Write up on June 1st, 2011

[weatherwiz]

I've always been real interested in doing write ups, or follow ups of major events across our region but I've never really got around to really doing so, or when I'd sit down and try to write I'm never really sure on how to go about it or how to explain it. For this event though I made sure I did something. I know some have already posted follow ups and they were really great but I think I need alot of work in this department so I'm hoping I can get as much feedback as possible so I can hopefully become better at this.

I tried to input as much meteorological input as well and tried to explain it all b/c I do post these things on facebook and I do have many friends who enjoy reading things I write and obviously they don't have a clue on the background behind everything so I always try to explain things as clearly as possible...I've even gotten a few of my friends to actually take an interest in weather lol.

On Wednesday, June 1st, 2011 a strong cold front pushed into a very hot and humid airmass which had been in place over the Northeast for several days. Temperatures had been in the 80's to near 90°F at times with dewpoints in the mid and upper 60's. The combination of high temperatures and dewpoints helped to create a highly unstable airmass. This all lead to help transpire the biggest tornado outbreak in the state of MA since July 3rd, 1997 and the deadliest since the infamous F4 tornado which hit Worcester, MA on June 9th, 1953.

High end severe weather outbreaks are fairly rare in New England but tornado outbreaks are much more rare. Unlike the Great Plains and mid-west regions the ingredients needed to produce high end severe weather outbreaks and tornado outbreaks rarely come together here. However, on June 1st, 2011 the pattern that was in place was perfect and all the ingredients needed to produce a high end severe weather/tornado outbreak all came together.

The synoptic setup was one in which a strong ridge was in place across the southern US. New England was located just on the crest of the ridge. Bring on the crest of the ridge allowed for very warm temperatures and high dewpoints to work into the region and it also allowed the flow aloft in the mid-levels of the atmosphere to be more westerly/northwesterly which is a very good trajectory for potent severe weather events in New England.

The placement of the ridge was also special as it was in a favorable position to allow the advection of an elevated-mixed layer into New England. Elevated-mixed layers (EML's) are absolutely crucial in getting high-end severe weather outbreaks in New England. Below is a map of the 500mb pattern setup, as you can see there is a strong ridge across the south with New England right on the crest of the ridge.

Elevated-mixed layers originate over the inter-mountain region and the desert southwest. They develop as air traversing over the Rockey Mountains dries significantly and then warms significantly when crossing over the desert areas. In EML's the temperatures from about 800mb to 600mb (~6500ft AGL-~14000ft AGL) will warm, sometimes significantly and the dewpoints in this layer will rapidly drop. The EML, as mentioned above, is an extremely crucial ingredient in high-end severe weather/tornado outbreaks.

EML's are associated with very steep mid-level lapse rates (change of temperature with height) and this can lead to extreme instability at the surface (depending on degree of solar heating at the surface and how high the dewpoints at the surface are). EML's can be visually seen by looking at a skew-t forecast sounding. Below are a few examples of an EML, including a few soundings from June 1st, 2011.

Here is a skew-t from Albany, NY. Skew-t's are derived from weather balloons which are launched into the atmosphere and record variables such as temperatures at different heights, dewpoints, and wind speed/direction. This sounding is from 8:00 AM EDT. If you look at the 800mb to the 700mb level you can see the EML.

Here is a skew-t from Upton, NY showing the EML very well over this area.

It is very rare to get EML's to work all the way into New England. Usually as they work through the Plains and move east they tend to weaken as they are influenced by weather across other portions of the region. The dry air begins to moisten up as moisture from the Gulf of Mexico works northward and the temperatures associated with them cool off a bit. There occurrence is much more common across the Plains which is also one of the reasons why they are much more susceptible to large-scale severe weather and tornado outbreaks. Below is a forecast sounding from Oklahoma City, OK taken at 7:00 PM on May 22nd 1981, as you can see from the sounding below the EML is much more visible down across this area.

Besides providing the potential for extreme instability EML's are also important because they provide what is called a cap, this is why EML's can also be referred to as capping inversions. While EML's are important because they are associated with steep mid-level lapse rates which helps to enhance instability as mentioned above, the capping inversion is very important as well. Capping inversion prevent clouds/showers/thunderstorms from developing too early in the day. This is very important because it allows for more solar heating and allows the atmosphere to destabilize even further.

