1. AVIATION VERIFICATION NWS KEY WEST 2005 Bill South Aviation Program Leader

2. OBJECTIVES Present KEYW and KMTH TAF statistics for 2005 using TAF Stats on Demand. Present KEYW and KMTH TAF statistics for 2005 using TAF Stats on Demand. Present TAF writing philosophies for improving verification results while providing quality service to our customers. Present TAF writing philosophies for improving verification results while providing quality service to our customers.

3. TAF WRITING PHILOSOPHY Many pilots find TAFs are often written with a level of complexity that they lose utility. Verification statistics prove that PROB and TEMPO groups are overused, and can hurt the value of the forecast.

4. TAF WRITING PHILOSOPHY Important thresholds, with large impacts on traffic do not necessarily occur at the thresholds of flight categories. Federal Air Regulations (FAR) 91.167 states that +/- 1 hr, LT 2000 ft, LT 3SM requires the filing of an alternate airport for IFR traffic. Major impact is that it costs approximately 10% of the cost of extra fuel just to carry that extra fuel. *Extra weight=Extra Fuel Burn *Extra weight=Extra Fuel Burn

5. TAF STATS ON DEMAND  TAF Stats on Demand breaks each TAF and observation into 288 discrete 5 minute blocks.  For this presentation, only the first six hours of scheduled TAFs (00Z, 06Z, 12Z, and 18Z) are verified.  Forecasts within TEMPO groups are verified.

6. TEMPO GROUPS TAF Stats on Demand checks TEMPO groups for justification. A TEMPO group is considered justified if conditions change twice or more during a period of three hours or less.

7. TEMPO GROUPS If the TEMPO group is justified, each 5 minute interval is evaluated with the forecast from either the prevailing or TEMPO condition, which ever condition produces the most favorable verification score. If the TEMPO group is not justified, each 5 minute interval is evaluated with the forecast representing the lowest (worst) condition, the condition for which the pilot must plan.

8. AVIATION GPRA GOALS The aviation GPRA goals for TAFs are Instrument Flight Rules (IFR) and Thunderstorm (TS) Probability of Detection (POD) and False Alarm Ratio (FAR) in the first six hours of the TAF. The NWS is required to share these statistics with the FAA. (Government Performance & Results Act)

9. Remember… All verification results are based on one verification point. The TAF area encompasses a circle within 5 statute miles of the airport. Quality control of observations by the tower can be inconsistent at best. Our verification system is not nearly a perfect system, but it is what it is.

10. 2005 TS POD +4.5% +3.7% +0.9%

11. 2005 TS FAR +0.6% -1.2% +4.5%

12. 2005 IFR POD +20.0% +13.1% +4.4%

13. 2005 IFR FAR +26.9% +16.1% +8.2%

14. WHAT ARE WE DOING RIGHT? From 2003-2005, we showed gradual improvement in TS POD, IFR POD and IFR FAR for 0 to 6 hours. From 2003-2005, we showed gradual improvement in TS POD, IFR POD and IFR FAR for 0 to 6 hours. Right now, we are better than the NWS current skill scores for TS POD, IFR POD and IFR FAR for 0 to 6 hours. Right now, we are better than the NWS current skill scores for TS POD, IFR POD and IFR FAR for 0 to 6 hours.

15. WHERE CAN WE IMPROVE? From 2003-2005, we showed little to no improvement in TS FAR for 0 to 6 hours. Right now, we are 20.6% worse than the NWS current skill score for TS FAR for 0 to 6 hours.

16. WHAT TO DO? So, it would seem statistically that it would behoove us to forecast TS rarely, if ever. BUT, we want to provide quality service to our customers and present the realm of possibilities. We need to find a way to balance service and verification as much as possible.

17. SOME SUGGESTIONS For the first 3 hours of a TAF, if you feel that TS are likely, pick the “most likely” hour and use a FM or TEMPO group during that hour. Otherwise, use CB and/or VCTS. This strategy will inform pilots of the risk, yet somewhat minimize the impact to our stats if there is a miss. Possible drawback is implied precision. Yes, you may pick the wrong hour, but that is what amendments are for, AND at least the presence of such convection in the TAF will inform the users.

18. SOME SUGGESTIONS Between 3-6 hours of a TAF, use of TEMPO groups for TS is discouraged, unless you have clear justification (e.g. squall line). Even then, be “brief”, monitor trends and amend if necessary. Preferred method, use CB and/or VCTS for situations where there is no clear justification.

19. SOME SUGGESTIONS Beyond 6 hours of a TAF, use of TS is STRONGLY discouraged (even though doing so would not affect our stats). Preferred method, use CB and/or VCTS. In rare instances, TEMPO groups are alright (well-timed strong cold front, for example).

20. AMENDMENTS NEVER write the unamendable TAF. Give it your best shot the first time, if you have to amend the forecast, you have to amend the forecast. Amendments MUST be proactive (2-6 hours) as often as possible, not reactive. NOWTAFing should be avoided if at all possible.

21. BOTTOM LINE… Focus on what WILL happen, not what COULD happen. Focus on what WILL happen, not what COULD happen. Use TEMPO and PROB groups sparingly and smartly, keep them short and specific. Don’t simply use them “just in case”. All FM groups are preferred in the first six hours of the TAF. Use TEMPO and PROB groups sparingly and smartly, keep them short and specific. Don’t simply use them “just in case”. All FM groups are preferred in the first six hours of the TAF. Be ESPECIALLY careful with TS usage. Consider using VCTS or a “stand-alone” CB in the cloud group. Be ESPECIALLY careful with TS usage. Consider using VCTS or a “stand-alone” CB in the cloud group.