Rare South Atlantic subtropical cyclone forms; severe weather season in U.S. underway

By: Dr. Jeff Masters , 2:10 PM GMT on March 10, 2010

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A rare weather event is underway in the South Atlantic Ocean, where the basin's 7th recorded tropical or subtropical cyclone of all-time has formed. An area of disturbed weather (Invest 90Q) off the coast of Brazil, near 30S 48W, attained a well-defined surface circulation, top wind speeds of tropical depression strength (35 mph), a warm core in the bottom portion of the atmosphere, and a cold core aloft last night. If this storm had been in the North Atlantic, there is a good chance it would have been named Subtropical Depression One. However, tropical and subtropical storms are so rare in the South Atlantic that there is no official naming of depressions or storms done. The cyclone had top winds of at least 35 mph as seen on an ASCAT pass at 7:02 am EST this morning (Figure 2), and satellite estimates of the storm's intensity topped out at 40 mph (minimum subtropical storms strength) last night. This morning, the satellite estimates are showing that the system has weakened to a 35 mph tropical depression. There is some moderate wind shear interfering with development, and sea surface temperatures are about 25°C, which is about 1°C below what is typically needed to support a tropical storm. The storm is headed eastward out to sea, and is not a threat to any land areas. The models show the storm will lose its tropical characteristics and get absorbed by a frontal system by Saturday.


Figure 1. Afternoon visible satellite image of the Brazilian Invest 90Q.


Figure 2. Satellite-measured winds from ASCAT clearly show the circulation of the cyclone in this pass from 7:02 am EST on March 10, 2010. Top winds as seen be ASCAT were 30 knots (35 mph), just below the 40 mph needed for it to be a tropical storm. Image credit: NOAA/NESDIS/ORA.

Brazil has had only one landfalling tropical cyclone in its history, Cyclone Catarina of March 2004. Catarina is one of only six known tropical or subtropical cyclones to form in the South Atlantic, and the only one to reach hurricane strength. Tropical cyclones rarely form in the South Atlantic Ocean, due to strong upper-level wind shear, cool water temperatures, and the lack of an initial disturbance to get things spinning (no African waves or Intertropical Convergence Zone exist in the proper locations in the South Atlantic to help spawn tropical storms). Today's storm is located close to where Catarina formed.

Severe weather season begins
It's March, and that means severe weather season will get underway in earnest for the Midwest U.S., and powerful spring storm systems draw warm, moist air from the Gulf of Mexico northward, to collide with cold, dry air from Canada. It's been a quiet early season, with only 42 tornadoes reported thus far this year (as of Sunday), compared to a normal 70 - 100 twisters. There was only one tornado in the U.S. in February, in a San Joaquin Valley oilfield in California two weekends ago. A year ago, there were 36 February tornadoes, and the year's deadliest tornado occurred on Feb. 10, 2009, in Lone Grove, Oklahoma, where eight people died in a storm with winds estimated at 170 mph. But thanks to a very wet winter and a continued active jet stream pattern that will pull strong storms through the Midwestern U.S. this month, expect at least an average March for severe weather. NOAA's Storm Prediction Center is forecasting a "slight" chance of severe weather across a large portion of the Mississippi Valley today, in association with a strong cold front that will be plowing through the region. Strong thuderstorms capable of generating damaging winds and large hail should develop along the front from southeast Kansas through eastern Oklahoma into NE Texas by middle/late afternoon. The storms should consolidate into broken bands and move into Missouri and and Arkansas by early evening. Isolated tornadoes are also possible in the entire "slight" risk area.


Figure 3. Severe weather forecast for today from the NOAA Storm Prediction Center.

Hurricane Hugo talk
I'm presenting a talk to a class at the University of Michigan this morning on my 1989 flight through Hurricane Hugo. You can listen in live starting at about 10:10 - 10:15 am EST by pointing your browser to http://samson.lecturetools.org/. You'll need to have Apple Quicktime installed. If all goes well, the talk will be recorded and you can view it later, as well.

