Historic winter storm progressing

Above image has been my favorite so far, explaining whats going on. Big problems LOL. Lots of this kinda thing but this was my favorite. Courtesy of Hedi Farrar (spelling) my last name is spelled farrer, wierd!

Strong wording from the Tulsa and Indianapolis weather offices suggests ongoing threat getting worse! The main low hasnt even really formed yet. The models are saying its going to form and move in a certain direction. Which is what we are mainly looking for as the big game changing factor! Ice pounding my windows as I type this. I am really keeping an eye on how much moisture is advecting in, to see just how bad things are going to get? Significant icing is possible for a large area. Not to mention all the possible snow!

Historic winter storm shaping up!

First Mesoscale discussion up now due to low level jet ramping up causing low level convergence. Forcing up precip in the form of freezing rain. The warmth of the roughly 850 mb layer is above freezing. This means that precip is falling melting and then re freezing on the ground. This is only the beginning of what looks to be a very large system impacting a great deal of the midwest. The 500mb map shows the scale of whats happening.

Hermine induced tornadic supercells

Hermine has been wreaking havoc on the TX country side. Causing major flooding all over central to northern TX. A recent threat however has come in the form of tornadic supercells. Mini supercells that is. Fast moving storms, that are not very tall or wide. But tight and able to spawn tornadoes due to the presence of instability and wind shear. As this once tropical system interacts with the jet stream or westerlies. It is encountering dynamics that are mostly inherent in extra tropical systems. Meaning it is transforming into a somewhat powerful extratropical cyclone. Stronger upper level winds are now interacting with the low level winds causing some significant wind shear, on the order of 300m/s SRH!

Above images of 500mb wind speeds, and Storm relative helicity. Showing enviroment capable of tornadoes! Below is a video shot from some height. Its great in that it shows the circulation on the ground look closely!

March 8th 2010 "cold core" event.

Image by cloud9tours. This image is important because it shows important structure. Which helps us evaluate what exactly we are dealing with here. This cell is actually more reminiscent of a classic supercell. And is probably more reflective of a somewhat higher cape higher shear event than a true cold core low type setup. So besides the classic cold core setup we are dealing with something of a hybrid. Temps were in the low 60s with dewpoints in the 50s. But with the extremely cold mid level temps cape values were a little higher than usually. Plus we had some very intense wind profiles! Overall nature always has the ability to surprise us. Even when we think we are starting to figure things out!

Surface analysis at 2107z right around the time the first towers were going up along the boundry. The boundry being what was labeled as a pacific front. But was really a dryline/occlusion due to surface heating. The occlusion was a dryline/warmfront. The surface heating was very important in raising the temp/dewpoint spread which slowly transforms the airmass into something very different than a cold airmass type frontal system. Which for reasons not well understood helps in the types of storms that are produced. Instead of Linear forcing, and subsequent forced convection. We have spotty non-linear convection. Which could be due to a bulge in the dryline/occlusion. But a bulge wasnt evident and convective initiation seemed to be due to surface convergence in key areas where good CAPE was present along with almost no CIN whatsoever. The greater convergence at the surface is also a key function of the compact system allowing the backing of surface winds just ahead of the surface low. Aiding in a triple point type convective situation. Or so it would seem.
Whats also important is the fact this is a vertically stacked system, which is common for cold core type systems. The system is compact and tight. Due to the dynamics, rapid cyclogenesis takes place at the surface which aids in the winds backing and increasing in strength near the low and just ahead of it. This can help speed up the occlusion process. Which in turn is important for convergence. This convergence pushes air in and up helping to fire storms.

The Hammon mini-supercell underway here on radar and satellite. Whats interesting and usually highly important is the dry slot wrapping around the low. Surface heating had a chance to augment the airmass and help with destabilizing the atmosphere ahead of the 500mb low. Whats also important is you can see dust being kicked up by the strong surface winds on the satellite image.

Modified RUC sounding showing some fat CAPE even for a cold core event. Due to the steep lapse rates and very cold upper level temps! The hodograph also shows some pretty decent shear. Interesting moisture profile.

RUC surface analysis. Confirming setup is prime for development and already underway. Alot of convergence along the dryline/pacific front, warm frontal occlusion. It also confirms what we were seeing on satellite with the dust being kicked up. 30 knots down in west central TX behind the dryline kicking up some dust!

RUC 500mb analysis for 23z showing strong negatively tilted closed cold core low. With temps at and around -20 C. Strong Jet max rounding base. This as you can see is a very compact, vertically stacked system which is important in cold core tornadic events. This system is supplying alot of shear and alot of upper level forcing!

Unlike alot of cold core events some parameters started to show up right around the time the Tornado was occurring. Although by this time its far too late and still doesn't really highlight an area of huge concern. Cape values around 1000 j/kg, co located with high SRH values (but still not that high) had painted a nice EHI bulls eye around the Hammon area.

Feel free to comment with questions and critiques afterall this is a learning process for all of us. And I certainly dont know much in the way of meteorology, I am no expert. So feel free to comment!

Big system Christmas Eve!

Awesome system, with severe weather all over the place. 992mb low with just an insane upper and lower level pattern. Vertically stacked even though it is highly baroclinic. The 500mb vort map below shows another low ejecting down and south towards the main system. With a Vort lobe extending south. Not sure what this is going to mean for the whole evolution. Besides keeping alot of snow falling up in the Dakotas.

Infrared map showing cloud cover and a somewhat atypical baroclinic leaf system. With rain falling throughout, LOL besides on the backside north and northwest. You can even see the cold frontal boundry in the gulf, it appears as a sharp line of clouds extending to the south.

Satellite image earlier today, showing the intense system. It shows up as a comma type cloud pattern in the south east. With strong jet wrapping in.

Surface pattern via RUC surface analysis.

500mb winds showing strong jet wrapping into system. This long wave trough is also negatively tilted. Showing lots of potential for extreme cyclogenesis. And with the secondary upper level low, we have a secondary cold front surging south behind the first system.

What this all means. Well with an occluded front and maturing wave. We have wide spread rain and wind and on the backside a major blizzard. Luckily all severe weather should be confined to the open waters of the gulf. Widespread wind should start to over spread the western parts along with frigid temps. Winds should also start to strengthen overnight on the eastern side as this low actually curves north. Fun fun fun!

Classic Nor'easter

A Nor'easter is developing and quickly deepening over the southeast! It is being driven by a pronounced shortwave trough at mid levels. At the surface we have a large mature wave moving quickly northeast through new england. A typical path for powerful cold core lows called nor'easters. This wave is mainly comprised of a cP air mass and a mT air mass.

Below is 500mb map showing the negatively tilted shortwave. Very powerful, rotating around a long wave trough bringing in a very cold air mass!

Surface analysis, showing a mature wave moving northeast, with moist warm air out ahead of a prefrontal surface trough/convergence zone thats forcing up a mean squall line. Along with cold front in blue. At this time squall line is ongoing through florida and up the coast!

Below is earlier today. Satellite image of the wave as it slowly gains strength before nightfall! Large system, very pronounced! Very large dense coma shape (common) as you can see.

Snow was falling on the backside of this system, as well as Tornado watchs on the leading edge of the warm front and south into the warm sector. Due to CAPE values in and around 2500 and SRH up around 500 in most places. Typical for these very powerful systems. The satellite image is very impressive just the size is amazing!

Oct 28th 2009

Severe threat possible ahead of developing severe squall line! This line is just starting to gain momentum. Threat could intiate an on going severe weather threat that may be on going through thursday! The severe potential tonight still remains out ahead of this developing line with any discrete cells that can form. Tornadoes are possible with any of these discrete cells but a qlcs or quasi linear convective system still has the potential at forming a tornado with the large shear in place.

Tomorrow looks even more potent as the system moves east. With an ongoing line expected the same story will apply. Discrete cells ahead of the line rooted in the boundry layer are going to have ample shear to develop low level rotation! This is an on going threat as low deepens and continues to pull in moisture along the gulf! Friday the models begin to diverge a little! But overall picture is pretty clear! Below is an image of the 850 millabar winds. Showing a very fast low level jet up around sixty knots (around 70 mph) thats a WOW! So any updrafts that do get going could just be sheared apart. But if any vigorous convection can get going and sustain itself on the partially moist LLJ! Look out!

Another thing to note is the partially backed but strong low level flow, which is leading to largely curved hodographs! Hodographs that denote definite tornado potential enviroments. Low level advection should not be an issue with a large deepening low, despite models. The main problem the models seem to suggest, is the upper level temps are just to warm. If this changes we could have a large outbreak of severe weather on our hands friday. If not the severe potential is going to be quite limited.

Radar image around 9:27pm is of a squall line forming in western TX. This could be ongoing through tomorrow!

July 8th 2009 Severe weather potential

Large trough and associated upper level low moves in over the upper northwest. At the surface a 999mb low is moving east through the northern plains. With an occluded front/surface trough extending north to another low center in Canada. Backing winds at surface look to converge with south westerly winds behind front later this afternoon. This should act to initiate storms, with forecasted dew points in the upper 60s and lower 70s ample moisture should be in place over ND and SD!

500mb RUC forecast for 20z showing the trough and associated jet streak. Low level jet should increase late afternoon to around 30 kts increasing low level shear. This coupled with steep mid level lapse rates and surface temps reaching the upper 70s lower 80s CAPE values should reach 2000 j/kg.

Hodograph for 23z southwestern ND. Note the turning and relatively decent speeds at lower levels. Should be an interesting enviroment for any storms in this area. Tornadic supercells are going to be very likely today!

2009 an analysis

Looking through the past couple events 2009 seems to be lacking something in the tornado market. What it is isnt exactly clear! Most explosive events with what seemed to be adequate shear have failed to produce with one or two exceptions. What it seems to boil down to is a lack of significant surface features. and when there seems to be adequate moisture the winds are lacking. The past two events that should have held high tornado potential specifically June 7th and June 5th which did yield a tornado before the cells were rooted on a cold/stationary front. June 7th seemed to yield the same results. With cells going up then moving into unfavorable air. Which is highly unlikely for a triple point event. Cells normally go up then move into the warm sector. With these events they seemed to take paths that lead them in the other direction. The lack of surface winds on the 7th really made a difference. It seemed the instability was obviously good but the cells on the 7th lacked good low level rotation. And maybe even in the lowest 1km.

It seems that 2009 is going to continue to be a frustrating year. Where most other years seemed to get better later on. Its interesting to study such cases in detail which I have yet to do. But its always a nice contrast from a learning perspective.

Chasing June 5th 2009 Live!!

Absoluteinstability.net will be teaming up with 4849 productions for the chase today and tomorrow! 4849 productions will have a live feed going for the chase through severe studios. So you'll be able to watch a chase live in the high plains today and tomorrow just follow the link below.

http://www.severestudios.com/cgi-bin/player.pl?username=walt.vanrheen