Aviation Cloud Forecasts – A True Challenge for Forecasters

Jeffrey S. TongueJeffrey S. TongueNOAA/National Weather Service - Upton, NYNOAA/National Weather Service - Upton, NY

Wheee !

Outline

• What are we forecasting?

• How are we doing “it” ??

• How “good” are we doing?

• How can we improve?

What are we forecasting ?

• Total Cloud Cover

• Cloud base height

• Cloud amount

Total Cloud Amount

• Done in GFE

• Percent of opaque clouds covering the sky on a 5x5 km CONUS grid.

Example

Cloud Base

• How high (ALG) will the clouds be?• Who Cares?

– Public? …maybe…– Aviation? …hopefully…– What’s important? …It Depends…

• Airport/Runway Minimum• Aircraft Minimum• Pilot Minimums• Airline Minimums• Airport Instrumentation

Example

Clouds Base

• What does the forecaster do?

• Forecast the Weather !

• Be cognizant of the impacts of the forecast.

• Forecast the Weather !

• Give it your best forecast

The Aviation Forecast

• The best forecast is the Correct Forecast.

• The worst forecast is the mushy CYA forecast.

• BKN030 TEMPO OVC008

The Forecast

• Is a Forecast

• A PIECE of the Planning tools for aviation weather.

What’s a Ceiling?

• 50% or more cloud cover – BKN or OVC.

• What about <50% cloud cover.

How much cloud cover is there?

How Good are we?

• GPRA Goals:– POD 46%– FAR 68%

Eastern Region < 1000’ ceiling

• 10/97 – 09/04– POD 35%– FAR 42%

• FY 05– POD 47%– FAR 61%

Do you think we can improve ???

How do you forecast a cloud?

• Advection?

• Convection?

• Persistence?

• Soundings?

• Satellite?

• Other Observational Tools?

How do you forecast a cloud?

• Numerical Weather Prediction models?

Models

• Relative Humidity???

• Model Clouds???

Model Soundings?

RH Time Section

Model Clouds and Bases

How good are Model at predicting the vertical profile of moisture and

ceilings????

OH NO !!!

What Can we Do????KEWR POD/FAR 2003-2005

0

0.10.2

0.30.4

0.5

0.60.7

0.8

0-6 6-12 12-18 18-24 total

Hours

Pe

rce

nt

FCST POD

MOS POD

FCST FAR

MOS FAR

Model Output Statistics!

• Good idea.

• Removes biases.

• Adds Climatology.

MOS Problem?

• Is the “Weather” in CAR the same as BTV and JFK and CTP?

• Regional Equations - 21

We need more

• Rules of thumb?

• “in this situation, the cloud base “usually” remains IFR until late morning.”

• CLIMATOLOGY!!!

• “Conditional” Climatology

AVNFPS

• Good Luck

MODCV

MODCV

• Simple

• Easy to use

• Customizable

• Intuitive

MODCV• Set up categories by clicking THEASHOLDS on

the main GUI

Using MODCV• Set Data Type• Set Climatology• Set the Month• the Current Hour or

“future” hour• Set Wind Direction

• Set Initial Conditions (if CONDITIONAL CLIMO)

Using MODCVGRAPHS

MODCV Graphs

• 4 Graphs – 2 types!– Categorical Probabilities

• 1-Hour

• 3-Hours

– Cumulative Probabilities• 1-Hour

• 3-Hours

• Clicking on the graph expands the individual graphic for all the time ranges.

ExampleIf it’s October in Cleveland and at 12Z the Wind was S and the ceiling was 1700,

Climatologically, what time would the ceiling become VFR ?

Another Example

• It’s Nov 5th at 05Z, it’s clear and wind is NE at 10KT. You confidently “forecast” BKN008 at 11Z, but you don’t know if the stratus will lift or not or will dissipate.

• Set MODCV to November at 11Z, place an initial ceiling of 800 ft and set the wind direction to NE

What Did you come up with?

• 11Z OVC008• 14Z OVC015• 15Z BKN025• 17Z SCT035Or maybe… • 11Z OVC008• 1430Z OVC015• 17Z SCT035

MODCV Table

MODCV Table

• Don’t go for the largest number, but look for trends.

• Ensure there are enough observations in the data set.

• If observations are low (<50), set the wind direction to all and/or use unconditional climatology.

Conclusion

• Cloud height forecasts remain a challenge for forecasters.

• A combination of all the tools are needed:– Observations– Model Output– MOS– Climatology

AVNFPS – Improvements?

Conclusion

• Cloud Forecasting Remains a “Challenge”

• Verification shows that forecasts are not very good.

• NWP models have a difficult time with moisture and clouds.

• Applied Climatology can help.

• MODCV (or its equivalent) is a “tool” that all aviation forecasts should use.

• Remember – The TAF is a FORECAST - NOT an Observation !