Atlantic hurricane season 07

[kold weather]

Well we are in 07 now so as per normal the pre-season 07 starts!

Looking at it breifly into he longer term much hinges on the current El nino situation. Most models are now going for a neutral-weak El nino being in place which may limit the chances of numerous hurricanes a little but I don't think quite as much as last year given that year also featured a hefty Bermuda high throughout.

Also one other thing t onote, the waters off the east coast are really warm right now as a strong Se USA ridge has just sat there heating the seas up quite neatly will be intresting to see if they are in the same place come the summer.

[Gray-Wolf]

My concerns with an established (and not forming) weak/moderate El-Nino is the prospect of many more re-curves this year or even Storms that form off Africa and develop as the head north up the African coast into the Med. Western Europe. As you say the SST's will play an important role in all of this so we must wait and see what anomalies crop up this year.

Two seasons ago we had my first European Hurricanes (however small/hybrid they may have been) and last year we had the altering upper level wind regimes to deal with. If we go into the season with an established upper air pattern then come late Aug/early Sept who knows?

Edited January 6, 2007 by Gray-Wolf

[kold weather]

The thing is will we have El nino by the time the hurricane season gets underway. its perfectly possible that the El nino could already be weakening quite neatly by that time and so its effects could well be quite limited, esp towards the latter half of the season.

SST's already looking decently above average right now though close t othe states and in the gulf as well.

Edited January 7, 2007 by kold weather

[Gray-Wolf]

So K.W. ,You are kinda hinting that activity will move back to the America's with the possibilities of large warm SST anom.s waiting to greet them?

Maybe we could be looking at an early start to the season?

I don't think we should ignore any SST anom's that form this side of the pond. The West African 'Blob' which fed up a lot of our moisture last summer may also be back, bigger (if global temp forcasts for the summer are correct) allowing systems to form further north and pick up their steering influences from futher north too.

[P.K.]

The thing is will we have El nino by the time the hurricane season gets underway. its perfectly possible that the El nino could already be weakening quite neatly by that time and so its effects could well be quite limited, esp towards the latter half of the season.

SST's already looking decently above average right now though close t othe states and in the gulf as well.

El Nino looks to me to have been weakening a little recently. It may have already peaked.

[kold weather]

Indeed SOI teleconnections has also been a little higher overthe last 30 days then recently, though still fairly -ve overall at the moment, though these do tend to step change I've noticed in the past.

G.W, a little too early to tell to be honest. Globally the last 2 months have been very like 94-95, and obviously the hurricane season of 95 was very active. I'll be keen to wait at elast another 3-4 months before even attempting to see where has the most risk as I have few doubts things wil lchange. Certainly the SSt's are above average enarly everyhwer ein the atlantic right now though.

[summer blizzard]

At this stage i am looking towards a very active hurricane season, for several reasons, these are:

1) Models are currently overplaying the El Nino, most expected a peak in November and values to stay around that mark until January before weakening, this would follow the 1994 anologue however December recorded a MEI value, of 0.9, much weaker than the consensus of the models, this indicates that we could be in a weak La Nina over the summer, rising to moderate during the Autumn

As far as i am aware, a MEI value between 0 and -1 is best for an active hurricane season.

2) An easterly QBO signiture will be observed by March, this means that we are looking at a moderate to strong easterly QBO over the summer

At this stage, i would go for something between average and 1995, so above average but not record breaking.

Edited January 11, 2007 by summer blizzard

[kold weather]

I think a lot depends on what happens, global pattern has been quite similar to early 1995 so far and one can only assume given the ENSO and the way thats falling apart right now SB i wouldn't be suprise dif indeed it does turn out to be quite similar to 1995. a Long way to go yet and i think we have to atch to see how dry the air is between April-June as it comes off Africa to get a good idea of what moisture will be like. i also agree about your timings with the ENSO, i think we wil have La Nina by August, mod by Oct-Dec.

Here is the latest:

CURRENT STATUS as at 31st January 2007

Next update expected by 21st February 2007 (three weeks after this update).

There has been a sustained cooling of the equatorial Pacific since early December, with current SST anomalies now close to their El Niño thresholds. This is the clearest sign that the El Niño event is weakening and it bodes well for a switch towards average or wetter than average conditions across eastern Australia sometime in the late summer or autumn. In fact, we've already seen a southward extension of tropical moisture which resulted in heavy rain over the NT, SA and the western parts of Queensland, NSW and Victoria. This can be taken as a sign that rainfall patterns are beginning to change across Australia, the timing of which is consistent with that observed during previous events.

