Only four weeks to the official start of the Atlantic hurricane season and advanced forecasts suggest an above active season.
One example here, a decent paper from the Dept Atmospheric Science at Colorado State Uni:

http://tropical.atmos.colostate.edu/forecasts/2013/apr2013/apr2013.pdf

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From the wikipedia page on the subject, a table of current predictions from organisations:

TSR           (Apr 5th):    15 named, 8 hurricanes, 3 majors
WSI/TWC (Apr 8th):   16,            9,                  5
CSU            (Apr 10th): 18,            9,                  4
NCSU         (Apr 15th)   13-17,      7-10,             3-6

 

The long term average is 12.1 named storms, 6.4 hurricanes and 2.7 major hurricanes, so there is a full consensus for an above average season, potentially very active.

TSR prediction details: "cumulative Accumulated Cyclone Energy (ACE) index of [131], citing the forecast for slower-than-average trade winds and warmer-than-normal sea surface temperatures. While no value was placed on the number of expected landfalls during the season, TSR stated that the landfalling ACE index was expected to be above average"

WSI: "[referenced] above average sea surface temperatures in the Main Development Region of the Atlantic. The main forecasting uncertainty involved whether or not an El Niño develops prior to the peak of the season"

CSU: "calling for a potentially hyperactive season"... "the agency stated that above-average sea surface temperatures in the MDR, below-average forecast wind shear, and the unlikeliness of an El Niño developing prior to the peak of the season would enhance tropical cyclone activity. The probabilities of a major hurricane hitting the Gulf Coast and East Coast were much above-average, while the probability of a major hurricane hitting anywhere along the USA coastline were well above-average as well."

 

All cause for some nervous residents across the U.S.A. in particular.

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Expanding on the previous post, here's an excellent map of the latest SST anomalies:

http://www.tropicaltidbits.com/analysis/cdas-sflux_ssta_global_1.png

It sure is cooking down in the MDR, in fact it looks to be near record-breaking to my eyes. There's a huge contrast between there and the Gulf of Mexico, which has been chilled by anomalous cold spilling south, just as we saw around the UK as a result of March.

The Caribbean is on the toasty side until you reach Florida's longitude, from which point eastward there are neutral, then negative, anomalies. Conditions in Texas have been phenominally cold (relatively speaking) of late, as is very much apparent in the waters there!

The neutral ENSO state is visible as a mix of +ve and -ve anomalies.

There is an interesting large area of +ve anomalies in the NE Pacific, which accompanies the persistent Pacific High there, the feature driving the central-U.S. trough pattern. This is keeping that region cool and wet, which is very different to many recent years, when a large part of the U.S. has been hot and dry, which may have introduced more dry, stable air into the atmosphere over the tropical Atlantic, interfering with the numerous storms that formed during each of the past three seasons, keeping many from developing as much as anticipated. It could be that conditions are much more favourable for particularly intense storms this year.

Another key feature could be the active jet running through the Mediterranean, which has brought westerlies across N. Africa and kept the Saharan dust and dry air from making much progress into the tropical Atlantic.

 

It seems to me that the dice are really loaded, so no wonder the forecasts are on the high side. Personally, I think 2013 could give 2005 a run for it's money, though the storm tracks might tend to be further north and towards the East Coast. While recurving storms would then be the usual expectation, this year there is a fairly strong signal for anomalous heights near or over Newfoundland and Canada, which could promote tracks similar to Hurricane Sandy of 2012. A scary prospect indeed

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Everything about this year looks rather omnious with regards to the Atlantic hurricane season. A La Nina looks like it is developing and SST's in the tropical Atlantic are reaching very high anomalies now. I can imagine the mean temperature for the MDR for May will be close to 2005 and 2010 now.

We have got a dipole pattern setting up ATM with below average temperatures around the Azores and above average temperatures between Newfoundland and Greenland. This is likely to have been caused by the exceptional blocking in March so the above normal temperatures in the tropical Atlantic are likely to persist.

An interesting point though is that in 2011 and 2012 SST's in the main development region were also very high but these only had an ACE value of 126 (there or there abouts) while 2004 and 2005 had ACE values of 224 and 255 respectively (2005 has recently come in 2nd in the series after a re analysis of 1933 showed that year was more active).

2011 and 2012 both had more tropical storms form then 2004 curiously. Dry air is likely to have been the issue inhibiting development. IMO this has been caused by the US drought but I havn't seen any research on this. However a lot of inactive hurricane seasons (e.g 1934, 1939 and 1956) occured when there was major drought in the USA.

