A Case Study in Weather Forecasting:

Thunderstorms in the Gulf Coast Region



This case is told by Petty Officer Trisha Bednarczk, a forecaster at the NASP METOC. She has been forecasting since 1990, including service at NAS-Dallas, Crete and Baharain. She has logged over 13,300 hours at forecasting and forecasting-related tasks.



The Observer at a Detachment is the "eyes and ears" of the regional Forecaster, who is often busy with various responsibilities and is not able to keep close tabs on smaller-scale weather events in the detachment regions. In such cases, the Observer has additional responsibilities, needs to make independent judgments, and must have the confidence to take the initiative. This is illustrated in this case of thunderstorms generated by an outflow that deviated from the typical scenario in unexpected ways. An additional feature of this case is that it illustrates the fact that all forecasters sometimes miss things, and "bust" their forecasts. This put the Observer in the situation of having to "go out on a limb."



Summer 1993.

NAS-Dallas.

I was Assistant Forecaster but was working as Observer since someone was on vacation.

 

 

 

Midwatch is an Observer's watch.

The Observer is the only person on duty.

The Forecaster had left and the field was closed.

The only thing to do on this shift was put out warnings, do some hand chart work every half-hour and take observations about every hour.

 

Action

6:00 PM

My goal at this point was to "kick back."

I only had dash-1s to do.

 

Decision

 

When I cam on duty the passdown was a forecast of thunderstorms.

 

Observation or situation awareness

 

 

The situation was typical for summertime.

Thunderstorms typically top above 45,000 feet.

 

Decision

 

I skywatched, as always.

 

Action

 

When I came on duty I would have looked at the charts.

I would have taken observations at about 6:15.

I skywatch--always.

I remember something was moving down Oklahoma---a trough behind a front or something.

The wind was out of the northwest.

A weak trough had moved through.

 

Observation or situation awareness, Decision

6:15 PM

It was not a severe situation.

This fit the standard scenario, when a front from the southwest moves through.

 

Decision

 

We monitored radar, made direct observations, looked at GOES images, and listened to public weather broadcasts (television and NWS broadcasts).

 

Observation or situation awareness

6:00 PM on

The SRF at Corpus Christi was busy doing DD-175-1's.

The SRF was busy with thunderstorms in southern Texas.

He was too busy to deal with the situation up in Dallas.

 

Observation or situation awareness

10:00 PM

This is difficult for them because they handle three fields--Kingsville, Corpus Christi, and Dallas.

They have a lot to do: Put out 36-hour forecasts and lots of other things.

 

Decision

 

Thunderstorms moved through Dallas from the south-west.

 

Observation or situation awareness

 

10:00 - 11:00 PM

I just thought I'd be done when the first set of storms moved through.

I'd start doing some of my homework.

 

Decision

 

We watched it.

We observed lightning and rain from the quarterdeck.

Onstation we had lightning and rain.

We saw the storms on radar and GOES infrared.

 

Observation or situation awareness

 

This was a no-brainer.

A standard thunderstorm scenario up to this point.

 

Decision

 

They were headed up toward Oklahoma, which is about 100 miles north of NAS-Dallas.

They had 50,000 foot tops.

We could see this on radar and GOES.

 

Observation or situation awareness

 

They got up to the Red River and the cells collapsed.

We could see this in changes in radar reflectivity--you begin to see the outflow's concentric circle.

A novice might have missed it.

Observers often do not have to look.

It is a matter of personal initiative.

 

Observation or situation awareness

 

But the outflow boundaries intersected.

It is like throwing rocks into a pond.

I knew enough from working with the senior Forecaster what this was.

A novice might have missed it, may have seen it as just an anomaly.

 

Observation or situation awareness,

Decision

 

This implies it is an unstable atmosphere and the outflow is a catalyst.

I'd see this happen before.

 

Decision

 

Whenever a big cell collapses you need to look for outflows, to see where new thunderstorms might develop.

This was the same as it here at NASP.

Apprentices get some of this in C-school, but a less experienced person might have missed it completely.

 

Decision

 

By midnight all the warnings had been put out and Corpus Christi said it was dying down, but it built back up.

 

Observation or situation awareness

 

12:00

We could see this on radar and GOES.

From out on the quarterdeck, I could feel the gust front winds.

 

Observation or situation awareness

 

 

T-2 was extended and when the storms got within 10 miles of the Base I put out a T-1.

 

Decision

1:00 AM

The previous watch NAS-Dallas Forecaster had gotten it wrong in his TAF.

He had storms through midnight.

He said it would move out of the area.

He did not expect thunderstorms to remain as intact as they did.

 

Decision

 

There were no alternative courses of action at this point.

 

Decision

 

Usually they move through, unless they are air mass storms when stuff pops up all over.

Observers usually know about air masses.

But usually you do not see stuff move up into Oklahoma and then move back down south.

That is more like what you see closer to the coastal regions.

The situation here happened because of the real strong outflow.

 

Decision

 

Another line of storms built up and pulled the outflow line back down south to just where the outflows were intersecting.

