The upcoming changes to the Day 1-3 Conv. Outlook
Apr 22, 2014 11:49:05 GMT -6
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Post by Briella - Houma on Apr 22, 2014 11:49:05 GMT -6
From the SPC page:
link
Q: How are the outlooks changing for Day 1, Day 2 and Day 3?
A: The SPC will revise Day 1 through Day 3 categorical severe weather outlooks to better communicate risk and describe the likelihood of severe weather. Format changes will also improve the use of SPC severe weather forecasts for customers who incorporate SPC outlooks into GIS systems.
The SPC is expanding the risk categories from four to five and clarifying the risk previously labeled as "See Text." That descriptor will be replaced by a categorical line and the term "Marginal" to denote areas with a 5 percent probability of severe weather. The upper end of the "Slight Risk" category will be renamed "Enhanced" (short for "Enhanced Slight") to denote a threshold 30 percent probability of severe wind or hail and/or a 10 percent chance of a tornado during the Day 1 period. For Days 2 and 3, the "Enhanced" risk category will denote a 30 percent total severe probability. The Moderate and High risk thresholds will remain essentially unchanged.
Current:
1. See Text
2. Slight (SLGT)
3. Moderate (MDT)
4. High (HIGH)
Proposed:
1. Marginal (MRGL) - replaces the current SEE TEXT and now is described with Categorical line on the SPC Outlook.
2. Slight (SLGT)
3. Enhanced (ENH) - will replace upper-end SLGT risk probabilities, but is not a MDT risk
4. Moderate (MDT)
5. High (HIGH)
current:
New:
The examples below juxtapose the proposed (left) and the current (right) outlook graphics for the marginal (MRGL) categorie as opposed to the current SEE TEXT labels which does not clearly define the geographical areas of concern.
current:
new:
Below is an example of a proposed Public Severe Weather Graphic that includes the new categories. This graphic is enlarged on the area of greatest risk and designed for use by media partners and social media.
Q: Why is the SPC proposing to do this?
A: A primary goal of these changes is to bring better consistency to the risks communicated in SPC outlooks, from the short-range Day 1 outlooks through the extended range Day 4-8 outlooks. The changes are being made based on customer feedback and to better meet their needs.
Example: Currently, a 10 percent tornado probability including a risk of a significant tornado (>=EF2) is categorized as a Slight Risk. This is the same category used for a "low end" 15 percent risk of severe thunderstorm wind and hail events. In the new scheme, a 10 percent tornado probability that includes the chance of significant tornadoes would be categorized as an Enhanced Risk.
In addition, "See Text" does not currently convey a threat area, due to the lack of a contour in any "See Text" categorical forecast. And the current "Slight Risk" category covers too broad a range of severe weather probability values.
Q: Are there cases where the current categories will change based on the underlying severe weather probabilities?
A: The thresholds for traditional risk categories are essentially unchanged but there is some refinement in the underlying definitions to remain consistent with evolving trends in severe weather reporting. These refinements would only impact a couple of Day 1 tornado and severe wind outlooks during any year. A 15 percent tornado probability without a threat of an EF-2 or greater tornado at Day 1 will qualify as an Enhanced Day 1 tornado risk as opposed to the current scheme where it is a Moderate Day 1 Tornado Risk. Likewise, a 45 percent severe thunderstorm wind probability without a significant threat at Day 1 will qualify as an Enhanced Day 1 wind risk as opposed to the current scheme where it is a Moderate Day 1 wind risk.
Q: Why not a more comprehensive overhaul of all categorical outlook words (i.e. SLGT, MDT, HIGH)?
A: The categorical words Slight, Moderate and High have been used by SPC for nearly 35 years and are generally understood by the weather risk communication community. Making measured changes to the current system, we believe, is more effective than a wholesale change. These measured changes include: 1) moving to de-emphasize the specific words; and 2) working to communicate the level of risk to the public in multiple ways. This includes numerical risk categorization, appropriate colors to indicate severity, and strategic use of icons and symbols. Social scientists have encouraged us to communicate on multiple levels and not just with a single word, label or category.
Q: When will this change occur?
