Thursday, August 27, 2009

T.S. Danny and a bit of "green" irony

Tropical Storm Danny was named yesterday morning and is now a storm with 60 mph wind moving northwest across the western Atlantic, northeast of the Bahamas. The storm is not well-organized with the strongest wind well removed northeast of the center of the storm. Current projections indicate that interests from the Outer Banks of N.C. up through New England should keep a close eye on the storm. The latest forecast track, satellite imagery, etc. are posted on the MWN Tropical page.

Elsewhere, I find it a bit ironic that one method of reducing greenhouse emissions in order to supposedly have a positive impact on weather and climate may be causing another weather problem. As reported by the Associated Press ("Wind Farms Can Appear Sinister To The Weatherman"), National Weather Service meteorologists are finding that wind farms that are springing up across the country are affecting the quality of their Doppler radar data. In some cases, the complex computer algorithms that process the radar data are erroneously alerting radar operators to tornadoes over the wind farms! In many cases, wind turbines located within several miles of a Doppler radar are causing poor data quality in the velocity (wind) data that meteorologists use in the detection of hazardous weather. An excellent write-up with examples of the poor radar data can be found on the NWS-Buffalo website.

So, let me get this right... to help offset the effects of "human-induced climate change" and produce clean energy, we build wind farms that subsequently cause false warnings of tornadoes and other potentially bad weather! Obviously, it's up to the radar operators to filter out these false warnings before alerting the public, but the best case may be to shut these turbines down when hazardous weather is affecting the area around the wind farm (besides the fact that this type of interference should be considered before nstalling these turbines). Be sure to read the articles linked above for more info.

Finally, the MWN Forecast will not be updated from Friday through Sunday as I will be out of town participating in my sister's wedding. Have a great weekend!

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Tuesday, August 25, 2009

Possible new tropical development

The National Hurricane Center is keeping a close eye on "Invest 92," an area of development northeast of Puerto Rico that could become Tropical Storm Danny in the next couple of days. The NHC places a "high probability" of formation on this storm system: "THIS SYSTEM CONTINUES TO SHOW SOME SIGNS OF ORGANIZATION... AND UPPER-LEVEL WINDS ARE FORECAST TO BECOME MORE CONDUCIVE FOR DEVELOPMENT DURING THE NEXT DAY OR SO... " Visit the MWN Tropical page for the latest on this storm. Computer model forecast tracks indicate that the Bahamas and possibly parts of the U.S. East Coast should keep an eye on this system.

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Monday, August 24, 2009

Is it still August?

What a fabulous weather weekend across the Mid-South! Canadian high pressure dominated just as predicted and brought the region a re-lapse of our near-record cool July! Highs topped in the lower 80s at best over the weekend while many places outside the city proper dropped into the 50s in the early morning hours. Can't ask for much better! In fact, my friends in Jackson, TN saw a record low Sunday morning (54) and a record cool max Sunday afternoon (78). My station in Bartlett dropped to 58 Sunday morning and 57 this morning.

As for humidity levels, they were basically non-existent compared to a "normal" August day in the Bluff City. Normally, surface dewpoints (a measure of the actual water content in the air) average in the 65-70 degree range this time of year. The official dewpoint at Memphis International has been at or below 60 (mostly in the 50s) since just after midnight Saturday morning - a streak of 63 hours and counting. I expect that streak to come to an end during the day tomorrow, but 3 days of very low humidity is certainly something we'll take.

As we head into the meat of the work week, temperatures will moderate some as that high pressure moves east and more southerly wind emerges, bringing dewpoints and humidity levels back up slightly over the next couple of days and temps will return to the upper 80s to near 90. There will be some rain chances late in the week and early this weekend, though it appears that starting next week we may get another one of those great big Canadian highs to bring us another shot of atypical weather to close out the month! Let's all cross our fingers for that! All the details can be found in the MWN Forecast.

In the tropics, Bill has become extratropical and is headed across the northern Atlantic towards, of all places, the British Isles. Forecasters are now watching what could become "Danny" in the western Atlantic. Check the MWN Tropical Page for the latest on this developing storm. Forecast models indicate it could strengthen into a storm later this week and become a threat to the U.S. East Coast over the weekend.

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Friday, August 21, 2009

Video of Thursday morning's weather

Many of you who were getting ready to leave for, or on your way to, work or school Thursday morning will recall the very ominous cloud bank that moved into the metro area in the 7am hour, enveloping the area in clouds worthy of a Weather Channel special. The arrival of this massive outflow (learn more about outflow boundaries and gust fronts in my previous posts) was accompanied by gusty northwest wind (30-40 mph in many cases) and then bands of heavy rain for the next 30 minutes or so.

