Friday, April 27, 2012

One-year anniversary of the Super Outbreak of 2011

Today marks the one year anniversary of the 2011 "Super Outbreak" - the largest outbreak of tornadoes since April 3-4, 1974.  While the Memphis area wasn't directly affected by any of the tornadoes that day, April 27 was the last in a 3-day onslaught of severe weather that affected the southeastern U.S.  (Actually, severe weather continued to a much lesser extent into the Mid-Atlantic on the 28th as well.)  During that string of days, the metro received severe weather in the form of flooding, large hail, wind damage, and a couple of rotating supercells that prompted tornado warnings but no touchdowns.

We'll take the opportunity to recap exactly what happened those three days, focusing especially on April 27 and the Smithville, MS tornado - the only tornado to affect the NWS-Memphis warning area.  We'll include lots of links that have exceptional information on the outbreak as well.  The first graphic below is the Storm Prediction Center's long-range outlook issued on April 23.  Even that early, there was a sense that this period could bring a severe weather outbreak with long-track and violent tornadoes.

SPC's long-range outlook issued on April 23 indicated potential severe weather on April 26-27

A summary of all severe weather reports from April 25-27 received at the NWS-Memphis office

April 25, 2011

The day started with a moderate risk of severe weather over southwest TN, northwest MS, and southern AR. Multiple waves of storms, one at mid-day that prompted Tornado Warnings in the metro and another late in the evening that formed into a squall line, brought many reports of severe weather.  There were no confirmed tornado touchdowns in the metro, however a couple of funnel clouds were reported with the mid-day storms.  The evening squall line hit between 10-11pm and caused some straight-line wind damage. Much of the day's severe weather occurred in the ArkLaTex near where low pressure was moving along a stationary front that was draped across the southern Plains into the Mid-Mississippi Valley, while wind reports also lined up from NE Arkansas into central KY.

April 25 morning SPC outlook overlaid by preliminary storm reports
Storm reports received by NWS-Memphis on April 25 - not all were confirmed

April 26, 2011

The day started with another moderate risk of severe weather over the entire Mid-South area, but by mid-morning the metro area was upgraded to a rare “high” risk signaling the potential for a major severe weather and tornado outbreak. By mid-afternoon, supercell storms exploded over central Arkansas and moved northeast toward the metro, prompting numerous Tornado Warnings through the evening hours. Though no tornadoes were confirmed locally, there were many areas of straight-line wind damage and hail, along with funnel clouds. As the storms began to congeal into several storm clusters and squall lines that continued into the overnight hours, widespread flash flooding began to develop. The majority of the tornadoes on this day occurred in northern Louisiana near a secondary area of low pressure.

April 26 morning SPC outlook overlaid by preliminary storm reports

Storm reports received by NWS-Memphis on April 26 - not all were confirmed 

April 27, 2011

The most prolific day of the outbreak began with an initial round of tornadoes that caused damage and fatalities in Mississippi and Alabama during the early morning. Meanwhile, in the metro, the repeated showers and thunderstorms continued to exacerbate flooding conditions for the next several hours. Another rare high risk area had been issued, this time centered on northern Alabama, while the metro was within the slight to moderate category. Clearing skies during the late morning to early afternoon allowed an already volatile airmass over the entire Southeast to become even more dangerous and soon new supercell storms were exploding, first in MS and then AL. Many of these cells would grow into monsters, producing some of the most violent tornadoes of recent memory, and tornadoes would continue well into the night across Georgia, east Tennessee, and even up the Appalachian chain as far north as New York, leaving many towns devastated and many lives lost. By great fortune, the Memphis metro escaped this most violent round of weather almost entirely, with only a few storms with isolated hail, though tornadoes did touch down as close as Jonesboro, AR and Oxford, MS. A loop of regional radar for the entire day (caution: large file) assembled by UA-Huntsville grad student Cody Kirkpatrick can be viewed here.