Jeff Masters

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alright I'm out, it's way too beautiful out to be inside. 70 and sunny, and time for some good ole Indiana basketball!

take care all
Member Since: June 28, 2006 Posts: 25 Comments: 8360
Quoting Jeff9641:
I'll be sure to pass a lot of CROW to you guys on here that doubted me on this one. I am really good at severe wx forecasting and maybe some of you will listen next time. I've been forecasting this for days and I still think the bigger outbreak may come Friday all the way into parts of the Ohio Valley.


Jeff if the thunderstorm cell we got off the GOM this morning in the Florida Panhandle is any indication I have to agree with you. This system will probably have the biggest outbreak of severe weather we've seen so far this year. I woke up this morning and it was muggy and in the low 60's, this is the first time this year we've seen warm moist air like this! Things are going to rock tonight through tomorrow, you can see the dry line forming as we speak!
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comma going poof!
though, the developing line itself seems to be getting clearer. more commas coming...
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Quoting tornadodude:
uh oh, here we go



That's a nice airmass contrast with that front.
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oh Happy Birthday Press!
Member Since: June 28, 2006 Posts: 25 Comments: 8360
First visible images coming in from GOES-11. You can see the mesoscale low and yes this is going to look impressive on the high-res passes as you can see the eye-feature even on this image:

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Hello strangers, hunting seasons over so I'll be lurking around again!

I have to agree with the Doc that the severe season has started. This morning about 3:30 I was awakened by some of the loudest thunder I've heard since the end of last summer! We had a storm that came in off the GOM and you knew the lightning was close because you could see the flash and hear the thunder at the same time! I looked around this morning and luckily didn't see any lightning damage in the neighborhood, I thought there might be with the frequency of the cloud to ground lightning in that storm!

It's been a cold winter in the Florida Panhandle this year so I welcome the warmer weather even if that comes with the risk of stronger thunderstorms!
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Member Since: June 28, 2006 Posts: 25 Comments: 8360
uh oh, here we go

Member Since: June 28, 2006 Posts: 25 Comments: 8360
Quoting CycloneOz:


That track is going to take it right over Terrel!

SOUND THE HORNS!


They had a severe thunderstorm warning out for that cell but discontinued it a little wile ago, still holding together pretty well. Losing the higher echo tops.
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Member Since: June 28, 2006 Posts: 25 Comments: 8360
Quoting StormChaser81:




That track is going to take it right over Terrel!

SOUND THE HORNS!
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Quoting CycloneOz:


Step outside, look! Tornado! Run down street...get some footage. Chase over.

Faulty transmission repair: $1,000
Cost of mini-van you cannot afford: $3000
Being able to chase in your own neighborhood: Lucky as all get out!



hahah right on!

will def have to see what happens
Member Since: June 28, 2006 Posts: 25 Comments: 8360
Quoting Minnemike:
a tight little comma swooping south of Dallas..


I took that loop when I returned from last year's Ida. I remember looking out to my south right there and back to Dallas just north and behind me.

I shook my head...

I wouldn't want to live there.
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Quoting tornadodude:


that would definitely be cool


Step outside, look! Tornado! Run down street...get some footage. Chase over.

Faulty transmission repair: $1,000
Cost of mini-van you cannot afford: $3000
Being able to chase in your own neighborhood: Lucky as all get out!
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Quoting Minnemike:
a tight little comma swooping south of Dallas..


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a tight little comma swooping south of Dallas..
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Quoting Levi32:


Let's please not talk down on people that disagreed with you, or brag that you were right. That doesn't help you at all. Make the forecast, and people will notice if you made a good one.


its a group effort here
with many inputs
comes a reasonable
forecast
Member Since: July 15, 2006 Posts: 174 Comments: 54398
Quoting Jeff9641:


look at the CU field building in East TX right now on the Visible Sat. Also a nice dryline moving east.


yeah, and it is almost 70 and sunny here with dewpoints in the mid 50's
Member Since: June 28, 2006 Posts: 25 Comments: 8360
From the NWS Anchorage, AK:

... Snowfall totals from the March 9th snowstorm...