What makes the capping inversion from preventing clouds/showers/thunderstorms from forming? As mentioned earlier the capping inversion, or EML, is a layer within the atmosphere where the temperatures warm and the dewpoints drop. Water parcels which are in the atmosphere thanks to evaporation and transpiration will continue to rise only as long as they remain cooler than the surrounding air. Once the parcels reach this capping inversion they can no longer continue to rise, therefore, they will not reach the level of condensation and will not develop into clouds until this inversion is broken.

The presence of the EML along with a very warm and moist low-level airmass characterized by surface temperatures well into the 80's and dewpoints close to 70ºF lead to an extremely unstable airmass across the region. There are several different indices on measuring how stable or unstable the atmosphere is; surfaced-based cape, mixed-layer cape, most-unstable cape, normalized cape, and the Lifted-Index.

Surfaced-based cape (SBcape) is a measurement of the total convective available potential energy (Cape) available to a parcel of air originating at the surface to it's level of free convection (LFC). The LFC is the altitude in the atmosphere where the temperature of the environment decreases faster than the moist-adiabatic lapse rate of a saturated air parcel at the same level.

Mixed-layer cape (MLcape) represents the mean potential energy conditions available to the parcels of air located in the lowest 100mb (~3000-3500ft AGL) of the atmosphere when lifted to the LFC.

Most-unstable cape (MUcape) measures the total amount of convective available potential energy (cape) available to the most unstable parcel of air found in the lowest 300mb (~3000-6000ft AGL) of the atmosphere while being lifted to it's LFC.

Normalized cape (Ncape) is used to give an indication of how much of the atmosphere is unstable or how "fat" the cape profile is. It's possible you can have large amounts of cape but it can all be loaded into the lower levels of the atmosphere. You want to see a good "fat" cape profile, or lots of cape throughout the column of the atmosphere. Values of 0.1 to 0.2 suggest a rather tall and "skinny" cape profile while values greater than 0.3 and 0.4 are more suggestive of a large and "fat" cape profile.

The Lifted Index (LI) is the temperature difference between a parcel of air lifted adiabatically and the temperature of the environment at about 500mb (~18000ft AGL).

Below is a table describing the above mentioned indices with numerical values pertaining to how unstable the atmosphere is.

Thanks to the EML that had advected over the region the mid-level lapse rates were between 7.0-7.5 C/KM. These lapse rates were measured in the 700-500mb (10,000-18,000ft AGL) layer. Temperatures across the region were well into the 80's with dewpoints right around 70°F. The combination of steep mid-level lapse rates, very warm temperatures, and high dewpoints all lead to an extremely unstable airmass. SBcape values ranged from 3000-5000 J/KG, MLcape values ranged from 2000-3000 J/KG, MUcape values ranged from 3000-5000 J/KG, Ncape values ranged from 0.3 to 0.4, which suggested a very fat cape profile, and LI values ranged from -6C to -10C. All these parameters suggested the atmosphere was extremely unstable. The more unstable the atmosphere, the better likelihood of strong and severe thunderstorms as the more unstable the atmosphere is the faster upward acceleration of air parcels and the more energy there is available for storms to feed off of.

Not only was the atmosphere favorable for severe weather instability wise but there was a great deal of wind energy aloft thanks to the region being on the crest of the ridge and an area of low pressure with a piece of potent shortwave energy passing just to the northwest of New England, just north of the US/Canadian border.

Winds with the mid-level jet from about 700-500mb (10,000-18,000ft AGL) were in the 45-55 knot range with winds with the low-level jet from 925-850mb (2000-5000ft AGL) between 25-35 knots. Winds with the upper-level jet at about 300-200mb (30,000ft-35,000ft AGL) were about 45 knots, however, the region was located in the right exit region of a 60-80 knot jet max that was just northwest of the region. (Depicted below)

When located in the right exit region of the upper-level jet upper level divergence can be vastly increased. This is important as divergence in the upper levels of the atmosphere increases vertical motion and can increase the potential for thunderstorms.

With the mid-level jet being pretty strong (45-55 knots), this created a good deal of vertical wind shear, 0-6km shear values (this is used to measure vertical shear or bulk shear) were between 40-45 knots. This is quite impressive. Vertical shear is an important factor in storm organization and can also be in an important factor for the development of supercell thunderstorms. Usually you'd like to see about 30-35 knots to get good storm organization, and once you get over 35-40 knots you then look at the potential for supercell thunderstorms, or for thunderstorms to take on supercell characteristics. Once you get above these values the upward motion is vastly increased and can actually lead to rotation of the storms updraft.

