Subtropics rule the season

Hurricane Chris set the tone for the remainder of the Atlantic hurricane season

Hurricane Chris set the tone for the remainder of the Atlantic hurricane season

It has been a rather odd hurricane season so far. I say this because most of the activity, the stronger activity anyway, has developed well outside of the usual breeding grounds of the deep tropics.

Hurricane Chris, which formed back in the latter half of June, did so at 41.1 N latitude! That is incredible for so far north so early in the season.

Next up was hurricane Ernesto, the only hurricane to form south of 20 N latitude this season out of eight total hurricanes so far. However, Ernesto struggled to become a hurricane until right before landfall, another common trait this season as we’ll see with Isaac.

Gordon became the season’s third hurricane and again, well outside of the deep tropics, attaining hurricane status at 34.0 N latitude while heading for the Azores Islands.

Then there was Isaac. Several times during Isaac’s life span it looked as though it could become a powerful hurricane. Instead, Isaac struggled with dry air and the lack of an inner core all the way in to the north-central Gulf of Mexico. One private weather firm loudly proclaimed that Isaac could be another Katrina or worse! And yet the fourth hurricane of the season only managed to reach 80 miles per hour before making landfall in Louisiana. While Isaac was a large hurricane and caused significant flooding from surge and fresh water flooding, it was not a very convectively active hurricane with a well defined inner core. This kept the winds at flight level that were being measured by recon from reaching the surface. Fortunately for residents of the central Gulf Coast, Isaac was only a fraction of the intensity that we all know it could have been had environmental conditions been more favorable.

It took all the way until hurricane Kirk on August 30 to finally get a category two hurricane. And of course, this happened while Kirk was well out of the deep tropics, affecting only shipping interests.

Leslie also had promise to become a large and intense Atlantic hurricane but it too fell far short of that potential and spared Bermuda with only passing tropical storm conditions. Stronger winds and more pronounced effects were felt in Newfoundland but even here conditions were not as bad as what could have been experienced had Leslie been a much stronger hurricane.

Michael is the season’s only category three hurricane so far and guess what? It made it to this intensity at 29.6 N latitude while out over the open central Atlantic over water temps of about 80 to 81 degrees. That’s it. Just enough to get the small hurricane to really ramp up – and it maintained a strong eye feature for several days. Luckily, Michael was far from land and only padded the ACE index score for the season.

We are still tracking Nadine which has been on the map since the 11th of this month. Nadine became the season’s eighth hurricane on the 14th at 30 N latitude. This is remarkable and a sign that something is definitely “wrong” in the deep tropics this year.

I have heard everything from El Nino to mid-level dry air being responsible for the lack of intense cyclones in the deep tropics. I am sure researchers such as Dr. Philip Klotzbach at Colorado State University will be looking in to the source of this unusual pattern and I look forward to learning more about it myself at next year’s National Hurricane Conference in New Orleans. The obvious benefit here has been a substantial reduction in damage resulting from less intense hurricanes impacting land. What if Ernesto had become a 140 mph cat-4 at landfall along the Yucatan? What if Isaac had become another Katrina and brought 30 feet of surge instead of 12? We know the answers….it would have been horrible. Been there, done that. I am sure no one is complaining about the feeble nature to this season’s hurricanes. I hope too that people are curious as to why? Why would conditions be so hostile in the deep tropics? What was the root cause if it can be pin-pointed down to something that simple? Will this pattern continue for the next several seasons? While we can be thankful for the lack-luster performance of this year’s hurricanes thus far, I think understanding the mechanics of such good fortune (it’s relative, I know, as plenty of people are still cleaning up after Isaac) is important in case we see the reverse take place next season or next month for that matter.

In any case, it all boils down to this: the tropics have been strange this season and strange has meant fairly benign events for us to deal with. So far, it looks to stay that way for the next week at least. Although, once again, we will be looking for possible storm development out in the open central Atlantic, well north of the deep tropics which seem to be closed for repairs….

I’ll have more tomorrow.

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Tropics nice and quiet except for pesky Nadine

The Atlantic, Caribbean and Gulf are Mostly Quiet with the Exception of TS Nadine Near the Azores

The Atlantic, Caribbean and Gulf are Mostly Quiet with the Exception of TS Nadine Near the Azores

The Atlantic Basin is unusually quiet for this time of the hurricane season and I do not see that changing anytime soon.

We are tracking TS Nadine out near the Azores but that’s it and even Nadine is not that much of an issue.

Some people are blaming El Nino for the quietness, I do not think that the tropical Pacific is really all that warm compared to normal and we are certainly not in an official El Nino period as of yet. In fact, the central Pacific SST anomalies cooled by .30 degrees C in the recent week – and this is also not typical of an El Nino. So what is the reason behind the quiet time? It’s most likely the MJO phase which is currently not favorable in the Atlantic Basin. In other words, we are not in a pattern that supports upward motion in the tropics across the Atlantic, Caribbean or Gulf of Mexico. The lack of instability and generally unfavorable conditions are simply not allowing for any new development.

Looking at the long range models, I do not see any signs of change over the next week to 10 days either. We may escape September with no additional named storms in the Atlantic.

As for October? We’ll wait and see. Without a solid El Nino in place, it is possible that we could have a normal October with a couple of hurricanes developing somewhere – but that’s the key, where? Time will tell. For now, the tropics are of little concern and look to stay that way for quite some time.

Be sure to catch today’s video blog in our iPhone app as it covers these topics graphically. Also, we are anticipating a new update to the app within the next few days that I will address in tomorrow’s blog post.

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Bermuda could be impacted by Leslie as September looks to be quite busy due to lack of El Nino

Leslie Could Impact Bermuda This Weekend

Leslie Could Impact Bermuda This Weekend

TS Leslie developed some very deep convection over night with cloud tops reach an astonishing -88 degrees Celsius. Those cold cloud tops, however, did not wrap all the way around the center of the storm. This is due to the continuation of vertical wind shear which has been just enough to keep Leslie from strengthening much. I do think the burst of deep convection is a sign that Leslie will intensify given the right upper level conditions.

The current forecast track has not budged much from recent ones and it looks like a slow and steady course to the north-northwest throughout the week ahead makes the most sense considering the pattern. There will simply not be enough western Atlantic ridge to push Leslie back to the west enough to directly impact the U.S. That being said, I do believe that an increase in long period swells is coming – especially once Leslie becomes a hurricane. Its slow movement will allow for quite a build-up of energy in the ocean and this means a great surf weekend coming up for portions of the East Coast. It also means an increase in rip currents and as such, people heading to the beach need to be mindful of this hazard. We are still a few days away from the swells reaching the U.S. and I will address this again later in the week.

As for Bermuda, it looks as though Leslie could come fairly close to the island by the weekend as a strong hurricane. Some of the intensity models suggest that Leslie could approach or exceed category three intensity towards the end of the week. Interests in Bermuda need to pay close attention to the future track and strength of this storm. It also looks like Leslie will be quite large with an expanding wind field so even a brush with Bermuda could mean a period of high winds and very rough seas for the area.

Looking at the rest of the tropics, we have invest area 99L well out in the east-central Atlantic. It may develop some but is small in size and poses no threat to land areas.

In the eastern Pacific, TS John has formed to the southwest of the Baja peninsula and will move swiftly off to the northwest and not be a bother to Mexico.

SST Anomalies from August 3

SST Anomalies from August 3

Checking on the current state of the El Nino, we see that it has, in fact, backed off quite a bit in recent weeks. Comparing the SST anomaly maps from August 2 and the one from today, it is clear that the warming trend has stopped and even reversed in the eastern Pacific. This means that the threat of a significant El Nino event during the hurricane season is likely minimal at best. In other words, the negative conditions that a Pacific El Nino would typically bring to the Atlantic Basin are probably not going to be there.

SST Anomalies from September 3, Notice the Decrese in SST Temps in the East Pacific

SST Anomalies from September 3, Notice the Decrese in SST Temps in the East Pacific

The reason El Nino affects the Atlantic is similar to how a large hurricane, with its well established outflow, affects other tropical waves moving across the Atlantic. Remember TS Jean which formed east of Isaac? The large scale upward motion of Isaac led to strong outflow high in the atmosphere and this literally tore Jean apart and caused it to weaken and dissipate. An El Nino event, especially strong ones, causes tropical convection to persist across a good deal of the Pacific. This upward motion on a basin-wide scale acts to spread strong upper level winds across the deep tropics of the Atlantic, much like the outflow from a hurricane. This shear stops developing Atlantic systems in their tracks. Because we are not seeing a significant El Nino event taking shape right now, I suspect that September will be quite busy with a shift in activity more towards the Caribbean Sea and Gulf of Mexico. This is a natural evolution in any season when we see the tropical waves that come off of Africa lose their punch and the build up of low pressure in the western part of the Atlantic and Caribbean leads to development there.

The long range models, and we’re talking beyond 10 days here, indicate this pattern change is coming. Once Leslie moves out, we will probably only wait a few days, if that, before we have yet another named storm.