April 27 morning SPC outlook overlaid by preliminary storm reports
"Rotation tracks" for April 27, 2011 - tracks of storms that were rotating (not necessarily producing tornadoes)

Storm reports received by NWS-Memphis on April 27 - not all were confirmed 
The most devastating damage closest to Memphis on the 27th was in Smithville, MS, about 130 miles southeast of the Bluff City. At 3:45 in the afternoon, and for the first time since 1966, an EF-5 tornado struck the state of Mississippi and literally leveled this small town. According to the National Weather Service, peak wind reached 205 mph and the tornado width in the Smithville area was 1/2 mile. The tornado's path started just southwest of Smithville and continued for over 35 miles into northwest Alabama.  A total of 17 persons lost their lives in Smithville with an estimated 40 injured. The post office, police station, and water and sewage systems were destroyed and several other businesses, mostly on Highway 25, or Main Street, were severely damaged.

The following pictures were taken by MWN meteorologist Erik Proseus 3 months after the Smithville tornado, following the debris clean-up effort but before much re-building began.

In all, the following sobering statistics were collected (all stats from NOAA):
  • April 2011 tornado count: 758 (most active month ever, beating May 2004 [542])
  • More than 200 tornadoes in 5 states from April 25-28
  • Fifteen violent (EF-4 or EF-5) tornadoes
  • Eight tornadoes with path lengths of 50 miles or longer
  • Two tornadoes that each killed 60 or more
  • 321 people killed from April 25-28, 316 on April 27 (4th most in one day), and 360 for the month
  • Of the 316 deaths on April 27: 31 were in MS, 234 in AL, 32 in TN, 15 in GA, and 4 in VA
  • More than 2,400 injuries
  • Total damage: over $4.2 billion
  • All fatalities occurred in areas where tornado warnings were in effect
  • Mean tornado warning lead time (from when tornado warning was issued until tornado touched down) was 22.1 minutes
Links from NOAA and the National Weather Service:
Links from other sources:
There are many other accounts, stories, pictures, video and reflections on the web.  These are just a few of the highlights.  As we remember those that perished, their loved ones, and the countless others whose lives were affected in many ways, MWN encourages you to use this time to re-focus on preparedness.  While this particular event may have been a once-in-a-lifetime or generational outbreak, it doesn't take 10 or 100 or more tornadoes to affect you.  It only takes one, in the wrong place at the wrong time.

Memphis is a part of what is called "Dixie Alley" - the area of the country that is the deadliest during severe weather.  Know your plan, practice it, and share it with family.  Have a plan for home, work, school, or wherever else you frequent, including on the road.  Include in your plans multiple ways of receiving severe weather information, especially at night or away from home.  The MWN Storm Center has more information and safety tips that you should review with your family.  Our prayer is that everyone is properly prepared for severe weather and that nothing remotely close to April 27th occurs again in our lifetimes.

--Erik Proseus/Kevin Terry

For information on personalized severe weather alerts in the palm of your hand, check out StormWatch+.

For weather information for Memphis and the Mid-South, where and when you need it, visit on the web, on your mobile phone, download our iPhone or Android apps, or visit us on Facebook or Twitter.

Wednesday, April 25, 2012

Warm temperatures are back, but what about rain chances?

Welcome to MWN Blog post #950! 

After a stretch of below normal temperatures for the last few days in the Mid-South, the warmth came back in a hurry over the last 24 hours as strong and gusty southwest winds sent the numbers back above the 80 degree mark, with much higher humidity levels returning as well.  It looks as if the warmer weather will be sticking around a while, but is there any significant rainfall chances in the offing as the Memphis area now approaches an 8-inch rainfall deficit for the year?

While a few weak systems have brought isolated to scattered rainfall to the area over the last several weeks, the last significant and widespread rainfall (greater than an inch) was way back on March 16! This pattern is in sharp contrast to one year ago this week, as a multi-day historic severe weather outbreak and flooding event began to unfold across the Mississippi Valley and Southeast U.S.

Looking ahead, a cold front will be approaching from the north on Thursday. Unfortunately, the cold front looks to stall just north of the area, meaning the best rain chances may again avoid the metro area. Nevertheless, as the front makes it closest approach late Thursday afternoon through Thursday night, a few thunderstorms may develop and drift into parts of the area, with those north of I-40 having the best risk of seeing rain. Still, significant and widespread rainfall is not expected during this period.