Well, my good friend and owner of Gemini Media Transfer Service got the video camera out and mounted it in his driveway in Bartlett and let it run, then time-lapsed the 30 minutes of film into a one-minute quick flick. The results are below. Amazing video - and a time-lapse makes it even cooler. Thanks to Ande and Gemini MTS for capturing it and allowing me to share with you.

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Thursday, August 20, 2009

Life cycle of summertime diurnal thunderstorms

On Tuesday evening (8-18-09), thunderstorms erupted over the greater Memphis area, dropping flooding rains (due to very slow movement of the cells) and creating copious cloud-to-ground lightning. These storms provide the opporunity to describe the classic life cycle of diurnal ("heating of the day") thunderstorms.

The typical life cycle of single cell thunderstorms, or small clusters of storms, on a hot summer day involves initial growth of a few cells which then produce an "outflow boundary," or gust front, as the storm falls apart. A downrush of air from a collapsing thunderstorm reaches the ground and spreads out, generally in all directions. The leading edge of this cooler airmass (or outflow) is the outflow boundary or gust front. See the life cycle diagram below and note the downrush of air in the dissipating stage (image courtesy: Wikipedia).

The outflow boundary itself serves to ignite new storms (or intensify existing cells) as it acts much like a cold front with converging air on its leading edge and cooler air displacing warmer air, which then rises. As the warmer air rises, clouds form and with enough lift, new showers or storms can form. The new storms mature, then collapse, creating their own outflow, and the cycle continues. See the diagram from Wikipedia below.

This is exactly what happened on Tuesday evening. The radar imagery captured that evening shows just how these types of storms have their own life cycle, using energy from nearby collapsing storms to invigorate existing storms or create new growth. The gust fronts in this movie loop are seen as thin blue lines eminating out from the larger cells. Notice that as they reach younger cells, those cells intensify (notice in particular the new storms that fire up just north of Millington and showers in central Shelby County that explode as the southward moving outflow boundary passes through those areas, causing rapid growth just east of Bartlett along I-40 [the red line]).

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Possibility of severe weather today - 8/20/09

The Mid-South region is under a SLIGHT RISK for the potential of severe weather today and tonight. The primary threats are damaging wind and large hail. This morning's showers and thunderstorms may be a fly in the ointment for the potential for severe weather later today, as the atmosphere is stabilized a great deal in the wake of the system this morning. If clouds can break and sufficient heating can occur, the threat increases for later this afternoon.

I also expect a line of storms to accompany the cold front as it sweeps through the region late tonight. These storms also pose the threat for gusty wind and heavy rain.

Stay with for the latest on the possibility of severe weather, including interactive radar, severe weather watches and warnings, and the most accurate forecast in Memphis.

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Wednesday, August 19, 2009

Recap of Tuesday's storms and a "cool" forecast

As covered on MWN's Twitter feed as it occurred, last evening the metro area experienced frequent lightning, seemingly continuous thunder, and localized downpours that dropped up to 2-3" of rain (see rainfall estimate map below; click for larger image) and caused flash flooding in parts of east Memphis, more of the same may be on the way. The weather pattern, which features a tropical airmass overhead and plenty of instability, has not changed significantly from yesterday, so thunderstorms could again rumble over the region this afternoon and evening.

One more day of this type of weather is expected on Thursday, though things change drastically as we head into the start of the weekend. A fall-like upper-level trough, strong for this time of year, will swing into the region from Canada on Friday and linger through the weekend. The trough will be accompanied at the surface by a strong cold front which will bring thunderstorms, some of which are likely to be severe, to the Mid-South late Thursday afternoon through the overnight hours into early Friday. The area is currently under a SLIGHT RISK of severe weather for Thursday and Thursday night with damaging wind from a possible squall line and large hail being the main threats. See the day 2 severe weather outlook below.

For the weekend, cooler and much drier air invades the region with humidity levels falling to autumnal levels and temperatures reaching only into the mid 80s. Morning lows will be in the 60s, while a few upper 50s cannot be totally ruled out in typically cooler outlying areas. The MWN Forecast has all the details.

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Monday, August 17, 2009

GOES-14 produces first full disk infrared image

If you recall from a previous post on this blog, or from other sources, a new GOES satellite was launched into space aboard a Delta IV rocket in late June to help watch Earth's weather from 22,000 miles up. This satellite reached geostationary orbit on July 8 and was named GOES-14. It produced its first full disk (hemispheric) infrared image earlier today, which included a view of Tropical Depressions Ana and Claudette, Hurricane Bill, and Tropical Storm Guillermo in the central Pacific. Check out the photogenic first look at the western hemisphere from GOES-14 above(click for larger image).

