Atlantic Tropical Action 2013

[thewxmann]

Maybe it's something simple though... the convection over the East Pacific is still pretty strong- alot of upper-level divergence going on there... Very similar to an El-Nino state. 

 

 

I'm wondering if we need the East Pac to tame down first for the Atl to get going... My simple week 1-2 diagnostics due suggest increased suppression to make its way over the east Pac in the next 1-2 weeks.. Could be something to watch.

 

 

 

You know, I've always felt like we've been in an El Ninoish state with regards to the tropics this year. Lots of CPAC/EPAC storms (even though they've been of crappy quality as well). Has shear in the ATL been above-average this month?

[Derecho!]

You know, I've always felt like we've been in an El Ninoish state with regards to the tropics this year. Lots of CPAC/EPAC storms (even though they've been of crappy quality as well). Has shear in the ATL been above-average this month?

 

 

Not really; below average if anything.

 

[thewxmann]

^Well, I guess that nukes that hypothesis.  

[Mike.Ventrice]

Not really; below average if anything.

 

 

Do you know what levels and area this is being averaged over? I know that eastern MDR has been poisoned by a ton of easterly shear forced by a stronger than average West African Monsoon.  Further, for most of the month of July and early August, the western Caribbean had a screaming low-level Caribbean easterly jet that was inhibiting development..

[DaculaWeather]

Mike, these are the regions:

 

[Derecho!]

Do you know what levels and area this is being averaged over? I know that eastern MDR has been poisoned by a ton of easterly shear forced by a stronger than average West African Monsoon.  Further, for most of the month of July and early August, the western Caribbean had a screaming low-level Caribbean easterly jet that was inhibiting development..

 

Mike,

 

It's off the formation probablity product page. The area I posted is the whole area south of 20N from 60W to over Central Africa. They have a map showing the various areas there; at least for the MDR, for this month, the problem hasn't been shear, but if you look at all the graphs it had other problems:

 

http://www.ssd.noaa.gov/PS/TROP/TCFP/atlantic.html

[Mike.Ventrice]

Thanks guys!

[Ed Lizard]

FIM 8 has been weaker, and further East, each 0Z/12Z run, from a Cape Cod hurricane to a near miss TS passing Nova Scotia.  The models with fairly fast development, FIM, Canadian, NavGEM, all look fishy.

 

I think the Euro scenario of the Pseudo-Invest 25L weak system getting as far West as the Bahamas and in weak steering, loitering near the Gulf Stream, may be the best shot for North American landfall, barring a BoC miracle in a about 6 days, barely hinted at in GFS and Euro runs

 

BoC miracle, 12Z GFS below, Euro, couple of runs, 850 mb vorticity and a weak surface trough.  And did Fernand look much better from 6 days away?

[jconsor]

Mike,

 

Here's a graphic of past 45 day shear anomalies in the tropical Atlantic that shows both the features you mentioned - easterly shear in the e. Atlantic and westerly shear in the Caribbean.

 

 

Here's the link:

 

http://www.cpc.ncep.noaa.gov/products/hurricane/

 

 

Do you know what levels and area this is being averaged over? I know that eastern MDR has been poisoned by a ton of easterly shear forced by a stronger than average West African Monsoon.  Further, for most of the month of July and early August, the western Caribbean had a screaming low-level Caribbean easterly jet that was inhibiting development..

 

[thewxmann]

Well, in jconsor's maps, you can clearly see the semi-permanent W ATL TUTT that has nuked many a fledgling TC.

[Ed Lizard]

But it seems like a semi-permanent shearing TUTT and strong low level Easterlies in the Eastern and Central Caribbean are an almost annual feature July into the first half of August.  TUTT has been a bit stronger, the shear extends a bit further West into the Caribbean than usual, but nothing looks nuclear weapons grade dead season.

 

 

Yes, I follow JB on Twitter...

