Strong Tropical Wave WSW of CV Islands (INVEST 94L is up)

[tatertawt24]

What are some other years that we've got so many strong tropical waves in June?

[Hammy]

What are some other years that we've got so many strong tropical waves in June?

2010 I believe was mentioned a few weeks ago as having a similar occurrence--and that year had quite an active MDR.

[StormTracker]

000
AXNT20 KNHC 291000
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
600 AM EDT Thu Jun 29 2017

A tropical wave extends just west of the coast of Africa from
20N19W to 07N14W, moving westward at 10-15 kt. The wave is
embedded within a rather large envelope of deep moisture as seen
in the latest satellite animation. Scattered showers and thunderstorms
are observed south of 12N between 15W-20W.

[StormTracker]

ZCZC MIATWOAT ALL
TTAA00 KNHC DDHHMM

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
200 AM EDT Thu Jun 29 2017

For the North Atlantic...Caribbean Sea and the Gulf of Mexico:

Tropical cyclone formation is not expected during the next 5 days.

$$
Forecaster Avila
NNNN

Still nothing. Maybe by the end of the day...ST

[Gustywind]

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
600 AM EDT Thu Jun 29 2017

A tropical wave extends just west of the coast of Africa from
20N19W to 07N14W, moving westward at 10-15 kt. The wave is
embedded within a rather large envelope of deep moisture as seen
in the latest satellite animation. Scattered showers and thunderstorms
are observed south of 12N between 15W-20W.

[Siker]

12z GFS develops this into a minor tropical storm as it traverses the MDR. Parallel GFS has too much interaction between this wave and the one behind for any consolidation.

[cycloneye]

Yes,I saw the change to this wave in this run,Hmmm. Wave of this thread has the 1013 mb and wave that developed this model in past runs is behind.

[Alyono]

the strongest waves are often in July. However, we usually have SAL outbreaks that prevent them from developing this time of year

In years that do not, like 2005, we got our strongest MDR developments from a wave in June and another in early July. Those became Dennis and Emily

[TheStormExpert]

Some of you all keep saying how bad the SAL is but it doesn't look that bad when compared to the last several years just going by memory. Too bad we don't have an archive for the SAL images. Mid-Level dry air though may be more of an issue when compared to previous years.

[aslan]

Hi, it's my first post here but I will probably not be really active. I register and come here to post an URL. As a French forecaster, I have access to other websites than thus usually seen here. I think this resource it not known to this forum and so could help for tropical waves coming out of Africa :

http://misva.sedoo.fr/

I don't know why, but next to impossible to find it with google
And an old site:

http://fenoc.sedoo.fr/

To bring a bit of context. Once upon a time ^^ Senegal was a French colony (Saint Louis, Dakar, you name it...). Since the decolonization, France is still heavily involved in the region, from all points of view. And beside this, the deep drought in Sahel during the 70s and 80s brought the need to better study the african monsoon. So France and countries of the Sahel region -with also the involvement of NASA and NOAA- organized a big campaign to study the monsoon. This was the AMMA, Analyses Multidisciplinaires de la Mousson Africaine or African Monsoon Multidisciplinary Analysis:

http://www.amma-international.org/spip.php?rubrique2

http://www.amma-international.org/IMG/p ... _blanc.pdf

Given the strong ties between Senegal and France, following the AMMA campaign a partnership was put in place to help weather forecasters from Senegal and other countries, years after years. Main objective remains of course to be able to anticipate a drought... But in the end, some of the stuff is freely available on Internet via the hereinbefore website.

So the main target of the website is the African monsoon but it can also be used to monitor easterly waves; and allows to see this waves not near the "edge" of an Atlantic map, but on the center of an African map.

Some funny stuff includes hovmüller of easterly waves (links are for a given day). Here more specifically anomalies for Precipitable Water and V wind at 925 hPa to the left; vorticity at 850 hPa and vertical speed at 700 hPa to the right:

http://misva.sedoo.fr/source/display.ph ... timepwvort



Propagation of waves is easily spotted.

Rainfall maps from TRMM are available:

http://misva.sedoo.fr/source/display.ph ... recipdaily



And a detailed analysis showing the progression (or lack of progression...) of the monsoon toward the North:

http://misva.sedoo.fr/source/displayBis ... SOnsetTRMM

There is also some good stuff comparing radiosoundings values with climatology and forecasted data:

http://misva.sedoo.fr/source/displayBis ... 017LSPWSen

A diagram with major sources of variability in tropics (MJO, kelvin waves, Rossby waves, MRG) onto Velocity Potential (VP, or chi in with a Greek letter) at 200 and 700 hPa:

http://misva.sedoo.fr/source/display.ph ... eEvolution

http://misva.sedoo.fr/source/display.ph ... DIVFLT_700

The regional ANASYG (a Meteo France word meaning I don't remember what -MF likes strange acronyms by the way...- which is intended to say a map with conceptual objects describing the state of the atmosphere. A bit like a surface front chart mixed with an upper atmosphere analysis):

