Ramblings of a Graduate Student

Today was a travel day.  The armada is leaving Nebraska for (hopefully) stormier pastures to the south.  Other than this, not much more to share.  Tomorrow should be an operations day.  Here’s to hoping.

The armada spent the night (again) in Hot Springs.  Today they headed south to play some marginal supercell environments in Nebraska.  I was unable to participate in today’s marginal operations because of my college roomate’s wedding (Congratulations Mr. and Mrs. Thompson!).  While I have not heard of any successful stories, I do know there was at leats one tornado near I80.  This tornado was not the result of larger scale environmental processes, but storm interactions and mesoscale (near storm) processes.  However, the simple fact that the atmosphere produced a tornado is an improvement in VORTEX II’s fortunes.  Let’s see how the upcoming week pans out…

Tomorrow may have a play to the north or will be a travel day so the armada can head south.  We’ll decide this tomorrow morning.

I’ll be back in the loop tomorrow.

Have we reached rock bottom?  I guess I can’t answer that question right now, but if we haven’t hit rock bottom, I sure don’t want to find it.

The armada spent the night in Hot Springs, South Dakota.  The rationale was that since the better shear was located in the northern United States, and the possibility of upslope flow in eastern Wyoming, that a supercell thunderstorm might develop west of the Black Hills.  The armada “deployed” in far southwestern South Dakota and watched a multi-cell (non-severe) thunderstorm struggle to sustain itself to their north-northwest, near Custer, SD.  By the time it was clear that thunderstorm turned shower had no hope of redeveloping it was too late to target any other storms.  The armada called an end to operations around 6PM MDT.

Hope is still being held for the possibility of stuff in the southern plains late in the weekend / early next week.  If it does pan out, the armada will need to hurry back down to the Texas panhandle from South Dakota.  That does not sound like a fun drive…

Today was a travel day.  The armada spent last night in Alliance, Nebraska scattered about four hotels.  While the idea is to target the same general area tomorrow, the armada moved to a bigger city in hopes of getting everyone in the same hotel.  Tomorrow is about about as bad (for supercells and tornadoes) as we have had on any day so far.

Some more statistics on just how bad this is…

Typically the week of 17 May through 23 May is one of, if not the, most active severe weather week of the year.  On average, the Storm Prediction Center issues a combined 30 severe thunderstorm and tornado watches during this seven day period.  The lowest number of watches issued was in 1984 when only 10 were issued, and 1989 was the most active with 59.  So far in 2009 a grand total of 0 watches have been issued.  We have 2 days left to go in the week and it doesn’t appear that severe weather will be a threat during these next 2 days.  In fact, it doesn’t appear that there will be much of a severe weather threat over the next 10 days at this point.  Simply put, what is currently going on in the atmosphere is amazing.

Anyways, if something doesn’t change soon, VORTEX II will be in even more trouble than they are now.

Same song, different verse…

After spending the last two nights in Ogallala, Nebraska (west of North Platte on I80), the armada targeted an extremely marginal setup today in the northwest Nebraska panhandle.  This region of the country has an extremely poor road network for conducting tornado research (which is why it is not included in the “official” VORTEX II domain), not to mention that the Nebraska Sand Hills are located in this region as well leaving poor visibility.  Nothing exciting happened meteorologically to the armada today, however they did at least witness several thunderstorms.  The next few days look to be even worse than today.

I wanted to write a few words tonight on just how bad of a weather pattern we are experiencing.  The last severe thunderstorm or tornado watch was issued on 16 May 2009 for New England (it was a Severe Thunderstorm watch).  There has not been a reported tornado in the VORTEX II domain since 15 May 2009, and that was in the Texas panhandle.  It is absolutely unheard of for the Storm Prediction Center to go four days (and it appears it will be even longer) without issuing a watch during May.  This is peak severe thunderstorm / tornado season after all.