In addition to the surface cooling, there has been substantial cooling below the surface; a situation that is likely to promote further weakening of the surface El Niño pattern. However, the SOI, Trade Winds and central-western Pacific cloudiness have seen their decline towards neutral values arrested somewhat during January, in association with a westerly wind burst mid-month. The westerly burst has now dissipated, so it is expected that these other ENSO indicators will continue their general trend towards neutrality over the coming months, in keeping with the weakening of the El Niño event. Furthermore, computer modelling supports the view that the El Niño will continue to decline.

* Equatorial Pacific SSTs have cooled and are close to or below El Niño thresholds.

* Negative subsurface anomalies have strengthened and spread further east along the thermocline and have nearly reached the surface in the eastern Pacific.

* The SOI has a current (29th January) 30-day value of −9.

* Trade Winds have generally been somewhat stronger than average apart from a weakening in the central-west Pacific in the middle of the month.

* Cloudiness near the date-line has recently been above average.

* Most computer models predict the decay of El Niño conditions in the first half of 2007.

[summer blizzard]

Indeed, though the MEI value actually rose in January to 1, which was once again moderate and may explain the warmer January.

Looking at years observing a weak December and moderate January, there are no anologues, so all we have to go on is a moderate January, almost certainly followed by a weak February.

Other moderate Januaries are:

2003

1995

1987

1988

1958

1966

[Gray-Wolf]

I would tend to agree that this year does not seem to be presenting the same amount of obstacles to storm formation as were present through the majority of the Atlantic Basin last season. I'm starting to wonder whether certain 'indicators' may start to become 'unreliable' if any type of step change occurs climatically. The 'sudden' emergence of El-Nino over the season last year and the need for storm number reassessments causes me this concern.

It's kind of a horse and cart thing. If air pressure can move waters then waters should be able to move air pressure so if cold water displaces warm waters into El-Nino stations is it an El-Nino? If Southern ocean summer melt runoff is excessive and leaches north pushing equitorial waters to the equator what would we call it?

[kold weather]

Hi SB, I still like the 1995 anologue because its the cloest one this year to the peak of the El nino and also is the only one other then 2003 that has occured in the active phase of the Atlantic plus occured close to the solar min while 2003 occured with the solar max just gone by but I agree none are a perfect match

I'm more confident then I was that this could be a active season, I think La nina is actually very close right now, the el nino is decaying very rapidly. Subsurface profiles show a rather large mass of cold sea temps forming where the old El nino used to be (down to -0.4C now overall.) and the el nino temp prfile has pretty much gone.

It may by the case SB that that Feb's MEI comes in neutral if the cold pooling sub-surface keeps rising like it nhas done in the last 30 days.

Gray-wolf---the el nino certainly wasn't sudden, there were major signs of it occuring before hand. firstly the MEI rose in the summer, the sub-srface plots showed some impressive warming away from the La nina we ha and also the SOI showed strong drops which is a good indication of a el nino forming, in fac tthat began in April. This occuring when it did obviously meant the 06 season was going to be a dud compared to what the NHC were expecting, esp because they didn't put enough weight on the El nino when it turned out to be a major player, without rally ever showing itself on the surface until October.

Going to be intresting to moniter the possible development of La nina and also watch April-June to see how Africa is developling its waves and how bad SAL is this year.

[summer blizzard]

Kold Weather, the main issue i have with 1995 is that while we are looking similar in terms of the MEI, 1995 observed a westerly QBO which goes against the grain of La Nino events.

http://jisao.washington.edu/pdo/PDO.latest

One thing i have noticed, is that 1933, 1995 and 2005 all observed a three month spell in which the PDO value was above +1.

This year looks very similar to 2005 to me, though i expect more of a La Nino event.

Edited February 13, 2007 by summer blizzard

[Gray-Wolf]

If we are expecting the hottest year on record (Meto/University of East Anglia) then maybe we need be mindful of possible extremes in localised areas that may lead to 'complications' in forcasting both developoment/track. I'll be interested to see if the 'Jamiacan loop' re-appears this year as, with normal wind patterns, small features are given extra potential to become large features inside the Caribbean and away from any troublesome SAL. Again, if a warm one, will we see hybrids forming on this side of the pond? I am kinda both looking forward too and getting worried about this coming season. Time will tell all!

K.W. I thought that more than one of the ENSO indicators didn't point towards El-Nino replacing La-Nina, that neutral was the pre season forcast. I must be slipping in my dotage (LOL)

Edited February 13, 2007 by Gray-Wolf

[summer blizzard]

Does anybody have a link to the Met Office ESNO forecast, i found this to be the most accurate last year.