A strong winter storm gripped much of the area Monday night and
Tuesday. Snow began to fall in Anchorage early Tuesday afternoon and
picked up in intensity late in the evening. Drifts as high as three
feet were reported in Homer and were noted across the city of
Anchorage as well to varying heights. Many of the observations may
not have been exact... due to the difficulty of measurement from
blowing and drifting snow.

... .Location... . amount obs / date

Girdwood 34.0" M 11:30 am 3/9
N. Wasilla Fishhook 21.5" 4:45 PM 3/9
upper o'malley 18.0" M noon 3/9
upper dearmoun 16.0" 8:15 am 3/9
east Anchorage / hillside 15.0" 8:30 am 3/9
Butte / Maud Rd 12.0" E 1:00 PM 3/9
Glen Alps 14.0" 11:00 am 3/9
upper o'malley and fire station 11.0" 11:00 am 3/9
Seward 8.0" E 10:15 am 3/9
Abbott Road and birch 8.0" 7:30 am 3/9
birch Road and dearmoun 7.0" M 3:25 PM 3/9
Lake Otis and Dowling 6.5" M 9:55 am 3/9
bragaw and Glenn Highway 6.0" 11:00 am 3/9
Kenai 4.0" 9:40 am 3/9
bragaw and Glenn Highway 6.0" 11:00 am 3/9
NWS Sand Lake office 5.4" M 9:00 am 3/10
trunk Rd and Palmer Highway 5.3" 11:00 am 3/9
Chugiak 5.2" M 9:20 am 3/9


M denotes a measured value
E denotes an estimated value
denotes an unspecified measurement value [unknown if measured or
estimated]

Ss/dp Mar 10
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alrighty then....
Member Since: June 28, 2006 Posts: 25 Comments: 8360
Here is where my house is on the radar image. It remains to be seen if the "eye wall" will move over me.

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Quoting Jeff9641:
I'll be sure to pass a lot of CROW to you guys on here that doubted me on this one. I am really good at severe wx forecasting and maybe some of you will listen next time. I've been forecasting this for days and I still think the bigger outbreak may come Friday all the way into parts of the Ohio Valley.


Let's please not talk down on people that disagreed with you, or brag that you were right. That doesn't help you at all. Make the forecast, and people will notice if you made a good one.
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Member Since: June 28, 2006 Posts: 25 Comments: 8360
Member Since: June 28, 2006 Posts: 25 Comments: 8360
Quoting Jeff9641:


You could get some strong storms in your area tonight.


that would definitely be cool
Member Since: June 28, 2006 Posts: 25 Comments: 8360
Quoting Jeff9641:
I'll be sure to pass a lot of CROW to you guys on here that doubted me on this one. I am really good at severe wx forecasting and maybe some of you will listen next time. I've been forecasting this for days and I still think the bigger outbreak may come Friday all the way into parts of the Ohio Valley.


Its not that I doubted that there would be an outbreak, read what I said, I doubted the severity of the outbreak
Member Since: June 28, 2006 Posts: 25 Comments: 8360
Member Since: June 28, 2006 Posts: 25 Comments: 8360
Ok here's what I can do for you guys.

This is a NOAA-19 AVHRR IR pass from 3 hours ago, which shows the mesoscale low near the center of the image, under the latitude line, over Cook Inlet. You can see an eye-like feature right under the latitude line (*grins*)

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Lafayette, Purdue University Airport
Lat: 40.43 Lon: -86.93 Elev: 623
Last Update on Mar 10, 11:54 am EST

Overcast

64 °F
(17 °C)
Humidity: 67 %
Wind Speed: S 10 G 24 MPH
Barometer: 29.67" (1004.6 mb)
Dewpoint: 51 °F (11 °C)
Visibility: 10.00 mi.

wow its almost too warm right now :p

Member Since: June 28, 2006 Posts: 25 Comments: 8360
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Quoting Chicklit:
Levi, then would this be a "snowicane?"