A: A 45-Day Public Comment Period regarding the proposed outlook changes will end on June 17, 2014. After assessing the feedback and incorporating any needed adjustments, a Service Change Notice will be issued at least 75 days prior to the implementation of changes to the outlook categories. Currently, a change is most likely to occur in September 2014.
link
Q: How are the outlooks changing for Day 1, Day 2 and Day 3?
A: The SPC will revise Day 1 through Day 3 categorical severe weather outlooks to better communicate risk and describe the likelihood of severe weather. Format changes will also improve the use of SPC severe weather forecasts for customers who incorporate SPC outlooks into GIS systems.
The SPC is expanding the risk categories from four to five and clarifying the risk previously labeled as "See Text." That descriptor will be replaced by a categorical line and the term "Marginal" to denote areas with a 5 percent probability of severe weather. The upper end of the "Slight Risk" category will be renamed "Enhanced" (short for "Enhanced Slight") to denote a threshold 30 percent probability of severe wind or hail and/or a 10 percent chance of a tornado during the Day 1 period. For Days 2 and 3, the "Enhanced" risk category will denote a 30 percent total severe probability. The Moderate and High risk thresholds will remain essentially unchanged.
Current:
1. See Text
2. Slight (SLGT)
3. Moderate (MDT)
4. High (HIGH)
Proposed:
1. Marginal (MRGL) - replaces the current SEE TEXT and now is described with Categorical line on the SPC Outlook.
2. Slight (SLGT)
3. Enhanced (ENH) - will replace upper-end SLGT risk probabilities, but is not a MDT risk
4. Moderate (MDT)
5. High (HIGH)
current:
New:
The examples below juxtapose the proposed (left) and the current (right) outlook graphics for the marginal (MRGL) categorie as opposed to the current SEE TEXT labels which does not clearly define the geographical areas of concern.
current:
new:
Below is an example of a proposed Public Severe Weather Graphic that includes the new categories. This graphic is enlarged on the area of greatest risk and designed for use by media partners and social media.
Q: Why is the SPC proposing to do this?
A: A primary goal of these changes is to bring better consistency to the risks communicated in SPC outlooks, from the short-range Day 1 outlooks through the extended range Day 4-8 outlooks. The changes are being made based on customer feedback and to better meet their needs.
Example: Currently, a 10 percent tornado probability including a risk of a significant tornado (>=EF2) is categorized as a Slight Risk. This is the same category used for a "low end" 15 percent risk of severe thunderstorm wind and hail events. In the new scheme, a 10 percent tornado probability that includes the chance of significant tornadoes would be categorized as an Enhanced Risk.
In addition, "See Text" does not currently convey a threat area, due to the lack of a contour in any "See Text" categorical forecast. And the current "Slight Risk" category covers too broad a range of severe weather probability values.
Q: Are there cases where the current categories will change based on the underlying severe weather probabilities?
A: The thresholds for traditional risk categories are essentially unchanged but there is some refinement in the underlying definitions to remain consistent with evolving trends in severe weather reporting. These refinements would only impact a couple of Day 1 tornado and severe wind outlooks during any year. A 15 percent tornado probability without a threat of an EF-2 or greater tornado at Day 1 will qualify as an Enhanced Day 1 tornado risk as opposed to the current scheme where it is a Moderate Day 1 Tornado Risk. Likewise, a 45 percent severe thunderstorm wind probability without a significant threat at Day 1 will qualify as an Enhanced Day 1 wind risk as opposed to the current scheme where it is a Moderate Day 1 wind risk.
Q: Why not a more comprehensive overhaul of all categorical outlook words (i.e. SLGT, MDT, HIGH)?
A: The categorical words Slight, Moderate and High have been used by SPC for nearly 35 years and are generally understood by the weather risk communication community. Making measured changes to the current system, we believe, is more effective than a wholesale change. These measured changes include: 1) moving to de-emphasize the specific words; and 2) working to communicate the level of risk to the public in multiple ways. This includes numerical risk categorization, appropriate colors to indicate severity, and strategic use of icons and symbols. Social scientists have encouraged us to communicate on multiple levels and not just with a single word, label or category.
Q: When will this change occur?
A: A 45-Day Public Comment Period regarding the proposed outlook changes will end on June 17, 2014. After assessing the feedback and incorporating any needed adjustments, a Service Change Notice will be issued at least 75 days prior to the implementation of changes to the outlook categories. Currently, a change is most likely to occur in September 2014.