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Hastings, Nebraska National Weather Service Considerations for TAF Composition

Hastings, Nebraska National Weather Service Considerations for TAF Composition. UNK Aviation Department October 12, 2006. NWS Hastings TAF Site. Grand Island (KGRI) Located 2 miles east-northeast of Grand Island Elevation: 1846 ft. MSL. NWS Hastings TAF Site. Grand Island (KGRI)

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Hastings, Nebraska National Weather Service Considerations for TAF Composition

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  1. Hastings, Nebraska National Weather Service Considerations for TAF Composition UNK Aviation Department October 12, 2006

  2. NWS Hastings TAF Site • Grand Island (KGRI) • Located 2 miles east-northeast of Grand Island • Elevation: 1846 ft. MSL

  3. NWS Hastings TAF Site • Grand Island (KGRI) • Airport is serviced by an ASOS • Augmentation of observations is performed by Grand Island Control Tower personnel from 0600 to 2200 local time • Occurrences of precipitation or thunderstorms are manually appended to observations as a remark

  4. NWS Hastings TAF Site • Grand Island (KGRI) • Main forecast considerations • Diurnal pressure gradient winds • Thunderstorm intensities during convective season • Low ceilings/visibilities during stratiform precipitation events • Radiation Fog

  5. NWS HastingsTAF Preparation • Current surface weather 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 12 hours to gain understanding of weather history and evolution • Helpful in “persistent” or “progressive” patterns

  6. NWS HastingsTAF Preparation • Graphical weather model data • Numerical guidance • Meteograms • Tabular • Seasonal climatology • Knowledge of local effects • Pilot reports (if available)

  7. NWS HastingsTAF PreparationSpecial Considerations • Low ceilings/visibilities • Most prevalent during the winter • Typically associated with large (multi-state) low pressure systems

  8. NWS HastingsTAF 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

  9. NWS HastingsTAF 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

  10. NWS HastingsTAF PreparationSpecial Considerations • Non convective low level wind shear (LLWS) • LLWS may be associated with: • Frontal passages • Inversions • Low level jets

  11. NWS HastingsTAF 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.

  12. NWS HastingsTAF 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

  13. NWS HastingsTAF PreparationSpecial Considerations • Thunderstorms • Thunderstorms that occur over the Central Plains can be of the most severe nature • Thunderstorms elements include: • Extended periods of heavy rainfall • Large to enormous hail • Strong straightline winds • Occasional tornadoes

  14. NWS HastingsTAF PreparationSpecial Considerations • Thunderstorms • Best forecast tools to use: • Visible and infrared satellite imagery • Track developing storms • Storms typically begin along an identifiable boundary • KUEX 88D Hastings Doppler Radar • Correlate locations of storm centroids with what is seen in satellite imagery

  15. NWS HastingsTAF PreparationSpecial Considerations • Thunderstorms • Best forecast tools to use: • Upper air sounding • Helps to determine general instability of atmosphere • Identify wind speed and direction which frequently acts as main steering flow for storms • Model data

  16. NWS HastingsTAF PreparationSpecial Considerations • Any other forecasting considerations that you would like to discuss?

  17. Any general questions?Thank you for visitingNWS Hastings!

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