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Atlantic hurricane season/invest thread

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Well after a bit of a bust in 2013 what are we thinking about the upcoming 2014 season? Surely it has to be a little busier, in the hurricane formation sense, than last year?

Are we looking at a transition into a Nino summer and will this have impacts on storm formation/tracks should it materialise?

Edited by Somerset Squall

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Well after a bit of a bust in 2013 what are we thinking about the upcoming 2014 season? Surely it has to be a little busier, in the hurricane formation sense, than last year?

 

Are we looking at a transition into a Nino summer and will this have impacts on storm formation/tracks should it materialise?

 

El Nino has been coming for 2 years and has not arrived yet, i'm pretty skeptical and expect neutral conditions allied to a -QBO.

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I take we find your rationale in here;

 

http://www2.physics.ox.ac.uk/sites/default/files/2012-03-08/1_watson_pdf_10210.pdf

 

if so I'd advise of the uncertainties of Eurasian snow cover esp. after the recent dive?

 

As it is I'm waiting for the ITCZ to be over the equator before I start to look for the changes ( early April) that will precede the warm bulge flooding back east ( collapse of the resilient HP over the N.Pacific allowing the trades to fall light?)?

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A new thread for the 2014 Atlantic hurricane season. The thread is for discussing Atlantic systems developing up to and including Invest status. The 2013 Atlantic Hurricane Season was a rather quiet one, let's see whether the 2014 season will become more active.

 

First, a summary of potential indicators of hurricane activity will be given. 

 

El Nino

 

The first will be ENSO (El Nino/Southern Oscillation). ENSO is a multidecdal oscillation which is a measure for anomalies of sea surface temperatures (SSTS) in the Equatorial Pacific. An El Nino event (positive phase of the ENSO) indicates positive anomalies (warmer than normal SSTS) near the Central/South-American coast. A La Nina event (negative phase of the ENSO) indicates negative anomalies (cooler than normal SSTS) near the Central/South-American coast. 

 

There are numerous very significant impacts all over the globe due to an El Nino event. For the Atlantic hurricane basin, an El Nino event usually indicates higher than normal shear values, inhibiting tropical development.

 

For the 2014 Atlantic hurricane season, a weak positive El Nino event is forecast by the Climate Prediction Center. However, there seems to be considerable spread in the forecast, with some members indicating ENSO-neutral conditions to persist. 

 

The CPC indicates the uncertanity below:

 

 

Nearly all model forecasts indicate the persistence of ENSO-neutral (Niño-3.4 index between -

0.5°C and 0.5°C) through the Northern Hemisphere spring 2014, but afterwards, an increasing number of 
models suggest the possible onset of El Niño (Fig. 6). Strong surface westerly winds in the western 
Pacific and the slight eastward shift of above-average temperatures in the subsurface western Pacific 
potentially portend warming in the coming months. However, the spring is also historically associated 
with lower forecast skill, so the chance of El Niño developing after the spring is not much different from 
ENSO-neutral. The consensus forecast is for ENSO-neutral to continue through the Northern Hemisphere 
spring 2014 (see CPC/IRI consensus forecast).

 

 

The CPC also has an ensemble forecast for the ENSO, showing the SSTS anomalies in the Equatorial Pacific. When the SST anomalies are above 0.5*C, an El Nino has become established. The ensemble can be seen below:

 

Posted Image

 

Note that all ensemble members forecast positive SST anomalies in September-November, but only a few indicate an El Nino event to develop.

 

Concluding, though there is a weak signal for an El Nino to develop, the spread is too large to justify any prediction. Many runs will be needed to see wheather a real El Nino event will become established.

 

SST anomalies in the Atlantic

 

Because a tropical cyclone needs high sea surface temperatures to develop (usually in excess of 27*C), positive sea surface temperatures are favorable for development. The chart of the current SSTS anomalies can be seen below:

 

Posted Image

 

The blue colors indicate lower than average SSTS, while yellow-orange colors indicate higher than average SSTS.

 

Note the large negative anomaly area to the west of Africa (most pronounced near the Cape Verde islands). Because this is the main area of hurricane development in the Atlantic, this argues for a less active hurricane season. However, there is also a decent positive-anomaly area over the Gulf Stream, making TC development more likely over that area.