Curiously though, we have yet to have a major hurricane this season in the Atlantic. The layer of persistent dry air has really put a lid on things, literally. I think that Leslie has a chance to become a category three hurricane as it nears Bermuda as the global models indicate what looks like a favorable upper level wind pattern for it to develop. We may have had a lot of activity, but no intense hurricanes just yet.

I will go over a lot of what I have outlined here in today’s edition of the Hurricane Outlook and Discussion video for our iPhone app. I will also post an update here in the blog this evening to reflect the very latest on Leslie and whether or not I may be taking a trip to Bermuda later this week.

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Atlantic virtually dormant while east Pac keeps churning them out

Wow, things could not be much more quiet than they are now across the Atlantic Basin. I see no areas of significant convection that show any signs of development over the next few days. This certainly spells great news for coastal locations all over the Atlantic, Caribbean and the Gulf of Mexico. Now keep in mind that climatology suggests that it is towards the end of August and obviously through September that the tropics normally ramp up. We’ll see just how close to climatology we are as we move through the next few weeks. For now, enjoy the quiet.

In the east Pacific, the storms just keep coming off what seems like an assembly line. Right now, there is TS Hector which poses no threat to land and a new area of slowly organizing convection near the coast of Mexico that is destined to develop. This system (actually labeled as 95E) could run parallel to the Mexican coastline in the days ahead, bringing heavy rains and squally conditions to the region. We’ll have to watch it closely this week since it is already impacting land and could continue to do so. I’ll have more here tomorrow, including a look at the growing El Nino, SST anomalies and what the long range models are showing as we move in to the traditional heart of the hurricane season. I’ll also have an update on our iPhone app which has an update due out soon that will add new tracking maps and add some ease-of-use enhancements.

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Ernesto on its way to becoming a hurricane as it heads towards Belize

TS Ernesto over the Caribbean Sea

TS Ernesto over the Caribbean Sea

Conditions around Ernesto have improved and now the storm is really starting to ramp up. The main issue was dry mid-level air and the storm’s fast forward motion. It simply could not line itself up vertically and allow for the convective process that drives its heat engine to work efficiently.

Water temps are plenty warm and it is obvious by looking at satellite imagery that the outflow is well established now. Ernesto should become a hurricane before the day is out.

The threat to the U.S. is all but gone now and so the focus will be on Central America, specifically Belize.

As it looks now, Ernesto will be intensifying as it makes landfall. This is never good news. As I have written about before, it has been our experience in dealing with hurricanes in the field that when they hit while intensifying, their effects are amplified. This is due to the convection or upward motion of the clouds that act to bring the strong winds down to the surface. We noticed this most notably during hurricane Charley in 2004 and never forgot what it was like. While Ernesto is not expected to become as strong as Charley, I hope that folks in Belize realize that this is not going to be a weak, sheared and dried out tropical storm when it hits- not anymore. Wind damage could be a real issue with Ernesto along with the other hazards of coastal storm surge and torrential rains.

Farther up the Yucatan where Cancun and Cozumel are, the impacts will be far less. Since Ernesto is not an especially large storm, its effects will be confined to the areas south of the northeast tip of the Yucatan. There may very well be some passing squalls from the outer rain bands but I do not see any reason to believe that Ernesto will post any big problems for Cancun and vicinity. In fact, that area is only under a tropical storm watch at this time. If you have plans to visit the area, do not cancel as Ernesto is only a problem farther south.

Once the soon-to-be hurricane crosses the Yucatan, it could get buried over Central America and rain itself out. This will obviously have negative impacts on the region with excessive rainfall a possibility. The official track does take the storm back out over the extreme southern Bay of Campeche with a final landfall in Mexico near the end of the week. How much time Ernesto spends over land will likely determine how strong it can get once it reaches the water again, if it does not simply die out over land.

The rest of the tropical Atlantic is quiet for now. Florence has dissipated and will likely not be able to make any appreciable comeback. We’ll see, you never know in August.

In the east Pacific, the NHC is keeping tabs on invest area 92E which is forecast to become a tropical depression and eventually a hurricane by many of the intensity models .However, the steering pattern continues to favor a general westward track away from Mexico. This is not typical of an El Nino year and lends more evidence to the fact that the atmosphere is not behaving as if we were in El Nino conditions. With a fairly strong high pressure area over the eastern Pacific it is no wonder that recent hurricanes in the east-Pac have moved westward. It is also keeping the progress of the developing El Nino at a slow pace which could have implications on the Atlantic season from here on out. I’ll discuss that in more detail in tomorrow’s blog post.

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