http://misva.sedoo.fr/source/display.ph ... 2017Anasyg




I don't remember neither all the symbols (as a side note, my classes are stored in the attic of my parents, if someone wants a fine tuned explanation of all the stuff plotted, I will have to go back exploring the attic...). But the main objects are as following. The subtropical jet stream is the big arrow in orange. The blue line is the FIT, front intertropical (NOT the ITCZ. FIT it is the place where the warm, moist air coming from the south encounters the extremely hot and dry air of the Sahara. Convergences -the ITCZ- take place in the moist, warm air, to the south of the FIT). FIT is usually plotted by forecaster with the gradient of dew point and the confluence of trades wind. Double black line has a double meaning. The one oriented North-South is the axis of a tropical wave (if it is dotted, it is an inactive one -being inactive is rather subjective depending on the mood of the forecaster by the way...-). A alphanumeric chain is associated. For example, O07_07E means the 7th Easterly Wave (OE pour Onde d'Est) and centered around 07°E. "C850" means cyclonic max at 850 hPa. "S" is for Sable -sand-. Thick black lines (dotted or continuous) are tropopause anomalies. Same as for front or waves, dotted means inactive, continuous means active. Convergence lines are in orange. CBs in red are, well, CBs The jet in green is the African Easterly Jet (AEJ). And so on.

By the way, the better remains to explore by himself. But if someone has a question, I will try to answer (or go back to the attic to find an answer ).

[TheStormExpert]

12z GFS develops this into a minor tropical storm as it traverses the MDR. Parallel GFS has too much interaction between this wave and the one behind for any consolidation.

In the long range it develops into a hurricane on it's way out to sea.

By the way the GFS has been rather persistent for being long range it tracking this out to sea for the past several runs.

Honestly I don't think it'll develop and is probably just convective feedback from the current exiting favorable MJO phase.

[cycloneye]

The GFS-Para and ECMWF do not develop so I am not bullish on this wave at this time unless those join GFS operational.

[RL3AO]

Honestly I don't think it'll develop and is probably just convective feedback from the current exiting favorable MJO phase.

Can you expand on this thought? How does a weak MJO signal over Eastern Africa/Western Indian Ocean relate to a strong tropical wave now in the eastern Atlantic? Sometimes I feel phrases like "convective feedback" just get thrown out there as a buzzword without a lot of support.

[Alyono]

Honestly I don't think it'll develop and is probably just convective feedback from the current exiting favorable MJO phase.

Can you expand on this thought? How does a weak MJO signal over Eastern Africa/Western Indian Ocean relate to a strong tropical wave now in the eastern Atlantic? Sometimes I feel phrases like "convective feedback" just get thrown out there as a buzzword without a lot of support.

agreed. Most here have no clue what convective feedback even means

What we saw earlier in the week with the EC was convective feedback. We had a very small hurricane form rapidly and then dissipate just as rapidly. Likely due to issues with its 9km resolution. A TC that slowly develops through the forecast period of not convective feedback.

If you want to argue that the MU is off due to paramaterization allowing it to survive the shear, we can have that discussion

[Kalrany]

Hi, it's my first post here but I will probably not be really active. I register and come here to post an URL. As a French forecaster, I have access to other websites than thus usually seen here. I think this resource it not known to this forum and so could help for tropical waves coming out of Africa :

http://misva.sedoo.fr/

I don't know why, but next to impossible to find it with google
And an old site:

http://fenoc.sedoo.fr/
........
By the way, the better remains to explore by himself. But if someone has a question, I will try to answer (or go back to the attic to find an answer ).

Very interesting and a new source. Is there a way to add to the master list? I thought that somewhere there was one............

[cycloneye]

@TropicalTidbits
Nice-looking wave in region just off Africa where natural low-level convergence exists. Waves can get short window of vorticity enhancement.

 https://twitter.com/TropicalTidbits/status/880488959343824900

[cycloneye]

18z GFS operational super bullish.

[RL3AO]

Here's my take away from the 18z GFS

Positives:
* Strong easterly wave
* Positive 850 zonal wind anomalies
* 200mb flow is mostly anticyclonic and westerly
* TUTTs are well west and north (western Caribbean and N of PR)

Negatives:
* Some dry air to the north and west of the wave (recent SAL outbreak)
* Large scale subsidence (-MJO/-CCKW)
* It's June 29th

I can see why the GFS is developing it. I can also see why other models aren't. Not sure what to think.

[cycloneye]

I thought after PR it would weaken but it gets more energetic in the Bahamas.What a longtracker for early July standards.

[AutoPenalti]

18z GFS operational super bullish.

Is that the Togo wave or the one infront of it?