1. Aviation Climatology
Andrew Rorke
WFO LOX
Los Angeles / Oxnard

2. What Is Aviation Climatology
A database of observations for a given TAF site
The database contains Ceiling, Visibility, Wind Speed and Wind Direction data for every day and hour for (hopefully) the past 30 years.

3. What Good Is Aviation Climatology?
Given a fairly normal climatological day, climatology is probably the best forecast tool for ceiling and visibility changes.
For any given ceiling and visibility aviation climatology will produce a cig/vis forecast for the next 1 to 6 hours.

4. Drawbacks of Aviation Climatology
The day has to fairly normal.
There has to be low ceiling (040 AGL or less) or a low visibility (5SM or less)
It does not predict good flying weather turning to bad flying weather
It does, however, predict, bad weather getting worse

5. Aviation Climatology in the NWS
Consists of two programs
Ceiling and Visibility Distribution
Determines how normal the day is
Ceiling and Visibility Trend
Forecasts changes in Cig and Vis based on current conditions and climatology

6. Ceiling and Visibility Distribution

7. Ceiling and Visibility Distribution

8. Ceiling and Visibility Distribution Visibility

9. Ceiling and Visibility Distribution Joint Ceiling and Visibility

10. Ceiling and Visibility Trend

11. Ceiling and Visibility Trend

12. Ceiling and Visibility Trend
Pick The TAF Site
Pick the Element
Visibility only
Ceiling only
Joint (combined to flight cat)
Chose the number of hours ahead to forecast

13. Ceiling and Visibility Trend
Chose a range of dates to pull data from
Smaller range might be more accurate, but might not sample low frequency events
Defaults to +/- 30 days from current

14. Ceiling and Visibility Trend
Choose your start hour for initial conditions
Default may be too much – try to use 1 or 2 hours

15. Ceiling and Visibility Trend
Enter the wind information
Again a smaller range will be more accurate provided there is enough data to sample

16. Ceiling and Visibility Trend
Enter the Ceiling and Visibility information
Unlike this example… try not to cross flight categories

17. Ceiling and Visibility Trend There Must Be An Easier Way!

18. Ceiling and Visibility Trend

19. Ceiling and Visibility Trend Results
Vis Only – VFR is inferred – Count refers to total data points

20. Ceiling and Visibility Trend Results
Cig Only – VFR is inferred – Count refers to total data points

21. Ceiling and Visibility Trend Results
Both Cig and Vis – VFR is inferred – Count refers to total data points
Note that the data points go down

22. Ceiling and Visibility Trend Summery
A great forecast tool when properly used.
Best for predicting burn off or changes to a pre-existing ceiling or fog obscuration
Works best during normal conditions

23. Aviation Climatology In The Southwest
Ceiling based Aviation Climatology is not ideally suited for the Southwest
The vast majority of Ceiling and Visibility restrictions occur on the coast
Aviation Climatology gives very little information on arrival times of lower flying conditions
Aviation Climatology does not make wind predictions (important to many SW airports)

24. KLAX – Los Angeles International
Concerns:
Ceiling Visibility Arrivals
Ceiling Visibility Changes
Ceiling Visibility Improvement
Sea Breeze Front
East Winds
Traditional Climatology only helps with 2 of the five problem areas

25. Need To Look For Something New

26. Pressure Gradient Aviation Climatology
Stratifying the observational data base using pressure gradients.
Would generate wind forecasts
Would give information on ceiling and visibility arrivals
Initially it might provide information on “not” events, but hopefully when combined with other information will be able to provide arrival forecasts.(KPRB combined with KSNS ceiling info)

27. Pressure Gradient Aviation Climatology
Which Gradient Values to use?
Must be chosen for each TAF site
Look At:
The Current Gradient
The 24 hour Change
The 12 hour Change (how different is it from the normal diurnal change)
The 3 hour change

28. Pressure Gradient Aviation Climatology
Calculate these gradients and trends and link them to their corresponding observational values
Use a database program such as Filemaker Pro
Use the database to search and sift the data
Use the database’s GUI creation capabilities to design a front end for the aviation desk

29. Pressure Gradient Aviation Climatology
KLAX
KPRB
Use LAX-DAG and LAX-BFL
Good with “not” forecast of sea breeze front
Good with east wind forecast with rain
So-so results with summertime east winds
Use SNS-PRB and SFO-SBA
By itself good with “no cig” forecast
Needs to be linked with current conditions at KSNS for better arrival time forecast

30. Andrew Rorke andrew.rorke@noaa.gov
Questions?
Andrew Rorke