The US severe weather outbreak 23/4/2010

Hey folks,
Thought for a bit of hype before I make my chase trip in May, that I might look into the forecast dynamics in the US...now that there is something to forecast over there (See my friend Patrick Marsh's Blog for a better forecast effort, im still learning the ropes over there).

Yesterday (US time) saw a reasonable number of tornadoes develop from discrete supercells along the ejected trough. A cold front came through late in the evening to end the interest.

Now, to post some of the information for the next two days, which both have Moderate risks, and will like produce a large number of tornadoes, with discrete supercells, strong rotation and long/dangerous tornadoes a distinct possibility. However, the chase country for this outbreak is tough or more the case nearly impossible. The outbreak is now moving into Arkansas, and the Missippi valley, which makes chasing hard due to all the trees. There is still a potential for tornadoes in the alley, but the dynamics are far superior in eastern Texas and further east...particularly in terms of strong low level shear (a primary ingredient), and dynamics to allow the storms to persist until after dark (which is not the case in the alley as far west as Colorado.

You can see NWS is concerned for tomorrow:
CONFIDENCE IS INCREASING IN POTENTIAL FOR MULTIPLE TORNADOES OVER
CATEGORICAL MDT-RISK AREA...SOME POSSIBLY STG-VIOLENT. ATTM MOST
PROBABLE SCENARIO IS FOR AT LEAST TWO TEMPORALLY SEPARATED SVR
EPISODES WITH SOME SPATIAL OVERLAP...
1. AFTERNOON/EVENING FROM S-CENTRAL/ERN TX THROUGH ARKLATEX
REGION...AND
2. OVERNIGHT AND CONTINUING INTO DAY-2 PERIOD...ESPECIALLY OVER
PORTIONS LA/MS.
ONE OR TWO CORRIDORS OF RELATIVELY CONCENTRATED/STRONG-VIOLENT
TORNADO THREAT MAY DEVELOP WITHIN BROADER OUTLOOK AREAS NOW
DELINEATED. CONCERNS ABOUT COVERAGE/DURATION OF FAVORABLE SUPERCELL
MODES PRECLUDES GREATER CATEGORICAL OUTLOOK THIS SOON.

Basically the warning here is Eastern Texas, Arkansas, Missisippi, Louisana for the greatest risk of multiple tornadoes....why is this?
Strong Instability (CAPE above 1500 J/kg), combined with very strong deep shear (50-70 knots), more than sufficient for supercell thunderstorms. Furthermore, strong low level shear, and the depth of the shear means the rotation is deep and favouring the usual right moving supercell type. The rotational shear is also potentially strong enough to likely produce cyclical type supercells, meaning supercells that produce multiple tornadoes, with long life cycles, and generally are the source of the most potent and dangerous tornadoes. This is expected to continue overnight (meaning dangerous night tornadoes) into the MS valley. Interestingly for this early in the season there is significant capping, such that cells will remain isolated and separate.

And Saturday:
THIS SUGGESTS A HIGH
LIKELIHOOD OF MULTIPLE BANDS/CLUSTERS OF SUPERCELLS CAPABLE OF
DAMAGING WINDS...LARGE HAIL AND TORNADOES PERSISTING THROUGH THE
PERIOD.

THE GREATEST THREAT FOR CYCLIC SUPERCELLS CAPABLE OF SIGNIFICANT
TORNADOES WILL EXIST FROM THE VICINITY OF THE SECONDARY LOW TRACK
SEWD INTO THE WARM SECTOR /I.E. LARGELY DELINEATED BY MDT RISK
AREA/. HERE...ENVIRONMENT WILL BE CHARACTERIZED BY DEEP EFFECTIVE
INFLOW LAYERS YIELDING EFFECTIVE SRH IN EXCESS OF 200-300+
M2/S2...MODERATE INSTABILITY AND 50-70 KT OF DEEP-LAYER SHEAR.
SEVERE STORMS CAPABLE OF MAINLY DAMAGING WINDS AND TORNADOES WILL
CONTINUE THROUGH THE NIGHT WITH THE THREAT EXTENDING NWD THROUGH THE
OH RIVER AND AS FAR E AS THE CNTRL/SRN APPALACHIANS AND ERN GULF
STATES.

This sort of follows the previous as the trough moves, with a nasty potential for dangerous cyclical supercells likely to produce strong tornadoes in reasonable numbers.

The only question for chasers now, is what effect will the outflow boundaries from the last nights convection have on the system...and where things happen, not to mention where is the triple point (interesection of cold and warm fronts). And of course, where can you get the best chase country in tandem with the best possible conditions.

I'll continue to update as this event unfolds.

What is this Blog

Well, after procrastinating away for some time I decided I should enter the world of blogging.
Why you ask? I need to improve the quality of my writing, so why not do so while posting regular information on the meteorological happenings in Australia and around the world. This first post will give a bit of information about me and what I am about.

A bit about me:
I am a PhD student in meteorology at the University of Melbourne, spending my time looking at the environments producing severe thunderstorms. I am really a bit of a 'weather wienie'. I like to observe weather via radar, satellite and keep track of synoptic conditions. However, I also firmly believe that observational meteorology is very important to the field, not just the latest model output. For this reason I enjoy getting out in the field to observe the weather in action, including chasing storms. This being said I do not look favourably at those who place themselves in danger to obtain extreme footage of storm events. I instead believe that chasing storms should be about understanding and observing the dynamic conditions associated with these awesome displays of the power of nature. Therefore, I believe chasing should be undertaken in the safest possible fashion by observing a storms behaviour. This should allow you to avoid not placing yourself in danger, which would require outside intervention if everything was to go wrong. I guess what I am saying is, if you intend to stormchase, do it responsibly.

So I guess I should start off with what is likely to eventuate over the next couple of days:
Today we should see the warmest day in Melbourne until the spring, as the pattern is starting to become more winter like. The change will be abrupt as per usual. The next few days should become unsettled with thunderstorms and rain developing as a trough moves through. There is the potential for storms to be severe and organised. I am not entirely sure if I will be able to chase as there are a myriad of things on.

Finally, I guess I should explain why I called this blog "Forecasting from in the Pouch"
15 Months after starting my PhD I recieved an email from the department secretary informing me that I was not on the books as a PhD student for the department. Upon further investigation it turned out I had been enrolled as a Zoology PhD student for 15 months, and nobody noticed. Therefore I figured I should probably have an appropriate thesis title for this enrolment as well:
"Kangaroo Casting: Forecasting conditions from inside a Kangaroo Pouch."