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Sunday, August 16, 2009

Tropical alphabet soup

In just a matter of a couple of days, the very late-starting Atlantic tropical season (one of the slowest in 20 years) has taken off and there are now three named storms swirling in tropical waters - Ana (pronounced Ah-na) and Bill in the Atlantic and newly-formed Claudette in the eastern Gulf of Mexico.

Starting with Claudette, this tropical storm is offshore the west coast of FL moving northwest. It is expected to make landfall in the FL Panhandle west of Apalachicola this evening as a moderate tropical storm with 50-60 mph wind in a fairly concentrated core. The biggest threat from this storm will be copious rainfall - widespread 3-6" totals with higher localized amounts. Of course, any land-falling tropical system has the potential to bring isolated tornadoes and damaging wind gusts.

The remnants of Claudette could affect the Mid-South Monday night and Tuesday so my forecast reflects slightly above forecast model precipitation chances and slightly below the models on high temps for the first part of the week, assuming some residual affects from the storm.

The first storm to form, Ana, has been downgraded (again) to a tropical depression as it moves quickly west towards the Lesser Antilles. Assuming it survives interactions with the islands (and that is a stretch), it is forecast to continue towards Hispaniola and Cuba, where it will likely die a natural death and should not pose a threat to the U.S. mainland, other than possibly some showers for south Florida.

The last storm, Tropical Storm Bill, is following in Ana's footsteps and appears ready to power up to hurricane strength tonight or Monday and possibly become a major hurricane (category 3+) in 48-72 hours. This storm will bear watching as far as its eventual track. Right now, the large-scale models are forecasting a fairly significant trough over the eastern U.S. by mid-late this week which could turn the storm northwest, then north, up the east coast of the U.S. We'll keep an eye on it.

For more on tracking tropical weather, I suggest you check out MWN's Tropical Page, as well as an excellent online resource called StormPulse.

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Saturday, August 15, 2009

It is with great pride that I announce today that and have become "sister websites" operating from one location in the suburbs of Memphis. Both websites are being run by yours truly, effective August 12. (JWN), serving Jackson and west Tennessee outside the Memphis metro area, was started in 2003 by a good friend of mine, Eddie Holmes, a meteorologist from Jackson who is well-known to many in the region. JWN is widely used and highly regarded within the Jackson community as well as throughout west TN, including Milan, Dyersburg, Martin, Union City, Ripley, Lexington, and Selmer. I am honored to have the opportunity to continue the tradition of exceptional service Eddie has started and look forward to serving the good folks of Jackson and the rest of west TN.

For those who have been dedicated users of over the years, I want to assure you that you can continue to expect the same high-quality products and service you have become accustomed to from JWN and I expect that over time the site will continue to grow. Eddie will continue to maintain his weather blog, so you can catch his discussions and thoughts on west Tennessee weather there.

With the good fortune of having both websites under one roof, I am excited to be able to provide high-quality weather information to all of west Tennessee - from Union City to Union Avenue and everywhere in between! I wish Eddie nothing but the best in his future endeavors - he will be a hard act to follow.

Please feel free to contact me at any time with questions, comments, or suggestions via the Contact page on

Erik Proseus
Webmaster and Forecaster

Wednesday, August 12, 2009

New NOAA supercomputers to take forecast models into the future

As of noon CDT today (1700 UTC 8/12/09), the National Centers for Environmental Prediction (NCEP), a division of NOAA, declared operational two new massive supercomputers that will spit out weather model data used by forecasters throughout the world. Model data, a mainstay for all meteorologists in determining what the weather will be like over their forecast area, provides information of the expected state of the atmosphere from a few hours in the future to as far as several days, or even weeks, in advance. The new supercomputers are named Stratus and Cirrus, after two of the four main cloud types (cumulus and nimbus being the others). The computers have been thoroughly tested and benchmarked to ensure that there is no significant difference in the model output from the previous computers, but will provide the horsepower required to accomodate advances in weather prediction technology over the coming years.

The operational status of these two computing beasts was originally scheduled to be Tuesday, August 18, but in anticipation of an increase in hurricane activity in the Atlantic Ocean over the coming weeks, the operational date was accelerated "to minimize the effect of the transition on NWS operations."

To read the NWS announcement about the changes, click here.

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Tuesday, August 11, 2009

Slight risk of severe weather today





Monday, August 10, 2009

Quick-hitting front blows through Shelby and Tipton counties

Photos taken of the gust front / thunderstorm outflow as it quickly approached from the northwest, then engulfed the north Bartlett area. Right on its heels, a pretty good thunderstorm with 30-40 mph wind and heavy rain moved overhead. Over .25" of rain was measured in just 15 minutes with the storm.