WRF Model for Thursday evening. Scattered t'storms will likely be ongoing near front, with best chances north of Memphis metro.
This front will meander north of the area through Friday and Saturday, likely keeping conditions dry here though an isolated risk for a shower or storm remains. The front will make another push into the area on Sunday, and models are showing a bit more progress on this attempt, meaning our best rain chances arrive then with scattered showers and thunderstorms possible. However, it again doesn’t appear to be shaping up to be an event that will put a major dent in the growing rainfall deficit.

NWS weather forecast map for Sunday morning, with near-stationary front close to metro, bringing our best rain chances.
Finally, in a reversal from thinking a few days ago, this front then looks to lift back north of the region at the start of next week. This means a cooldown earlier thought possible appears off the table, with temperatures for the next seven days reaching the 80s and mild overnights expected as well. More scattered rain chances may enter the picture around next Tuesday and Wednesday, but we may be waiting for next widespread one-inch or greater rainfall event for a while longer.

Stay with MemphisWeather.Net for the very latest on rain chances in the days ahead. You can find the full and updated forecast details on MWN's forecast page.

--Kevin Terry, MemphisWeather.Net

For weather information for Memphis and the Mid-South, where and when you need it, visit on the web, on your mobile phone, download our iPhone or Android apps, or visit us on Facebook or Twitter.

Thursday, April 19, 2012

Outdoor warning sirens - part 3: the warning process and future of severe weather warning systems

This part of the series is a long time coming, but here it is!

In the first two posts of this series on outdoor warning sirens, we examined the role of the Emergency Management Agency during severe weather (including the activation of warning sirens) and the role of outdoor warning sirens themselves, which was to warn people who were outdoors of adverse weather.  In this post, the final in our 3-part series, we take a look at the future with regards to dissemination of severe weather warnings.

Background on the current warning process

In 2007, the NWS changed policy with regards to issuance of Tornado, Severe Thunderstorm, and Flash Flood Warnings to one based on the actual area threatened versus alerting entire counties. The NWS draws storm-based warnings, or "polygons," to highlight the expected path of the storm, with little regard for political boundaries (see the example from March 15, 2012 below).  This policy change had several intentions, one of which was to limit the area being warned, thereby hopefully reducing the perceived false alarm rate created by warning an area that the NWS is fairly certain will not be affected.

A Severe Thunderstorm Warning polygon ("storm-based warning") that identifies a small section of eastern Fayette Co. and a larger portion of Hardeman Co. as having a threat of large hail and damaging wind.  There is no threat of severe weather in Moscow or Middleton, even though there is in other parts of their counties.
Unfortunately, some 5 years after changing to storm-based warnings, NOAA Weather Radios, many outdoor warning siren systems, and even some local broadcaster's warning plotting software - the top 3 ways that citizens get severe weather information - still alert based on the COUNTIES affected, rather than the actual AREA affected. In the example above, the storms are moving northeast and, based on the yellow polygon, there is no threat to Moscow, Macon, or Middleton.  However, for those with Weather Radios in those locations, the alert tone would sound for all three towns.

Another example is below - this one even closer to home for many of you.  A Tornado Warning was issued shortly after 10pm on January 22, 2012 for southern Shelby County and northern DeSoto County. A squall line (not depicted) was approaching the river and a possible tornado was detected in the portion of the line that would affect the areas inside the red box.  Sirens sounded and weather radios alerted across Shelby County (excluding DeSoto County for this example).  Except for the southern part of the city and the eastern suburbs, there was no imminent threat from a tornado.  It could be said that although the NWS intended to only warn 242 sq. mi. of Shelby County, the sirens and weather radios ended up warning 754.5 sq. mi. or more than three times the area.  (In this example, there was sporadic wind damage reported, including a 105 mph gust that lifted a large roof from a commercial structure, all within the confines of the warned area.)

