MAweatherboy1's Blog

A Check of the Global Tropics

By: MAweatherboy1, 9:21 PM GMT on July 09, 2014

Good evening. We are now close to a third of the way through July, and that means we are moving closer to the climatological peak of the Atlantic hurricane season. The basin is currently quiet, as is the neighboring East Pacific since the somewhat surprising dissipation of Fausto earlier today, so I think now is a good time to take a look at the bigger picture on where we stand globally for tropical cyclone activity in 2014, and where we are heading in the next few months. Looking at ACE, or Accumulated Cyclone Energy, which I find to be the best overall indicator of seasonal activity (all my ACE numbers are taken from Dr. Ryan Maue's model page on weatherbell.com), we can see that the globe as a whole is running below average so far this year, with about 87% of normal ACE so far. The Southern Hemisphere, whose season is now well over, had a near to slightly below normal year featuring 94% of average ACE. Since its season occurs during our winter, the Southern Hemisphere is by far the majority contributor to global ACE at this stage of the season. We can, however, start to get an idea of how the Northern Hemisphere is doing. The two basins lagging behind so far are the North Indian and West Pacific, with North Indian ACE running at less than two thirds of average, with most of it coming from Cyclone Nanauk, the second of two storms in the basin. With fairly average conditions present for this basin and near to slightly above normal sea surface temperatures, I would expect ACE in this basin to finish near to below average this year, likely 80-90% of normal. The other below average basin so far is the West Pacific, which has produced just over three quarters of its average ACE so far. This is a significant jump over just a week or so ago, however, as Super Typhoon Neoguri has tallied about two thirds of this year’s West Pacific ACE so far in just the past several days. Without Neoguri, ACE in this basin would only be running at about a third of average so far! So what do we expect here? Well, with extremely warm SSTs in the basin and generally favorable atmospheric conditions, I fully expect the West Pacific to continue picking up the pace in the coming months, and current Invest 92W may be the next system to boost ACE out there further. The slow start has taken my expectations down slightly for the basin, as it has wasted quite a bit of time before kicking into gear (activity in the West Pacific can happen any time of year, but it is most active from our spring through fall), but I am still expecting an above average season with ACE likely ending up 125-150% of average. Now for the two basins which are above average so far, and happen to be the two closest to most of us on this blog. I’ll start with the East Pacific, which as expected is off to a hot start, with six early storms pushing ACE to over 200% of normal so far, mostly due to Major Hurricanes Amanda and Cristina. While the expected El Nino continues to waver, conditions overall remain favorable in the East Pacific, with warm water and low shear. I would expect things to continue running active in this basin, and I believe ACE in the East Pacific will finish at around 150% of average. Finally, we move to the North Atlantic, where, early in the season, the basin has racked up a staggering 360% of normal ACE! This is a bit of a mathematical mislead, however. The Atlantic has seen one storm in the first month and a half or so of the season, the impressive Hurricane Arthur which tallied over 7 units of ACE, while the average for this time of year is only 2. Arthur formed over an area of favorable conditions where we expect much of our activity to occur this year, off the East Coast of the United States. As I mentioned a week or so ago, however, don’t be fooled. This is poised to be a very quiet Atlantic hurricane season, though Arthur did decrease the odds of a really historically quiet season in terms of ACE. With a general state of high shear, significant and nearly constant outbreaks of Saharan Air Layer (SAL) dust, and cooler than normal waters in the main development region, it is still a bleak situation for the Atlantic, and I would expect ACE this year to finish at only about 50-70% of average, and the Atlantic is by far the most likely candidate for a basin to be below average this year. So, that is a look at where we stand so far. But I’m not through yet. Now, I’ll take a look at what to expect over the next few weeks. The first big thing to watch is, as I briefly mentioned, invest 92W in the West Pacific. I’m not going to be getting specific today, but there is a chance that this could become a strong typhoon, as the GFS depicts that happening, but it may also struggle as the ECMWF shows little to no development. The point here, however, is that from this point forward and even more so as we get a little later into the year is that development threats will be almost nonstop in the West Pacific, and with favorable conditions to work with it is highly likely we will see multiple super typhoons like Neoguri in the coming months, so landmasses in the West Pacific best be on guard as they will face some typhoon threats. Closer to home, with the