You can also view a time-lapse video of the front below. You will see first see the initial clouds come in from the west, then the front itself appears out of the northwest and "boils" overhead as eddies in the turbulent atmosphere seem to "roll out" from under the front. The strong wind is evident as well in the trees as the front crosses over. Great footage and editing by ANDe of Gemini Media Transfer Services!

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Wednesday, August 5, 2009

Cordova, TN tornado claims its first victim - indirectly

Anyone who witnessed the destruction caused by the EF-1 tornado that hit the Countrywood area of Cordova, TN on Thursday afternoon, July 30, would be surprised to learn the storm caused no injuries or fatalities even though it plowed through a high-traffic commercial area and a large subdivision during rush hour. Unfortunately, one young man paid the ultimate price - an indirect result of the storm as he was cleaning up debris left behind.

Brian Ball, 34, a firefighter with the city of Bartlett and family man with a wife and two young boys (2 and 3 years old) was killed by a falling tree as he worked with a private tree removal service in Countrywood on Monday afternoon, August 3 - his day off from firefighting duties. Brian was also a graduate of Bartlett High School and in the same senior class as this weather forecaster.

I wish to offer my deepest condolences to Brian's wife Pam, his boys, and extended family, as well as to his comrades on the B-shift and all members of the Bartlett Fire Department, upon this tragic loss. I pray that they will find peace in due time and that they all have nothing but fond memories. An article from The Commercial Appeal on Brian's life with respect to his career with the BFD can be found here.

Rest in peace, Brian.

Sunday, August 2, 2009

A cool and wet July in 2009

Thanks to a persistent upper level trough over the eastern U.S., July saw an active storm track over the Mid-South, resulting in more clouds and rain than normal which, consequently, held temperatures at bay. The month ended up much cooler and wetter than normal, though not quite record-breaking. This is in direct contrast to June, which was much warmer and drier than average. Following are climate summaries for Memphis and Bartlett, TN.

Memphis International Airport, Memphis, TN
At the airport, the average temperature was 79.3 degrees, which was 3.2 degrees below normal and 2.0 degrees cooler than June. This also makes July 2009 the 5th coolest July on record. The highest temperature for the month was 95 degrees on the 15th and the lowest was 64 on the 18th and 19th. A total of only 13 July days saw highs at or above 90 degrees, while normal highs for the month are above 90 degrees every day. A record minimum high temperature was set on the 28th as the high topped out at only 79 degrees - one of 3 days that failed to reach 80.

Precipitation totaled 8.46", which was double (or 4.24" above) the normal and more than 6" above June's total. July 2009 goes down as the 4th wettest July on record. There were 10 days with measurable rainfall recorded and 5 days in which more than an inch of rain fell. A record 2.02" fell on the 30th, which was also the greatest amount on a calendar for the month. The peak wind gust was 41 mph, recorded on the 26th. Click here for the NWS climate recap for July.

Bartlett, TN
WXLIVE! also recorded a cool and wet month. The average temperature for July was 78.0 degrees (2.2 degrees cooler than June), with a max of 96.6 on the 15th (one of only 11 days above 90) and a min of 58.9 degrees on the 18th. A good deal of rain was recorded as well, totaling 6.70" for the month. [NOTE: a manual "NWS-style" rain gauge operated for the CoCoRaHS precipitation collection program and located next to the automated WXLIVE! equipment totaled 8.76" for July, which is likely much more accurate.] The peak wind gust was 29mph on the 16th. Click here for the MWN recap.

Saturday, August 1, 2009

Another day, another round of t'storms and flash floods

Unfortunately, after one of the wettest Julys on record, this is becoming old hat... Another potent upper-level trough and accompanying cold front (stronger than usual for this time of year), will move into the Mid-South today.

At 8am, storms are already firing in central AR and pushing in our general direction. The atmosphere has plenty of moisture to serve as fuel for the storms and with that abundant moisture in place, the National Weather Service has issued a Flash Flood Watch for the entire region through 7am Sunday due to the threat of 1-2" of rain from this system. We are also on the edge of a SLIGHT RISK of severe weather, as issued by the Storm Prediction Center, which encompasses much of AR, northwest MS, northern LA, and eastern TX and OK (see map above).

The main severe threat with these storms will be the possibility of damaging wind gusts. Timing for today's weather will be mainly after noon through the early overnight hours, with the best time for possible severe weather between 3-10pm. Rain could continue through a good part of the overnight hours. Sunday look to be dry and mild. Following this front, the pattern returns to a more "normal" August setup with temps in the 90s and isolated to scattered t'storms each day for most of next week.

Stay with for current radar and severe weather watches and warnings as this event unfolds and be sure to follow MWN on Twitter and Facebook for even more coverage.

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