March 13, 2018

Managing Storm Chase Convergence

CHASER CONVERGENCE IS THE GATHERING OF STORM CHASERS & THEIR VEHICLES IN THE VICINITY OF A STORM. THIS IS NOT AN EDITORIAL ON THE DEGREE TO WHICH CONVERGENCE IS OR ISN'T A PROBLEM. IT IS A REFLECTION ON HOW I MANAGE CONVERGENCE AS ONE OF THE MANY CONDITIONS THAT MAY COME WITH A STORM.

On the morning of a storm chase, well before the cap breaks and storms fire, I anticipate whether it will be an active day with many chasers, or whether it’s likely to be a quiet one. If I mentally prepare myself for a busy day, I feel more confident out there when it is a little crowded. So, I consider factors that may contribute to convergence:

  1. How was the event forecast? I expect more chasers out on days that have been a) forecast with significant lead-time, and b) predicted to be major systems.
  2. What is the timing of the event? Peak season is usually more crowded than off season and weekends are busier than weekdays. Long weekend setups are particularly active.
  3. Where will I be chasing? IMO some states – Oklahoma for example – are considerably busier than others, regardless of other factors.
  4. What will the road network be around my target? Mile-by-mile grids afford chasers options and spread them out; limited roads may result in crowding.

Once the storm has fired and my chase is on, I evaluate and consider the impacts of key factors, and one of them is the other chasers around me. I weigh the volume on the roads just as heavily in my decision making as I weigh real-time weather information or visuals. For example, I consider congested roads to be a heightened chase hazard, just as I consider high-precipitation storm mode to be a heightened chase hazard. If I am on a storm that is crowded, I specifically consider:

  1. How will traffic affect my escape route? I am always cautious when my escape route is southbound and terminates at a T-intersection; if I need to turn left (east) to stay ahead of the storm or continue to a safer position, there may be a steady flow of traffic that makes the turn difficult or delayed. This is especially true if there is no stop sign for the west-east vehicles. If it is an all-way stop, traffic may back up with a significant delay for the flow in all directions.
  2. Do I need to pass through a town? I often try to move through a town before stopping to watch a storm. Even if this means I must wait longer to get a visual than other chasers, that’s fine. I would rather position on the lee side of town so that I don’t have to get through the community when I need reposition or evacuate to safety.
  3. How will traffic affect my maneuverability? Traffic can impact the ability to do some turns or U-turns, to pull-off or re-enter the traffic flow, or to drive up to the posted limit. If congestion is at a level where maneuverability isn’t as good as I want it to be, this becomes a safety consideration as important as any other.
  4. How are the other vehicles around me driving? Are other chasers driving focused and responsibly? Is the behavior of non-chaser vehicles impacted adversely by the storm? My vehicle is far from the only vehicle I need to consider.

If any of these factors have me uneasy I remove myself from the vicinity, and as a matter of habit I try to be the first on the move to reposition or evacuate from an advancing storm. Just as I would keep more distance from a violent tornado than, say, a landspout, I keep more distance from a storm when conditions are crowded as opposed to when they are not.

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