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Atlantic Tropical Action 2013


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And again it won't make it past 50W. I wonder what's with the subsidence and shear in the ctrl ATL this season...

 

4th year in a row now of that more stable than normal conditions out there.

 

http://www.wunderground.com/blog/JeffMasters/archive.html?year=2012&month=11

 

Unusually stable air over the Tropical Atlantic in 2012

For the third consecutive hurricane season, 2012 featured an unusual amount of dry, sinking air over the tropical Atlantic and Caribbean Sea. Due to warmer-than-average sea surface temperatures and an active African Monsoon that generated plenty of African waves, a remarkably high number of tropical storms managed to form, but the unusually stable air in the hurricane genesis regions made it difficult for the storms to become strong. When we did see storms undergo significant intensification, it tended to occur outside of the tropics, north of 25°N, where there was not as much dry, sinking air (Sandy's intensification as it approached landfall in Cuba was an exception to this rule.) If we look at the last nine hurricane seasons (Figure 2), we can see that the hurricane seasons of 2010, 2011, and 2012 all featured similar levels of highly stable air over the tropical Atlantic. This is in marked contrast to what occurred the previous six years.

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I do not agree based on IR2 of where the center is.

 

AL, 92, 2013081706,   , BEST,   0, 206N,  926W,  25, 1010, LO,

 

I thnk it is a couple of degrees North, and thus that guidance is not particularly useful.

I think you might be looking at the mid level low:

 

TROPICAL WEATHER DISCUSSION

NWS NATIONAL HURRICANE CENTER MIAMI FL

805 AM EDT SAT AUG 17 2013

HE SURFACE TROUGH IN THE GULF OF MEXICO EXTENDS FROM 26N90W

THROUGH A WEAK 1010 MB LOW NEAR 21N93W TO S MEXICO NEAR 17N94W.

A MID/UPPER LOW IS TO THE NE NEAR 22N90W.

 

 

Of course, that doesn't mean the low can't relocate NE either. 

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I think you might be looking at the mid level low:

 

TROPICAL WEATHER DISCUSSION

NWS NATIONAL HURRICANE CENTER MIAMI FL

805 AM EDT SAT AUG 17 2013

HE SURFACE TROUGH IN THE GULF OF MEXICO EXTENDS FROM 26N90W

THROUGH A WEAK 1010 MB LOW NEAR 21N93W TO S MEXICO NEAR 17N94W.

A MID/UPPER LOW IS TO THE NE NEAR 22N90W.

 

I think I might, in a way, but that old LLC is not long for this world.  As I said yesterday, the old naked swirl LLC is weakening, and I think a new one is forming closer to the MLC.  I can see rotation even in the 10C (not that cold) cloud tops.  Or 700 mb level, which I consider the lower end of the mid levels or the upper end of the low levels.  Much closer to the deep convection as well.

 

Hotlink below- I see what they are calling the center, and I am pretty sure it is not where any center actually occurs if this develops.

 

swir_lalo-animated.gif

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I think I might, in a way, but that old LLC is not long for this world.  As I said yesterday, the old naked swirl LLC is weakening, and I think a new one is forming closer to the MLC.  I can see rotation even in the 10C (not that cold) cloud tops.  Or 700 mb level, which I consider the lower end of the mid levels or the upper end of the low levels.  Much closer to the deep convection as well.

 

Hotlink below- I see what they are calling the center, and I am pretty sure it is not where any center actually occurs if this develops.

 

swir_lalo-animated.gif

I would agree that if the convection near the MLL continues, we'll likely see a relocation of the LL center toward its location.  I edited my previous post to say that as well.

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At 1200 UTC, 17 August 2013, LOW INVEST (AL92) was located in the North Atlantic basin at 20.7°N and 92.8°W. The current intensity was 25 kt and the center was moving at 2 kt at a bearing of 235 degrees. The minimum central pressure was 1010 mb.

Models could never resolve the right solution with the low level LLC...the Euro from a couple days ago might have been right...just south of Tampico as a weak disturbance. Most of the weather will be for the N/C GoM, though

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And again it won't make it past 50W. I wonder what's with the subsidence and shear in the ctrl ATL this season...

There has been an unusually persistent series of cut-off lows (TUTTs) this year. This has been a trend since 2005 and particularly since 2010. Does anyone have an explanation for them?

 

Anyway, this could result in a number of busted forecasts...as seasonal wavelengths deepen into the fall, I would only expect the number of upper lows / TUTTs to increase through September / October.

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Anyway, back to the BoC low. Conditions aloft look good, and convection is starting to go off near the center...structure has a long way to go, though, so I expect some modest intensification as it moves WNW. I expect a simple low to a max of a 45kt TS at landfall somewhere in Tamaulipas in a couple of days.

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Re: Erin... I think it's neat when you have a weak naked swirl almost entirely composed of low-level cloud cover which suddenly has a burst of convection... and when you look at it on satellite, you can see the single tower of heavy clouds boiling up.  You could almost imagine being in the Atlantic and watching a giant tower of clouds sprouting up.

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