Outdoor warning sirens and the polygon warning

Now that the warning process is better defined, what is the future of weather warning dissemination?  Perhaps from these examples you can already start to see it: storm-based warning dissemination, rather than county-based.  While NOAA Weather Radio and some progressive county governments are beginning to make strides in this area, it will be some time before these systems are fully taking advantage of the benefits of the current storm-based warning program.

In Shelby County, TN, EMA Director Bob Nations indicates that they are "taking a serious look at new technology" and "exploring all the options" as they work towards system upgrades mandated by the Federal Communications Commission (FCC).  The FCC program, called "narrowbanding," opens up additional radio frequencies by essentially squeezing all of the current frequencies closer together in the radio spectrum. Narrowbanding will require a significant purchase of new hardware or upgrades to current infrastructure to meet a federally mandated January 1, 2013 deadline.  How does this affect the siren program?  The sirens are activated by radio frequencies that will change under the  narrowbanding program.

Part of the infrastructure upgrade will include new siren controllers on 111 warning sirens under the purview of the City of Memphis, which will be replaced with equipment that allows individual sirens to be sounded should a change in siren policy be made.  In addition to hardware, new storm-based warning software would also be required to activate individual, or banks, of sirens.  Nations is quick to point out that, while a change to siren policy might be possible with the new infrastructure, there would have to be agreement from policymakers who may not be willing to take the risk of storms remaining within the warned area.  Any changes to public policy will require the approval of those who write the policy.  Due to potential liability issues, any change to the current methodology of warning the entire county "would have to work every time," according to Nations.

So while (and until) the infrastructure upgrade and public policy process plays out (should there be a decision to move in that direction), citizens are strongly encouraged to consider all means of protecting themselves in the event of severe weather.  As discussed in part 2 of this blog series, outdoor warning sirens are not the "end all, be all" and are simply not designed to alert you if you are anywhere but outdoors, no matter what strategy is employed to sound them.

The future of weather warning systems

The best solution is that we move to faster-pace, more technological solutions that are available today. With the preponderance of smartphones and the capability of these devices to use GPS to determine your precise location,  it's no wonder their worth in targeted warning information is being utilized more and more.  There are several mobile apps that are available to warn you, in your specific location, to the threat of impending weather.  Of course, we highly recommend ours, but any will likely fit the bill depending on the features you are looking for.

The app for Android and iPhone includes StormWatch+, a push notification system that will warn the user of severe weather watches and warnings that are issued for 2 pinpoint locations of their choosing.  It includes an audio alert that is loud enough to wake you up at night provided the phone is nearby and not silenced.  There are other services available as well, including some phone services that will call your registered numbers should severe weather threaten.

It is vitally important that you have multiple ways of receiving severe weather information, for your location if possible (or for your county if not), that will alert you at any time of day or night.  Outdoor sirens are one way, but they CANNOT be the only way.  NOAA Weather Radio is highly recommended as the baseline, but for even more pinpoint warnings that take advantage of the storm-based warnings issued by the NWS, you should add another service like StormWatch+ to your severe weather toolkit.  Severe weather can strike in any month and at any time of the day in the Mid-South.  "An ounce of prevention is worth a pound of cure."

For weather information for Memphis and the Mid-South, where and when you need it, visit on the web, on your mobile phone, download our iPhone or Android apps, or follow us on Facebook or Twitter.

Sunday, April 15, 2012

Mid-South storm chasers injured while providing aid

Storm chasers Brandon Bridges (standing) and Vincent Webb after a scary interstate accident.
Photo courtesy Vincent Webb.
On their way back from a day of chasing in the Plains, in which they videoed at least one tornadic storm, Mid-South storm chasers Vincent Webb and Brandon Bridges were struck by a vehicle on I-40 near Fort Smith, AR on Sunday afternoon, April 15.