While there was a good deal of speed shear present (change of wind speed with height) as mentioned above there was also a great deal of directional shear (change of wind direction with height) present. When dealing with the potential for tornadoes directional shear is extremely important as it is this changing of the wind direction with height that allows for thunderstorms to rotate and potentially lead to tornadogenesis, the development of a tornado.

The level of directional shear is measured by helicity, "atmospheric spin". The stronger your speed shear is and the stronger your directional shear is the higher your helicity values are going to be. Helicity is measured from 0-1km and from 0-3km, with the units of m2s2. When dealing with the potential for tornadoes you want to see these values at least higher than 150 m2s2, once you start getting above 200-250 m2s2 the potential for tornadoes is highly increased.

On June 1st there was a great deal of helicity present across the region. The low-level wind fields backed much more than forecast models had indicated. Surface winds were mainly from the south with winds in the lowest 925-850mb (2000-5000ft AGL) coming from a more southwesterly direction. Winds in the mid/upper levels of the atmosphere from 700-300mb (10000-30000ft AGL) coming from a more westerly/northwesterly direction. This created a great deal of directional shear and with the above mentioned strong speed shear values helicity values were very high. In facxt, 0-1km helicity values ranged from 150-200 m2s2 and 0-3km helicity values ranged from 200-300 m2s2. With 0-1km vertical shear values in order of 20-30 knots this indicated the potential for tornadic supercells was a strong possibility.

Given the degree of instability in place along with the level of shear it was becoming quite apparent not only was there going to be a fairly potent severe weather event, but the possibility also existed for tornadoes and even a strong tornado or two.

By noon time showers and thunderstorms had already began developing just ahead of a pre-frontal trough across portions of northern and eastern NY. Just prior to 2:00 PM EDT cells begin to develop across eastern NY just to the west of MA and were pushing eastward into an extremely unstable environment. By 3:00 PM EDT severe storms were now under way across portions of southern VT and western MA as supercell thunderstorms were now in progress, these storms were already in an extremely unstable environment and were working into an area of extremely high helicity. It wouldn't be too long before these storms really began taking off and start to rotate big time.

As 4:00 PM EDT then 5:00 PM EDT rolled around the strongest of the supercells were right across west-central MA. Supercells showing strong signs of rotation were badgering down on the Springfield, MA area. Reports of funnel clouds/wall clouds came in and soon after a tornado warning was issued, a tornado was already in progress, not only a tornado but a fairly large one and long-lived one.

The tornado first touched down just west of Springfield in the Westfield area then continued on through parts of Springfield, then Wilbraham, continuing through Monson, Brimfield, and then finally Charlton. It was estimated that the tornado was on the ground for 67 minutes which is an extremely long time, most tornadoes on average are only on the ground for about 5 minutes. In these 67 minutes the tornado traveled an estimated 39- miles, which is the second longest track on record only behind the Worcester F4 of 1953 which tracked 40 miles.

In it's path the tornado caused major destruction and because of this it was rated a high end EF3, the first tornado rated a 3 in the state of MA and in New England since the Great Barrington, MA F4 tornado on May 29th, 1995. The tornado was responsible for as many as 72 injuries and 3 deaths, making this tornado the deadliest in New England since the Worcester F4 which killed 94 people.

Between 5:00 PM EDT and 6:00 PM EDT yet another supercell developed right over the Springfield area and quickly intensified as it moved eastward. This supercell went on to spawn another tornado in the Wilbraham area, this one much weaker though, classified as an EF1 and was on the ground for about an estimated 8 minutes and traveled just over 3 miles. The time of this touchdown was around 6:32 PM EDT and lifted right around 6:40 PM EDT.

This same supercell then went through a recycling process and ended up producing yet another tornado, this one hitting the Brimfield area which was hit for the second time. This tornado was also rated an EF1 and was only on the ground for 3 minutes traveling just a little over a mile. Luckily there were no injuries or fatalities reported with these two tornadoes.

Just after 7:00 PM EDT a line of severe thunderstorms had developed from western MA down through northern CT and worked eastward, while there was some rotation within a few of these cells, they failed to produce any tornadoes but they did produce some severe weather with damaging winds and large hail.

