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SOO Workshop: CIPS Analog Exercise

This 60-minute exercise guides a forecaster in applying the CIPS Analog Guidance. During the forecast periods presented below, specific aspects of the analog guidance are highlighted. Once completed, the forecaster will have a better understanding in how to apply the analog guidance into the forecast process.

In this exercise, you are a forecaster at the WFO in Jackson, MS (JAN CWA) and are using various runs of the analog guidance leading up to an event in April 2014. Rather than navigating through the entire CIPS Analog Guidance web site, links are provided to specific pages of the analog guidance.

Extended Analogs: Days 6 - 8

First, take 10 minutes to quickly analyze the deterministic GFS Model Output initialized at 0000 UTC on 22 April 2014. You are investigating the potential for high-impact weather during the extended period of the forecast (i.e., F144-F192).

Note: It is understood that the forecaster has other model guidance to analyze during this time period. However, the GFS deterministic model output was chosen due to time limitations.

Here is the National Center guidance available on the morning of 22 April: Storm Prediction Center, Weather Prediction Center, and Climate Prediction Center

Discussion Question 1: Does the large-scale pattern suggest the potential for high-impact weather in and around the JAN CWA?

To identify the hazards from similar historical events based on the 6-8 day GEFS model output, for the next 5 minutes, examine the Extended Analog Hazard Guidance.

Reminder: The extended analog hazard guidance is composed of the top 5 analogs from the control run and each GEFS member. This results in guidance based on 105 analogs.

Discussion Question 2: Does the extended analog guidance support the potential for high impact weather?

Short-Term Analogs: Day 4

Between the deterministic GFS model output initialized at 0000 UTC on 22 and 25 April 2014, the forecast of the large-scale atmospheric fields were similar. For this latest run, the forecast period of interest is between F084 and F108.

Here is the National Center guidance available on the morning of 25 April: Storm Prediction Center and Weather Prediction Center.

Over the next 5 minutes, examine the suite of Mean Analysis Maps from the 4-day Analog Analysis Guidance. The mean of the analogs are shown with black contours and the 96-h GFS forecast is shown with red contours. Based on the mean analog fields, think about the following questions ...

Discussion Question 3: What would be the severe weather threats associated with this pattern?

Discussion Question 4: What would be the most prominent threat: hail, wind, or tornadoes?

Discussion Question 5: If tornadoes are a threat, do you think significant and/or long-track tornadoes are possible?

Over the next 5 minutes, examine the Analog Hazard Guidance based on the 96-h GFS forecast.

Discussion Question 6: How does the hazard guidance compare with the threats discussed in questions 3-5?

Discussion Question 7: Let's assume the 15 analogs were chosen randomly, in your opinion, how likely would it be to have 9 analogs with at least one severe report within the JAN CWA? (FYI 9/15 = 60%)

Pro Tip: The percentages shown throughout the analog guidance are not probabilities. They represent the fraction of the 15 analogs meeting or exceeding a threshold. For example, a region within a 60% contour has at least 9 of 15 analogs exceeding the threshold.

Short-Term Analogs: 36-Hour

The NAM model output initialized at 1200 UTC on 27 April 2014, the outlook from the Storm Prediction Center, and QPF guidance from the Weather Prediction Center continue to indicate the potential for high-impact weather over the next 24 to 48 h in the JAN CWA.

Over the next 5 minutes, examine the 36-h Analog Hazard Guidance.

Discussion Question 8: How has the hazard guidance changed?

Up to this point, we have only examined the guidance constructed using the top 15 analogs. However, additional insight can be obtained by analyzing the individual analogs and evaluating their associated impacts, which can be easily accomplished by utilizing the Analog Thumbnail Guidance.

For the next 10 minutes, review the 48-h Unified Precipitation Data thumbnails of the top 15 analogs. Find the most extreme event, click on the date, and compare and contrast the fields associated with that analog and the 36-h NAM model output.

Discussion Question 9: Do you think the atmospheric fields in this analog are similar enough to the NAM model output to anticipate extreme precipitation amounts?

Next, spend 10 minutes comparing and contrasting two of the top 15 analogs. The two analogs, 0000 UTC 21 April 1995 and 0000 UTC 1 April 2007, have similar atmospheric patterns but appreciable differences in severe weather hazards for the JAN CWA. As you are comparing these analogs, consider the following questions...

Discussion Question 10: Which atmospheric fields could be critical in explaining the differences in the number and location of the severe weather reports?

Discussion Question 11: In your opinion, how important is it to monitor how these critical fields change in model output leading up to the event?

End of Exercise

29 April 2014 Event Details

The 29 April 2014 event was a significant severe weather outbreak. Within the 24-h period centered on 0000 UTC 29 April there were 61 observed tornadoes, 156 wind reports, and 91 hail reports. The distribution of severe reports occurs along an axis that extended from Louisiana to Virgina. Precipitation over the 24-h period ending on 1200 UTC 29 April exceeded 1.5 inches from the Gulf Coast to southern Ohio and over 3 inches near Mobile, AL. The meteorological fields and impacts for this event can be found here.