Webb (@msstormchasing on Twitter) and Bridges (@bbridges18) were traveling in Webb's storm chase vehicle on I-40 with Jeremy Johnson (@memphisjdj) and Nick Hellums (@midsouthchasers) on their way back to the Memphis area and reached a stretch of I-40 that had experienced showers. They encountered a rollover accident on the opposite site of the interstate and pulled over to offer assistance. After crossing the interstate by foot, Bridges and Webb were helping the motorist in the rollover vehicle when another vehicle hydroplaned and careened towards the scene. Both Bridges and Webb tried to get out of the way, but were struck by the approaching vehicle and thrown several feet into the grass along the interstate.  Johnson and Hellums were bystanders and not injured.  Both Webb and Bridges were transported to the hospital for precautionary purposes with minor injuries.  Their chase vehicle, owned by Webb, was on the opposite side of the interstate and not involved.

I spoke with Bridges by phone Sunday afternoon and he indicated that their injuries were minor and he hoped that they would be back in the Memphis area very late tonight.

Following the recent death of storm chaser Andy Gabrielson, we are again reminded that the storms themselves are only one threat chasers face as they attempt to provide a service to the community and the National Weather Service by providing reports of severe weather that aid in the protection of life and property. Frequently, as in this case, they are "first responders" on the scene after disaster strikes and are always ready to call off the chase to provide assistance wherever required. Please keep all of these chasers in your prayers.

For weather information for Memphis and the Mid-South, where and when you need it, visit on the web, on your mobile phone, download our iPhone or Android apps, or visit us on Facebook or Twitter.

UPDATED: Details on potential severe weather threat overnight


Following yesterday's Central Plains severe weather outbreak, Mid-Southerners are a little uneasy about the threat here as the same storm system makes it's way through the region tonight.  Fortunately for us, the impressive dynamics that spawned nearly 100 tornado reports (at last count, that number will likely fall a little as reports are verified) on Saturday are much weaker and will be well-removed from this portion of the country as the system moves east.  However, a potent cold front will still push a line of storms through the region during the overnight hours.
Reports of severe weather in the Plains on Saturday, April 14, 2012
The Storm Prediction Center has placed western sections of the Mid-South under a Slight Risk for severe weather this evening and tonight (updated graphic below).  This is due to strong to severe thunderstorms, some with damaging wind and hail threats, that have fired ahead of the cold front over western MO, eastern OK, western AR, and far northeast TX.  As this system moves east, this evening, storms are likely to coalesce into a squall line as they move through central and eastern AR.  As they do, however, the atmosphere they are moving into is not quite as unstable.  Part of this lessening in instability is due to timing - the storms will be moving into the area after peak heating when instability typically wanes.  However, because they will build up a head of steam moving across AR, some of the storms will still have the potential to bring strong to severe straight line wind (50-60 mph) and small hail.  And, as we typically warn in these scenarios, spin-ups within the squall line have the potential to drop brief tornadoes, though the threat of tornadic damage is not high.
Updated 8pm severe weather outlook from SPC showing a slight risk for the metro tonight
As for timing, models indicate storms could initially arrive in the metro anytime between 9pm and 1am and would last on the order of 2-4 hours.  MWN is forecasting the storms to arrive during that window (or 11pm to midnight) and last for 3-4 hours projected from the current location and movement of the line in Arkansas.  The line is generally following the lead of the high resolution model data from early this afternoon.

Hi-res computer model (HRRR) output showing "forecast radar" as of midnight CDT
In summary, Memphis metro residents should be prepared for the possibility of a narrow line of storms moving through the metro around 11pm to midnight bringing the possibility of strong straight-line wind and an isolated threat of hail or an isolated tornado. The line will be followed by general thunderstorm activity that will last into the wee hours Monday morning.  All of this activity will be out of the area prior to the Monday morning rush hour.  Only a few lingering showers are possible early Monday morning.

Follow us on Facebook and Twitter (links below) for the latest on the severe weather threat, as well as complete nowcasting coverage as the line moves through.

For weather information for Memphis and the Mid-South, where and when you need it, visit on the web, on your mobile phone, download our iPhone or Android apps, or visit us on Facebook or Twitter.

Saturday, April 14, 2012

Central Plains tornado outbreak today, then storms march east towards the Mid-South

Tornado Alley will be given a chance to live up to it's name today as the Storm Prediction Center has placed a very large area from Nebraska to Oklahoma under a High Risk for severe thunderstorms, predicting a "significant outbreak of strong to violent, long-track tornadoes" for the region (see first graphic below).

