The Weather Forecasting Forum

Hi Guys,

I've been trying out a script to plot potential areas of fog using the fog Stabilty Index.

The index is set arround the formula:
FSI=2(surf temp-850mb temp)=2(surf t - surf dew point)+850mb Wind speed in knots.

The script contours the index and overfills areas most at risk from fog
(values of less than 20).

I often "put my foot in it" where these things are concerned, but I think this works quite well.

Anyway, feel free to give it a go.

#Fog stability Index-------FSI=(Surf temp-850mb temp)=(Surf temp-Surf Dew point)+850mb windspeed.#
analyze,over fill color=124:124:124 lsth=5 stor=1
analyze,over fill color=128:128:128 grtn=10 stor=1
analyze,over fill color=192:192:192 grtn=15 stor=1
analyze,over fill color=255:255:22 grtn=20 stor=1
analyze,over fill color=255;255:166 grtn=25 stor=1
analyze,over fill color=255:255:255 grtn=25 stor=1
analyze,cont equa=20 color=255:0:0 line=2 stor=1
stor=1 analyze,cont dots cint=5 dash stor=5 ssum=1:2 stor=2 vknt wspd h850 stor=1 ssum=2:3 stor=2 sdif=1:2 stor=1 temp hsfc stor=2 temp h850 stor=3 sdif=1:2 stor=1 temp hsfc stor=2 dwpt hsfc
analyze,cont dots cint=5 dash stor=5 ssum=1:2 stor=2 vknt wspd h850 stor=1 ssum=2:3 stor=2 sdif=1:2 stor=1 temp hsfc stor=2 temp h850 stor=3 sdif=1:2 stor=1 temp hsfc stor=2 dwpt hsfc
stamp


I welcome any feed-back, unkind or otherwise, and any advice from any one who can do it better or has any suggestions.

Regards,

Dave Exton, UK.

Dave I gave it a try, but it is not plottting anything for me. Could well be I have done something wrong in copying the script. Maby we can get some input from others.

Hi Kinetic,

Sorry it hasn't gone according to plan.

Just to make sure with coming from the same starting place, I'm assuming that you've download some upper air data and some surface data.

Being in the UK, I tend to use SYNOP rathet than METAR's but I cant see how that would make a difference as long as you've got plenty of temp and dew-point data.

I get my radiosone data from two sources namely COD and Albany (just to make sure!).

I plotted some charts before I went to bed last night both for The States and Europe and they plotted just fine. There were a couple of glitches where the overfll plotted in big square areas, but that seemed to fix after I closed DAWS and re-opened it again.

Have I helped?

Good luck and regards,
Dave.

ps I've just had another go and it's still working!

Dear Kinetic,

Having looked again at the script I've noticed an error.
I've asked it to plot values greater than 25 twice both with different colours .

The line that reads:
analyze,over fill color=255;255:166 grtn=25 stor=1
needs to be deleted.

This should give:-
#Fog stability Index-------FSI=(Surf temp-850mb temp)+(Surf temp-Surf Dew point)+850mb windspeed.#
analyze,over fill color=124:124:124 lsth=5 stor=1
analyze,over fill color=128:128:128 grtn=10 stor=1
analyze,over fill color=192:192:192 grtn=15 stor=1
analyze,over fill color=255:255:22 grtn=20 stor=1
analyze,over fill color=255:255:255 grtn=25 stor=1
analyze,cont equa=20 color=255:0:0 line=2 stor=1
stor=1 analyze,cont dots cint=5 dash stor=5 ssum=1:2 stor=2 vknt wspd h850 stor=1 ssum=2:3 stor=2 sdif=1:2 stor=1 temp hsfc stor=2 temp h850 stor=3 sdif=1:2 stor=1 temp hsfc stor=2 dwpt hsfc
analyze,cont dots cint=5 dash stor=5 ssum=1:2 stor=2 vknt wspd h850 stor=1 ssum=2:3 stor=2 sdif=1:2 stor=1 temp hsfc stor=2 temp h850 stor=3 sdif=1:2 stor=1 temp hsfc stor=2 dwpt hsfc

Try copying and pasting the above.

Regards,

Dave.

Hello Dave

I did a quick test. I think more things can be deleted. The below script give the same results as the original script.

#Fog stability Index-------FSI=(Surf temp-850mb temp)+(Surf temp-Surf Dew point)+850mb windspeed.#
erase
analyze,over fill color=124:124:124
analyze,over fill color=128:128:128 grtn=10
analyze,over fill color=192:192:192 grtn=15
analyze,over fill color=255:255:22 grtn=20
analyze,over fill color=255:255:255 grtn=25
analyze,cont equa=20 color=255:0:0 line=2
analyze,cont dots cint=5 dash stor=5 ssum=1:2 stor=2 vknt wspd h850 stor=1 ssum=2:3 stor=2 sdif=1:2 stor=1 temp hsfc stor=2 temp h850 stor=3 sdif=1:2 stor=1 temp hsfc stor=2 dwpt hsfc
stamp

In the first script there was a mistake in the formula in the first line. Because I don't know what the right formula is I searched on internet and there I found another formula: 4*Ts-2*(T850+Tds)+W850. So my first question is: what is the right formula?

Greetings

Fred

I looked again to the script and according to me it cannot work. First some colours are displayed (from what??) and then the calculations are made.

Greetings

Fred

I tried to make another script based on the formula I found on internet. Is the formula and the script correct?

#
# Fog Stability Index
#
# Formula: 4*Ts-2*(T850+Tds)+W850
#
# > 55 Low
# 31-55 Moderate
# < 31 High
#
erase
ANALYZE,STOR=9 SSUM=7:8 STOR=8 VKNT WSPD H850 STOR=7 SDIF=2:6 STOR=6 SMLC=5:2 STOR=5 SSUM=3:4 STOR=4 DWPT HSFC STOR=3 TEMP H850 STOR=2 SMLC=1:4 STOR=1 TEMP HSFC
ANALYZE,OVER FILL COLOR=255:000:000 FILS=0
ANALYZE,OVER FILL COLOR=255:255:000 FILS=0 GRTN=30
ANALYZE,OVER FILL COLOR=255:255:255 FILS=0 GRTN=55
ANALYZE,CONT CINT=5 DASH COLOR=200100
STAMP

Fred and Dave

When I run Fred's script I get this

http://cascadwx.com/MAPS/fog.gif

not sure what I am looking at.

Hello Kinetic

Can you also try my latest script because this is a complete different one.

Fred

Fred I give the new one a try. Here is more on fog

http://www.meted.ucar.edu/dlac/website/ups.htm