2017 indicators: SST's / MSLP / SAL / Steering / Instability

[Kingarabian]

WWBs are associated with low level westerlies (usually measured at 850mb). These were 200mb westerly anomalies, usually associated with anomalous large scale tropical convection.

I'm not sure if WWB's at 200mb and Kelvin waves go hand to hand, but there may be another similarity in 2014. Since Kelvin waves can be detected @ 200mb, a downwelling Kelvin wave means the reversal of the winds from east to west to west to east. Are those winds effected by Kelvin waves at 200mb since Kelvin waves are also filtered at 200mb? If so, 2014 also had a very strong (one of the strongest ever seen) downwelling Kelvin wave around early spring. I may be wrong here, but this would give that CFS forecast of the WWB @ 200mb some credence.

[Alyono]

MU has below average shear through the next 16 days for the tropical Atlantic

However, it has very strong shear for the Caribbean. Looks to be 30-50 kts for the next 16 days. Too many upper troughs

[Ntxw]

Courtesy of Mike Ventrice's site



African convection has been under favorable CCKW/MJO influence even if subtle as of today and the past 2-3 weeks. Sinking air will be making its way through though week 1 and 2 so even convection there will be diminishing temporarily. I'm not sure I buy any development until at least mid or late July when more favorable rising motion returns.

[tarheelprogrammer]

 https://twitter.com/MJVentrice/status/880788057955467264

[TheStormExpert]

 https://twitter.com/nwscpc/status/880850029661097984

[BigA]

 https://twitter.com/MJVentrice/status/880788057955467264

Although a positive NAO tends to be associated with stronger trade winds (due to a stronger Azores High), the ECMWF (and other models) continue to forecast weaker-than-average low-level easterlies over the MDR during the next 10 days. Interested to see if and how SST responds to these prolonged period of anomalously weak winds.

[Hurricaneman]

And with weaker trades maybe pop a tropical cyclone or 2

[Hammy]

CFS has really been backing off of apparent activity over the last few weeks of runs--even the shorter term has a significant drying (and below average rainfall) over most of the tropical Atlantic for July and early August.

[srainhoutx]

The morning Updated MJO and CCWV data suggests keep a keen eye on the Mid July to early August timeframe for potential Tropical Development across the Atlantic Basin...

[cycloneye]

@MichaelRLowry
The main development region (MDR) of the Atlantic recorded its warmest June since 2011

 https://twitter.com/MichaelRLowry/status/881160554831912960

[Hammy]

The morning Updated MJO and CCWV data suggests keep a keen eye on the Mid July to early August timeframe for potential Tropical Development across the Atlantic Basin...

There are some weird similarities here with 1998--subtropical low in April (this year's developed), several strong tropical waves moving into the Lesser Antilles as well as the Gulf Coast (and again, two of those developed), and now it's looking likely that we could have a lull for several weeks (the first storm that year developed in late July.) Could all be coincidences but something to take note of if nothing else.

[cycloneye]

@philklotzbach
Atlantic Main Development Region SSTs have anomalously cooled a bit over past month but remain above normal.

 https://twitter.com/philklotzbach/status/881907569228341248

[Kingarabian]

Westerly Wind Burst or a WWB is a word or term we use a lot when monitoring ENSO and for development across the Pacific and Indian oceans. Very rarely is it associated with the Atlantic basin. However, this season we've seen two WWB's assist or induce TC development twice, in the western Atlantic (Cindy) and most likely in the Atlantic MDR (future Don). In my 8 years here, I've never seen anything like this before. Very interesting. So down the line, I would say folks should start to monitor the wind anomalies in the Atlantic.

[weathaguyry]

SST wise, 2005 unfortunately looks to be the best analog, but the SST profile is hard to compare with any other year, 2013 is no longer a good analog, since the flip to a -AMO was very evident by now with extremely cold water off the coast of Spain, which is not present at all this year. 2009 Also had a -AMO, and 2006 is generally not a good analog, since the AMO was not + or-.

2017:

2005:

[Ntxw]

Suppressed phase of CCKW has been passing through the Atlantic. Westerlies helped TD4 for a time but dry, sinking air associated such phase certainly was not a plus. Another suppressed phase (thank you to Dr Ventrice's site for its great work) should pass again mid July. Beyond that perhaps late in the period the MJO may swing through the Maritime continent phases which favors the Atlantic. But for the time being the westerlies will slow and easterlies should return. Waves will be flying across the MDR most likely.

[gatorcane]

Wow Africa is really lighting up with convection and look how far north the convection is

[weathaguyry]

Is there any chance that the cold water on the equator south of West Africa can enhance some of the convection?

[Hurricaneman]

Is there any chance that the cold water on the equator south of West Africa can enhance some of the convection?

Usually it does due to the thermal gradient which causes more conversion and amplifies a tropical wave also known as higher vertical instability

[NDG]

After all the fake news by the models of a potential busy July over the Atlantic is time to realize that conditions are not there yet over the basin, is just a typical July, we are going to have to wait until August, the strong waves that come out of Africa will continue to struggle with the SAL over the Atlantic MDR and then windshear over the Caribbean, which by the way it has continued despite the CFSv2 persistently forecasting it to come down.
Time to get entertained in the EPAC.

[weathaguyry]

Shear isn't too bad in the MDR, but you have SAL to deal with, and SAL isn't bad in the Caribbean, but there is a lot of shear to deal with, so once one of those factors goes away, activity will start to pick up