Ramblings of a Graduate Student

VORTEX II was once again forced to call a down day because the atmosphere just wasn’t willing to cooperate. Fortunately for the crew, tomorrow appears to hold more promise for thunderstorms in their general area.

So, with all these down days recently, I wondered how the 2010 tornado season has compared to the tornado seasons of years past. I’ve previously mentioned that 2010 has been a below normal year for tornadoes through the first three months of the year. Now that another (almost) 2 months have passed, and VORTEX II has begun, where do things stand now?

In the image above (which I’ve described previously here), the average over the last five years is marked in grey, and actual events for this year are plotted in red. As you can see, we are still nearly 200 tornadoes below the average over the last five years. This is not a good sign for the VORTEX II crew. Here’s to hoping the next few days and weeks are better for researchers.

A few days ago, I blogged about a satellite signature (thermal couplet) that is indicative of an intense thunderstorm. This satellite signature is identifiable when using the infrared channel. This is because the infrared channel essentially measures the temperature of the object being viewed.

So, what does the satellite “see” in the infrared channel when there are no clouds in the sky? To examine this, take a look at the image above (and below), focusing on Arizona – which for the most part was sunny all day. You should quickly notice the extremely dark colors (indicating warmer temperatures) over most of the state. You might also notice the small sliver of cooler colors (indicating cooler temperatures) extending from northcentral to central to eastcentral Arizona. What is this? Answer below the picture.

The sliver of cooler temperatures is satellite “seeing” the tops of the mountains, which have a cooler surface temperature than the areas closer to sea-level.

What is really cool is to watch a twenty-four hour animation of infrared satellite imagery. You’ll see the colors of the southwest change during the day, going from the cooler colors during the night to the warmer colors during the day. Click here to view a current infrared satellite loop.

As for VORTEX II. They had a day for repairs, laundry, and mission reviews. Hopefully they’ll be back in operation soon – if Mother Nature cooperates.

The Eastern Pacific Ocean (EPAC) has had its first named tropical system of the 2010 Hurricane Season. Tropical Storm Agatha was named, made landfall, and has weakened below tropical storm intensity throughout the course of today. Peak winds topped out at 45mph earlier today, before weakening after landfall. Tonight’s images are of Tropical Storm Agatha.

As a review:

Tropical Depression (TD) has winds less than 39 mph.
Tropical Storm (TS) has winds between 39 mph and 74 mph.
Category 1 Hurricane has winds between 74 mph and 95 mph.
Category 2 Hurricane has winds between 96 mph and 110 mph.
Category 3 Hurricane has winds between 111 mph and 130 mph.
Category 4 Hurricane has winds between 131 mph and 155 mph.
Category 5 Hurricane has winds greater than 155 mph.

Please note that Category 3 hurricanes and stronger are considered “Major Hurricanes”.

As for VORTEX II, today they attempted to target storms in the Thedford, Nebraska area. (You can see the tops of the Nebraska thunderstorms at the very top of tonight’s images!) Although storms did develop, the storms managed to remain in an area devoid of a enough roads for a possible intercept. Thus, the armada remained close to storms but were unable to collect much data. Tomorrow doesn’t look any better for the armada so they have opted to rest, archive data, and do mission summaries/reviews.

Here’s to hoping Monday provides more opportunities for data collection.

As I alluded to on Day 145, a very warm, and humid airmass was poised to affect the southeast United States for most of this week. As a result, afternoon showers and thunderstorms have developed the last several days over much of the southeast. The image above depicts several clusters of ongoing thunderstorms throughout the southeast. The storms in Alabama have wreaked havoc with the Southeastern Conference baseball tournament that is underway in Hoover, AL. Numerous rain/lightning delays have been experienced and more are possible as the evening continues.

As for VORTEX II, a strong cap aloft has prevented thunderstorms from developing in their anticipated target area. As such, V2 is currently traveling to position themselves for tomorrow. Hopefully the atmosphere will cooperate.

Today the National Oceanic & Atmospheric Administration released their official outlook for the 2010 hurricane season.  As you can see above, it doesn’t bode well for those in the Atlantic…

For those wondering about VORTEX II, today was a travel day so no operations took place. The next few days appear to be operations day, so more V2 posts will be in the offering!

Today was day 26 of VORTEX II and the armada operated in the suburbs of Denver in northeast Colorado. Before the armada could even leave the hotel, a very strong thunderstorm developed in the vicinity of Denver International Airport and produced a brief tornado. The armada scrambled southeast toward the storm as quickly as they could and were able to get an extended deployment on this very slow moving thunderstorm. Unfortunately for VORTEX II (yet fortunately for the residents of northeast Colorado) the thunderstorm appears to have been unable to produce a second tornado. In any event, this will once again be an interesting dataset to analyze!

