September 28, 2010

Tropical Depression 16 Headed to FL

Filed under: Forecasting,Tropical — Erin @ 3:30 pm

As expected, the disturbance formerly known as 96L was classified today as Tropical Depression 16. The depression will probably strengthen to Tropical Storm Nicole. The models are forecasting the depression to get picked up by a trough and carried away as it becomes extratropical, with the GFS from 12Z indicating a rainmaker for most of the East Coast. (Lucky punks.)

This is impressive model agreement and indicates that they have a good handle on the strength of this trough.

Despite extremely warm water in its path, there probably isn’t enough time for it to strengthen into a hurricane, and shear associated with the trough is expected to increase before it makes its landfalls in Cuba and Florida. The SHIPS model shows a modest increase of 28 knots in the storm’s intensity before it weakens again.

In the longer term, this system—along with its predecessor, Matthew—probably heralds a shift in the type of tropical cyclone that will be forming in the remainder of the season, as well as the likely players that will be influencing the path of whatever does form. With the demise of the persistent ridge that brought the Southeast such oppressive heat for weeks upon weeks, and the establishment of a fall-like troughing pattern, we should see a greater threat to the Gulf Coast from anything that brews up—and, statistically, it is approaching the time of year when the Cape Verde conveyor belt shuts down and the tropical threat from “home-grown” systems increases. Additionally, this is a La Nina hurricane season; those have a tendency to start late and finish late, and by no means should the Gulf Coast consider itself safe from threats, including significant systems. In 1999, also a La Nina year, Hurricane Lenny almost reached Category 5 status in November. Even last year, during an El Nino, Hurricane Ida entered the Gulf in November and reached Category 2 status. We’re still in this.

August 15, 2007

Dean strengthening, TD5 in Gulf

Filed under: Tropical — Erin @ 4:32 am

Good morning!

TS Dean has maintained its intensity of 45 knots overnight. Satellites from around 0900Z indicate that Dean is trying to wrap convection around an “eye”-like structure, which may in time develop into a true eye. The system has taken on the classic recognizable “comma” shape of a tropical cyclone, and in the face of low shear, should develop into a symmetrical and photogenic hurricane. Dean is in very low shear now, having escaped the 20kt that limited its intensification previously. This is good for development. However, since it’s happening during the day, Dean’s ability to utilize this may be limited. We’ll have to see.

NHC’s forecast has taken a westward shift, in line with what the computers are indicating. As I said in my previous blogs, I am on board with a Caribbean –> Gulf storm and do not intend to change this prediction unless the ridge is eroded too much for it to happen.

The GFDL and HWRF, our two tropical cyclone-specific models, are both in unfortunate agreement in their 00Z runs of taking Dean to a borderline Cat 3/Cat 4 in the central Caribbean and sending it south of Hispaniola. If this pans out, there is a chance that he will enter the Gulf as a Cat 3 or Cat 4 without ever having hit a large landmass.

I’m not happy about this. In such a scenario, we’d have to hope for shear towards landfall, because the very hottest Gulf waters are right offshore.

Closer to home, TD5 has formed in the Gulf, although according to the NHC it seems to have some problems getting together. Well, it’s a new system. That’s what usually happens. Quite honestly, in my opinion, TD5 could landfall in Texas as anything from a depression to (if conditions are perfect and it takes advantage) a low-end Category 1 hurricane. The NHC is forecasting a 40kt landfall. I think that, if TD5 gets organized in time, it has the potential for rapid development, and this forecast could be too low. With the depression, everything comes down to the timing of its organizing.

February 16, 2007

Global Warming Would Drown the Coastal Hurricane Defenses

Filed under: Climate change — Erin @ 6:24 pm

The barrier islands of the Gulf Coast are an important defense against hurricanes. Mostly uninhabited, they are the first landforms that a Gulf Coast hurricane strikes. While they do not weaken the hurricanes (they aren’t large enough), the islands take the brunt of the hurricane’s storm surge, diffusing it somewhat before the eye makes landfall on the mainland. They are also an important defense against tsunami, a real (if little-known) threat. Significant seismic activity has occurred in the Gulf of Mexico fairly recently.

Global warming is predicted to melt part of Greenland and/or West Antarctica, raising sea levels worldwide up to 20 feet (more if all of Greenland and some of West Antarctica melted). This would have horrific consequences on coastal cities around the globe, of course. This blog, however, will focus on one specific area — the United States Gulf Coast. (Ha, doesn’t it always?)

If global warming raised sea levels as predicted, most of low-lying Louisiana — as well as the critical barrier islands — would be underwater. The low-lying swampland of Louisiana, which has been receding for years now, is another natural barrier for the coast, as well as an environmental treasure. It too would be covered in water.

The coastline would lose its natural defenses against hurricanes.

And, as research is indicating, global warming would also intensify the hurricanes themselves.
The EPA produced a series of pictures showing the coastal areas that are most at risk from global warming-induced inundation. Red indicates areas that are less than 1.5 meters above sea level. The images can be clicked on to show a larger view.

Here is an image of Louisiana and Texas:

And here’s one of Mississippi, Alabama, and Florida:

It’s hard to see on these maps, but the barrier islands are the thin trail of red south of the main coastline. They would be underwater.

More disturbingly, from the National Environmental Trust, here is a QuickTime movie of how Biloxi, MS (and its barrier island) would be affected by a rise in sea level. (WARNING for dial-up users: 3 MB file!) I’ve linked to the movie from this graphic I’ve made showing how the coastline would be inundated.

The barrier island protecting the city would no longer exist. Sure, the projection of the land would still exist underwater, and would serve to slightly lessen the impact of a storm surge, but it isn’t at all the same as having a true island above the sea. A dry, projecting landmass stops the flow of water, at least temporarily, and breaks the waves. A former island that has gone underwater obviously doesn’t keep the water from flowing.

Also, as you can clearly see, the city itself would be partially underwater. This includes the glitzy new development that is taking place on this part of the coast in response to Hurricane Katrina — very shortsightedly, I ought to add. Whether this is because of the government of Haley Barbour, who is very likely a global warming skeptic, or because the businesses are aware of the risk but decided to hedge their bets, I do not know.

The Katrina recovery and rebuilding process is not taking global warming into account at all. When the next really bad hurricane strikes, its impact could be compounded by the effects of global warming. The coast will be farther inland due to rising waters, there will be fewer natural barriers, and the hurricane itself is likely to be stronger and wetter than it would be without global warming. And, as unfortunate as it is for me to say this, at this point it’s not enough to simply drive less, replace incandescent light bulbs with fluorescent, cross our fingers, and hope that we’ve stopped the problem.

I absolutely support cutting carbon emissions. If we don’t, the consequences will be even more horrendous than the scientists are daring to predict right now. But we’ve reached a point where it would be nothing short of grossly irresponsible to fail to look into preparation for the potentially disastrous changes that we have brought upon ourselves.

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