 

Joe Bastardi ‏@BigJoeBastardi 28 Aug

It appears that the total intensity (ACE) of the hurricane season thru the end of August may be the lowest since 1977. Have to recheck

[bluewave]

Do you know what levels and area this is being averaged over? I know that eastern MDR has been poisoned by a ton of easterly shear forced by a stronger than average West African Monsoon.  Further, for most of the month of July and early August, the western Caribbean had a screaming low-level Caribbean easterly jet that was inhibiting development..

 

Yes, that resulted in the higher than normal shear over the Caribbean.

 

[Mike.Ventrice]

Mike,

 

Here's a graphic of past 45 day shear anomalies in the tropical Atlantic that shows both the features you mentioned - easterly shear in the e. Atlantic and westerly shear in the Caribbean.

 

shear_200-850_atl_60d_45.gif

 

Here's the link:

 

http://www.cpc.ncep.noaa.gov/products/hurricane/

 

 

Yes, that resulted in the higher than normal shear over the Caribbean.

 

ts_al_car_VSHD.gif

 

 

Ah ok yes this shows it nicely, thanks!

[phil882]

Count the number of TUTT lows lol

 

[PSUBlizzicane2007]

You know, I've always felt like we've been in an El Ninoish state with regards to the tropics this year. Lots of CPAC/EPAC storms (even though they've been of crappy quality as well). Has shear in the ATL been above-average this month?

 

I'd be willing to bet, too, that the ACE in the EPAC is actually decently below normal.  Keep in mind the EPAC peak is in mid-August.

[bluewave]

I'd be willing to bet, too, that the ACE in the EPAC is actually decently below normal.  Keep in mind the EPAC peak is in mid-August.

 

Yeah, the EPAC is running 53% of normal with the WPAC at 47% and the Atlantic really lagging at 28% of normal ACE.

[wxmx]

Count the number of TUTT lows lol

 

 

 

Not that bad...yes, there are one too many, but generally pinched off ULLs are less shearing inducing than full fledged troughs. ULLs at this time of year usually retrograde west or SW, helping ventilate w moving TWs. Of course, having too many makes upper level conditions above 15N rather hostile, but below that, it's pretty decent.

[Amped]

 

FWIW this site shows the strongest bullseye it's shown all year on day 30.  It is a fish storm region though.  Also showing a small positive formation anomaly near the SE coast centered around 9/9.  And that's abut all I have to over-analyze.

[wxmeddler]

HS3 Global Hawk has been station for about 8 hours now..

[yoda]

Hi ho hi ho 96L recurvin it will go -- https://pbs.twimg.com/media/BS4oomMCIAEZo9J.png:large

 

(it was posted on twitter fyi)

[wxmeddler]

29 Global Hawk Dropsondes ingested and assimilated into the 0z GFS! (Note the 26th's were rejected (pic#3), but not tonight!)

[Amped]

Hi ho hi ho 96L recurvin it will go -- https://pbs.twimg.com/media/BS4oomMCIAEZo9J.png:large

 

(it was posted on twitter fyi)

 

Euro actually gets it down to about 1000mb 12z Saturday before it starts weakening.

[Ed Lizard]

There isn't a single 18Z ensemble member that shows at a strength of 1008 mb or below that doesn't start fishing 96L within 5 days.  A couple get it to 1000 mb or stronger on the way.  Euro barely develops it but fishes the remnant 850 mb vorticity.

 

 

Oh well, at least it is something..  And the central Atlantic quasi-invest 25L is finally getting some convection near what IR2 suggests is the circulation center,  A tiny blob, but near -70C)

[phil882]

96L is like watching the same horrible movie over and over again... like Dorian and like Erin, the wave is emerging during the overnight period where the diurnal max for convection + a strong CCKW should aid in initial genesis. However, the system should gain latitude rather quickly, the consequence of a very weak 500 hPa ridge that is bisected by a pesky, larger, and persistent upper level trough located near the Azores. This feature has literally been in the same place for the last two weeks, and is highly anomalous for this time of the year. This is the same pattern that ripped apart Erin. 

