Reconsidering Use of “Low” in TCIG Level

Descriptors

Rob Molleda

National Weather Service

Miami/South Florida

Forecast Office

Impact Levels are Relative, But...

• Users may not be thinking in same relative sense.

• Impact severity is subjective.

• Local user feedback suggests that the term “Low” in the potential impacts can unintentionally send the wrong message.

Also...

• Fairly wide range of impacts within the Low category.

• Example: Low wind hazard describes impacts ranging from borderline TS to borderline Cat 1.

Examples of Current “Low” Definitions

• Inland Flooding: Flood waters may prompt a few evacuations and brief road closures.

• Wind:  Unsecured light-weight objects easily blown about and become dangerous projectiles. Dangerous driving conditions on bridges and other elevated roadways, especially for high profile vehicles.

• These definitions fit better and can be better described under a separate “Elevated” category between Low and Moderate, with “Low” reserved for very minor impacts.

SPC Has Similar Issue

• SPC will experiment with an additional “Enhanced” risk level in 2013.

• Enhanced risk will be between SLGT and MDT

Proposed Changes

• 1. Replace “Low” with “Elevated (or similar wording).

• 2. Add a separate “Elevated” category between Low and Moderate.

• Color scheme would be: Low (light blue), Elevated (yellow).

• Personal preference is for #2 due to greater consistency with experimental SPC categories.

Pros/Cons

• Pro: Separate borderline moderate conditions from very minor ones (think SPS/SVR or Urban Flood Advisory/FFW. Less potential for underestimation of threat by public.

• Con: Adding an extra category could slightly add to forecaster workload.

Recap

• Current use of “Low” descriptor in TCIG may be correct in a relative sense, but can mislead the public into thinking that a low threat is unimportant.

• “Elevated” or a similar-worded term to cover borderline moderate conditions can more effectively convey a significant threat to life and/or property.

Questions?

Thank you for your time!

National Weather Service

Miami/South Florida Forecast Office