Atlantic Hurricane/Invest Thread 2012/2013

[Coast]

Mandarin in the Atlantic.

 

Old push-bikes in the Thames???? :unsure: 

[summer blizzard]

Now a cherry. Visible suggests this is probably a TS.

[lorenzo]

Interesting article in relation to dust and the impact on the storm season, relates back to early 80s dry period and hints at another atmospheric cycle being present, which as yet is not understood.

 

http://www.sun-sentinel.com/news/broward/fl-african-dust-outbreaks-20131014,0,1753512.story

[Vorticity0123]

Interesting article in relation to dust and the impact on the storm season, relates back to early 80s dry period and hints at another atmospheric cycle being present, which as yet is not understood.

 

http://www.sun-sentinel.com/news/broward/fl-african-dust-outbreaks-20131014,0,1753512.story

Interesting read. Much research has to be done to help getting a better understanding of this possible multidecadal cycle.

Another interesting article discussing the same subject is from a blog on weather underground.

 

http://www.wunderground.com/blog/24hourprof/the-lack-of-atlantic-hurricanes-the-saga-of-low-relative-humidity-con

 

The article states that there might be a link between low RH's in the Main Development Region and low RH's in the Southern Hemisphere (mainly in the South Atlantic). I don't know if this is well-known science or new, but it would be interesting to find out wheather the link between the low RH's has anything to do with the possible cycle of dust coming from Africa.

 

I'm new here, so please accept the possible bad grammar!

[lorenzo]

Interesting read. Much research has to be done to help getting a better understanding of this possible multidecadal cycle.

Another interesting article discussing the same subject is from a blog on weather underground.

 

http://www.wunderground.com/blog/24hourprof/the-lack-of-atlantic-hurricanes-the-saga-of-low-relative-humidity-con

 

The article states that there might be a link between low RH's in the Main Development Region and low RH's in the Southern Hemisphere (mainly in the South Atlantic). I don't know if this is well-known science or new, but it would be interesting to find out wheather the link between the low RH's has anything to do with the possible cycle of dust coming from Africa.

 

I'm new here, so please accept the possible bad grammar!

 

Welcome along to the forum Vorticity and thanks for the link, great satellite loop included in that story.

 

https://www.e-education.psu.edu/worldofweather/files/worldofweather/SAL-6hrs-Aug23Sep05.gif

 

Don't worry about grammar at all - hope you find plenty here to keep you occupied.

 

If you can add your location to your profile, something we usually ask new folks to do that would be great.

[summer blizzard]

Can't say I'm convinced that SAL has been the problem this year, there have been far worse years for that which have produced the goods. Additionally the eastern Atlantic has actually been largely favourable. A very unusual disappointment considering that we had the slight Nina response (lower than average pressure over the Tropics), we had near average monsoonal activity (normal number of storms coming off Africa) and for most of the summer we had a +NAO with decent MJO activity.

 

My personal view is that the difference between the west and eastern Atlantic is what may be the key in terms of synoptic response but until September there was a +PNA, +NAO which allowed for a broader HADLEY cell and should have led to fertile conditions in the deep tropics, only since September did we see a less favourable pattern in the eastern Atlantic but not overly so.

 

Perhaps then we just had some bad luck in the Gulf as Andrea, Barry, Fernand and Ingrid were only really held back by land interaction and perhaps we can put Karen down to poor synoptics but really even if my assertion for reasoning was true that still does not explain why Chantal, Dorian, Erin and Gabrielle were so poor when they should arguably in a normal season had a shot at major hurricane status and even this season had a good background pattern.

 

We probably have a final throw of the dice if the MJO becomes more active between the 25th-15th. After that, season over.

Edited October 16, 2013 by summer blizzard

[Vorticity0123]

Welcome along to the forum Vorticity and thanks for the link, great satellite loop included in that story.

 

https://www.e-education.psu.edu/worldofweather/files/worldofweather/SAL-6hrs-Aug23Sep05.gif

What also seems interesting to this loop, is that there is continuously some dry air present near 10 N, 20W. Could it be that this dry air is ingested by the tropical waves, and then being taken with the waves to the Caribbean, thus interfering with development?