Several notable actions were taken in preparation for this event, including a very rare Day 3 Moderate Risk issued Thursday, a Day 2 High Risk issued yesterday (only once has this ever been done before), a Public Severe Weather Outlook from SPC (issued only when an outbreak is expected), and a 45% tornado risk area for parts of NE and KS (see second graphic below), meaning there is nearly a 1-in-2 chance of a tornado within 25 miles of any point within that area.  The greatest tornado risk is this afternoon and evening, followed by the formation of a squall line over eastern KS and into OK this evening into the overnight hours.

A very large high risk area has been issued for the Plains in advance of an expected outbreak of violent tornadoes
Tornado risk for today - percent chance of a tornado within 25 miles of a point
On Sunday, a slow-moving squall line is expected to move east from the Plains as a Pacific cold front begins pushing east.  Low pressure moving out of the Central Rockies that is providing the necessary low-level wind shear across the Plains for tornadoes today will move northeast into the western Great Lakes Sunday, so a significant tornado threat is not expected further south, thus wind and possibly some hail will be the primary threats during the day from the Mid-Mississippi Valley into northeast Texas (see Day 2 severe risk graphic below).

You'll notice that Sunday's slight risk area extends to just west of the metro.  This is because the line of storms is expected to move east of the slight risk after midnight, when atmospheric conditions are least conducive for severe weather.  I expect the line to weaken as it approaches the river after dark Sunday night and move through the metro before dawn Monday morning as a "general" line of thunderstorms.  A remnant wind threat is still possible with the line, but the chance of severe weather is relatively low.

The bottom line: while tornadic storms are likely in the Plains today, the storms become more of a wind producer as they approach the Mid-South Sunday and will weaken further as they enter the metro area early Sunday.  Until then, we'll experience warm, humid, and windy springtime conditions, followed by more typical springlike weather in the wake of the front and for the first half of next week.

For weather information for Memphis and the Mid-South, where and when you need it, visit on the web, on your mobile phone, download our iPhone or Android apps, or visit us on Facebook or Twitter.

Tuesday, April 10, 2012

Cool temps make a brief visit, then focus shifts to next rain chances

With the passage of a cold front this morning, parts of the metro area saw a few quick-hitting showers to start the day. As the system moved to our south this afternoon, mostly sunny skies returned to the area,  but the biggest impact of this front’s passage will be felt beginning tonight and continuing through Thursday as below-normal temperatures make an unusual stop in the Mid-South, at least considering the past few months!

With Canadian high pressure settling in from the north, the cooler temperatures will begin filtering in to the area under northeast winds this evening. Expect numbers in the mid 40s across most of the metro when you wake up Wednesday morning, with temperatures only rising into the mid 60s during the afternoon even under sunny skies.

However, as the high pressure area makes it closest approach to the region late Wednesday, and winds lighten, the setup will be in place for the coolest night in the Mid-South in about a month, as readings in the city of Memphis drop into the lower 40s by Thursday morning. Outlying areas of the metro will likely dip into the upper 30s. At this time, the threat for any frost looks to remain mostly north and east of the metro area with freezing conditions possible closer to the Tennessee River.

NWS forecast for Thursday morning, as high pressure makes closest approach to the Mid-South, in southern Indiana
As the high slides to the east of the Mid-South during the day Thursday, southerly wind flow will begin to return to the area, marking the start of a warming trend that will have temperatures back into the 80s by the weekend. Meanwhile, a series of storm systems developing over the Plains states will likely bring multiple rounds of severe weather to that area. Here in the Mid-South, though slight chances for rain and thunder may begin as early as Friday, it appears most of this activity will stay west of our area until at least Monday afternoon.

By that time, a slow moving cold front will finally begin to gain some momentum and head east toward the Mid-South, increasing our rain and thunderstorm chances for Monday night into Tuesday. It’s unclear at this point whether this system will bring any threat of severe weather to our area, but confidence is starting to increase in this period being the most active over the next week. More details will emerge as the week progresses on this system’s impacts to the Mid-South.

