Tornado season: why so active?

By: Dr. Jeff Masters , 10. huhtikuuta 2006 klo 16:22 (GMT)

Share this Blog
0
+

Friday's tornado outbreak in Tennessee featured at least 46 tornadoes across eight states. Three strong F3 tornadoes touched down (winds of 158 to 206 mph), including the Gallatin, Tennessee tornado that killed nine people and damaged or destroyed 700 to 900 homes in Sumner County. The April 2 outbreak had six F3 tornadoes among the 56 reported, and the March 9-13 outbreak had 11 F3 tornadoes and one F4 tornado among the 84 that touched down.


Figure 1. Departure of Sea Surface Temperature (SST) from normal in early April for 2005 and 2006. SSTs were near normal in 2005 in the Gulf of Mexico, but were about 1-2 degrees C warmer than normal this year. Other things of interest: the cool water signature of La Nina is obvious in the Eastern Pacific in 2006 but not 2005; water temperatures in the Caribbean and tropical Atlantic are cooler this year than last year, which may mean a delayed onset to this year's hurricane season compared to last year. Image credit: NOAA.

Why has this year's tornado season been so violent? According to NOAA,, "The difference this year is the abnormally warm temperatures and dry conditions during the winter throughout the southern and central United States that kept water temperatures warm in the Gulf of Mexico." If we look at a plot comparing this year and last year's change ino Sea Surface Temperature (SST) from normal (the anomalies, Figure 1), we see that the Gulf of Mexico is indeed significantly warmer this year. Plenty of warm moist air from the Gulf of Mexico certainly doesn't hurt, but the primary reason that this year's tornado season has been so bad is that we've had an unusually active and strong jet stream. The reasons for this are complicated and not well-understood, but have more to do with large scale global circulation patterns such the the presence of La Nina and the negative phase of the North Atlantic Oscillation (NAO) that has predominated this Spring.

The latest 2-week forecast from the GFS model shows that the jet stream is now expected to grow less active for the next 10 days, and no further major tornado outbreaks are expected during that period. A more active pattern may return late in the month, however.

Jeff Masters

Tornado Damage (pluto)
Automobiles at car dealership in Gallatin, Tennessee, resulting from toranado which hit April 7, 2006.
Tornado Damage
Tonado North of Winona Mississippi (StonevilleHead)
Taken from McDonald's on Highway 82 at 5:35pm on April 7, 2006
Tonado North of Winona Mississippi

Reader Comments

Comments will take a few seconds to appear.

Post Your Comments

Please sign in to post comments.

or Join

Not only will you be able to leave comments on this blog, but you'll also have the ability to upload and share your photos in our Wunder Photos section.

Display: 0, 50, 100, 200 Sort: Newest First - Order Posted

Viewing: 121 - 71

Page: 1 | 2 | 3Blog Index

121. caribbeantracker01
1. huhtikuuta 2012 klo 21:13 (GMT)
Quoting Snowfire:


With shear like this, I can't understand all the excitement. Until it drops below about 20kt where it matters, I wouldn't take all this too seriously.


but this says 2008
Member Since: 21.05.2008 Posts: 0 Comments: 493
120. oriondarkwood
12. huhtikuuta 2006 klo 14:07 (GMT)
Just posted my first hurricane prediction on my blog:

http://www.wunderground.com/blog/oriondarkwood/show.html
Member Since: 5.07.2004 Posts: 51 Comments: 41
118. MZT
12. huhtikuuta 2006 klo 02:30 (GMT)
If anything shows up in these conditions, though - it'd be another shallow - 'Greek' type storm.

Member Since: 24.09.2005 Posts: 0 Comments: 793
116. Snowfire
12. huhtikuuta 2006 klo 01:27 (GMT)


With shear like this, I can't understand all the excitement. Until it drops below about 20kt where it matters, I wouldn't take all this too seriously.
Member Since: 29.06.2005 Posts: 24 Comments: 308
114. DAVIDKRZW
11. huhtikuuta 2006 klo 23:54 (GMT)
where is dr m update to day any way
113. globalize
11. huhtikuuta 2006 klo 23:47 (GMT)
Michael STL..that's probably because I don't have a blog site..just like to visit this one now and then. I have a question about ocean water salinity and acidity and its relationship to heat absorption. I may do a few personal experiments in a week or two in the Keys. Somebody clue me in.
Member Since: 30.08.2005 Posts: 0 Comments: 1150
112. RL3AO
11. huhtikuuta 2006 klo 23:35 (GMT)
I hope this doesnt add gas to the fire...
110. DAVIDKRZW
11. huhtikuuta 2006 klo 23:13 (GMT)
my blog is update
109. ForecasterColby
11. huhtikuuta 2006 klo 22:55 (GMT)
I, also, get that error. Mail WunderYakuza about it, he's the site's technical guy.
107. globalize
11. huhtikuuta 2006 klo 22:31 (GMT)
Don't need a knee hair mental image, thanks.
Member Since: 30.08.2005 Posts: 0 Comments: 1150
106. rwdobson
11. huhtikuuta 2006 klo 22:01 (GMT)
it won't. even if it forms a TD, which is unlikely, it won't become a named storm.
Member Since: 12.06.2002 Posts: 0 Comments: 1574
104. rwdobson
11. huhtikuuta 2006 klo 21:51 (GMT)
boy it sure doesn't look impressive on the water vapor loop. looks like there is plenty of dry air and shear around.
Member Since: 12.06.2002 Posts: 0 Comments: 1574
103. ForecasterColby
11. huhtikuuta 2006 klo 21:44 (GMT)
Ack, what am I saying? I was reading the stupid shear map wrong *pokes self in eye*

We might see something kick up out of this.
102. ForecasterColby
11. huhtikuuta 2006 klo 21:42 (GMT)
Well, I'll be darned! Shear's too high ATM, but it does look like it has more chance to develop into a TC than my knee hair.
101. HurricaneKing
11. huhtikuuta 2006 klo 21:37 (GMT)
CARIBBEAN/GREATER ANTILLES/SERN MEXICO...
THE CAN/GFS ARE BACK TO FORMING A SUBTROPICAL/TROPICAL LOW NR
HISPANIOLA DURING THE SHORT RANGE PD AND TRACKING IT WWD THROUGH
THE WRN CARIBBEAN AND SRN GULF OF MEXICO. SINCE AN UPR CYC IS
CLOSING OFF ATTM NR CUBA...A SFC LOW IS PSBL. FOR NOW...PER
COORDINATION W/TAFB...HAVE INTRODUCED AN ELY WAVE MOVG THRU THE
WRN CARIBBEAN AND SRN GULF OF MEXICO. THE CANADIAN FCST A SIMILAR
SITUATION BACK IN FEBRUARY...AND NOTHING MORE THAN A SFC TROUGH
DVLPD. SEE THE LATEST DISCUSSIONS FROM TAFB/TPC ON THIS SYS.

ROTH/CLARK
Member Since: 6.07.2005 Posts: 71 Comments: 2449
100. rwdobson
11. huhtikuuta 2006 klo 21:36 (GMT)
the moisture is not all that substantial. really. that's why KC probably won't get any rain today, again, despite the front coming through. and that moisture plume, such as it is, is coming from the pacific for now...
Member Since: 12.06.2002 Posts: 0 Comments: 1574
96. rwdobson
11. huhtikuuta 2006 klo 21:23 (GMT)
buster: "There is to much of a temperature difference between the two air masses for it not to happen."

it takes more than just a temperature contrast to spark severe weather....it requires moisture, instability at the surface, upper air support, etc.
Member Since: 12.06.2002 Posts: 0 Comments: 1574
95. RL3AO
11. huhtikuuta 2006 klo 21:04 (GMT)
what is going on with the extra list to be named by the WMO?
94. DAVIDKRZW
11. huhtikuuta 2006 klo 21:01 (GMT)
MichaelSTL


can you pos this in my blog

Link



so i can add it on top
91. DAVIDKRZW
11. huhtikuuta 2006 klo 20:43 (GMT)
MichaelSTL can you help me on my blog


Link

i try to post this on my blog but it look like it did not work
89. DAVIDKRZW
11. huhtikuuta 2006 klo 20:38 (GMT)
88. DAVIDKRZW
11. huhtikuuta 2006 klo 20:38 (GMT)
Link


Link


look at this oh no
83. weatherguy03
11. huhtikuuta 2006 klo 20:09 (GMT)
Cyclone went from tunnels to small vorts. Oh boy:)
Member Since: 5.07.2005 Posts: 589 Comments: 29691
81. weatherguy03
11. huhtikuuta 2006 klo 20:08 (GMT)
Last time it was getting this dry was 1998. But we are not even close to that yet. I know some people are trying to make that 1998 comparision, but its too early to say whether it will be as dry. We will see what the rest of April brings us, but right now its not looking to wet.
Member Since: 5.07.2005 Posts: 589 Comments: 29691
80. ForecasterColby
11. huhtikuuta 2006 klo 20:02 (GMT)
Hawkeye, the very dry floridian pattern is charictaristic of a La Nina, though we're actually not much below average despite only having been rained on twice. One time was like the sixth wettest day in Tampa history, and as this front went through we got a bit more.
78. ForecasterColby
11. huhtikuuta 2006 klo 20:00 (GMT)
74. ForecasterColby
11. huhtikuuta 2006 klo 19:54 (GMT)
Uhhh, Myles? *points at the Azores* :)

Cyclone, breathe. It's a vortex. I had one in my yard earlier that had more chance of becoming a TC than that does. It's north of the 26C isotherm, barely has a circulation, and is frontal. RELAX!
73. HurricaneMyles
11. huhtikuuta 2006 klo 19:53 (GMT)
I see a small bit of T-Storms over Jamacia, however, no spin in the area.
Member Since: 12.01.2006 Posts: 5 Comments: 827
72. HurricaneMyles
11. huhtikuuta 2006 klo 19:49 (GMT)
I guess it did go very near the Azores. Cant really tell if it made landfall or not.
Member Since: 12.01.2006 Posts: 5 Comments: 827

Viewing: 121 - 71

Page: 1 | 2 | 3Blog Index

Top of Page

About JeffMasters

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

Local Weather

Mostly Cloudy
59 °F
Pilvistä