Interesting observations from Dakar,Senegal

#1 Postby **cycloneye** » Wed Jul 07, 2004 1:26 pm

http://weather.noaa.gov/weather/current/GOOY.html

The pressures are falling as wave axis gets closer to that location and the wind is from the north meaning there is a circulation that is with this wave that will emerge west Africa tonight.

#2 Postby **Dean4Storms** » Wed Jul 07, 2004 1:40 pm

This next TW shows up well in visible imagery from Meteosat 7 and has a very well defined circulation but somewhat void of deep convection. It will be interesting to see if the previous TW helped moisten the LL's from the SAL which may very well be what we are seeing along 20w as the western extent of this circulation gets over water.

Rainband · #3 Postby **Rainband** » Wed Jul 07, 2004 1:42 pm

Thanks Luis and Dean for that info. Time will tell!! :wink:

Derecho · #4 Postby **Derecho** » Wed Jul 07, 2004 1:49 pm

The 18GMT obs are in from across Senegal, and the Eastern Senegal stations (Matam and Podor) are down to 1006 mb.

Sadly the countries south of Senegal are violence-wracked crapholes and really have limited obs...and the wave axis is SE of Senegal.

Sfc pressures are better than convection to track waves, but the best, definitive way is to look at upper-air observation skew-T diagrams.

Unfortunately I don't completely understand how to interpret them in the sense of tracking a wave passage.

Once I have them figured out I'll attempt to post on them. Dakar has a RAOB regularly, and the countries to the east do somewhat erratically.

Rainband · #5 Postby **Rainband** » Wed Jul 07, 2004 1:53 pm

Thanks Derecho :wink:

Derecho · #6 Postby **Derecho** » Wed Jul 07, 2004 1:53 pm

Dean4Storms wrote:This next TW shows up well in visible imagery from Meteosat 7 and has a very well defined circulation but somewhat void of deep convection. It will be interesting to see if the previous TW helped moisten the LL's from the SAL which may very well be what we are seeing along 20w as the western extent of this circulation gets over water.

Yeah, it's possible 95L died so that this might live, it does moisten the atmosphere behind it.

The Dakar sfc obs from 18Z will be in the 0Z models tonight so an actual representation of the wave may turn up in something besides the GFS tonight.

#7 Postby **cycloneye** » Wed Jul 07, 2004 1:53 pm

You are right Derecho about observations from other countries in west Africa being very poor data from those as I haved tried to look to those places but little data available and that is why Senegal offers plenty of data that can be seen and analized.

#8 Postby **HURAKAN** » Wed Jul 07, 2004 2:56 pm

Is good to see that the pressures are low in that area.

SupertyphoonTip · #9 Postby **SupertyphoonTip** » Wed Jul 07, 2004 3:13 pm

The pressure is rising in Bamako, Mali (8W), which is about 620 miles southeast of Dakar.
http://weather.noaa.gov/weather/current/GABS.html

Therefore, the wave axis is most likely around 10-12W, and those stations in eastern Senegal should have their minimum pressures soon. Coastal stations are suggesting that there is a surface circulation, with winds from the north becoming more westerly as you move south.

#10 Postby **MWatkins** » Wed Jul 07, 2004 4:03 pm

Derecho wrote:The 18GMT obs are in from across Senegal, and the Eastern Senegal stations (Matam and Podor) are down to 1006 mb.

Sadly the countries south of Senegal are violence-wracked crapholes and really have limited obs...and the wave axis is SE of Senegal.

Sfc pressures are better than convection to track waves, but the best, definitive way is to look at upper-air observation skew-T diagrams.

Unfortunately I don't completely understand how to interpret them in the sense of tracking a wave passage.

Once I have them figured out I'll attempt to post on them. Dakar has a RAOB regularly, and the countries to the east do somewhat erratically.

I think...and I could be wrong though...is to look at the changes in the flow around 700mb down in Skew-T wind direction analysis.

For example...wave passage at TFFB (Guadeloupe) occured at 12Z on 7/6 according to the TWD. Check out this loop of Skew-T plots for TFFB...

http://weather.uwyo.edu/cgi-bin/soundin ... STNM=78897

First...wind-shifts are observed in the low-levels at 900 then 800mb...consistent with wave passage...and these preceed similar shifts by about 12 hours at 700MB. (east...then ene to ne then east then southeast back to east).

Also...PWAT's jump quite a bit in tandem with these wind shifts...then go back down after passage. The dewpoint line shifts to the right...closer to the temp line...(also reflected in the pwat calculation) as the wave axis passes.

That's just my take...and it sounds reasonable...but I could be wrong.

MW

The Dark Knight · #11 Postby **The Dark Knight** » Wed Jul 07, 2004 4:13 pm

We'll find out soon enough......

#12 Postby **MWatkins** » Wed Jul 07, 2004 5:47 pm

One other thing...I would bet that stronger waves would reflect a little further up than 700MB...I forgot to include that in the last post...

MW

Anonymous · #13 Postby **Anonymous** » Wed Jul 07, 2004 6:26 pm

Good post Luis. Atleast we know this won't become a Luis.

#14 Postby **cycloneye** » Wed Jul 07, 2004 6:30 pm

The pressures are starting to rise at Dakar,Senegal station meaning wave axis has passed that location.

#15 Postby **HURAKAN** » Wed Jul 07, 2004 6:34 pm

Tomorrow the wave should have fully be over water.

Interesting observations from Dakar,Senegal

Interesting observations from Dakar,Senegal

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