GFS model forecast for Tuesday morning, April 17th, depicting cold front just west of the region 
Stay with MemphisWeather.Net for the very latest on the upcoming cool temperatures as well as our next significant rain chances. For the latest complete forecast, be sure to visit the MWN forecast page

--Kevin Terry, MemphisWeather.Net

For weather information for Memphis and the Mid-South, where and when you need it, visit on the web, on your mobile phone, download our iPhone or Android apps, or visit us on Facebook or Twitter.

Thursday, April 5, 2012

Recap of today's thunderstorms and a pleasant pattern ahead!

We began the day in a Slight Risk area for the possibility of some severe weather thanks to a potent upper-level low pressure system that was traverse the metro this afternoon. During this time of year, with some heating ahead of one of these lows, it is possible to get large hail in any thunderstorms that form thanks to the cold air aloft and lower freezing levels. Instead of large hail, some areas saw buckets of small hail!  Below are a couple of pictures from Summer Avenue near White Station around 10:10am where so much hail fell it covered the ground!

Small hail covered the ground on Summer and White Station around 10am. Photo courtesy @bengalkatlady (Twitter)
A couple of hours later, this was the scene as the hail was washed into a low lying area in the parking lot:
Remnants of the hail 30 minutes later. Photo courtesy @bengalkatlady (Twitter)
This storm developed very quickly over the city and moved slowly east. Below is a sequence of cross-sections of the storm put together by Weather Channel meteorologist Stu Ostro.  Note the cell on the right size of the storm, which went from a small green dot in the top frame to a large red core held aloft by a developing updraft in the middle frame, and finally collapsed to the ground as pinks and reds (hail) in the bottom frame.
Time sequence cross-sections of the Memphis hail storm. Courtesy Stu Ostro. 
From the south (backside) of these storms, mammatus clouds were present on the underside of the thunderstorm anvil clouds.  The picture below was taken from Memphis International Airport looking north. Mammatus clouds are typically indicative of severe weather and extreme turbulence.

Mammatus clouds on the storm producing hail to the north of this location. Photo credit MWN.
After a brief respite, a line of storms moved into the metro from the west after the lunch hour. As the storms approached, they pushed out an outflow boundary, or gust front, that produced a photogenic shelf cloud.  The pictures below show the shelf as it approached southeast Memphis and Collierville, respectively.  Though no severe weather was associated with this storm, there were reports of near-severe size hail in north Mississippi in association with the line of storms.

Shelf cloud as it approaches Mendenhall south of Mt. Moriah. Photo courtesy @nas38117 (Twitter)
Shelf cloud from a distance, taken in Collierville by Michael Hardeman.
Precipitation rapidly diminished in the metro by 2pm as the upper-level low responsible for the day's weather moved nearly overhead and conditions stabilized behind the previous storms.

Looking ahead, a seasonal and very welcome pattern change is expected.  Thanks to the rain today, for only the second time since March 11, temperatures remained below 70 degrees!  As we head into the Easter weekend, high pressure will dominate, bringing very pleasant conditions with abundant sunshine, reduced humidity, and high temperatures in the upper 60s Friday and lower to mid 70s this weekend. A weak cold front will pass through early Sunday morning but only an increase in cloud cover is expected.

Another cold front that brings a shot of much cooler air arrives around Tuesday, further reducing temperatures to the 60s for the middle of next week. Overnight lows will be in the 40s Friday night and again for the middle of next week! Models are hinting at more rain chances late next week, but it's too early to say for sure now.  In the meantime, enjoy some truly SPRINGLIKE conditions. A detailed look at the extended forecast can be found on the MWN Forecast page.

For weather information for Memphis and the Mid-South, where and when you need it, visit on the web, on your mobile phone, download our iPhone or Android apps, or visit us on Facebook or Twitter.