 

Perhaps then we just had some bad luck in the Gulf as Andrea, Barry, Fernand and Ingrid were only really held back by land interaction and perhaps we can put Karen down to poor synoptics but really even if my assertion for reasoning was true that still does not explain why Chantal, Dorian, Erin and Gabrielle were so poor when they should arguably in a normal season had a shot at major hurricane status and even this season had a good background pattern.

 

There does seem to be an overall lack of cyclone activity, as the East Pacific also hasn't produced a major hurricane yet. The west-Pacific is currently very active, but before October it also seemed to become a below-normal season. So perhaps there could be some global link in the lack of activity?

[Coast]

U.S. storm forecasting tactics questioned as 2013 hurricane season ends with a whimper

 

Despite dire predictions to the contrary, the 2013 hurricane season is turning out to be a dud. With a little over a month left in the North Atlantic hurricane season, it’s now clear that the long-range U.S. forecasts issued in the spring — all calling for a high level of storm activity — weren't even close.

 

In May, the U.S. National Oceanic and Atmospheric Administration predicted unusually warm ocean temperatures would spawn between seven and 11 hurricanes, and that three to six could become major hurricanes churning out winds in excess of 178 kilometres an hour.

 

So far this year, there have been only two hurricanes — Ingrid and Humberto in early September — both of which were relatively weak storms, rated at Category 1 on a scale that reaches up to 5. Ingrid, however, brought heavy rain to parts of Mexico, where flooding and landslides claimed dozens of lives. In all, there have been 12 named storms, including tropical storm Lorenzo, which is expected to weaken to a tropical depression as it moves east over the Atlantic. A dozen named storms is about average for a season, which spans from June 1 to Nov. 30. But the number of hurricanes and major hurricanes is well below average. The last time a season passed without a major hurricane was 1994.

 

In Halifax, where the Canadian Hurricane Centre keeps track of tropical cyclones, forecasters have issued bulletins for only two storms this year, Andrea in June and Gabrielle in September. Both had little impact on the Atlantic region. Chris Fogarty, the centre’s program supervisor, says the spring predictions were so far off base that U.S. meteorologists should consider issuing seasonal forecasts without hard numbers. “We haven’t had such poor pre-season forecasts since the early 1990s,†he said, adding that unlike meteorologists in the U.S., Environment Canada forecasters do not issue long-range predictions for the number and severity of North Atlantic storms. “I think it hurts the credibility of these long-range forecasts.â€

 

Dennis Feltgen, a meteorologist with the National Hurricane Center in Miami, said the season isn’t over yet. “However, the odds that the season will produce the expected numbers of hurricanes and especially major hurricanes are rapidly decreasing,†he said in an e-mail. As for the credibility of the long-range forecasts issued by the U.S. Climate Prediction Center, he said these predictions should never be used as guides to decide whether or not to prepare for hurricane season. “Anyone living in a hurricane-vulnerable area can be affected, regardless of whether the season is quiet or busy. ... It only takes one storm hitting your area to make it a bad year. And storms do occur in November.†Fogarty said there are a number of reasons why the predictions were a bust.

 

Scientists have recorded an unusually low level of moisture in the tropics and the oddly persistent downward motion of air masses. Together, these phenomena have kept the tropics relatively cloud free. No clouds, no hurricanes. “There’s something going on globally at a larger scale that was causing a general downward motion in the Atlantic,†said Fogarty. “It seemed to be kind of stuck in one position. There’s a lot of little questions there.†As well, unusually strong winds in the upper atmosphere have been tearing apart emerging storms. “We know where to start looking, but there’s not a smoking-gun answer,†he said.

