With the exception of TS Nadine, which is gradually losing its tropical characteristics, and 94L, itself a sub-tropical type storm system, the Atlantic Basin is very quiet. There are no additional organized areas of deep convection noted and none of the global computer models develop anything over the next several days.
In the east Pacific, invest area 93-E shows signs of becoming the next tropical depression but it will move away from Mexico. Thus we will likely end September without a hurricane threat to the U.S. or Mexico. Leslie did bring near hurricane force winds to Newfoundland earlier in the month but that’s it, we have escaped the peak month without a serious landfall event. Remarkable considering all of the activity that we have seen but since it has all been out of the deep tropics and over the open ocean, the result has been no issues to speak of for land.
How about October? What can we expect as we enter the last significant month of the hurricane season? Well, climatology suggests that a lot can happen. The patterns shift back to the western Atlantic and especially the western Caribbean Sea in terms of development potential. Sea surface temps in the region are at their peak with plenty of deep ocean heat content available. We’ve seen some incredible October hurricanes with the most notable in recent times being Wilma seven years ago. It developed towards the end of the month and was at one time the most intense Atlantic hurricane ever recorded with a central pressure of at least 882 millibars and a 2 mile wide eye. Wilma went on to menace the Yucatan before making landfall in SW Florida on the 24th of October. That was the last time any hurricane has made landfall in Florida, much less a major hurricane.
Will this October have something to track in the western Caribbean? Obviously I do not know for sure but there are couple of things to look for which might help to uncover a few clues.
First, as I mentioned, climatology suggests that we should see at least one hurricane develop in the western Caribbean or vicinity during October. This region is favored with plenty of development taking place over the past 100 years. In other words, we would normally look to the western Caribbean and/or Gulf of Mexico in October for the highest potential for development.
Second, the MJO or Madden-Julian Oscillation. The best way to describe this phenomenon is to think of it as a period of time when upward motion in the tropics is favored, thus allowing for deep convection to develop and sustain. The MJO typically moves around the globe once every 30 to 40 days and helps to kickstart tropical convection. Sometimes it is quite weak and hardly noticeable. Other times, it is very prevalent and leads to a burst of several tropical cyclones over a two week period or more. Right now, the MJO favors western Pacific development and none of the dynamic models indicate that it will move in to the western Caribbean anytime soon. However, once we get past the end of the month, I suspect that we’ll see some changes and as we approach mid-October, I would not be surprised at all to see a chance of something developing. If we get a favorable MJO pulse, those odds will go up considerably.
Finally I think that the lack of a significant El Nino event will also help to increase the chances of an October hurricane in the western Caribbean. El Nino usually means stronger than normal winds cutting across the Caribbean due to an increase in upward motion over the tropical Pacific. So far, the warming in the Pacific has been weak at best and we are not officially in an El Nino yet. This may be just enough to allow for one or two more hurricanes to develop before the season ends on November 30.
For now, the tropics are of no concern and won’t be for the next few days and probably longer. Once we get in to October, we’ll have to watch the climatologically favored areas for the possibility of something coming along to track. Let’s see how these other indicators help with monitoring conditions that may lead to such development. In the meantime, have a great weekend and enjoy the Fall weather. I’ll have more here on Monday.