 

Observation or situation awareness

about 12:00 midnight

 

This was my mental model of the situation.

I figured it was a trough or a wind shift.

At this point I couldn't have known precisely what it was since I had limited data.

A novice might have had no clue and may not have been mental modeling the situation.

 

Decision

 

I could see on the satellite imagery, radar, and PIREPS what was going to happen.

The PIREPS mostly provided information about the first line of storms.

By later on most of the flights are done.

After than the PIREPS were from civilian aircraft.

One C-9 had to divert.

 

Observation or situation awareness,

Decision

 

This was not forecast at all.

This was going a little out on a limb because the storm wasn't forecast at all.

The day Forecaster's forecast was a bust.

I was watching and knew what would happen.

The day Forecaster at NAS-Dallas hadn't anticipated it.

He had been Forecaster for about four years.

He was not sure why he missed it.

He had forecast a typical pattern and just happened to not get it.

When you are an Observer you watch the situation.

I knew this was going to happen.

 

Decision

 

There were no alternative courses of action for me at this point.

I had to keep a watch on it and recommend that Corpus Christi look at it.

Someone with less experience might have waited until the last minute, or caught something when doing the hourly observation and then called Dallas or someone would have called them to inquire about the lightning that people could see.

 

Action

 

The SRF at Corpus Christi was barely watching it.

The SRF at Corpus Christi wasn't handling the situation.

He was dealing with a major thunderstorm down there.

 

Observation or situation awareness

 

I called the SRF at Corpus Christi and said, "Look at this. Sign off on these warnings."

He said, "No, nothing's going to happen," but I knew it was coming back down.

I had to depend on my own judgment.

I was confident.

Observers at a Detachment actually have to do stuff, especially in the days before the Internet.

 

Action

Decision

 

I could see the outflows on GOES and did some skywatching.

 

Decision, Observation

or situation awareness

 

12:00 - 1:00 AM

 

I could have not looked outside, but I wanted to know what was coming up.

Besides, I had to go and check the observations.

 

Action

 

Upper-level charts came out only twice per day.

There was no time to do my own chart analysis.

If I had had time I would have done charts, if only for the practice.

I was taking observations and putting out warnings.

I issued a T-1 at about 1:00 AM

I was answering phone calls coming in from people at the Base after the T-1 was issued.

Would we get hail? Gusts?

 

Action, Decision

1:00 AM

I could see it come closer.

I could see lightning.

I watched it for over an hour, starting about midnight.

The only option would have been if it were severe and I'd have to upgrade the warning.

I couldn't know that at that time.

The largest gust we had gotten was 30 - 35 knots.

 

Observation or situation awareness, Decision

12:00 - 1:00 AM

A gust front came back onto the NAS-Dallas.

 

Observation or situation awareness

About 1:00 AM

Back then the forecast was not done by Corpus Christi.

So there was no TAF to modify.

 

Decision

 

I wrote warnings and sent them down to Corpus Christi

I made lots of phone calls.

I advised the Base to tie down the planes.

The only choice was whether to fax or just telephone the information to Corpus Christi right away or wait until later.

A less experienced person may have waited.

I do not like to wait until the last minute.

 

Decision, Action

About 1:00 AM

We got small hail of less than 1/4-inch, and flooding on the quarterdeck.

We got a good light show.

 

Observation or situation awareness

 

Small tornadoes were reported in the area.

On the radar we could not see them--this was an older radar system.

The only indication was citings.

 

Observation or situation awareness

 

The SRF was very glad I was watching it.

He was busy and I was his "eyes and ears."

He accepted my input for the next 36-hour forecast.

 

Decision, Observation or situation awareness

 

About 1:00 - 2:00 AM

I pointed out what had happened to the Forecaster when he came back in that morning.

He poured over the charts to figure out why he had missed it.

 

Decision

5:00 AM

Analysis

 

All of the decisions I made in this case were the right ones.

 

 

 

 

Decision Requirements

 

Cues and

Variables

 

Skywatching is a critical activity, especially for thunderstorm events.

        "I skywatch--always."

Needed

information

 

Local Knowledge

        "This fit the standard scenario, when a front from the southwest moves through."

        "This implies it is an unstable atmosphere and the outflow is a catalyst. I'd see this happen before. Another line of storms built up and pulled the outflow line back down south to just where the outflows were intersecting."

        "Usually they move through, unless they are air mass storms when stuff pops up all over. Observers usually know about air masses. But usually you do not see stuff move up into Oklahoma and then move back down south. The situation here happened because of the real strong outflow."

 


 

 

For Thunderstorm Events

GOES images and loops, radar images and loops, pilot reports, and direct observations provide critical data.

        "We observed lightning and rain from the quarterdeck. Onstation we had lightning and rain. We saw the storms on radar and GOES infrared. They had 50,000 foot tops. We could see this on radar and GOES."

        "They got up to the Red River and the cells collapsed. We could see this in changes in radar reflectivity--you begin to see the outflow's concentric circle."

        "It built back up. We could see this on radar and GOES. From out on the quarterdeck, I could feel the gust front winds."