 

Still, he says the season could end with a bang, even though a NOAA study found that in the past 100 years only 10 per cent of recorded Atlantic hurricanes have formed after Oct. 25. Sandy, described as a superstorm, was a massive post-tropical storm when it roared ashore near Atlantic City, N.J., last Oct. 29, causing widespread flooding and wind damage along the entire eastern seaboard and farther inland. The 1,600-kilometre-wide storm killed 72 people in the Caribbean before making its way up the Atlantic Coast, where it killed more than 100 people in 10 states, and left more than 8.5 million people without power

 

.

http://www.theglobeandmail.com/news/world/us-storm-forecasting-tactics-questioned-as-2013-hurricane-season-ends-with-a-whimper/article15039912/

 

[Vorticity0123]

As the Atlantic season is nearing its end, it will be interesting to see wheather we can expect another TC developing in this region. For that reason, I'll try to make very basic forecast.

 

I will start with sea surface temperatures. The chart below shows that SSTS in the southern GOM and the Caribbean will be sufficient to support a TC, with temperatures in the Caribbean as high as 29 Celsius.

 

Next is wind shear (which to my eye doesn't seem to be predictable in the far future, though i'm likely wrong). The map below shows that shear values in the Caribbean, as well as in the in GOM are very high, ranging between 20 and 50 knots. Those shear values are very unfavorable for TC development, though those values can change much in the short- or long term.

 

 

For the next part, moist/dry air will be discussed.

In the water vapor image below, one can clearly see that there is a large swath of dry air in the western Caribbean (brown color), as well as a large area of dry air lurking at the central Atlantic. With the current tropical wave in the Caribbean not going to develop (also because of wind shear, see above), it seems that dry air will keep things calm in the Caribbean for quite some while.

 

For a more long-term indication of TC formation potential, we take a look at the MJO. It shows that the MJO is currently in phase 8/1,

and it will stay in that phase for the next few days. Phase 8/1 cause in general rising air over the Atlantic, which increases the odds of TC formation. More information on the MJO can be found here: http://typhoon.atmos.colostate.edu/Includes/Documents/Publications/klotzbach2010.pdf

 

 

Now, I will try to get into a part of TC formation, of which my knowledge is not very high, called Kelvin waves. The graph below shows the 200 hPa velocity potential, with on the Y-axis the time, and on the X-axis the latitude. The output is from the GFS-model. The active phase of Kelvin waves are indicated with the red color.

Kelvin waves seem to enhance the chances on TC formation. A paper with more information regarding Kelvin waves can be found in this link: http://www.atmos.albany.edu/student/ventrice/documents/publications/Dissertation.pdf

 

In this particular image, one can see that an active phase of a Kelvin wave is forecast to move into the Atlantic just behind the end of the forecast period (around Nov 10.) with some extrapolation. This could increase the chance of a TC forming in the Atlantic around Nov. 10.

 

 

And finally, a look at the current GFS output. It shows no TC activity over the next 180 h in the Atlantic, which would deny above theory.

http://www.wetterzentrale.de/topkarten/fsavnwt.html

 

A short summary: TC development in the short term is highly unlikely, but in the long term there are indications that we might get a last shot at a potential storm. The signals are mixed, though.

 

Finally, a nice read about the prospects of a hurricane developing in the atlantic can be found here: http://dutch.wunderground.com/blog/JeffMasters/comment.html?entrynum=2568

 

 

Sources:

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

http://tropic.ssec.wisc.edu/real-time/windmain.php?&basin=atlantic&sat=wg8∏=shr&zoom=&time=

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

http://mikeventrice.weebly.com/forecast.html

http://dutch.wunderground.com/blog/JeffMasters/comment.html?entrynum=2568

Edited November 1, 2013 by Vorticity0123

[Vorticity0123]

The inactive 2013 hurricane season is up for a (potentially final) subtropical cyclone in the mid-Atlantic. A low pressure area is currently in the process of developing in the open tropics. NHC is currently giving it a 50% chance of developing in the next 5 days (10% in the next 48 hours), as it moves slowly northward.

