ATL: DANNY - Remnants - Discussion

[chaser1]

Ozonepete or anyone else, I have a question about the shear. Looking at the 00z GFS's shear forecast maps on Tropical Tidbits (and those from previous runs) the heaviest band of shear begins to match Danny in pace, constantly impinging on his front side out through 78 hours. Is this how these upper atmospheric interactions typically work? Danny's meager anticyclone pushes upper level troughing along with it, creating a perpetually unfavorable environment? Or is that shear moving as the result of some other factor?

I think the easiest way to explain it is this. A large and well developed hurricane might typically have its own anticyclone (upper high) parked smack overhead; all the while massive amounts of air is rising up and into its core and that air is constantly being evacuated up and out the top of that "storms chiminy". Under ideal conditions that outflow might be screaming out in all directions, even at speeds over 30 mph. Here, the hurricane is using the atmosphere to ventilate itself (which ultimatly aids the ongoing convergence of surface inflow). Upper level shear is not difluent however. Sure, on one hand it does kinda ventilate air rising out of the eye, but upper level shear kind of puts out the fire.... rather than simply helping to fan the fire. If you've ever watched Survivor when someone is trying to make fire, you might notice how they gently blow to cause the delicate little ember to catch fire. Now imagine the outcome if they were to blow as humanly strong as possible, LOL. That little ember would be immediately extinguished. Upper level shear will tend to cause that same result to occur to hurricane; instead of being difluent air aiding a storms outflow, the shear is acting more or less "convergent" and acting to extinguish the storms whole outflow mechanism.

Not sure if that answered your question. .. more importantly though, hopefully I didn't confuse you evrn further lol

[tolakram]

Putting up a good fight.

[Siker]

Ozonepete or anyone else, I have a question about the shear. Looking at the 00z GFS's shear forecast maps on Tropical Tidbits (and those from previous runs) the heaviest band of shear begins to match Danny in pace, constantly impinging on his front side out through 78 hours. Is this how these upper atmospheric interactions typically work? Danny's meager anticyclone pushes upper level troughing along with it, creating a perpetually unfavorable environment? Or is that shear moving as the result of some other factor?

I think the easiest way to explain it is this. A large and well developed hurricane might typically have its own anticyclone (upper high) parked smack overhead; all the while massive amounts of air is rising up and into its core and that air is constantly being evacuated up and out the top of that "storms chiminy". Under ideal conditions that outflow might be screaming out in all directions, even at speeds over 30 mph. Here, the hurricane is using the atmosphere to ventilate itself (which ultimatly aids the ongoing convergence of surface inflow). Upper level shear is not difluent however. Sure, on one hand it does kinda ventilate air rising out of the eye, but upper level shear kind of puts out the fire.... rather than simply helping to fan the fire. If you've ever watched Survivor when someone is trying to make fire, you might notice how they gently blow to cause the delicate little ember to catch fire. Now imagine the outcome if they were to blow as humanly strong as possible, LOL. That little ember would be immediately extinguished. Upper level shear will tend to cause that same result to occur to hurricane; instead of being difluent air aiding a storms outflow, the shear is acting more or less "convergent" and acting to extinguish the storms whole outflow mechanism.

Not sure if that answered your question. .. more importantly though, hopefully I didn't confuse you evrn further lol

Haha no confusion, I understand the difference between negative shear and helpful ventilation. My inquiry was more about finding out what causes the band of highest shear to move in tandem with Danny on the GFS.

[Hurricaneman]

One thing I can say is it looks like even if its sheared it might keep popping convection which could help it make it through the shear zone to the low shear on the other side in 3 to 4 days

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[AutoPenalti]

This might sound funny but from the looks of it, it may be trying to sacrifice the outer flow to protect the inner-core. Sort of like damage control.

I don't know, is that a thing?

[CourierPR]

Danny is truly a remarkable storm.

[Weatherlover12]

It's such a small system I can't see how it will survive the shear and dry air. Even a larger hurricane would be running into a shredder. I think it's quick demise is going to surprise some people.

You may be right but it was surprising to see how fast the storm formed. We need to wait in the morning and wait for the recon flights. This storm is very interesting and shouldn't be taken lightly
Have a good night -weatherlover12

[AJC3]

Ozonepete or anyone else, I have a question about the shear. Looking at the 00z GFS's shear forecast maps on Tropical Tidbits (and those from previous runs) the heaviest band of shear begins to match Danny in pace, constantly impinging on his front side out through 78 hours. Is this how these upper atmospheric interactions typically work? Danny's meager anticyclone pushes upper level troughing along with it, creating a perpetually unfavorable environment? Or is that shear moving as the result of some other factor?