You could call it that. It's a miniature polar low and the precipitation is convective in nature. I can't tell how wound up this mesoscale thing is because the pressure gradient is quite weak now. The cold air has all moved in and the winds are calm. I guess we're about to find out.

I will post visible pics when I get them but as I said the sun is just rising so it will be a while before I get a high-res polar-orbiting satellite pass.

Current Conditions, moderate snow falling:


Current Conditions

Homer, Alaska (Airport)
Updated: 30 min 20 sec ago

9 F
Snow Freezing Fog
Windchill: -3 F
Humidity: 79%
Dew Point: 3 F
Wind: 7 mph from the NNE

Pressure: 29.24 in (Steady)
Visibility: 0.2 miles
Elevation: 82 ft
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Quoting Floodman:
Howdy folks...had pea to marble sized hail here in Colleyville TX about and hour ago...dry line is supposed to drape across Dallas, leaving us Fort Worth folks with high winds but no rain this afternoon

How's everyone doing today?
I am well...And you?
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Levi, then would this be a "snowicane?"
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Quoting Levi32:
Oh snap....mini-hurricane headed our way. There's no way to tell how heavy the snow within this mesoscale low is. It is showing up on radar so it could be pretty potent. Bracing myself....just 5 more inches and my 60-inch snowstake will disappear for the first time since I've had it.




Wow!

thats crazy!

pictures would we be incredible
Member Since: June 28, 2006 Posts: 25 Comments: 8360
Quoting jeffs713:

That is just impressive. I would love to see a visible satellite pic of that mesoscale low.


Sun just now rose here...it will be a while before I can get a high-resolution satellite pass.
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Quoting Tropicsweatherpr:
Bastardi forecasts an active 2010 Atlantic hurricane season.


So is everyone else...
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Quoting Levi32:
Oh snap....mini-hurricane headed our way. There's no way to tell how heavy the snow within this mesoscale low is. It is showing up on radar so it could be pretty potent. Bracing myself....just 5 more inches and my 60-inch snowstake will disappear for the first time since I've had it.


That is just impressive. I would love to see a visible satellite pic of that mesoscale low.
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Howdy folks...had pea to marble sized hail here in Colleyville TX about and hour ago...dry line is supposed to drape across Dallas, leaving us Fort Worth folks with high winds but no rain this afternoon

How's everyone doing today?
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Quoting CyclonicVoyage:


And that's why I don't live in Alaska, lol.


Lol I would just love for some of you guys to have been here when this monster hit us on January 31st, 2009:

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Quoting Tropicsweatherpr:
Bastardi forecasts an active 2010 Atlantic hurricane season.

Link

Don't mention the competition.
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Quoting Levi32:
Oh snap....mini-hurricane headed our way. There's no way to tell how heavy the snow within this mesoscale low is. It is showing up on radar so it could be pretty potent. Bracing myself....just 5 more inches and my 60-inch snowstake will disappear for the first time since I've had it.



And that's why I don't live in Alaska, lol.
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Ok, its going past 80 for the first time in a long time.
Member Since: November 25, 2007 Posts: 0 Comments: 959
Afternoon All.

Could get dicey across the FL peninsula Thurs/Fri, for real this time, lol. Temps are finally breaking into the upper 70's and low 80's which, unlike past events, could provide the instability one would expect this time of year. Still a lot of sub surface cooling to overcome though. Cooling that these parts haven't experienced in some time. It's been ruining many a forecast thus far.
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Oh snap....mini-hurricane headed our way. There's no way to tell how heavy the snow within this mesoscale low is. It is showing up on radar so it could be pretty potent. Bracing myself....just 5 more inches and my 60-inch snowstake will disappear for the first time since I've had it.

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

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