The meteorological reasoning for this amazing streak of little to no severe thunderstorm activity is the result of two rare events and one highly unusual event occurring simultaneously.  First, last Friday and Saturday a strong cold front pushed south through the US Plains and into the Gulf of Mexico.  This cold front pushed all the deep atmospheric moisture very far south into the Gulf of Mexico.  While this is certainly not a common occurrence, it is by no means rare or highly unusual.  What happened next, however, is rare.  A tropical low pressure system (known as a TUT, or Tropical Upper-Troposphere, low) moved west across Florida and strengthened as it interacted with the remnant cold front located across the Gulf of Mexico.  This strengthening system resulted in strong northerly winds across most of the Gulf of Mexico that pushed the remaining moisture south, out of the Gulf of Mexico.  This strong low pressure (which is not a hurricane or tropical storm) located over Florida and the lack of moisture across the entire central United States are both extremely rare events for May.  Furthermore, a strong mid-tropospheric high pressure developed in the middle of the US Plains.  This strong high pressure results in calm winds and warm temperatures aloft and sinking air near the surface.  All three of these things are big negatives for severe thunderstorm development.  Couple this with the absolute lack of moisture means that severe thunderstorms will be nearly impossible.

This atmospheric pattern does not appear to change anytime soon.  Numerical forecast models keep most of the stronger mid-troposhperic winds in the far northwestern US and into Canada for as long as they can forecast.  Additonally, most models keep the tropical-like low over the Gulf of Mexico for the next few days…meaning moisture in the northern US will be hard to come by.  It might take until the end of the first week of June to break out of this pattern…if we ever break out of it.  All of this spells big trouble for VORTEX II research.  A lot of tough decisions will have to be made in the coming days about what to do if this pattern continues any longer…

Still down…sort of.

The armada attempted to study microbursts today in northeast Colorado.  Severe thunderstorms, supercells, and tornadoes were really nowhere to be found across the domain so this was the next best thing.  They armada investigated several “high based” thunderstorms (cloud bottoms ~10,000 – 15,000 ft above ground) that developed in the dry air of northeast Colorado.  As the rain from these high based thunderstorms falls into the dry air, the air cools and becomes heavier than the air below.  This cool air then rushes down to the ground very quickly and is called a microburst.  Microbursts are an extreme hazard to the aviation community, resulting in several airline crashes in the past.  Nowadays most large cities have one or more Doppler radars at airports (known as Terminal Doppler Weather Radars; or TDWR) that specifically look for microbursts.  Since the adoption of releatively widespread use of TDWRs airline crashes resulting from microbursts have become non-existant.

Anyways, the armada is holding out hope for a chance of “real” thunderstorms tomorrow.  We shall see…

Well, we are still down.  However, the good news is the armada is leaving Hays, KS and heading toward western Nebraska for a potential (albeit slim) deployment in eastern Montana tomorrow.  We’ll see how that goes…

One of the reasons we are “down” right now is a ridge of high pressure in the middle atmosphere has moved into the central Plains.  This high pressure aloft causes air to sink down toward the ground, which is exactly opposite what you need for thunderstorms.  Furthermore, a subtropical low pressure is developing across the eastern Gulf of Mexico (near Florida).  Although, this low will help alleviate the current drough conditions in Florida, it spells doom for forseeable future in terms of tornadoes in the Plains.  The reason is that the flow around this low pressure causes winds to be out of the north on the west side of the low.  This north wind is located over most of the Gulf of Mexico and is advecting moisture south toward southern Mexico and not toward the Plains.  This lack of moisture in the Plains means a necessary condition for thunderstorm development will be severely lacking for most of this week.

Models hint that this subtropical low will hang around the Gulf of Mexico for a few days / rest of the week.  This is wonderful news for Florida, however it means that moisture mill continue to be pushed further away from the armada.  Once the subtropical low dissipates or moves off the east coast it will take a few days for the moisture to return to the Plains.  Thus, with the exception of marginal chances across the far northern portions of the US, the armada is in a wait and see mode for the forseeable future.