CybrTeddy's tropical weather blog

Watching Invest 99L for the threat of development - 7/30/12

By: CybrTeddy, 3:33 PM GMT on July 30, 2012

Good morning and welcome to my tropical weather update for Monday, July 30th, 2012. The tropics have finally ignited in activity with Invest 99L currently located in the Atlantic with a chance to develop into a tropical cyclone. Satellite reveals a relatively disorganized system, thanks to an abundance of Saharan Air entering into the system. However that being said it appears that this system will be able to create a moisture field around itself and be able to fend off the dry air as most Cape Verde systems are able to do.

(figure 1. Current satellite image of Invest 99L)

The CMC, GFS, NOGAPS, and UKMET have all been showing some consistency on developing this system. The past few days, most noticeably the GFS and CMC, have had the models drop the system and then only to pick it up again with the next run. However, the last 36 hours or so the models have finally become more consistent on development with the GFS only predicted a moderate tropical storm from this before meeting its death in the Caribbean. The CMC believes this will go north of the islands and become your typical Cape Verde hurricane. I somewhat favor the CMC track, as it appears that there will be a shortwave trough situated off the US Coast during this time. If 99L manages to separate itself from the ITCZ and begin to intensify it will probably go north of the islands. However, if it takes the GFS path it will face a wall of shear in the Caribbean and meet it's death without becoming anything more than a 50mph tropical storm. Right now, it's hard to say where exactly this might go as usual, all we need is patience.

(figure 2. Current model runs on Invest 99L)

The intensity forecast is going to be problematic. The CMC and GFS both show two totally different situations, the CMC is showing that if it goes north of the islands it will be able to intensify into a major system. However if it takes the GFS track it will die in the Caribbean, thanks to strong easterlies in the Caribbean due to the development of the El Nino in the Eastern Pacific. Based on what we know so far, I will not make an intensity forecast and it would be much rather to my liking just to sit back and watch the next few days.

(figure 3. Current shear over the Atlantic, note the high trade winds over the Caribbean)

Based on all this, I will not give a specific forecast yet on 99L given that there are too many factors coming into play. This situation will probably be no where near as tough as Debby was last month to forecast, and we have a lot of time to watch this system. Cape Verde season is now in effect, it's all a matter of time before we get another system.


Finally watching for development in the Atlantic - 7/28/12

By: CybrTeddy, 6:54 PM GMT on July 28, 2012

Good afternoon and welcome to my tropical update for Saturday, July 28th, 2012. It's finally time to come out of my blog posting downtime because finally for the first time this month, some models are showing development - period. This month has been very benign with only one invest in the Atlantic, invest 98L that lasted for only a day. This is in thanks to the downward MJO phase over the Atlantic that has been present for over a month, combined with SAL outbreaks and persistent high wind shear over the MDR, has been keeping July to such a low key with activity.

(figure 1. Current satellite image of the Atlantic.)

What we are going to be watching this week and into next week is the possibility of a tropical wave emerging off Africa and developing in the relative short term. The GFS, CMC, and NOGAPS have all been showing off and on for the last week or so that this might happen, The GFS is starting to show 'some' consistency that a TD/TS will form off the African coast this week. Still a little early for CV season to get cranking, but it happens. The model kills it off once it reaches the islands due to high shear being there. This system would have to go north of the islands to survive and intensify, which is a possibility. I want to see more consistency, but it is within the GFS's vaunted 5 day accuracy period. Let's wait 2-3 more runs before we come to a conclusion on this.

(figure 2. 12z GFS 138 hours out with a system off Africa.)


Atlantic is quiet, what to expect for the remainder of July - 7/14/12

By: CybrTeddy, 8:55 PM GMT on July 14, 2012

Good afternoon and welcome to my tropical weather update for Saturday, July 14th, 2012. The tropics are very quiet and is expected to remain so for the next 5 days. The Eastern Pacific has been rolling hurricane after hurricane, with currently Hurricane Fabio making the headlines. The EPAC season will probably be one of the more active Julys, today we will discuss what to possibly expect not only for the rest of July but possibly for the rest of the season.

(figure 1. The tropical Atlantic as of this update)

Chances are now very likely that 2012 will become an El Nino year, but what we don't know is how exactly this will hurt our hurricane season. There have been no disturbances in the Atlantic since Debby thanks to the Madden-Julian Oscillation leaving our basin. However, we are still above average in named storms and will continue to be so for about another month assuming no more names develop. This El Nino event will probably persist and become even stronger as the year goes on, bringing higher shear to the Main Development Region and limiting the amount of Cape Verde majors we will see this year. That being said, we have already had two US landfalls this year, Debby and Beryl, which shows that even in El Nino years such events can happen and it really only takes one.

(figure 2. SST anomalies reveal the continued development of El Nino in our basin.)

Wind shear in the Atlantic is high and will probably continue to be high in our basin. However, there is a fair chance that the next two weeks we might have to be looking off the US East Coast for development of a trough split. These are hard to predict and often benign in nature, especially in July. The El Nino so far has kept in check the SST's being too high but they are still somewhat above average, especially over the Gulf Stream. I believe that if we do get a named storm this month that is how it will develop.

(figure 3. SST anomalies reveal that we are generally above average but much above average off the US East Coast)

Based on this, I believe the chances are about ~30-50% of us seeing another named storm before August. However, if 2009 is any indicator we will probably have a large blowup of 2-3 named storms in August followed by a slow pace after that. I see no reason though thanks to the early padding of named storms we have seen we won't get to at least 11 named storms, but in general it will be a near average season. However, like I said earlier it really only takes one to cause a difference.


The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.