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Thoughts on the 2014 Atlantic Hurricane Season

   Posted by Levi at 10:57pm on March 14, 2014  - 10 comments

Spring is upon us, and it is time to start looking toward this year’s Atlantic hurricane season. Readers should be instantly dubious of any hurricane season forecast, such as this one, due to their inconsistent skill. Last year, myself and every major forecasting agency that I know of predicted a more active hurricane season than normal, and we were all wrong. In fact, 2013 turned out to be one of the top 10 least active seasons since 1950, with only 2 hurricanes and an ACE of 34% of normal. In hindsight, there are a couple of possible reasons for this, such as an apparent faltering of the Atlantic thermohaline circulation and the local Atlantic Hadley Cell.

Regardless of how well hurricane activity is predicted in advance, you the reader should be aware that nobody can predict individual hurricanes months in advance, and no matter what the season as a whole is like, there is always the potential for a hurricane to form and impact you. Hurricane Andrew destroying south Florida during the otherwise completely quiet 1992 hurricane season is the poster child example of this. With this in mind, and despite forecasting failures like 2013, meteorologists can usually glean useful insight into how active the hurricane season will be before it has even begun. Here, I will offer my thoughts on what 2014 may bring.

The video above is there so that I don’t have to type a long post and so you don’t have to read a long-winded analysis. Some basic points are outlined here, but watch the video discussion for details.

Read more…


Karen Forms in the Gulf of Mexico – Will Bring Blustery/Wet Weekend to North Gulf Coast

   Posted by Levi at 5:13pm on October 3, 2013  - 29 comments

Tropical Storm Karen has formed in the southern Gulf of Mexico from a disturbance that moved out of the Caribbean. Thunderstorm activity remains limited to the eastern side, and the circulation appears to be tilted to the east with height due to some southwesterly wind shear. Such shear is typical with October storms in the gulf, and it is unlikely to go away. In fact, as an upper trough digs in from the west as Karen nears landfall, this wind shear should get worse. Thus, the storm is likely to remain eastern-weighted, with most weather impacts occurring east of landfall in 60-72 hours. The NHC has increased Karen’s winds to 65mph after recon data during the night, but the thunderstorm activity has weakened since that time, and a new plane will re-assess Karen’s intensity. The maximum winds were very localized already, and with a central pressure of only 1005mb, Karen in reality is a pretty weak tropical storm at this time.

The GFS has been throwing a fly into the ointment by forecasting Karen to strengthen substantially before landfall, reaching minimal hurricane strength, along with a track farther east well into Florida. The GFS so far is the only global model to do this, as the ECMWF, UKMET, and CMC are not as bullish. I consider the GFS solution to likely be erroneous feedback, given that Karen is already struggling to get vertically stacked, and wind shear will only get worse with time. In addition, the low-level inflow pattern currently in place with large-scale anticyclonic (clockwise) flow in the SW Atlantic is not conducive for storms, as Karen will lose her moist inflow channel from the Caribbean as she moves north. The environment favors the ECMWF/UKMET/CMC solutions of a weak-moderate tropical storm moving into the north gulf coast, farther west than the GFS ahead of a mid-latitude trough. The NHC is forecasting Karen to become a hurricane and then weaken slightly before landfall, likely due to her initial intensity already being 65mph. Karen currently appears to be weaker, and if the next recon plane affirms this, then Karen’s chances of becoming a hurricane currently seem dim. Blustery, tropical storm force conditions and heavy rain will impact the north gulf coast east of the center at landfall late Saturday and Sunday.


Invest 95L Unlikely to Become Very Strong – Blustery Rain-Maker for Gulf Coast

   Posted by Levi at 6:11pm on September 18, 2013  - 12 comments

In what seems to be the theme this year, another low pressure area has crossed the Yucatan Peninsula and made its way into the Bay of Campeche. Unlike its predecessor, Hurricane Ingrid, Invest 95L will not be able to develop quickly. A northwesterly flow aloft over the BOC, in part due to the upper ridge left behind by Ingrid, is piling up and causing air to sink in front of 95L, while simultaneously shearing the system. This is not allowing convection to develop to its north or west. Such hostile conditions will persist until around Friday night, when 95L will be aligned more with the upper ridge axis, where there will be less shear.

By this time, 95L may be within a couple hundred miles of the Mexican coast, but right now it seems unlikely to actually move inland there, as a shortwave trough digging towards the north gulf coast will erode the mid-level steering ridge to the north of 95L. The result will likely be that 95L stalls and then moves northeastward. However, true strengthening will likely remain difficult. The trough will bring a cold front towards the gulf coast, and the orientation of the front (SW to NE) suggests that 95L will become strung out to the northeast along the front, or even split into two pieces: a tropical system to the south and a baroclinic (non-tropical) system attached to the tail-end of the front. While a splitting could allow a tropical system to remain intact, with the front to the north spreading energy out, significant strengthening seems unlikely.

Another potential scenario is that instead of 95L staying separate from the front, it merges with it and strengthens non-tropically, a scenario portrayed by the UKMET. This would in some ways be analogous to Tropical Storm Lee from 2011. The strengthening would not be tropical in nature, and winds would likely not exceed low-end tropical storm force. Either of these scenarios is possible, but both would mean a blustery autumn rainstorm from Louisiana eastward, and not much more than that.

Current information on 95L including its satellite floater and model track forecasts can be viewed here. Also don’t forget to check my Facebook feed for more frequent updates than here on the blog.


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