NOAA's update to the Atlantic hurricane season forecast

By: Angela Fritz , 6:09 PM GMT on August 04, 2011

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In a press release this afternoon, NOAA has increased the number of predicted named storms, and increased their confidence in an above-average season from 65% to 85%.

The updated NOAA forecast is:

• 14 to 19 named storms
• 7 to 10 hurricanes
• 3 to 5 major hurricanes

According to NOAA, the long-term averages in a season are:

• 11 named storms
• 6 hurricanes
• 2 major hurricanes


Table 1. 2011 hurricane season forecasts from various organizations.

So far this season the Atlantic basin has seen 5 named storms: Arlene, Bret, Cindy, Don, and Emily. This is already above average for the season to date; usually only 1 to 2 named storms have formed by now.

On a somewhat related note, it's been 1,056 days since a U.S. hurricane landfall: Hurricane Ike of 2008.

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15. Angela Fritz , Atmospheric Scientist (Admin)
2:48 AM GMT on August 10, 2011
Quoting gcollins:
What do you think this season holds for the gulfcoast?


It's hard to tell. At first glance the climate models seem to be suggesting a weaker Bermuda high, which would mean storms will recurve to the open Atlantic before U.S. landfall. But so far this season, we've had quite a few tropical waves make it into the Gulf, even if they didn't develop. This week the models have been forecasting some strong waves that could stay pretty far south and enter the Gulf of Mexico in about 1.5 to 2 weeks.
14. gcollins
1:52 AM GMT on August 10, 2011
Katrina was the 12th depression of the season on Aug 22nd 2005, we have already had 5 named by August 9th,2011. What do you think this season holds for the gulfcoast?
Member Since: August 16, 2007 Posts: 0 Comments: 1
8. NavarreMark
5:45 PM GMT on August 08, 2011
Quoting cyclonebuster:
Hi Angela,

What you think of my idea?


Yes, I have spoken with Patrick, and, yes, a scheme somewhat like the one he describes could weaken hurricanes threatening places like Miami that have strong western-margin currents just offshore. There are, however, numerous qualifications.

The scheme that we discussed involved an array of several rows devices across the Gulfstream. Each device would be a rectangular duct 140 m long and 10 by 14 m in cross section. Normally the devices would be moored horizontally at a depth of 100m with their long axes aligned with the current flow. They would be nearly neutrally buoyant. When a hurricane approached, ballast at the downstream end of the channel would be released, allowing the device to float up to a 45 deg angle. Cold water entering the upstream end would flow up to the surface and mix with the warmer water there. Since the mixture would be negatively buoyant, it would sink. But mixing due to several (3-10) lines of these devices could cool the surface waters of the Gulfstream by 1-2C, enough to weaken an Andrew-like hurricane from category 5 to category 3. A rough calculation indicates that a device every 100 m on each line of moorings (~1000 devices per ~100 km line) and 3-10 lines of moorings would be required. My guess is that it would cost $250K to fabricate and deploy a single device, but there might be economies of scale. One might also be able to optimize the size and spacing of the devices.

Let's say that careful calculation told us that 4 lines of 1000 devices each would do the trick. At $0.25M per device, the cost works out to 4*1000*($0.25M) = $1000M. The actual cost might range from a few hundred million to a small multiple of a (US = 1000M) billion. One would want to do a detailed simulation before defining the scope of the project, but the basic notion is conversion of some of the kinetic energy of the Gulfstream into gravitational potential energy of the mixed water column. Again, I've not done that detailed simulation, only back-of-the-envelope calculations.

Activation of the array would require accurate forecasting since it would take several days for the effect to make its way from south of the Dry Tortugas (optimum location for protecting the maximum amount of shoreline) to the landfall point.

South Florida gets hit by a category 4 or 5 hurricane at every few years, but the really damaging ones like Andrew tend to be once-a-generation events, or less frequent. The array would need to be deployed and maintained for a long time between activations that actually safeguard property, although false alarms would not be particularly costly. Annual maintenance could easily exceed 10% of initial deployment cost. Bear in mind that Key West to Jacksonville is the only stretch of US coastline where this strategy would work. The other vulnerable sites, Houston-Galveston and New Orleans, lack the necessary strong offshore currents. While Georgia and the Carolinas also experience many hurricane landfalls and have the Gulfstream offshore, most of these cyclones are already weakening because of vertical shear of the horizontal wind so that a second installation north of Jacksonville would be much less useful.

There has been a lot of talk about using wave and current energy to cool the ocean ahead of hurricanes. My general conclusion is that while these ideas might be made to work, the proponents underestimate the scope of the required effort, as well as the political will and recurring cost necessary to keep the project going in the long intervals between really damaging hurricanes. Skeptic that I am, I think that wiser land-use policy and more rigorous building standards are much more cost-effective and more politically feasible. A proof-of-concept that might entail deploying a half dozen devices has some appeal, but I think that there are more promising ways to spend disaster-prevention money.

Best regards,

Hugh Willoughby




Please don't pitch that idea to congress. If ya do, we'll be down graded again real quick.
Member Since: September 2, 2010 Posts: 0 Comments: 3981
7. rod2635
11:26 AM GMT on August 08, 2011
Hello Angela,

I am new to bloggin. I notice that there are +,-,!, show/hide icons or features when someone makes a comment. I don't see these when I comment on the other blogs. Is there any significance to this?

What exactly is a post vs a comment? Also I note that at the bottom there is apparently a choice to 'ignore user'. This does not appear when my comments come up on the screen. Is there any significance to this?

Finally, there seems on some posts to be a number, ie +0 or +1 or something next to the icons. Can you tell me what this means?

Would just like to be knowledgeble, make sure I have input any required settings, and adhere to any protocols necessary to participate.
Member Since: January 27, 2011 Posts: 0 Comments: 373
6. Tropicsweatherpr
1:42 AM GMT on August 05, 2011
Hello Angela. Also CSU and TSR made their August updates and both are as NOAA for a very active rest of season.
Member Since: April 29, 2009 Posts: 75 Comments: 14760
5. HarryMc
6:58 PM GMT on August 04, 2011
Looks like we have more confidence that we're having an active season. Guess I'll have to pace myself again this year and try to avoid excessive all-nighters.
Member Since: March 30, 2010 Posts: 4 Comments: 343
4. JFV2011
6:49 PM GMT on August 04, 2011
2. TomTaylor
6:33 PM GMT on August 04, 2011
Thanks Angela. Also, not sure if you saw this, but CSU released their latest forecast. They are still calling for 16 named storms, 9 hurricanes, and 5 majors, for a combined ACE of 160.

Link
Member Since: August 24, 2010 Posts: 19 Comments: 4358
1. LakeWorthFinn
6:30 PM GMT on August 04, 2011
Thanks :)
Member Since: October 6, 2005 Posts: 67 Comments: 7411

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About angelafritz

Atmospheric Scientist here at Weather Underground, with serious nerd love for tropical cyclones and climate change. Twitter: @WunderAngela