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) – 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

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

NWS Hastings TAF 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 H elpful in “persistent” or “progressive” patterns

NWS Hastings TAF Preparation Graphical weather model data Numerical guidance – Meteograms – Tabular Seasonal climatology Knowledge of local effects Pilot reports (if available)

NWS Hastings TAF Preparation Special Considerations Low ceilings/visibilities – Most prevalent during the winter – Typically associated with large (multi-state) low pressure systems

NWS Hastings TAF Preparation Special 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

NWS Hastings TAF Preparation Special 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

NWS Hastings TAF Preparation Special Considerations N on convective low level wind shear (LLWS) – LLWS may be associated with: Frontal passages Inversions Low level jets

NWS Hastings TAF Preparation Special 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.

NWS Hastings TAF Preparation Special Considerations N on convective low level wind shear (LLWS) – Best forecast tools to use KMAX WSR-88D vad wind profiler Upper air sounding Pilot reports

NWS Hastings TAF Preparation Special Considerations T hunderstorms – 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

NWS Hastings TAF Preparation Special 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

NWS Hastings TAF Preparation Special 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

NWS Hastings TAF Preparation Special Considerations Any other forecasting considerations that you would like to discuss?

Any general questions? Thank you for visiting NWS Hastings!