[kold weather]

Yep its quite close to 2005 as well thinking about it tohugh as you said the La nina really didnt't get going at all until the Autumn of 2005 and so it was really a neutral season, I think thats going to be the big difference this year.

also while still to oearly to tell I don't think the monsoonal trough will set up the same as 2005. This feature was the main reason why we had hardly no storms develop east of 60 degrees that year, bar the far NE storms of course, it was a ultra rare event, comparable to 62-63 British winter if you want to put it another way.

About the QBO, thats indeed ready to change which may mean the latter half of the season is different but I think it may take a little while to feed through globally, also it'll be intresting to see how strong it'll end up being in the easterly phase but i do agree its changing, latest obs from Jan make that quite likely.

also intresting to note aobut the PDO, thoguh the summe rof 83 was way above 1 and that was the quietest seasons in modern times.

As for the pre-forecast, your right they did forecast neutral and I suppose it was a neutral season if you really want to be technical but for all practical purposes it was actually El nino as early as September.

My early numbers would be:

15/9/5

Only early numbers from me though, may be forced tochange them but those numbers still represent a active season.

Edited February 13, 2007 by kold weather

[Gray-Wolf]

Here are a few 'ifs'.

If the season is unhindered by poor winds, SAL swamping, low sst's

Then I would expect (in line with prediction of 'how it will be') the percentage of named systems that make 'Hurricane status' to increase and the number of 'High number Hurricanes' (4's or 5's) as a proportion of the total number of hurricanes to increase.

[summer blizzard]

In order to forecast this hurricane season, i think that the five main variables are:

1) sea surface temperatures

These are 0.5C to 1C above average throughout much of the tropics, though they are below average in the Gulf Of Mexico and the eastern USA seaboard - favourable

2) MEI

At this stage i would say that we are looking at conditions similar to that of 2005 however i believe that we will see a more La Nina signiture, with a weak La Nina by September - favourable, though this could lead to a weakening of storms in the Carribean due to low sea surface temperatures

3) QBO

Again, the QBO will be very similar to 2005 however we are switching to an eaterly phase later than 2005 and as a result will lag behind, we are looking at a moderate to strong easterly QBO when averaged over the entire hurricane season - favourable

4) PDO

I personally think that a positive PDO leads to a more favourable hurricane season, because it causes a fairly strong Sub-Tropical ridge, though there is a danger of this leading to dry air ingestment, therefore i would prefer a neutral to positive PDO, as the January data is not available yet, i cannot give a reasonable opinion, however you can see that 1995 is an anologue, which featured a very active hurricane season.

2000

1995

1985

1982

1965

1960

1958

1953

1952

5) AO

As strange as it sounds, i feel that the state of the AO is very important in a hurricane season, a positive AO would reinforce a strong Sub-Tropical high, encouraging favourable conditions for development, unfortunately, i feel that the combination of a La Nina and an easterly QBO will encourage stratospheric warming and a negative AO.

Conclusion

At this stage, i feel that we will see a very active first half of the hurricane season, with seven named storms to have formed by the end of August, the second half of the hurricane season i think will see near record levels of activity, with around another twelve named storms forming, so i would go for 18-20 named storms forming, however i do not expect records to be broken in relation to the strength of the storms, as i fell that the storms will tend to weaken once in the western Gulf Of Mexico.

Could anybody post the average monthly number of hurricanes please.

[kold weather]

Intresting you mention a strong sub-tropical ridge. That can be more of a problem then a good thing. Lasdt summer had a strong Bermuda high and this in turn sheared everything to death for the first two months of the season (It also helped give us a beastly July) bar the stuff that made it ito the caribbean and the gulf region. After that it relaxed and a few hurricanes finally formed.

I agree with nearly everything else you say, I'd say the NAO rather then the AO has more of a influence on the Atlantic sid eof the tropics but then again the NAO really is just an extension of the AO signal I suppose.

A note on the gulf, don't let it fool you, its shallow compared to the ocean masses and so while its a little (not much either actually!) below average at present give it a giood burs tof May sunshine and it'll soon warm up again.

[summer blizzard]

Intresting you mention a strong sub-tropical ridge. That can be more of a problem then a good thing. Lasdt summer had a strong Bermuda high and this in turn sheared everything to death for the first two months of the season (It also helped give us a beastly July) bar the stuff that made it ito the caribbean and the gulf region. After that it relaxed and a few hurricanes finally formed.

I agree with nearly everything else you say, I'd say the NAO rather then the AO has more of a influence on the Atlantic sid eof the tropics but then again the NAO really is just an extension of the AO signal I suppose.

A note on the gulf, don't let it fool you, its shallow compared to the ocean masses and so while its a little (not much either actually!) below average at present give it a giood burs tof May sunshine and it'll soon warm up again.

