Weather Forecast Office Medford, Oregon Considerations for TAF Composition

1. Weather Forecast Office Medford, OregonConsiderations for TAF Composition Pilot’s Open House October 25, 2003

2. WFO Medford TAF Sites

3. WFO Medford TAF Sites • North Bend (KOTH) • Located on Coos Bay near the mouth of the Coos River ~ 5 miles inland from the Pacific Ocean • Elevation: 6 ft. ASL

4. WFO Medford TAF Sites • North Bend (KOTH) • Airport is serviced by an augmented AWOS III. • Augmentation is performed by North Bend Control Tower personnel from 0600 to 2200 local time • Occurrences of precipitation or thunderstorms are manually appended to observations as a remark

5. WFO Medford TAF Sites • North Bend (KOTH) • Main forecast considerations • Varying ceilings/visibilities associated with marine layer • Nighttime down valley winds from southeast • Radiation fog • Daytime sea breezes

6. WFO Medford TAF Sites • Medford (KMFR) • Located on the floor of the Rogue Valley • Cascade and Siskiyou Mountains bound the valley to the east and south respectively • Elevation: 1297 ft. ASL

7. WFO Medford TAF Sites • Medford (KMFR) • Airport is serviced by an ASOS • Limited augmentation is now performed by the Medford Control Tower personnel around the clock

8. WFO Medford TAF Sites • Medford (KMFR) • Main forecast considerations • Summer • Variable ceilings/visibilities/winds associated with thunderstorms • Autumn-Spring • Strong southerly winds associated with frontal passages • Variable ceilings/visibilities associated with marine intrusions • Radiation fog

9. WFO Medford TAF Sites • Klamath Falls (Kingsley Field-KLMT) • Located on the floor of the Klamath River Valley • Cascade Mountains bound the valley to the west • Elevation: 4092 ft. ASL

10. WFO Medford TAF Sites • Klamath Falls (Kingsley Field-KLMT) • Airport is serviced by an ASOS • Limited augmentation is performed by the Kingsley Field Control Tower personnel from 0600 to 2200 local.

11. WFO Medford TAF Sites • Klamath Falls (Kingsley Field-KLMT) • Main forecast considerations • Is under the dry rain shadow produced by Cascades Mountains to the west • Variable ceilings/visibilities associated with frontal passages much less of a problem than experienced west of the Cascades. • Variable ceilings/visibilities associated with frontal passages about equally as problematic for summer thunderstorms.

12. WFO MedfordTAF Preparation • Current observations • At the very least…get the first period right! • Forecaster can declare a “NIL” TAF after 2 hours of missed observations at a site • Satellite imagery • View previous 24 hours to gain understanding of weather history • Especially helpful in “persistent” patterns

13. WFO MedfordTAF Preparation • Model data • Guidance • Graphical (meteograms) • Numerical (tabular) • Seasonal climatology • Knowledge of local effects • Pilot reports (if available)

18. WFO MedfordTAF PreparationSpecial Considerations • Low ceilings/visibilities • Most prevalent at the coast • Problematic inland west of the Cascades during frontal passages and very strong marine intrusions • Airmasses generally too dry east of the Cascades

19. WFO MedfordTAF PreparationSpecial Considerations • Low ceilings/visibilities • Best forecast tools to use: • Fog channel of satellite imagery • Differentiates better between the ground and low clouds/fog • NWS has many enhancement curves that are not always available to the general public. • Airport observations critical since pireps in these situations usually decrease dramatically

20. WFO MedfordTAF PreparationSpecial Considerations • Radiation fog • Best forecast tools to use: • Fog channel of satellite imagery • Differentiates better between the temperature of the ground and low clouds/fog • NWS has many enhancement curves that are not always available to the general public. • Temperature and dew point spread information from observations • Tabular model guidance

21. WFO MedfordTAF PreparationSpecial Considerations • Non convective low level wind shear (LLWS) • LLWS may be associated with: • Frontal passages • Inversions • Low level jets

22. WFO MedfordTAF PreparationSpecial Considerations • Non convective low level wind shear (LLWS) • Should be included in TAF when: • Vertical shears of 10 kts or more per 100 feet in a layer more than 200 feet are expected, or observed within 2000 feet of the ground • Pireps received which indicate wind shear causing a gain or loss in airspeed of 20 kts or more within 2000 feet of the ground.

23. WFO MedfordTAF PreparationSpecial Considerations • Non convective low level wind shear (LLWS) • Best forecast tools to use • KMAX WSR-88D vad wind profiler • Upper air sounding • Pilot reports

26. WFO MedfordTAF PreparationSpecial Considerations • Summer thunderstorms • Thunderstorms that occur over the Pacific Northwest are generally unorganized and are not usually long lasting (pulse severe) • Thunderstorms can bring brief heavy rain, small to large hail, strong straightline winds and occasionally tornadoes

27. WFO MedfordTAF PreparationSpecial Considerations • Summer thunderstorms • Best forecast tools to use: • Visible and infrared satellite imagery • Track developing storms • Storms typically begin over higher terrain • KMAX 88D Medford Dopplar Radar • Correlate locations of storm centroids with what is seen in satellite imagery

31. WFO MedfordTAF PreparationSpecial Considerations • Summer thunderstorms • Best forecast tools to use: • Upper air sounding • Helps to determine general instability of atmosphere • Identify 700 millibar (~10,000 ft) wind speed and direction which frequently acts as main steering flow for storms • Model data

33. WFO MedfordTAF PreparationSpecial Considerations • Any other forecasting considerations that you would like to discuss?

34. Any general questions?Thank you for attending!