dissipation of Fausto in the East Pacific, that basin is quiet, and development there is unlikely for the next 5-7 days, though the NHC is noting one disturbance with a slight chance to develop in the next 5 days. This is a favorable East Pacific year, so we will have to watch for development at pretty much any time, but I would look for the next real kick out of this basin towards the start of August as the MJO comes back in, and after that we will likely see regular cyclone formation for much of the August-October period, though not to the extent that we would expect in the West Pacific. Finally we come to the Atlantic, which right now seems to be the trickiest to make a forecast of when we should expect activity. Certainly we will see more storms form this year, but the lack of favorable conditions make it hard to pinpoint possible opportunities when we should look for development. The MJO is never a bad place to start. Currently, it is moving into the West Pacific (albeit not that strongly) and is helping enhance development there, but as I mentioned it should move towards the Atlantic and East Pacific towards early August. Early August and especially towards mid-August is when we typically look for the Cape Verde season to start up in the Atlantic, and Cape Verde type storms are very much capable of developing without the aid of the MJO, but it does aid the chances. The MJO can also help create developments in the Caribbean, which so far this year has been a very hostile place for tropical cyclones due to strong shear. Shear should remain above normal in the Caribbean for most of the year, so even the MJO may not be able to spur many if any developments there. But back to the question of when we should expect activity. I would say that there is only about a one in three chance that we will see another storm form in July. I think we will have to wait for this MJO pulse for our next opportunity, and when that pulse arrives I think we should look further east for the possibility of our first purely tropical development of the season towards the MDR. It is possible we could see a couple storms this year that develop in the MDR and move west into the hostile Caribbean where they would dissipate, so we may see a setup like that. MDR development would certainly be dependent on a decrease in SAL dust, but climatology as well as the passing MJO pulse would tend to favor that SAL decrease. Beyond that, it will be time to start watching for on and off development chances from August through October, as again just by virtue of climatology that is when we should expect probably around 5-7 developments this year. I did not forecast any major hurricanes in my preseason prediction, and I stand by that, but should a major develop rather quickly in the MDR it is likely that it would recurve out to sea. Again, in close and specifically off the Southeast coast of the US is where I and many others feel we should watch this year, as we’ve already seen one rather strong storm get going there. My worst case scenario for a storm this year would be as follows: a wave emerges off of Africa (the wave train itself should be quite healthy this year, though most will struggle down the road with unfavorable conditions), and moves steadily westward, fighting for survival among moderate shear and a bit of Saharan dust. Slowly, conditions become marginally conducive for tropical development, and a tropical depression forms from the wave as it approaches the Lesser Antilles. Slowly pulled north of west by a pattern that should favor recurves overall, the system strengthens while passing north of Puerto Rico and Hispaniola. As it enters this year’s expected hot spot off the Southeast coast, the very warm waters there, combined with a large pocket of low shear and moist air allow it to strengthen rapidly into a hurricane and then a major hurricane, and while it does turn north as one would expect it is too late to avoid a significant hurricane impact to the entire US East Coast. We already saw something similar to this with Arthur, but I am thinking more along the lines of another storm like Irene, only I think a storm like that this year could better maintain its strength as it moved north towards the Mid-Atlantic and New England this year. So that is my worst fear for this year, and while a scenario like that and a hundred other “doom” scenarios are possible every year, I feel that is the biggest threat we’ll face in the US this year. As always, no matter where you are, if you live somewhere that hurricanes can strike, you must always be on guard, as even a year like this that should end up below average and perhaps significantly below average, it still only takes one storm to make a season, and we came not too far away from that with Arthur, as had a few things clicked just a little differently we could have been looking at a very, very bad situation. That is all for today. Thank you as always for reading, feel free to leave comments, questions, criticisms, etc., and enjoy the rest of your week!

-MAweatherboy1

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About MAweatherboy1

Average 18 year old weather nerd. Freshman at Plymouth State University, majoring in meteorology, with the goal of becoming a professional forecaster.