If you remember, 2005 also had a strong Sub-Tropical Ridge however it was located further north, directing most waves into the Carribean, that is what i expect this year, last year saw the ridge right over Florida most of the time.

Obviously, even if it was below average this summer, it would still be very warm however as La Nina strengthens into Autumn, i expect some negative anomolies to creep up in the western Gulf Of Mexico, so i dont expect any Wilma's.

Could somebody post the average amount of named storms per month??????

[Gray-Wolf]

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

No ,but I know a man who can........

[kold weather]

I NEVER expect to see anything like Wilma again in my life that was quite a stunning storm. Honestly it went from cat 1 to cat 5 in a stupidly small amount of time.

Also think about the pressure gradient it must have had. It had max winds of 185mph. However the hurricane force winds extended just 15 miles out. Mega tight graident and i suspect because of the small size it may wlel be the case that breifly it got down to below 880mbs.

Man, how I'd love to watch another 05 seasons...though without a Katrina strength storms hitting a major city of course.

[summer blizzard]

Thanks for the link, and i agree with you Kold weather, it was quite amazing.

Interestingly, i have been reveiwing records, and 2005 did not take the record for the highest number of major hurricanes, so it is possible that this season could take that, the record is eight, set in 1950, 2005 only achieved 7, though from memory, five of those seven were category four or five.

Having looked at the link given, i have realised that i miscalculated and expect nine storms to form, not seven in the first half of the hurricane season, therefore, my preliminary estimate is for 20-22 named storms.

[kold weather]

for waht its worth tohugh siome of the 1950 storms are highly suspect according to some people, so a few borderline ones have a chance of being downgraded and would therefore give 2005 that record by default so to speak!

Anyway latest about El nino....what El nino!

Summary: The 2006/07 El Niño has ended

The 2006/07 El Niño has ended. All the main ENSO indicators show that neutral conditions have returned to the Pacific Basin. Along the equator, sea-surface temperatures are cooling rapidly and have been below their El Niño thresholds for about a month now. The Trade Winds have mostly been close to or somewhat stronger than normal since December, the SOI has been neutral for three of the past four months and central-western Pacific cloudiness is close to average. Computer models indicate further cooling in the Pacific, with a La Niña not out of the question (see third paragraph).

What does this mean for Australia? Firstly, while the end of the El Niño would normally be associated with a return to more normal rainfall patterns, it should not be seen as a precursor to drought-breaking rains. This particularly applies to water supplies in parts of eastern and southern Australia, which in some instances require several years of healthy rainfalls to recover to a satisfactory level. Nonetheless, we can be cautiously optimistic that there will be a general easing of dry conditions in drought-affected areas over the next one to two seasons.

A La Niña in 2007?

The chance of a La Niña developing in 2007 is thought to be higher than the long-term average (which is about one in five or 20%) because (a) they have a tendency to follow an El Niño; ( the El Niño has decayed somewhat earlier than normal thereby giving time for a La Niña to begin developing during the critical March to June period; and © a large pool of cold sub-surface water has developed in the central to eastern tropical Pacific Ocean. La Niña events are generally associated with wetter than normal conditions across much of the eastern half of the country from about autumn.

In Brief

* Equatorial Pacific SSTs have further cooled and are below El Niño thresholds.

* Negative subsurface anomalies have strengthened and reached the surface in the eastern Pacific.

* The SOI has a current (19th January) 30-day value of −3.

* Trade Winds have generally been close to or somewhat stronger than average in the western Pacific during February.

* Cloudiness near the date-line has recently been close to average.

* Most computer models predict cool neutral conditions in the first half of 2007.

[Gray-Wolf]

Though I will appear foolish why cannot the cold water be a pulse from the 'Antartic' ( which I have 'monitored' from the SST' plots,sat images, weather station plots and the topography of the seafloor from ross outwards since early Jan)?

The 'unpresidented end' to the El-Nino was visible on these mediums so why are they not 'seeing it ' too? (making me sadly deluded)

As I said on another thread ,surely water temps can drive a system that is normaly a 'pressure drives water temps' one?

If this is remotely 'so' then 'El-Nino' conditions didn't 'go away' ,they were 'swamped' and , if so, strange resposes over the season may be reasonable to expect as other 'indicators' won't be affected.

[kold weather]

Not quite GW. ENSO is a most complicated as there are several things thatcan change it. Howeer the death of this El nino and the formation of the La nina actually can be pinpointed in this case to something occuring underneath the surface.

Its not so much that the cold water is swamping onto of the milder water...but the colder water is undercutting and bulging up from the deeper part of the ocean. The sub-surface loopa show this perfectly IMO:

http://www.cpc.ncep.noaa.gov/products/anal...wkxzteq_anm.gif