        "I could see on the satellite imagery, radar, and PIREPS what was going to happen. The PIREPS mostly provided information about the first line of storms. By later on most of the flights are done. After than the PIREPS were from civilian aircraft. One C-9 had to divert."

        "I could see it come closer. I could see lightning. I watched it for over an hour, starting about midnight."

 

 

Experiential Knowledge

        "They got up to the Red River and the cells collapsed. We could see this in changes in radar reflectivity--you begin to see the outflow's concentric circle. A novice might have missed it."

        "The outflow boundaries intersected. It is like throwing rocks into a pond. I knew enough from working with the senior Forecaster what this was. A novice might have missed it, may have seen it as just an anomaly."

        "Whenever a big cell collapses you need to look for outflows, to see where new thunderstorms might develop. This was the same as it here at NASP. Apprentices get some of this in C-school, but a less experienced person might have missed it completely."

 

Hypotheticals

 

 

        "The outflow boundaries intersected. It is like throwing rocks into a pond. This implies it is an unstable atmosphere and the outflow is a catalyst. Whenever a big cell collapses you need to look for outflows, to see where new thunderstorms might develop. This was my mental model of the situation. I figured it was a trough or a wind shift. At this point I couldn't have known precisely what it was since I had limited data.. A novice might have had no clue and may not have been mental modeling the situation."

 


 

Options

 

 

Forecasters sometimes have options, but sometimes they have no options.

        "I could have not looked outside, but I wanted to know what was coming up."

        "The only option would have been if it were severe and I'd have to upgrade the warning. I couldn't know that at that time. The largest gust we had gotten was 30 - 35 knots."

        "The previous watch NAS-Dallas Forecaster had gotten it wrong in his TAF. I had no alternative courses of action. I just pointed it out to the Forecaster when he came back in that morning."

 

Goals

 

 

On long periods of watch the forecaster's goals may include relaxation, doing homework, or other things.

        "My goal at this point was to 'kick back.' I only had dash-1s to do. I just thought I'd be done when the first set of storms moved through. I'd start doing some of my homework."

 

Rationale

 

 

Every forecaster misses things.

        "The previous watch NAS-Dallas Forecaster had gotten it wrong in his TAF. He had storms through midnight. He said it would move out of the area. He did not expect thunderstorms to remain as intact as they did. This was not forecast at all. The day Forecaster at NAS-Dallas hadn't anticipated it. He had been Forecaster for about four years. He was not sure why he missed it. He had forecast a typical pattern and just happened to not get it. Everyone misses some stuff. I pointed out what had happened to the Forecaster when he came back in that morning. He poured over the charts to figure out why he had missed it."

 

Situation

Assessment

 

        'This was going a little out on a limb because the storm wasn't forecast at all. The day Forecaster's forecast was a bust. I was watching and knew what would happen. When you are an Observer you watch the situation. I knew this was going to happen."

        "Someone with less experience might have waited until the last minute, or caught something when doing the hourly observation and then called Dallas or someone would have called them to inquire about the lightning that people could see."

        "I called the SRF at Corpus Christi and said, 'Look at this. Sign off on these warnings.' He said, 'No, nothing's going to happen,' but I knew it was coming back down. I had to depend on my own judgment."

        "I could see it come closer. I could see lightning. I watched it for over an hour, starting about midnight."

 


 

Time/effort

 

 

The Observer at a Detachment is the "eyes and ears" of the regional forecaster. When the regional forecaster gets busy, the Observer takes on special responsibilities.

        "The SRF at Corpus Christi was busy doing DD-175-1's. The SRF was busy with thunderstorms in southern Texas. He was too busy to deal with the situation up in Dallas. This is difficult for them because they handle three fields--Kingsville, Corpus Christi, and Dallas. They have a lot to do: Put out 36-hour forecasts and lots of other things."

        "A novice might have missed it. Observers often do not have to look. It is a matter of personal initiative."

        "This was not forecast at all. This was going a little out on a limb because the storm wasn't forecast at all. The day Forecaster's forecast was a bust. I was watching and knew what would happen. The day Forecaster at NAS-Dallas hadn't anticipated it. When you are an Observer you watch the situation. I knew this was going to happen."

        "The SRF at Corpus Christi was barely watching it. He wasn't handling the situation, he was dealing with a major thunderstorm down there. I called the SRF at Corpus Christi and said, 'Look at this. Sign off on these warnings.' He said, 'No, nothing's going to happen,' but I knew it was coming back down. I had to depend on my own judgment. I was confident. Observers at a Detachment actually have to do stuff, especially in the days before the Internet. The SRF was very glad I was watching it. He was busy and I was his "eyes and ears." He accepted my input for the next 36-hour forecast.

        "I could see it come closer. I could see lightning. I watched it for over an hour, starting about midnight."

        "I wrote warnings and sent them down to Corpus Christi I made lots of phone calls. I advised the Base to tie down the planes. The only choice was whether to fax or just telephone the information to Corpus Christi right away or wait until later. A less experienced person may have waited. I do not like to wait until the last minute."

 

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Insitute for Human and Machine Cognition
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