 

Because the SST anomalies are of February, there is no gurantee that the same SST anomalies will persist throughout the year. 

 

First seasonal prediction

 

The TSR (tropical storm risk) has issued their forecast, which yields a slightly above-average hurricane season. This is mostly based on stronger trade winds to the west of Africa and higher than normal SSTS over that area (as opposed to what the current anomalies indicate?).

 

The link to their forecast can be found below:

 

http://www.tropicalstormrisk.com/docs/TSRATLForecastDec2014.pdf

 

 

 

Let's look forward to another interesting hurricane season!

 

Sources:

http://en.wikipedia.org/wiki/El_Ni%C3%B1o

http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/ensodisc.pdf

http://www.nhc.noaa.gov/aboutsst.shtml

http://www.tropicalstormrisk.com/docs/TSRATLForecastDec2014.pdf

Edited by Vorticity0123
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I take we find your rationale in here;

 

http://www2.physics.ox.ac.uk/sites/default/files/2012-03-08/1_watson_pdf_10210.pdf

 

if so I'd advise of the uncertainties of Eurasian snow cover esp. after the recent dive?

 

As it is I'm waiting for the ITCZ to be over the equator before I start to look for the changes ( early April) that will precede the warm bulge flooding back east ( collapse of the resilient HP over the N.Pacific allowing the trades to fall light?)?

 

I take we find your rationale in here;

 

http://www2.physics.ox.ac.uk/sites/default/files/2012-03-08/1_watson_pdf_10210.pdf

 

if so I'd advise of the uncertainties of Eurasian snow cover esp. after the recent dive?

 

As it is I'm waiting for the ITCZ to be over the equator before I start to look for the changes ( early April) that will precede the warm bulge flooding back east ( collapse of the resilient HP over the N.Pacific allowing the trades to fall light?)?

 

Not really. 

 

My essential rationale is that while there are strong sub-surface warm anomalies in the central Pacific (likely the reason for the bullish Nino forecasts) the east pacific is fairly weak in its current indications both at the surface and sub-surface. For Nino to occur we'd have to see several strong MJO events to dilute the cold surface anomalies and allow the warm anomolies to make it to the surface. From there you have the problem of whether the Nino can spread east because in 2012 it tried and failed.

 

As of now however the atmosphere at both a 30 and 90 day interval is not supportive of a trend towards El Nino, far from it actually as the SOI numbers show.

 

http://www.longpaddock.qld.gov.au/seasonalclimateoutlook/southernoscillationindex/30daysoivalues/

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Dear moderators,

 

Could this thread be pinned, please?

 

Many thanks!

Edited by Vorticity0123

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ECWMF suggests a wall of death over the Carribean this season in line with El Nino.

 

As it is though, there's still some reason to be optimistic. Namely that monsoonal activity is still robust which if it maintains ~(depends how far east El Nino centers itself) will provide some good African waves but also that the western Atlantic is still above average in terms of sea surface temperatures. With this in mind as we get into May and June we should not discount a cut-off low becoming sub-tropical.

 

Posted Image

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In a one line brief summary, does anyone have a valid opinion of why last years outcome differed vastly from the seasons projection before events, or lack of, unfolded? (Albeit above avg EPAC activity but little in the way of major NA landfalls)

And in relation, what are the probabilities of the success of this years forecast? , I'm very sceptical of this years view from the onset but only just started divulging the info,,,

Edited by mezzacyclone

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In a one line brief summary, does anyone have a valid opinion of why last years outcome differed vastly from the seasons projection before events, or lack of, unfolded? (Albeit above avg EPAC activity but little in the way of major NA landfalls)And in relation, what are the probabilities of the success of this years forecast? , I'm very sceptical of this years view from the onset but only just started divulging the info,,,

 

The anomolies observed last year were an exact match for a pretty -PDO. That may have had an impact.

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In a one line brief summary, does anyone have a valid opinion of why last years outcome differed vastly from the seasons projection before events, or lack of, unfolded? (Albeit above avg EPAC activity but little in the way of major NA landfalls)And in relation, what are the probabilities of the success of this years forecast? , I'm very sceptical of this years view from the onset but only just started divulging the info,,,

 

I would have thought the strong Saharan Air Layer (SAL) played a pretty big role in quelling last years Atlantic tropical activity.