As previously mentioned, the targeted thunderstorm developed very near the Denver International Airport. The image above is a infrared satellite image of the thunderstorm taken very near the time of the tornado. Without going into all the details, an infrared satellite image is essentially displaying the temperature of the cloud top. In the image above the dark reds indicate the coldest temperatures and the grays indicate the warmer temperatures. A colder temperature means the cloud is higher in the atmosphere than a warmer temperature.

Overlaid on the satellite image are surface reports from various official weather stations in northeast Colorado. The observation that is important is the one overlaid on the thunderstorm as it is the Denver International Airport observation. The symbols to the immediate left of the “KDEN” text are the observed “weather” ocuring at the time the observation was made. One of the two weather symbols is what appears to be a funny looking “R”. This is the symbol for thunderstorm. The observation on the far left – the one that looks like “)(” is pretty unique – it is the weather symbol for “funnel cloud”. So in other words, at the time of this report, the weather observer was able to see a funnel cloud with the thunderstorm near the airport. Amazing!

That would make for an interesting blog post in and of itself, but there is something else unique in this image as well. A “thermal couplet” is displayed. In the image below, I’ve removed the observation to give you a clear look at the infrared image. Can you identify anything that might be considered a “thermal couplet”?

In case you were unable to identify the thermal couplet above, I’ve circled it below. In words, the thermal couplet in infrared satellite imagery is identified as an area of colder cloud tops located next to warmer cloud tops. In this particular set of images, the dark reds located to the southwest of the oranges.

So what is going on here, and why is it important? In simplest form, the answer is “warm air rises and cold air sinks”. The longer answer is a bit more complex. To understand, we need to briefly discuss the physics of thunderstorms.

The thermal couplet is the direct result of one of the two key components of a thunderstorm – the updraft. In the updraft warm, moist air from the surface is rapidly transported upward. As the air in the updraft rises, it expands and cools slightly, however, as long as the air in the updraft is warmer than the air immediately surrounding the updraft, the updraft will continue to rise. At some point the air surrounding the updraft will become warmer than the updraft itself causing the air in the updraft to fall back toward the ground. However, so much momentum will have built up in the updraft that it cannot stop immediately. Part of the updraft will continue to rise into the colder surrounding air before falling back into the main portion of the thunderstorm. This is known as an “overshooting top”. As the air falls back toward the main portion of the thunderstorm it warms slightly.

A good way to visualize this process is to put a water hose under the surface of a pool. If you point the hose toward the surface of the pool and then turn it on you’ll notice that bubbling effect of the surface of the pool. Namely, a hill in the water tends to develop on the surface in the direction of where the hose is pointed. This hill develops because the water streaming out of the hose can’t stop when it hits the surface of the pool. It rises out of the pool and then falls back into the water. This is essentially what is happening in an updraft.

So how does this tie into the image satellite image and create a thermal couplet?

The dark colored area circled above is the cold air associated with the overshooting top. When these dark spots begin appearing in the infrared satellite imagery, a meteorologists knows that an extremely strong updraft is present. This is a necessary ingredient for extremely strong thunderstorms.

The lighter colored area circled below is the relatively warmer air caused by the air falling back to the main part of the thunderstorm. It isn’t as concentrated as the updraft because as the air falls back toward the thunderstorm it is blown downstream by the strong winds located in the upper troposphere and lower stratosphere.

A thermal couplet is an indicator that a thunderstorm is intensifying or already extremely intense. The report of a funnel cloud by the weather observer at the Denver International Airport at the same time as this image just acts to confirm what we were able determine from looking only at satellite imagery!

Today was day 25 of VORTEX II and featured a drive south from Ogallala, NE to east central Colorado and west central Kansas. It was a frustrating chase with a lot of driving back and forth. In fact, one of the vehicles passed through the town of Sharon Springs, KS at least 6 times before I stopped counting. At the end of the day, a successful deployment was achieved on the Kansas, Colorado border and lasted for about an hour. I am looking forward to learning more about the awesome dataset that was collected.

Normally, I would make this feat the subject of my blog post, but we’re nearing the start of the Atlantic Hurricane Season and thought I’d discuss the anomalous happenings of the coast of the southeast.

Hurricane Season officially runs from 1 June through 30 November in the Atlantic Ocean and from 15 May through 30 November in the eastern Pacific Ocean. In other words, one hurricane season is already underway and the other is just beginning. The image above is a forecast of the potential for tropical development in the Atlantic Ocean. I’m sure I’ll be posting this image a lot in the coming months, especially since all indications are that this year’s Atlantic hurricane season could be a bad one.

The yellow circle above indicates a region where the National Hurricane Center (located in Miami, Florida) believes there is a 10% chance that a tropical system could develop. Although 10% seems rather low (and it is), the simple fact that we are discussing the possibilities of tropical systems in May is not a good sign. People along the coasts should begin preparing for the possibility of a hurricane now, so that when one approaches they already know what to do and can execute a well thought out plan.

The image above (and annotated below via a yellow circle) captures the upper-level low that is currently being monitored for possible tropical development. Even if this low does not develop into a tropical system, very heavy rains can be expected along the Atlantic coasts of southeastern states.