atlantic hurricane season Atlantic hurricane season/invest thread

[summer blizzard]

I'm a bit confused I take it this is 91L

 

Yes, currently a day 5 cherry.

 

Last nights GFS had it slam into Canada.

 

...............................

 

With peak season on the 12th i've taken a look at our Ace value and it looks like another season with less than half but a probable improvement on 2013. 

[summer blizzard]

18z takes it into Canada again after getting down to 972mb.. Atmosphere from days 5-8 looks about as good as you can get (bar possible SAL but it should be far enough north west to avoid).

 

[summer blizzard]

Now at 70%. 6z drops it to 987mb before it goes extra-tropical and develops the wave behind it.

 

Looks a bit more organised today but with dry air and and upper level convergence limiting potential outflow it will be a slow burner. 

 

[summer blizzard]

Well now, we have a very interesting candidate.

 

92L has been declared (which means i think an upgrade to Mandarin at the next update). It has no model support from the Euro or GFS.

 

It's a stalled wave sat off the coast drifting towards the Gulf, subsidence is high but other than that the atmosphere looks pretty good and convection has been building. Recon is due in tomorrow at around 17:30.

 

[summer blizzard]

92L now in the Gulf but looks much weaker, now at 30%.

93L is the wave that dropped off Africa and is at 30%. Convection is persistent and it looks great. Unfortunately, models don't really like it.

[summer blizzard]

Looks like we are competing with the 06 and 09 seasons for lack of overall development at 9/3/2 and 10/5/2 respectively. Being on 5/4/1 at the moment i had a look and since 06 the average October formation is 2-3 systems implying a maximum of 8/6/3 plus whatever we get the rest of this month (development afterward is obviously possible).

[summer blizzard]

Anybody get the feeling this could be October 06 all over again.

[summer blizzard]

99L is at 90% with recon due later. Dry air issues though.

 

[summer blizzard]

Expect 90L to be declared a TS when recon goes in. Looks like a Fish hurricane.

 

[summer blizzard]

ACE now upto 65 (coming up on 70% of average) so since 2000 we've beaten 02, 09 and 14 in that regard, next up are 06 and 07.

 

Our Azores Low may try and go sub-tropical and we have a wave in the Gulf.

 

[summer blizzard]

Recon have found a 1001mb closed low. 

 

NHC opted not to declare the system because of a lack of convection..

 

[Typhoon43]

Quick update: 93L became TD Nine which dissipated and became 94L which then strengthened to TS Hanna which dissipated again and is now 96L. (That's 3 invests for a system!)

We also have 95L with 20/30 chance near the Lesser Antilles. 

[summer blizzard]

Well, we're into April now and i can't say things look good. Much like last year we have El Nino developing in the east Pacific which will likely kill June-July. Hopefully it may become west based over time or fizzle. 

 

That being said, at least we broke out major hurricane duck. Last season really did give me an appreciation for quality over quantity.

[Somerset Squall]

We have a very early invest just east of Florida, 90L, which has a 60% chance of becoming a subtropical or tropical cyclone as it moves to the north according to NHC. Reminds me of the early TS Beryl in 2012. It's looking disorganised at present but models are fairly keen...

[Gray-Wolf]

Just spotted that SS ! They don't appear to be taking it too serious over on Jeff Masters WU blog......... maybe it'll prove them wrong?

[Somerset Squall]

I wouldn't have thought it would get that strong, but I think there is a good chance of Ana from this.

[Gray-Wolf]

It'd be a nice early start if it did!!!

 

With a big Nino in the offing we may be a little light on storms this time if shear over the basin becomes high?

[Somerset Squall]

Indeed, a below average season is expected. Conversely, the Pacific is expected to be above average in the Eastern and Western basins. Already, the West Pacific has gotten off to a hyperactive start!

[Vorticity0123]

Yes, this will definitely be an early start of a probably slow season if 90L develops into the first (sub)tropical storm of the 2015 Atlantic hurricane season.

 

90L

 

As of the moment of writing, the system looks fairly well-organized, with some convection existing in its northwestern quadrant and there is definitely some low-level spin present. However, upon looking more closely you can see that there are multiple swirls rotating in a cyclonic gyre. Recent aircraft data confirms this: http://www.tropicaltidbits.com/recon/

 

As long as 90L does not have one single well-defined low level circulation center, it will probably not be classified as a (sub)tropical cyclone.

 

Animated visible satellite loop of Ana.

Regarding the lack of convection in especially the southern half of the circulation, this can be explained nicely by taking a look at water vapour imagery of 90L:

 

Water vapor satellite image of Ana as of 18:45 UTC May 7.

 

The blue/green colours indicate moist air, while the yellow colours indicate dry air. It can be seen that there is a large area of dry air circulating into the cyclone from the west and south. This dry air is keeping convection very limited in the southern half of the system.

