Warmer than normal water temps likely to fuel Leslie as rest of tropics stay very busy

Atlantic Sea Surface Temperature Anomalies

Atlantic Sea Surface Temperature Anomalies

Sea surface temps are running at least one degree Celsius above normal across much of the northwest Atlantic. In fact, there are large areas of plus two and three Celsius just off the Canadian Maritimes. This translates in to added heat content and Leslie is poised to take advantage of it over the next week or more.

The current NHC forecast track has Leslie moving very slowly over the next few days as steering currents remain weak. The track takes the center just to the west of Bermuda but since Leslie is a large storm with a huge wind field, the effects will be felt on the island in the way of large, battering waves, heavy rain and high winds. I suspect it won’t be too much longer until we see a hurricane watch posted for the island.

With all of this warmer than normal water around, Leslie looks like it could strengthen in to quite a strong hurricane in the models. Add to this what appears to be a very favorable upper level outflow pattern and it is possible that Leslie becomes the first category three hurricane of the season. We have been in this pattern of seeing storms/hurricanes intensify out of the deep tropics and I don’t see any reason to believe that Leslie will be any different.

In the longer range, the Euro continues its westward forecast for Leslie, taking it very close to Nova Scotia and Newfoundland. Any further west and we could be looking at a possible brush with portions of New England as well. Much of this will have to do with the way a trough is supposed to develop in the Tennessee Valley this weekend and beyond. If it is weaker or digs in farther west, even by a little, then the high pressure area over the western Atlantic can build in more and push Leslie a degree or two of longitude west. I will be watching closely to see if this trough acts to capture Leslie and swing it north-northwest or whether the trough acts to push Leslie out to the north-northeast. How this plays out will determine what, if any, landmass is directly impacted.

One effect that I have made mention of for several days now is the increasing swells that will roll in to the East Coast. The NHC continues to make mention of this in their discussions and I want to emphasize the importance of understanding how dangerous rough surf can be- even with a storm/hurricane hundreds of miles off the coast. Check out this video that I produced last year as part of a preparedness campaign with Olympus Insurance out of Florida:

Elsewhere, we now have tropical storm Michael which will be officially named at 11am ET on the NHC advisory. The small storm will be short-lived and not affect land but it will bring the total number of named storms to 13 this season. While Michael is much smaller than Leslie, it is clearly a tropical storm and is of interest to shipping lanes in the open Atlantic.

The east Pacific is calming down and I do not see any new areas of concern developing anytime soon.

I will be working on the daily video blog for our iPhone app and will have it uploaded in just a little while. We are also eagerly anticipating the first major update to the app any day now. The update will greatly enhance the app and allow for manual refresh of the video blogs. As soon as it is approved by Apple, I will add a separate blog post. Speaking of blogs, I’ll update this blog later this afternoon.

 

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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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Hole in central Atlantic ridge should keep Leslie away

Kirk and Leslie both headed out to sea

Kirk and Leslie both headed out to sea

It’s back. The seemingly permanent weakness or hole in the Atlantic ridge that has turned numerous hurricanes away from the United States since 2008. Obviously Isaac was able to sneak in underneath; as did Irene last year. But Leslie? It will not. The pattern is such that there will be a trough too far east over North America for Leslie to make it much past 60 W longitude.

With the forecast calling for Leslie to become a hurricane, it should still produce a few days of nice long period swells for surfers to enjoy. Any increase would be nice I suppose. But that should be the extent of it as the global models are firm now in showing a turn away from the U.S. with the track.

Kirk is also heading out farther in to the North Atlantic and will lose its tropical characteristics within a day or two as waters underneath its circulation gradually cool.

The rest of the tropics are quiet and even in the east Pacific there are no areas of concern this weekend.

I am back at home in North Carolina and will resume the daily video blog for our app. On Monday, I will have a longer write-up about Isaac as well as announce plans for our first DVD since 2008. Have a great weekend!

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Window of opportunity for development approaching? We shall see

MJO Impact Forecast for 8/15 - 8/21

MJO Impact Forecast for 8/15 - 8/21

A look at the tropics this morning reveals that conditions just aren’t very favorable for development. What’s new, right? This seems to be the norm as of late as dry, stable air has been the dominate negative factor across much of the Atlantic Basin. Things may be about to change.

I was reading the latest forecast for the MJO or Madden-Julian Oscillation from the Climate Predication Center and there is a chance that a more favorable pattern is about to set up in the coming days. Basically, an increase in upper level divergence and in tropical convection is forecast for a good deal of the central Atlantic week after next. As you can see on the cropped image that I have embedded in today’s blog, the red areas indicate a high probability of tropical cyclone formation – according to the CPC analysis. As the enhanced phase of the MJO moves our of the east Pacific and across the Atlantic, we may begin to see an increase in development chances next week. However, there is enough uncertainty in the model forecasts for the MJO and how much of an influence it will have on the region that we’ll have to just wait and see if this actually happens.

Since we are also moving deeper in to the climatological peak time of the hurricane season, the chances of development go up anyway. It may be only a matter of time and we’ll see the dry air shrinking as more unstable, moisture-laden air moves in and provides a more fertile environment for tropical storm formation. There’s no way to know for sure so we’ll just have to monitor conditions as they slowly evolve towards the end of the month.

The one certainty for the short term is that there are no areas of immediate concern to deal with anywhere in the Atlantic, Caribbean or Gulf of Mexico. Even the east Pacific is quieting down which is usually an indication that the Atlantic is about to become more active. Time will tell.

Click here to view the full graphic mentioned above from the CPC website.

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95L poses no threat to land as tropics remain quiet

A non-tropical low pressure area, designated 95L, is the only area on the NHC’s tracking map worth noting this morning. It is located well out in the subtropical Atlantic, far from land areas. Even though it has gale force winds and some convective activity, it lacks a well organized warm core and is moving over progressively cooler sea surface temperatures. Even if it were to become a subtropical storm, it will continue to move to the northeast and not bother any land areas.

The rest of the tropical Atlantic through the Caribbean Sea and the Gulf of Mexico are, for the most part, nice and quiet. There is a notable increase in convection in the Caribbean which is partly due to the favorable MJO pulse moving through coupled with a tropical wave passing across the region. There is some chance for this energy to eventually develop in the western Gulf of Mexico later this week but I see nothing to suggest a major problem.

In the east Pacific, a large disturbance is moving eastward not far off the coast of Mexico. It has some potential for additional development before moving inland over Mexico later this week, bringing with it more heavy rains for the region.

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