It's easy to get frustrated, but the guys and gals at MLGW are working hard on their holiday weekend to try and make your day a little brighter (literally). Personally, I greatly appreciate their hard work and sacrifice, as well as all those in public service who are working extra this weekend, even though I don't have power yet either! 
Also, shout-out to all our colleagues in the weather enterprise, from SPC to US National Weather Service Memphis Tennessee to the TV mets and others, who did a phenomenal job leading up to, during, and after "Memphis in Mayhem!" 
Finally, I owe a huge debt of gratitude to MWN intern Meteorologist Alex Herbst who covered 95% of last night's event on my, and your, behalf. Between my working weather for 901Fest, racing home to beat the storm, then promptly losing electricity and most cell coverage when it hit, without Alex being on top of things the entire time, this feed would've been largely silent. I and MWN followers alike thank you for your dedicated service, Alex. You have a bright future ahead of you, at much larger endeavors than this one! 
Everyone stay safe, be grateful, and thank a utility worker this week! And don't forget it's Memorial Day weekend - take a minute to remember those who paid the ultimate sacrifice so that we can moan and groan over our #FirstWorldProblems
I appreciate each and every one of you who choose to follow MWN and tell others about this service...
Thanks again to all of you who have offered your appreciation for our presence before, during, and after the storm. Those comments keep us going!  We'll have a more detailed recap in the days ahead.  Be sure to follow us on social media at the links below for regular updates following this storm and updates on current weather in the Memphis area!

Best to you all on this Memorial Day,

Erik Proseus
MWN Meteorologist

Follow MWN on Facebook, Twitter, and Google+
Visit on the web or on your mobile phone.
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