I think the easiest way to explain it is this. A large and well developed hurricane might typically have its own anticyclone (upper high) parked smack overhead; all the while massive amounts of air is rising up and into its core and that air is constantly being evacuated up and out the top of that "storms chiminey". Under ideal conditions that outflow might be screaming out in all directions, even at speeds over 30 mph. Here, the hurricane is using the atmosphere to ventilate itself (which ultimately aids the ongoing convergence of surface inflow). Upper level shear is not diffluent however. Sure, on one hand it does kinda ventilate air rising out of the eye, but upper level shear kind of puts out the fire.... rather than simply helping to fan the fire. If you've ever watched Survivor when someone is trying to make fire, you might notice how they gently blow to cause the delicate little ember to catch fire. Now imagine the outcome if they were to blow as humanly strong as possible, LOL. That little ember would be immediately extinguished. Upper level shear will tend to cause that same result to occur to hurricane; instead of being difluent air aiding a storms outflow, the shear is acting more or less "convergent" and acting to extinguish the storms whole outflow mechanism.

Not sure if that answered your question. .. more importantly though, hopefully I didn't confuse you evn further lol

What you mean to say here is upper level shear is not necessarily diffluent. However, to be more accurate, what you really want to be saying is divergent, because diffluence doesn't necessarily mean that the total flow shows net divergence, although that is *usually* the case. Diffluence is simply the spreading of streamlines aloft and speaks nothing to the speed component of divergence, which can be significant.

The upper level flow pattern can have shear that is (1) divergent, (2) convergent or (3) neutral. (1) leads to rising air, (2) leads to sinking air, and (3) does neither.

[YoshiMike]

This might sound funny but from the looks of it, it may be trying to sacrifice the outer flow to protect the inner-core. Sort of like damage control.

I don't know, is that a thing?

I honestly dont know but that is a funny theory. Like they know they can do stuff to make em last.

[chaser1]

Ozonepete or anyone else, I have a question about the shear. Looking at the 00z GFS's shear forecast maps on Tropical Tidbits (and those from previous runs) the heaviest band of shear begins to match Danny in pace, constantly impinging on his front side out through 78 hours. Is this how these upper atmospheric interactions typically work? Danny's meager anticyclone pushes upper level troughing along with it, creating a perpetually unfavorable environment? Or is that shear moving as the result of some other factor?

I think the easiest way to explain it is this. A large and well developed hurricane might typically have its own anticyclone (upper high) parked smack overhead; all the while massive amounts of air is rising up and into its core and that air is constantly being evacuated up and out the top of that "storms chiminey". Under ideal conditions that outflow might be screaming out in all directions, even at speeds over 30 mph. Here, the hurricane is using the atmosphere to ventilate itself (which ultimately aids the ongoing convergence of surface inflow). Upper level shear is not diffluent however. Sure, on one hand it does kinda ventilate air rising out of the eye, but upper level shear kind of puts out the fire.... rather than simply helping to fan the fire. If you've ever watched Survivor when someone is trying to make fire, you might notice how they gently blow to cause the delicate little ember to catch fire. Now imagine the outcome if they were to blow as humanly strong as possible, LOL. That little ember would be immediately extinguished. Upper level shear will tend to cause that same result to occur to hurricane; instead of being difluent air aiding a storms outflow, the shear is acting more or less "convergent" and acting to extinguish the storms whole outflow mechanism.

Not sure if that answered your question. .. more importantly though, hopefully I didn't confuse you evn further lol

What you mean to say here is upper level shear is not necessarily diffluent. However, to be more accurate, what you really want to be saying is divergent, because diffluence doesn't necessarily mean that the total flow shows net divergence, although that is *usually* the case. Diffluence is simply the spreading of streamlines aloft and speaks nothing to the speed component of divergence, which can be significant.

The upper level flow pattern can have shear that is (1) divergent, (2) convergent or (3) neutral. (1) leads to rising air, (2) leads to sinking air, and (3) does neither.

Point taken. That does technically exhibit the subtle distinction between the two words.

On a lighter note, I might had done more justice to have simply answered the question by saying "strong uni-directional upper level wind - bad" verses "gentle upper level flow spreading out from center of hurricane in all directions - good".

[MaineWeatherNut]

Danny now as it encounters more hostile conditions is producing the strongest convection of it's life... Strange how these conditions seem to be having the opposite effect on Danny then we would think they would.

[AJC3]

Point taken. That does technically exhibit the subtle distinction between the two words.

On a lighter note, I might had done more justice to have simply answered the question by saying "strong uni-directional upper level wind - bad" verses "gentle upper level flow spreading out from center of hurricane in all directions - good".

Or a buzz cut.

[chaser1]

Meanwhile.... back to our scheduled programming:

Danny's convective cloud tops have been becoming a good deal colder. Its hard to say, but my eye is telling me that Danny has already crossed the 15N and 50W point; looks to me as if it will pass north of the forecast track. This of course wont be verified until either popping an eye on satellite again, or simple waiting for morning visible pics. Might not be much, but if so each incremental nudge a bit more to the north, simply means an equal re-calibration to the forecast track. At minimum, it certainly does imply that a more westward shift in track has yet to manifest.