All in all with this severe weather/tornado outbreak a total of 3 tornadoes were confirmed in southern New England, all in MA, and a total of 5 were confirmed in New England, with the other two occurring up in ME, 87 reports of large hail (1'' in diameter or larger), and 42 reports of straight line wind damage. Below is a map of the storm reports from the Storm Prediction Center website (SPC):

Below is a link to the Public Information Statement from the National Weather Service in Taunton, MA regarding the surveys done.

http://www.nws.noaa....data/BOX/PNSBOX

This was a historic day across New England, setups like this are quite rare and do not happen all that often, everything needed to produce a high end severe weather/tornado outbreak came together on this day. Without the EML in place the degree of instability would have likely been vastly less and the event would likely not have been as potent. With the EML the atmosphere was able to become extremely unstable with instability parameters you usually find out west. This is why the presence of the EML is extremely important for high end severe weather outbreaks.

[radarman]

Nice work Wiz.

[ineedsnow]

awesome job wiz!!!

[weatherwiz]

Thanks guys.

I think the two weak spots in here are the actual unfolding of the event as it was occurring and the final paragraph...something to sum it all up. Obviously for the event part that was difficult b/c I was at a baseball game so I tried going back to radar archives and such.

[OKpowdah]

Nice discussion!

One area that I think you might have mixed up is the jet quadrant. On that map, SNE is under the right exit region of the jet streak (the jet max is to the northwest, near northern Michigan). So we don't technically have support from the secondary ageostrophic circulation. Usually large scale lift due to vorticity advection downstream of the trough is of greater magnitude than that from the jet circulation anyway

[weatherwiz]

Nice discussion!

One area that I think you might have mixed up is the jet quadrant. On that map, SNE is under the right exit region of the jet streak (the jet max is to the northwest, near northern Michigan). So we don't technically have support from the secondary ageostrophic circulation. Usually large scale lift due to vorticity advection downstream of the trough is of greater magnitude than that from the jet circulation anyway

Yes you're right...thanks for pointing that out.

I always for some reason get this screwed up.

[weatherwiz]

I'll just have to go back and rework that part.

[weatherwiz]

I see it now...isn't upper-level divergence enhanced in a portion exit region of the jet stream? While in the left front quadrant that's where the upward vertical motion and severe wx potential is increased.

[OKpowdah]

Yes you're right...thanks for pointing that out.

I always for some reason get this screwed up.

No worries. It's not an integral part to your discussion anyway.

Nice work!

[weatherwiz]

No worries. It's not an integral part to your discussion anyway.

Nice work!

Yeah that's true

I can probably correct this pretty easily...I already redid the map...just gotta make a small little discussion on it.

Thanks!

EDIT: I corrected it.

[bobbutts]

Interesting read and I learned a few things. Thanks, nice post..

[CoastalWx]

I see it now...isn't upper-level divergence enhanced in a portion exit region of the jet stream? While in the left front quadrant that's where the upward vertical motion and severe wx potential is increased.

What made your point was more like a 200mb. At 200mb we started seeing the right entrance region developing on the jet at 21z. 300mb did not help us much here.

Also, notice there is a little divergence as the jet starts to turn clockwise away from SNE..thus venting us a bit here.

[weatherwiz]

What made your point was more like a 200mb. At 200mb we started seeing the right entrance region developing on the jet at 21z. 300mb did not help us much here.

Also, notice there is a little divergence as the jet starts to turn clockwise away from SNE..thus venting us a bit here.

Just went and looked back and I see your point. I didn't look at the 200mb level at all so if I did perhaps I would have caught it.

That divergence though did help us out though...at least a bit, no?

[CoastalWx]

Just went and looked back and I see your point. I didn't look at the 200mb level at all so if I did perhaps I would have caught it.

That divergence though did help us out though...at least a bit, no?

There was probably some venting (maybe just a little), but it is possible to be on the wrong side of a jet streak and still have severe. Jet streaks are weird. There can be a lot of mesoscale things that happen, that sometimes models don't pick up.

[weatherwiz]

There was probably some venting (maybe just a little), but it is possible to be on the wrong side of a jet streak and still have severe. Jet streaks are weird. There can be a lot of mesoscale things that happen, that sometimes models don't pick up.

If we had happened to be on the better side of the jet streak what would have been more different?

Yeah though, jet streaks can be really weird...especially in these cases. They obviously are important (talking about jet quadrants) but I almost feel as if they hold much more importance if there is something else lacking or there are a few things lacking...for the most part everything was going our way and we had all the ingredients and everything was coming together. If we were lacking something perhaps not being in a favorable quadrant would have hurt us a bit more.

[CoastalWx]

If we had happened to be on the better side of the jet streak what would have been more different?

Yeah though, jet streaks can be really weird...especially in these cases. They obviously are important (talking about jet quadrants) but I almost feel as if they hold much more importance if there is something else lacking or there are a few things lacking...for the most part everything was going our way and we had all the ingredients and everything was coming together. If we were lacking something perhaps not being in a favorable quadrant would have hurt us a bit more.