The drought this year though has eased substantially (though still persisting in the SW and Central Western USA). Frequent very heavy rains over Central Eastern USA has reduced the areas affected by very low rainfall and excessive heat(Goergia for example).

Atlantic hurricane activity is something I studied for my undergrad and intend to follow it up further for my masters, hence my keen interest

Unless Western Sahel rainfall is especially low  I can see 2013 having an ACE value between 200 - 250 being achieved, I hope not but this season is looking nasty.

2010 though for example had record breaking SST's in the main development region though along with an intense La Nina. Yet not a single hurricane hit the US and the final ACE value was 163 the median ACE value though is just 96). Interestingly SST's in the Gulf of Mexico are well below normal thanks to a cold Spring in the SE USA...

Hopefully we won't see anything as bad as 2004/ 2005 again but the ingredients are there.

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http://www.wunderground.com/blog/JeffMasters/comment.html?entrynum=2416

This article details all of the predictions for the season made in May 2013.

The consensus is for an above average season, possibly hyperactive.

So when might it all kick off?

Well... GFS has been thinking about a Gulf of Mexico storm for a while now, and it all starts with some energy in the Bay of Campache (SW Gulf of Mexico) as can be seen on the 12z ECM output:

http://raleighwx.americanwx.com/models/euro/12zeurotropical850mbVortSLP096.gif

The broad trough hangs around and doesn't get up to much for many days, but by day 8 it's lowered the pressure and started to organise some vorticity (yellows and browns):

http://raleighwx.americanwx.com/models/euro/12zeurotropical850mbVortSLP192.gif

Two days later, a strong tropical or subtropical storm makes landfall right where Isaac did last year, near the mouth of the Mississippi River and New Orleans:

http://raleighwx.americanwx.com/models/euro/12zeurotropical850mbVortSLP240.gif

So there's something to watch out for if you're headed to the regions lining the GOM (particularly the N, NE and E coasts IMO) or you just like tracking that sort of thing (count me in!).

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I enjoy this thread every year and especially the very informed discussion from the regular contributors to it, like Stormchaser and Yorkshire Lad

I wonder whether the mods could sticky it as this is a summer long thread? As far as I recall, this has been done some years in the past.

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Thanks Lionel

I enjoy taking a look at how things unfold down there. Some years I get a bit carried away

Once the season really gets going, so will the analysis and commentary

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Liam Dutton ‏@liamdutton 7m
Multiple-vortex tornado on the ground near El Reno, Oklahoma. Live streaming video from storm chasers here -

http://content.wdtinc.com/popout/index.php?M=14613&C=20643&O=10003 

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Heading into the summer and I think come the end of June we will have some big clues as to how active this hurricane season may be.

 

Since 1995 every year has seen a rise in SST anomaly in the tropocal Atlantic except 2002 and 2007. Now 2013 joins that list surprisingly we have seen a fair bit of cooling off the West coast of Africa through May. Indeed Spring this year has been unusual in that during March we saw a very negative NAO.

 

This led to a tripole pattern similar to 2010, however the Azores high has been much more stronger then in recent years during April and May.

 

So the tripole pattern to my surprise is struggling to maintain itself after becoming so clearly defined in March.

 

http://weather.unisys.com/surface/sst_anom_new.gif

 

 

Positive anomalies are starting to emerge in the central North Atlantic and I think these may strengthen during the Summer months and the negative anomalies near Spain will extend further south. 

 

High positive anomalies in the central Atlantic combined with weaker/ negative anomalies off the west coast of Africa weaken hurricane activity even during La Nina years.

 

IMO this season is appearing to resemble 1938, 1954, 1988 and 2007. All strong La Nina years which didnt see very high ACE totals (all near average). Though even in these years there was some very damaging hurricanes.

 

If we dont see cooling off the west coast of Africa and warming in the central Atlantic. I think ACE will be between 150 - 200, come June things will be clearer.

 

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Monthly data for May is now starting to come in and despite the lower anomalies off the West coast of Africa towards the end of May it still hasn't stopped the month from recording SST's over 1C above average over a substantial swathe of the main development region.

 

http://iridl.ldeo.columbia.edu/maproom/Global/Atm_Temp/Anomaly.html

 

We can also see negative SST's forming off the coast of Peru, indicative of a La Nina trying to materialise (I wouldn't be surprised if it did).

 

As things stand I think the following years since are similar with ACE listed too:

 

1950 - 216

1989 - 139

1996 - 176

2005 - 249

2008 - 144

All of these years saw  ACE much above average at least and there was 3 hyperactive seasons (2005, 1996 and 1950).