Wednesday, April 4, 2012

March 2012 Climate Data and MWN Forecast Accuracy

Following the 7th warmest meteorological winter (December-February) on record, March upped the ante!  The month ended up as the warmest March in recorded history in Memphis and many other locations across the eastern U.S. The average temperature of 64.8 degrees was 10.8 degrees above normal, more than 2 degrees warmer than the second warmest March (2007). With no low temperatures at or below freezing, the growing season officially started on February 21, or a little over a month earlier than normal. Memphis missed the earliest "last freeze" by 9 days (February 12, 1878).

Memphis International Airport, Memphis, TN
As mentioned, the average temperature for the month of March was 64.8 degrees, 10.8 degrees above normal. The average high temperature was 75.2 degrees and the average low was 54.5. The coolest temperature of the month was 34 degrees on the 4th, while the highest temperature was 85 degrees reached on the 20th and 31st.  There were only 3 days during the month on which the average daily temperature was below normal and 19 days on which the average daily temperature was 10 degrees or more above normal. There were 11 days in which the high reached 80 degrees or higher.

Precipitation for the month totaled 4.35", which was 0.81" below average.  There were only 7 days with measurable rainfall but four of those had 0.50" or more. The maximum 24-hour amount was 1.44" on the 8th. The peak wind gust was 44 mph (from the south) on the 21st with an average wind speed for the month of 9.5 mph. Click here for a daily statistical recap for Memphis International Airport.

Cirrus Weather Solutions, Bartlett, TN
The average March temperature at Cirrus Weather Solutions in north Bartlett was 64.6 degrees with a maximum of 89.0 degrees on the 31st and a minimum of 31.5 degrees on the 4th.  March precipitation totaled 3.85" in the automated gauge. A co-located manual gauge used for the CoCoRaHS program measured 4.07".  The peak wind gust was 33 mph on the 2nd. Average relative humidity was 61%. Click here for a daily recap on

MWN Forecast Accuracy
For the month of March, the average temperature error in all MWN temperature forecasts was 2.59 degrees. 55% of the MWN temperature forecasts for the month were within 2 degrees of the actual temperature. MWN's forecasts extend out five periods (or 2.5 days). For dewpoint accuracy, the MWN forecast averaged 3.26 degrees of error and fell within 2 degrees of the actual dewpoint nearly 49% of the time. Historical accuracy statistics can be found here.

For weather information for Memphis and the Mid-South, where and when you need it, visit on the web, on your mobile phone, download our iPhone or Android apps, or visit us on Facebook or Twitter.

Sunday, April 1, 2012

March 2012 was the warmest March in Memphis history

The table below lists the Top 10 warmest March months at Memphis, TN since records began back in the 1880s.  As the month ended, the average temperature for March 2012 was 64.8 degrees, which ranks as the warmest month of March in recorded history. Besides Memphis, other regional cities, including Jackson, TN, Tupelo, MS, and Jonesboro, AR, also ended with their warmest March on record!

A few other interesting climate facts for March 2012:

  • 27 days had "above normal" average temperatures
  • 18 days had average temperatures at least 10 degrees above normal
  • 6 daily temperature records were either tied or broken
  • The previous warmest March was over 2 degrees cooler than 2012 (typically the warmest months are tenths of degrees apart - 2012 wasn't even close!)
  • As of March 31, our average temperature for 2012 (Jan-Mar) is also 1.3 degrees higher than the previous record warm year (1907) and 6.8 degrees above normal

RankAvg Temp Year Departure
1 64.8 2012 +10.8
2 62.5 2007 +8.5
3 62.1 1907 +8.1
4 61.9 1910 +7.9
5 61.4 1921 +7.4
6 60.5 1938 +6.5
7 60.1 1945 +6.1
8 59.6 1908 +5.6
9 59.5 1878 +5.5
10 59.4 1946 +5.4

The spring outlook (below) indicates a likelihood of continued above normal temperatures for both the month of April and the 3-month period of April-May-June, according to NOAA/Climate Prediction Center.

April outlook from CPC calls for a 40% chance of above normal temperatures (27% chance of below normal)

April-May-June outlook from CPC calls for a ~50% chance of above normal temperatures (17% chance of below normal)
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