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Not really. 

 

My essential rationale is that while there are strong sub-surface warm anomalies in the central Pacific (likely the reason for the bullish Nino forecasts) the east pacific is fairly weak in its current indications both at the surface and sub-surface. For Nino to occur we'd have to see several strong MJO events to dilute the cold surface anomalies and allow the warm anomolies to make it to the surface. From there you have the problem of whether the Nino can spread east because in 2012 it tried and failed.

 

As of now however the atmosphere at both a 30 and 90 day interval is not supportive of a trend towards El Nino, far from it actually as the SOI numbers show.

 

 

 

Not sure I follow the bit about cold surface anomalies sb.

post-12275-0-13656600-1397222242_thumb.p

post-12275-0-34315400-1397222376_thumb.p

Edited by knocker

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Not sure I follow the bit about cold surface anomalies sb.

 

That was Feb, there was still a pronounced cold anomaly in the East Pacific.

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GFS starting to throw out model fodder as it does once we approach May.

 

The good news is that as yet we don't have the classic Nino pattern so let's hope it stays that way as we get close to the time when we start to look for cut-off lows.

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Well El Nino's here now but i'm not entirely sure it's going to destroy the season given the analogues i've looked at are relatively kind.

 

My prediction anyway (broad)...

 

Storms - 9 to 19

 

Hurricanes - 3 to 10

 

Major Hurricanes - 2 to 5

 

Analogues - 03, 09, 09, 12, 12

 

I believe the US coast took a major hit from a major in 03 and a look at the peak season anomaly does suggest that it would be possible to draw a hurricane to the coast..

 

post-1806-0-01501700-1400682496_thumb.pn

 

 

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Looking at some of the sst charts we see a 'ghost' nino signal across the Basin? Could this be part of the heat retained over a summer with little storm activity bleeding out the heat? Will it also enable warm ssts as the sun takes to heating the tropical ocean?

 

I wonder if nino will reduce numbers but sst's will mean a few majors making through?

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We have invest 90L

 

very close to Boris

 

Posted Image

Edited by cookie
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Atmosphere seems fairly hostile to development in the GOM.

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Atmosphere seems fairly hostile to development in the GOM.

 

Despite these seemingly hostile conditions (25 kt of shear as analyzed by CIMSS), the NHC has upped the chances of 90L developing into a tropical cyclone to 30%.

 

 

 

1. Showers and thunderstorms have recently increased near a low

pressure area over the southern Bay of Campeche. Despite strong

upper-level winds, some further development of this system is

possible over the next day or two if the low remains offshore of

eastern Mexico. An Air Force Reserve Hurricane Hunter aircraft is

scheduled to investigate this system this afternoon, if necessary.

This disturbance has the potential to produce extremely heavy rains

and life-threatening flash floods and mud slides over portions of

southeastern Mexico during the next few days.

* Formation chance through 48 hours...medium...30 percent.

* Formation chance through 5 days...medium...30 percent.

 

Currently (as of 15:00 UTC), 90L looks sheared from the west (as confirmed by CIMSS), yet convection continues to pulse  around the system. There is little evidence of cyclonic turning, though. This can be seen in the visible loop below:

 

Posted Image

Satellite image of 90L.

 

 

Sources:

http://tropic.ssec.wisc.edu/#

http://www.nhc.noaa.gov/gtwo_atl.shtml

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90L got close to becoming the season's first tropical depression, it had a well defined centre, but convection was constantly stripped away by shear. The LLCC has now moved inland over Eastern Mexico.

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No signs of anything really developing soon but at day 11 the GFS does tease us with this..

 

Posted Image

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Potential stalled fish off the Carolina coast in the next few days.

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The system SB is referring to has now been classified as invest 91L. NHC have assessed 91L's development chances as 40% over the next 48hrs and 60% in the next 5 days. Convection is gradually increasing over the low which has moved out over water off the coast of South Carolina. Conditions seem favourable for development as the system heads southwards east of Florida. Are we going to see the season's first storm?

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91L 

 

I think we could well do its looking more organized today. 

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Yeah, structurally it's looking good, however, dry air is preventing much convective development currently. As 91L dips further south, this may not be so much of an issue, so it may develop further.

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