I really don't know, but if we aren't strongly capped (which I don't think we were, but we did def have a cap), then perhaps you run the risk of too much forcing and having storms be discrete for only a brief period of time. I think we had just enough help from some PVA coming in from that ULL. Also, once you do get tstms to break that cap or reach the convective temp, it won't matter much about the jet. Those storms remained discrete thanks to the shear and just enough of a cap I think. For a minute, I thought they would form a cold pool when all those tstms piled into the Berkshires, but then the southern cell (the CEF cell) formed and had a nice supply of warm humid air to tap into.

Don't forget the atmosphere works in harmony. If the setup is there to produce tstms...chances are the jetstream configuration will also be there to possibly help out. It might be a non-factor, or it could be one of the larger reasons for developing tstms. My point is, with an upper level trough approaching and creating a setup for tstms, usually the jetstream configuration will not kill the chances of tstms. It usually doesn't create destructive interference.

[weatherwiz]

I really don't know, but if we aren't strongly capped (which I don't think we were, but we did def have a cap), then perhaps you run the risk of too much forcing and having storms be discrete for only a brief period of time. I think we had just enough help from some PVA coming in from that ULL. Also, once you do get tstms to break that cap or reach the convective temp, it won't matter much about the jet. Those storms remained discrete thanks to the shear and just enough of a cap I think. For a minute, I thought they would form a cold pool when all those tstms piled into the Berkshires, but then the southern cell (the CEF cell) formed and had a nice supply of warm humid air to tap into.

Don't forget the atmosphere works in harmony. If the setup is there to produce tstms...chances are the jetstream configuration will also be there to possibly help out. It might be a non-factor, or it could be one of the larger reasons for developing tstms. My point is, with an upper level trough approaching and creating a setup for tstms, usually the jetstream configuration will not kill the chances of tstms. It usually doesn't create destructive interference.

That's the thing as well, we just had the right amount of forcing in place to go with the amount of instability we had. Although look at the BRN that day I was actually surprised to see what it was...BRN values were between 60-80. Usually this is a good indicator for storm type as well as it takes into account instability/shear/forcing. But looking at what transpired we definitely had the right amount of forcing...not too weak and not overly strong.

I'm sure these storms did form at least some sort of cold pool, don't at least most supercells do? The wind alignment though was absolutely perfect though and the updrafts were actually strong enough to where it allowed the rain cooled air to remain from choking off the updrafts so the storms were able to get a continued feed of warm/moist air. I do see what you mean though, you thought they would form some cold pool extending outward and they may have impacted other convection but potentially disrupting the updrafts.

[CoastalWx]

That's the thing as well, we just had the right amount of forcing in place to go with the amount of instability we had. Although look at the BRN that day I was actually surprised to see what it was...BRN values were between 60-80. Usually this is a good indicator for storm type as well as it takes into account instability/shear/forcing. But looking at what transpired we definitely had the right amount of forcing...not too weak and not overly strong.

I'm sure these storms did form at least some sort of cold pool, don't at least most supercells do? The wind alignment though was absolutely perfect though and the updrafts were actually strong enough to where it allowed the rain cooled air to remain from choking off the updrafts so the storms were able to get a continued feed of warm/moist air. I do see what you mean though, you thought they would form some cold pool extending outward and they may have impacted other convection but potentially disrupting the updrafts.

Yeah cold pools eventually form, but like you said, the shear helped keep the updrafts and downdrafts separate.

[Hailstoned]

Though it has no doubt been forgotten considering the epic events of later that day, here in Monson there was an opening salvo of a brief thunderstorm around 9:00 in the morning of June 1 as the warm front moved through, displacing cooler breezy, less humid conditions. I thought this might result in some lingering cloud detritus, but the sky quickly cleared to the hot, humid conditions that brought on "The Beast".

[CoastalWx]

Though it has no doubt been forgotten considering the epic events of later that day, here in Monson there was an opening salvo of a brief thunderstorm around 9:00 in the morning of June 1 as the warm front moved through, displacing cooler breezy, less humid conditions. I thought this might result in some lingering cloud detritus, but the sky quickly cleared to the hot, humid conditions that brought on "The Beast".

Some of the more notable severe events in SNE featured just that. Warm front thunderstorms in the morning, followed by big severe in the aftn.

[weather01089]

Link to the June 1 tornado video I shot

Ray