 

1. A NON-TROPICAL LOW PRESSURE SYSTEM CONTINUES TO GRADUALLY DEVELOP
OVER THE CENTRAL ATLANTIC OCEAN SEVERAL HUNDRED MILES TO THE
SOUTHEAST OF BERMUDA. ENVIRONMENTAL CONDITIONS COULD BECOME
CONDUCIVE FOR THIS SYSTEM TO ACQUIRE SUBTROPICAL OR TROPICAL
CHARACTERISTICS EARLY NEXT WEEK WHILE THE LOW MOVES NORTHWESTWARD
TO NORTHWARD. THIS SYSTEM HAS A LOW CHANCE...10 PERCENT...OF
BECOMING A SUBTROPICAL OR TROPICAL CYCLONE DURING THE 48
HOURS...AND A MEDIUM CHANCE...50 PERCENT...OF BECOMING A
SUBTROPICAL OR TROPICAL CYCLONE DURING THE NEXT FIVE DAYS.

 

As the system hasn't been declared an invest yet, I'll be showing images of the Central Atlantic.

 

Current visible imagery shows some weak convection associated with the low pressure area, with no real turning evident yet.

 

 

 

The lack of convection might be becuase of the system having some problems with dry air currently to the west of the system. This can also be seen in the Water Vapor imagery below:

 

 

Because the system is currently extratropical in nature, it first needs to acquire some subtropical characteristics in order to become a subtropical cyclone. The FSU Phase Diagram below, a method to assess and predict to wheather a cyclone is tropical or subtropical, shows the system acquiring an asymmetric warm core (characteristic for subtropical cyclones), before transitioning back into a cold core system (as form the GFS model):

 

The image above shows the nature of the core of a low pressure area. Tropical cyclones usually have a symmetric warm core, while mid-latitude extratropical cyclones tend to have an asymmetric cold core. An asymmetric warm core is more a characteristic of a subtropical cyclone, as this cyclone is forecast to become. Note that the system isn't forecast to have a very pronounced warm core, which shows there is still some uncertanity as wheather this cyclone will actually become subtropical.

 

 

The forecast track of the GFS shows the system moving westward, and then slowly recurving northeastward in the westerlies. The image below also shows the SSTS, which will drop below 26 degrees Celsius after two days. Note that many subtropical cyclones have actually developed on SSTS much below 26 degrees, so development is still possible after the cyclone crosses the 26*C isotherm

 

 

Regardless of TC development, the GFS shows the system becoming a potent low pressure area with a minimum pressure below 995 hPa. Thereafter, the cyclone is forecast to become adsorbed by another low pressure area between Newfoundland and Spain, before moving as quite an intense cyclone toward Greenland (though this is in the less-reliable phase), as seen below in the forecast map below.

 

 

The chart below shows the system getting adsorbed in the low-left corner of the map at T114.

 

 

 

 

Summarizing, it would be very interesting to see what the long-term effects of this cyclone will be on the weather in Europe, as well as if this system could become a subtropical cyclone, or possibly even a hurricane. As models usually have difficulity resolving situations with TC's involved, it will take some time before the far future of this system becomes clear, as well as the implications on the weather in Europe and the forecasted blockade.

 

Sources:

http://www.wetterzentrale.de/topkarten/fsavneur.html

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

http://moe.met.fsu.edu/cyclonephase/

Edited November 16, 2013 by Vorticity0123

[Somerset Squall]

Now been declared invest 98L. Convection has been increasing today around the developing but still broad area of low pressure. NHC give a 40% chance of subtropical or tropical cyclone formation in the next 48 hours and 70% over the next 5 days.

Edited November 17, 2013 by Somerset Squall

[Sainsbo]

98L now has a 90% chance of becoming a Tropical or Subtropical low in the next 48 hours.

 

The models really have no clue on where it's going to end up.

 

[Summer Sun]

The quietest Atlantic hurricane season since 1982 is drawing to a close, the 2013 Atlantic hurricane season officially ends on Saturday

 

http://www.noaanews.noaa.gov/stories2013/20131125_endofhurricaneseason.html

[Coast]

I think these say it all about the World's helical storms today: