# Presentation: 124166

## Flash Flood Climatology over Central Pennsylvania: Identification of Significant Patterns in the Verification Data Peter JungNational Weather Service Forecast OfficeState College, PA

**Flash Flood Climatology over Central Pennsylvania: Identification of Significant Patterns in the Verification Data** ***Peter Jung******National Weather Service Forecast Office******State College, PA***

| Fulton County |  |
| --- | --- |
| Flash Flood Warnings Issued | 39 |
| Flash Flood Warnings Verified | 18 |
| Flash Flood Warnings Not Verified | 21 |
| Flash Flood Events | 14 |
| Flash Flood Events with Warning | 12 |
| Flash Flood Events with No Warning | 2 |
| Average Lead Time (minutes) | 58.4 |
| Percent of Events with Lead Time >0 | 85.7% |
| POD | 0.857 |
| FAR | 0.538 |
| CSI | 0.429 |

** –  ****STEP 1 –**
**Gather Verification Statistics**
**for all of your HSA from**
**NWS Performance Management**
**web page **
**https://verification.nws.noaa.gov/**

**~ OVERVIEW ~**
**In addition to monitoring real-time observed precipitation and forecast precipitation, flash flood forecasting should also include an awareness of regional flash flood climatology. Identifying geographic areas within a WFO’s Hydrologic Service Area which historically are more prone to flooding and examining potential forecast biases, is useful in the forecast and decision making processes. Additionally, identifying regions where over-forecasting; defined by the false alarm rate (FAR); and overall event detection skill; defined by the probability of detection (POD); should be incorporated in a “best-practice” forecast approach process by the WFO. **
**This presentation includes a detailed examination of the Flash Flood Climatology across the CTP Hydrologic Service Area (HSA). Using 14 years of flash flood warnings, a county-by-county breakdown of FAR, POD and Lead Times is presented. Findings of patterns found in the data are also shown. These findings may aid forecasters in the warning decision process for future events. Findings may also potentially point out biases in historic forecasts, and aid in identifying areas where Flash Floods are more, or less, prone to occur within the HSA.**
**The presentation can additionally serve as a template to assist other WFO Hydrology Program Managers to develop a similar climatology for their HSA.**

| Adams County |  |
| --- | --- |
| Flash Flood Warnings Issued | 46 |
| Flash Flood Warnings Verified | 30 |
| Flash Flood Warnings Not Verified | 16 |
| Flash Flood Events | 20 |
| Flash Flood Events with Warning | 18 |
| Flash Flood Events with No Warning | 2 |
| Average Lead Time (minutes) | 89.5 |
| Percent of Events with Lead Time  >0 | 80.0% |
| POD | 0.900 |
| FAR | 0.348 |
| CSI | 0.608 |

| Bedford County |  |
| --- | --- |
| Flash Flood Warnings Issued | 71 |
| Flash Flood Warnings Verified | 35 |
| Flash Flood Warnings Not Verified | 36 |
| Flash Flood Events | 35 |
| Flash Flood Events with Warning | 24 |
| Flash Flood Events with No Warning | 11 |
| Average Lead Time (minutes) | 41.9 |
| Percent of Events with Lead Time >0 | 69.0% |
| POD | 0.686 |
| FAR | 0.507 |
| CSI | 0.402 |

| Blair County |  |
| --- | --- |
| Flash Flood Warnings Issued | 50 |
| Flash Flood Warnings Verified | 34 |
| Flash Flood Warnings Not Verified | 16 |
| Flash Flood Events | 24 |
| Flash Flood Events with Warning | 21 |
| Flash Flood Events with No Warning | 3 |
| Average Lead Time (minutes) | 44.8 |
| Percent of Events with Lead Time >0 | 70.8% |
| POD | 0.875 |
| FAR | 0.320 |
| CSI | 0.620 |

| Cambria County |  |
| --- | --- |
| Flash Flood Warnings Issued | 51 |
| Flash Flood Warnings Verified | 37 |
| Flash Flood Warnings Not Verified | 14 |
| Flash Flood Events | 30 |
| Flash Flood Events with Warning | 26 |
| Flash Flood Events with No Warning | 4 |
| Average Lead Time (minutes) | 52.7 |
| Percent of Events with Lead Time >0 | 73.3% |
| POD | 0.867 |
| FAR | 0.275 |
| CSI | 0.653 |

| Cameron County |  |
| --- | --- |
| Flash Flood Warnings Issued | 14 |
| Flash Flood Warnings Verified | 9 |
| Flash Flood Warnings Not Verified | 5 |
| Flash Flood Events | 8 |
| Flash Flood Events with Warning | 8 |
| Flash Flood Events with No Warning | 0 |
| Average Lead Time (minutes) | 63.4 |
| Percent of Events with Lead Time >0 | 100% |
| POD | 1.000 |
| FAR | 0.357 |
| CSI | 0.643 |

| Centre County |  |
| --- | --- |
| Flash Flood Warnings Issued | 34 |
| Flash Flood Warnings Verified | 25 |
| Flash Flood Warnings Not Verified | 9 |
| Flash Flood Events | 20 |
| Flash Flood Events with Warning | 19 |
| Flash Flood Events with No Warning | 1 |
| Average Lead Time (minutes) | 57.2 |
| Percent of Events with Lead Time >0 | 90.0% |
| POD | 0.950 |
| FAR | 0.265 |
| CSI | 0.708 |

** –  ****STEP 2 –**
**Enter County-based Verification**
**Statistics Into EXCEL for**
**Sorting and Display**

- ...complete for all counties...

| Franklin County |  |
| --- | --- |
| Flash Flood Warnings Issued | 62 |
| Flash Flood Warnings Verified | 38 |
| Flash Flood Warnings Not Verified | 24 |
| Flash Flood Events | 33 |
| Flash Flood Events with Warning | 29 |
| Flash Flood Events with No Warning | 4 |
| Average Lead Time (minutes) | 66.6 |
| Percent of Events with Lead Time >0 | 87.9% |
| POD | 0.879 |
| FAR | 0.387 |
| CSI | 0.565 |

** –  ****STEP 3 –**
**Present Sorted Statistics**
**Graphically, to aid in**
**Pattern Recognition**

| Franklin County |  |
| --- | --- |
| Flash Flood Warnings Issued | 62 |
| Flash Flood Warnings Verified | 38 |
| Flash Flood Warnings Not Verified | 24 |
| Flash Flood Events | 33 |
| Flash Flood Events with Warning | 29 |
| Flash Flood Events with No Warning | 4 |
| Average Lead Time (minutes) | 66.6 |
| Percent of Events with Lead Time >0 | 87.9% |
| POD | 0.879 |
| FAR | 0.387 |
| CSI | 0.565 |

| Franklin County |  |
| --- | --- |
| Flash Flood Warnings Issued | 62 |
| Flash Flood Warnings Verified | 38 |
| Flash Flood Warnings Not Verified | 24 |
| Flash Flood Events | 33 |
| Flash Flood Events with Warning | 29 |
| Flash Flood Events with No Warning | 4 |
| Average Lead Time (minutes) | 66.6 |
| Percent of Events with Lead Time >0 | 87.9% |
| POD | 0.879 |
| FAR | 0.387 |
| CSI | 0.565 |

**- Counties with the highest number of events**

**- Counties with the least number of events**

**- Counties with the highest warning lead times**

**- Counties with the lowest warning lead times**

**- Counties with the lowest FAR**

**- Counties with the highest FAR**

**CDs with Excel and Word templates for          this project available upon request**