2011 ATL Hurricane Season: Coming to an End

[srainhoutx]

From the CSU Update:

A 47 percent chance that a major hurricane will make landfall on the Gulf Coast from the Florida Panhandle west to Brownsville (the long-term average is 30 percent).

[wxman57]

Does the WxMan57 sweat shop center for advanced atmospheric research put out a public forecast?

Yes.

[srainhoutx]

April update is out. He reduced the numbers to 16/9/5 (from 17/9/5):

http://hurricane.atmos.colostate.edu/Fo ... pr2011.pdf

Best analog years 1955, 1996, 1999 and 2008. 2006 was listed as an analog, but an El Nino developed during the peak of the season, something that's not likely this season. I still think 14-15 named storms may be more likely.

[Ptarmigan]

Analogs
1955 12/9/6 199
1996 13/9/6 166
1999 12/8/5 177
2006 10/5/2 78
2008 16/8/5 144

Total number can range from 10 to 16, while hurricanes can range from 5 to 9, and there could be 2 to 6 major hurricanes. The ACE ranges from 78 to 199. 2006 occurred when an El Nino develops unexpectedly. 2006 was predicted to be an active season on heels of 2005. All the analogs had a La Nina winter including 2006. 1955, 1999, and 2008 had persistent La Nina. 1996 went into Neutral.

Mean
12.6/7.8/4.8 152.8
13/8/5 153

Median
12/8/5 166

Standard Deviation
2.2/1.6/1.6 46.3

[Ptarmigan]

TSR 14/8/4 124
AccuWX 15/8/3
CSU 16/9/5 160

Mean
15/8/4 142

Median
15/8/4 142

Standard Deviation
1/0.6/1 25.5

[wxman57]

I was looking at TS and hurricane impacts for Klotzbach's analog years (1955, 1996, 1999 and 2008). He listed 2006 as a spring analog, but 2006 went El Nino during the season so he doesn't think 2006 will be a good analog for 2011.

What I plotted below is all hurricane landfalls for 1955, 1996, 1999 and 2008. Some storms made multiple landfalls, so each is indicated. Note the lack of landfalls in Florida, with the exception of Irene in 1999. Even when I plotted TS impacts, there were very few in Florida in the analog years.



An examination of the data reveals a general track pattern that is common in the analog years. The pattern appears to be one set that moves across the NE Caribbean then heads for the Bahamas and the Carolinas. The second path is similar to start with, but continues westward toward the Yucatan Channel then WNW toward either Mexico or south Texas.

The pattern is suggestive of a high pressure area over the central U.S. with a trof in the eastern U.S. It's actually somewhat close to the 2010 pattern, but with a weaker ridge over the U.S. and a stronger Bermuda High. The effect would be to increase the risk of a landfall in the NE Caribbean, the Carolinas, and the western Gulf, as indicated in my graphic below. I don't see the heightened risk to Florida indicated in any of the analog years - UNLESS the Bermuda high is even stronger. Think 1999's Floyd turning north a few hundred miles farther west.

[srainhoutx]

^
I see you stated 1955 in the opening statement and then changed to 1995 in the next paragragh when discussing analogs. Was that a typo? Regardless, we know that analog tracks of the past can be indicators of possible pattern similarities, but does not suggest these will be the track and storm strengths we can expect. Those finer details cannot be known at this time. With that said, the potential impacts on the Caribbean, MX and the US do look a bit more ominous than last season. I suspect we will have many a long days and nights ahead as we continue to transition toward Tropical Season 2011.

[wxman57]

Yes, that 1995 should read 1955 (fixed it). Analog years aren't "the law" as far as paths for 2011. They just suggest patterns that might be observed as far as development and movement. There are so many variables involved in determining where a hurricane eventually makes landfall. A small pocket of shear that develops in the mid Atlantic east of the Caribbean may delay development of a disturbance for a day. That delay in development might mean the difference in a Florida or East U.S. Coast hit or a Bermuda hit. Timing is everything. No one is safe from a possible impact because of any pattern indicated by analog years.

[unome]

I like the way mark Sudduth relays information - no hype, matter-of-fact kind of way

http://www.hurricanetrack.com/

Basically; "you should have your act together, always, to the degree you can afford to do so"

[srainhoutx]

The ECMWF Ensembles suggest a nice Bermuda Ridge developing...

[wxman57]

The seasonal range ECMWF sea level pressure forecast is more revealing. Forecasting a lot higher pressures over the subtropical Atlantic than in 2010, indicating that the Bermuda High will be stronger and farther west in 2011.

[srainhoutx]

Can we get an SLP anomaly chart for JJA or JAS?

April 15th is not all that far away...

[wxman57]

Can we get an SLP anomaly chart for JJA or JAS?

Ed,

The charts are issued once a month around the 20th-23rd with a valid time of the 15th. The new charts (MJJ) MAY be there by Friday the 22nd. They go out to 4 months, so they don't go out to the peak of the season yet. You can find the graphic I posted at the main Euro site:

http://www.ecmwf.int/

It's a bit hard to find. At the very top of that link, look under the "Products" header and select "Forecasts". Scroll down to the "Seasonal forecast" section and click "Forecast". A page with 2 bulleted links loads. Select the top link "Seasonal range forecast". On the next page, click on the map below "Spatial maps". Now you're nearly there.

In the left navigation frame, choose your parameter. You'll see "2m temperature", "mean sea level pressure", "rain" and "sea surface temperature". Click "mean sea level pressure". In the "Lead time" drop down menu choose 4 months. For the area, choose "South America". You're there! That was easy, wasn't it? There is some other good stuff there, too. Look around.

[wxman57]

I'm here at your service, Ed.

[srainhoutx]

Right on cue, or just a bit early, the Canadian is 'sniffing' out development in the Atlantic...

[srainhoutx]

The GFS has been 'sniffing' disturbed weather across Central America for about a week now. That model develops a storm in the EPAC that crosses MX and into the BoC...more model fanatsy, but certainly a hint that we are nearing that time of year...

[Ptarmigan]

NC State University 2011 Atlantic Tropical Cyclone Outlook
http://cfdl.meas.ncsu.edu/research/TCoutlook_2011.pdf

They use statistical models. Their prediction are:
13-16 named storms
7-9 hurricanes
3-5 major hurricanes

[wxman57]

Nothing in the BoC on today's GFS.

[srainhoutx]

The Euro, GFS, Canadian and the Nogaps suggest an easterly wave traversing across the Atlantic. It must be getting a bit closer to Tropical Season.

[srainhoutx]

The 12Z Euro suggests some spin with an area of disturbed weather near the Bahamas...