[tmagan]

Here is the latest Dakar sounding for the wave rolling off Africa.

[HurricaneJosh]

African waves lolz.  Booooooorrrrrrring.

[Mike.Ventrice]

Count the number of TUTT lows lol

 

 

This is a time where the GFS could struggling with the large-scale pattern. It's been extremely difficult forecasting the pattern over the U.S. in the medium-range, as the European and GFS solutions are in a complete 180 with regards to the pattern over the eastern U.S. late. European keeps digging a strong trough over the East around day 7-9, whereas the GFS is building a ridge. You can imagine the differences between the two models with regards to the downstream impacts over the Atlantic. I'm putting more favor into the trough solution over the eastern Atlantic, which suggests a stronger ridge developing over the northern Atlantic with less sub-tropical cut offs over the tropical Atlantic. This solution might favor better prospects for the weak easterly wave over the central MDR to spin up... Something to keep an eye on in future forecasts that's for sure.

[phil882]

 

 

This is a time where the GFS could struggling with the large-scale pattern. It's been extremely difficult forecasting the pattern over the U.S. in the medium-range, as the European and GFS solutions are in a complete 180 with regards to the pattern over the eastern U.S. late. European keeps digging a strong trough over the East around day 7-9, whereas the GFS is building a ridge. You can imagine the differences between the two models with regards to the downstream impacts over the Atlantic. I'm putting more favor into the trough solution over the eastern Atlantic, which suggests a stronger ridge developing over the northern Atlantic with less sub-tropical cut offs over the tropical Atlantic. This solution might favor better prospects for the weak easterly wave over the central MDR to spin up... Something to keep an eye on in future forecasts that's for sure.

 

 

I'm not seeing a favorable pattern on the ECMWF appear until the day 8-10 range. Until then, the TUTT is dominating the central atlantic above 15N. Part of the problem is likely due in part to how stable the tropical and subtropical Atlantic has been this year. Without a lot of deep convection, you don't have a primary mechanism to destroy upper level +PV anomalies via diabatic heating. 

 

 

This is also going to sound backwards, but I also think the very active African monsoon is partially to blame as well for the lack of activity in the MDR. Have you noticed that we haven't gotten very many waves hanging around 10N. Most have been emerging off much higher than usual, partially due this years active EKE and further northward extent of the heavy precipitation (note black contours are climatological values).

 

Now stronger waves normally are a good thing for TCG... and that's true to a point. They are definitely a better thing for early Cape Verde TCG (like what we witnessed with Dorian and Erin). However, strong waves also have a tendency to emerge off at a higher latitude, and tend to have a larger 500 hPa footprint. Therefore in order to prevent these waves from recurving (or moving into colder SSTs from the get go) there needs to be a strong 500 hPa ridge in place to steer them west or even south of due west in the first few days. Thats been largely absent this year thanks in part to the large upper level trough thats been hanging south of the Azores for the last few weeks. 

 

So its a combo of just bad luck... strong waves that are easily carried poleward in the absence of a strong mid-level ridge. If you want a robust cape verde season with many long tracked strong TCs, you need the strong mid-level ridge from the get go. 1995 is a prime example of that (although even in this case, a lot of TCs end up recurving). Note the distinct lack of TUTT features and that most of the TCs that do develop are on a westward heading. 

[HurricaneJosh]

Folks here talk like Africa is the only source.  Have fun with that!  

 

I still think looking to Africa for interesting events this year is a big waste of time.

[Mike.Ventrice]

Folks here talk like Africa is the only source.  Have fun with that!  

 

I still think looking to Africa for interesting events this year is a big waste of time.

 

Josh, I think I have a feeling where you are going with this...  these systems will likely recurve out over the Atlantic, posing minimal threat to the US. While that's the case on most occassions, you still get those easterly waves that develop, but then struggle and continue to propagate towards the west, reamplify and track up the East coast... you never know!