 

Much more information and highly informative videos about 90L can be found here: http://www.tropicaltidbits.com/

 

The NHC has upped the chances of development to 80% in the next 2 and 5 days, respectively.

 

Atlantic hurricane season

 

As mentioned before, in spite of the current activity, the Atlantic hurricane season seems to be becoming a rather inactive one. This is supported by recent sea surface temperature anomalies as seen in the Eastern Pacific:

 

SST anomalies as of 5 May 2015

 

Note the large swath of above-average sea surface temperatures (SSTS) extending across the Equator in the East Pacific. This is indicative of an El Nino event. Usually, such events are unfavourable for tropical cyclone development in the Atlantic. More information about this topic can be found here.

 

Also, there is a large area of below-average SSTS in the Main Development Region of the Atlantic (spanning from about 0 to 20N, and 20 to 60W). This is the area where most of the Cape-Verde type Atlantic tropical cyclones develop. Below average SSTS could significantly impede development in that region, though there is still some time for the SSTS to warm up in the coming months before the peak of the Atlantic hurricane season.

 

Finally, an interesting read about what to expect in the upcoming Atlantic hurricane season from Colorado State University can be found here:

 

http://hurricane.atmos.colostate.edu/forecasts/2015/apr2015/apr2015.pdf

 

In summary, they expect relatively very quiet season this year.

 

Summary

 

Despite the forecasts for a rather inactive hurricane season, the first (sub)tropical cyclone could develop very soon with a low pressure area in the western Atlantic slowly becoming more organized. However, this is by no means an indication that the season will be much more active than normal/forecasted.

 

Sources:

http://hurricane.atmos.colostate.edu/forecasts/2015/apr2015/apr2015.pdf

http://www.tropicaltidbits.com/recon/

http://www.ospo.noaa.gov/Products/ocean/sst/anomaly/

http://www.ssd.noaa.gov/PS/TROP/floaters/90L/90L_floater.html\

http://ww2010.atmos.uiuc.edu/%28Gh%29/guides/mtr/hurr/enso.rxml

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

 

[summer blizzard]

Summer Blizzard's 2015 prediction...

 

QBO+MEI+AO+PDO

 

1982

1992

1997

1993

2002

1967

1980

1978

 

Forecast:

 

8-11 storms

4-8 hurricanes

1-2 major hurricanes

 

ACE:

 

75% below average

 

Predicted Range is 64-41 (lowest since 2013).

[summer blizzard]

We have a cherry. 70% in the GOM.

[Vorticity0123]

We have awheels cherry. 70% in the GOM.

 

Yep, this may well become the second cyclone of the 2015 Atlantic hurricane season. If Bill would form out of this system, the season would have a rather active start. Still, given the El Nino that has developed, odds are still against an active season overall.

 

Looking more in-depth at this system, it does not seem to be very organized yet. Take a look at the analysis below:

 

Satellite image of 91L. Courtesy: NOAA.

 

There does not seem to be any convection over the center of the system (red cross, based on analysis from CIMSS and NOAA). Instead, a large, though rather linear area of convection is located on the northeastern flank of the system. CIMSS analyzes about 8 kt of northwesterly shear over the center, with much higher values to the east and west of the system. In such shear conditions, one would expect convection to be located much more to the southwest of 91L. So shear alone does not seem to fully explain the structure of the system itself.

 

However, the structure of the system can be explained when analysing the 500 hPa relative humidity:

 

COAMPS TC 12 UTC run 500 hPa relative humidity forecast for18 UTC 14 June. Courtesy: NRLMRY NAVY.

 

It can be seen that a large area of relatively dry air extends from the western flank all the way into the core of the system. This could be attributing to the lack of convection on the southwestern half of the system.

 

Another factor which could have been inhibiting convection so far is land interaction. Given that the invest is moving northwestward away from the Yucatan penninsula, this factor does not seem to be an issue until landfall somwhere in the southern US.

 

Finally, it appears that this system is already producing winds of almost gale-force, so if this system would be able to form a well-defined surface circulation it could be named immediately.

 

A very educative and in-depth video-update about 91L can be found here: http://www.tropicaltidbits.com/.

 

Sources:

http://www.ssd.noaa.gov/PS/TROP/floaters/91L/91L_floater.html

www.nrlmry.navy.mil/coamps-web/web/tc?&spg=&hend=120&sid=91L&ddtg=2015061412&scl=2&sec=2&var=relhum-500τ=6

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

https://en.wikipedia.org/wiki/2015_Atlantic_hurricane_season#Tropical_Storm_Ana

[summer blizzard]

Anybody know which MJO phases are best for July activity.

[summer blizzard]

94L gets 20% in 5 days..

 

 

[summer blizzard]

Now at 30% in 5 days. Neither GFS or Euro go for it though.