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.

Isaac weak now but has potential for significant strengthening as it keeps Florida and Gulf Coast on edge

Track map showing Isaac and Joyce

Track map showing Isaac and Joyce

Issac has been an under-performer so far and no one is complaining about that. The storm simply has not been able to “pull it together” and bundle all of the heat energy that it has been trying to tap for the last several days. Perhaps it never will but in case it finally comes together, people in its path need to be prepared. I am not talking about only Florida either, we first have to deal with Isaac’s impact on the Greater Antilles.

The current forecast track takes Isaac over Hispaniola and eastern Cuba where the rugged terrain will literally squeeze the moisture out of the storm, dumping excessive rain fall in a short amount of time. The flooding risk, especially in Haiti, will be substantial, even if Isaac remains a “weak” tropical storm. People in the region generally know this about tropical cyclones but each one poses a new challenge as to the track and intensity and how much rain actually falls. There is no doubt that freshwater flooding from tropical cyclones is a big problem and Isaac is likely to be no exception.

Right now, the storm is still trying to organize and once it does, it could intensify quickly over the very warm water of the Caribbean Sea. It has yet to develop a solid inner core as we saw last night with the fact that the center itself reformed entirely in a different location. Isaac is also a large storm with tropical storm force winds extending out from the center up to 140 miles. I think that once the inner core develops, Isaac will become a formidable hurricane. But the question is, when? When does this happen? If it happens soon, then the effects to  the Greater Antilles will be amplified. If it happens after Isaac passes over the islands, then the worst of it would be felt in Florida perhaps. Sadly, intensity forecasting is where the least amount of skill lies. So many factors are involved and modeling the inner core of a tropical cyclone is very difficult to do. Sudden changes, up or down, in wind speed often take place in hurricanes and tropical storms. With Isaac, it has been a slow, steady process all along. We just don’t know when or if that pace will pick up.

The track forecast is also a problem as it places a good deal of Florida under the threat of hurricane conditions. Right now, the current forecast track takes Isaac over a significant portion of eastern Cuba before emerging over the southeast Gulf of Mexico. Assuming that the storm does not get torn up completely, it has a chance over the high heat content waters of the Florida Straits to intensify rapidly. This means that the Florida Keys may have to deal with an intensifying hurricane passing through. It’s just so hard to know what will actually happen as so much depends on exactly how much time Isaac spends over Cuba.

Since Isaac has such a large wind field, it will affect a huge area of Florida. Even inland counties will have tropical storm force winds to deal with. And, Florida’s peninsula would be on the right-hand side of the circulation, usually the more active side of a hurricane. Flooding could be a problem with the constant barrage of rain bands that will move through, well ahead of the center. It has been seven years since any hurricane has affected Florida directly. I hope that people take this seriously. Even a weak storm can bring tremendous amounts of rain and as we saw with Fay in 2008, rain alone is enough to cause some serious grief. The time to begin preparing for Isaac’s impacts is now. Don’t wait to see what the final outcome may be. By then, you’ll be really stressed and have to deal with all of the other people who waited. Believe me, you don’t want that.

ECMWF 5 Day Forecast for Isaac

ECMWF 5 Day Forecast for Isaac

Obviously, the big question is where does Isaac make landfall, its final landfall that is? The NHC forecast track suggests that it is possible Isaac heads for the Florida panhandle by day five and six. Yet, if we look at the ECMWF model, it still shows Isaac swinging out farther to the west before turning more north. The GFS model, on the other hand, has Isaac closer to the peninsula all along. Either way, the possibility of an eastern Gulf of Mexico landfall seems to be increasing and let me tell you, if Isaac gets strong, storm surge in that area is a

GFS 5 Day Forecast for Isaac

GFS 5 Day Forecast for Isaac

big concern. We’ll deal with that later, no need to worry about something that may not come to pass just yet but the potential is certainly there, especially for areas to the east of where Isaac makes landfall.

I will cover all of these details and more in today’s Hurricane Outlook and Discussion that will be posted to our iPhone app shortly. I will also discuss the possibilities for our field work and how the app will help to keep you informed as we work in the landfall zone to bring you the latest information, video posts and live weather data. This is where our app will really shine and make a name for itself. I’ll have  a separate blog post about the app later this afternoon. In the meantime, I’ll have occasional updates here and on Twitter and our Facebook page. If you have any questions, please feel free to send an email or ask via one of our social media outlets. I’ll do my best to answer.