 

It wouldn't surprise me if ACE ended up between 175 - 200 this year possibly greater.

 

Accumulated cyclone energy by the way is the measure of the duration and windspeed of each tropical storm that forms in a season.

 

We have an invest in the gulf of mexico at the moment however I don't think it will develop into anything more, it's still early.

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Thanks for those thoughts yorkshirelad

In recent years neither El Nino or La Nina have played by the rules much, so it wouldn't surprise me if some strange hybrid scenario started to develop... not sure how feasable that is, but whatever

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Tropical Storm Andrea has now formed, sustained windspeeds of 35 knots, the wind won't do any damage though but it is forecast to move slowly clipping the US coast over the next few days, giving a substantial amount of rain for the east coast.

 

http://www.wunderground.com/tropical/tracking/at201301_5day.html

 

 

Pretty early for a first storm but not particularly unusual either. I think 2003 had a storm form in April for example. Peak of a hurricane season is usually early August to the end of October. 2005 being an exception being very active from early July onwards.

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Well, Andrea went to Florida's Big Bend and made landfall after peaking at 60mph (or was it 65?).

I didn't track that one as I was very busy. I'm still busy now, but do have enough time to mention tropical storm Barry which is about to make landfall in the state of Veracrux, Mexico, as a storm with sustained winds anywhere between 45mph (official intensity at last advisory) and 65mph (highest satellite estimate).

Normally the higher-end readings would be discounted, but the curvature of the Bay of Campache does support rapid increases in wind-speed within tropical systems located there, so max. winds of over 60mph are certainly possible.

They would only cover a very small area though, as Barry is one of those miniture storms like Marco of 2008.

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Couldn't see a thread covering this so hope the mods won't mind me starting one.

Looks like this year's hurricane season is keen to get started with Tropical Storm Chanatal: http://www.outerbanks.net/hurricane/7-2011/6-tracker
  She is unlikely to reach hurricane status but this satellite image does show her as being a cheeky little number anyway: http://www.fvalk.com/images/Day_image/GOES-12-1800.jpg (not sure how long this link wiill stay active for).

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Bump - bang!

http://www.nhc.noaa.gov/refresh/graphics_at3+shtml/083748.shtml?3-daynl

TS Chantal steaming along. If she survives Hispaniola she may stregthen rapidly near the Bahamas come Thurs/Fri. One to watch.

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Susan Powel reviews the progress of Chantal

http://www.bbc.co.uk/weather/feeds/23243331

and for good measure, the current typhoon and the delightfully named 'Plum Rains Front'

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Couldn't see a thread covering this so hope the mods won't mind me starting one.

I had to go back six pages, but I did find it.

I shall leave the decision about which thread to use to teh Mods, but in my experience if a thread is stickied then duplicates are much less likely.

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Couldn't see a thread covering this so hope the mods won't mind me starting one.

I had to go back six pages, but I did find it.

I shall leave the decision about which thread to use to teh Mods, but in my experience if a thread is stickied then duplicates are much less likely.

Yipee, my first thread merge

Thanks for the input Ian - must admit I fell asleep on the tropics for a while, and in fact this latest development has caught me out a bit.

I'll look into stickying this thread

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Couldn't see a thread covering this so hope the mods won't mind me starting one.

I had to go back six pages, but I did find it.

I shall leave the decision about which thread to use to teh Mods, but in my experience if a thread is stickied then duplicates are much less likely.

Yipee, my first thread merge

Thanks for the input Ian - must admit I fell asleep on the tropics for a while, and in fact this latest development has caught me out a bit.

I'll look into stickying this thread

Ah yes! Just noticed there is already a stickied thread based on this, much apologies but ta for putting my post in the right place anyway. [sn_blush] [sn_bsmil] But indeed I think it's time to look west and see what action the Caribbeans will come up with, will it be as quiet as the past two seasons?

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Chantal is an interesting case... racing along at 26mph at the moment, fighting dry air and moderate wind shear (and the fast forward motion is also unhelpful to her) and yet she's managing to hold on as a strong tropical storm with the potential to achieve 70mph maximum sustained winds before reaching Haiti and/or the Dominican Republic.

Seems Haiti/DR should deal her a heavy blow what with the high mountains there. Whatever remains of her afterwards will enter an environment of lower wind shear while moving at slow speed due to changes in the steering forces as a trough well to the north works against the NE flow generated by the subtropical high.

Then, there will be the chance for some serious development, but only if the storm has held together or at least remained reasonably well organised. If a ridge then builds in behind the trough, Chantal will be forced to turn west towards Florida. There lies the potential for a stronger system making landfall.

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