The dynamics at play here are really fascinating to me. This certainly is not a circumstance where a tiny hurricane is having much if any impact on the regions overall environment. Danny simply doesn't have the girth to do so. Yet, it would appear that Danny is simply at the western extension of an overall large easterly surge. I can see how that might help break down and filter out some of the dryer sinking air immediately to Danny's north and west. In fact, if one were to look very closely... it would appear that there is some low to mid level "lazy swirl" to Danny's west and keeping a westward pace ahead of the storm. It does not appear to be a weak cut-off low, because I am not seeing any correlation to the upper level shear flow. For that reason, I just can't make any correlation to how a easterly surge might lesson the upper level shear that is trying to impinge on Danny's outflow. Interesting stuff!

[chaser1]

Point taken. That does technically exhibit the subtle distinction between the two words.

On a lighter note, I might had done more justice to have simply answered the question by saying "strong uni-directional upper level wind - bad" verses "gentle upper level flow spreading out from center of hurricane in all directions - good".

Or a buzz cut.

Right? Better yet!

[YoshiMike]

http://www.ssd.noaa.gov/goes/east/catl/flash-wv.html

I can see what you're saying about the burst of convection. It is also really noticeable on the visible GOES imagery. Definitely looks like he is putting up a good fight. and you can definitely see him getting a haircut too

sorry, I don't know how to make it directly appear on the boards becuase it isnt a .gif or jpg/jpeg link

[AJC3]

Meanwhile.... back to our scheduled programming:

Danny's convective cloud tops have been becoming a good deal colder. Its hard to say, but my eye is telling me that Danny has already crossed the 15N and 50W point; looks to me as if it will pass north of the forecast track. This of course wont be verified until either popping an eye on satellite again, or simple waiting for morning visible pics. Might not be much, but if so each incremental nudge a bit more to the north, simply means an equal re-calibration to the forecast track. At minimum, it certainly does imply that a more westward shift in track has yet to manifest.

<snip>

It does indeed appear that Danny's current heading of 295 will need to bend more toward 275-280 pronto for significant land interaction between the GA and the center to eventually occur, *assuming there is a bona fide TC left to track by that time*. The 0545UTC SSD fix was already at 15.1N 50.0W, the same latitude as the 12Z forecast position, but at a full 1.4E of it. Assuming a heading of 285 degrees from where the center is right now would take the center just north of the NE tip of PR.

However, with each passing satellite image, the presentation continues to degrade, and it becomes very questionable what if anything will be left of Danny in 4-5 days.

[AJC3]

Meanwhile.... back to our scheduled programming:

Danny's convective cloud tops have been becoming a good deal colder. Its hard to say, but my eye is telling me that Danny has already crossed the 15N and 50W point; looks to me as if it will pass north of the forecast track. This of course wont be verified until either popping an eye on satellite again, or simple waiting for morning visible pics. Might not be much, but if so each incremental nudge a bit more to the north, simply means an equal re-calibration to the forecast track. At minimum, it certainly does imply that a more westward shift in track has yet to manifest.

<snip>

It does indeed appear that Danny's current heading of 295 will need to bend more toward 275-280 pronto for significant land interaction between the GA and the center to eventually occur, *assuming there is a bona fide TC left to track by that time*. The 0545UTC SSD fix was already at 15.1N 50.0W, the same latitude as the 12Z forecast position, but at a full 1.4E of it. Assuming a heading of 285 degrees from where the center is right now would take the center just north of the NE tip of PR.

However, with each passing satellite image, the presentation continues to degrade, and it becomes very questionable what if anything will be left of Danny in 4-5 days.

Another quick point on this subject...Over the years, there have been countless instances of the low level center of a TC repositioning itself downshear closer to the convection/mid level center as it attempts to maintain vertical coherency. We may see that to some degree with Danny as it encounters increasng shear, as long as the cyclone doesn't completely decouple, which it eventually might do.

[jlauderdal]

Putting up a good fight.

Yeah small storm only needs to sustain minimal advection to survive.

or small storm only needs minimal hostile conditions to get destroyed...i do appreciate the optimism on this board each year..its been a very tough 10 years for hurricane lovers..the overall conditions in the Atlantic remain unchanged and it will continue to be tough sledding for tropical systems

[Gustywind]

000
WTNT34 KNHC 220833
TCPAT4

BULLETIN
HURRICANE DANNY ADVISORY NUMBER 16
NWS NATIONAL HURRICANE CENTER MIAMI FL AL042015
500 AM AST SAT AUG 22 2015

...DANNY WEAKENS A LITTLE MORE...


SUMMARY OF 500 AM AST...0900 UTC...INFORMATION
----------------------------------------------
LOCATION...15.2N 50.8W
ABOUT 740 MI...1195 KM E OF THE LEEWARD ISLANDS
MAXIMUM SUSTAINED WINDS...100 MPH...155 KM/H
PRESENT MOVEMENT...WNW OR 290 DEGREES AT 10 MPH...17 KM/H
MINIMUM CENTRAL PRESSURE...982 MB...29.00 INCHES


WATCHES AND WARNINGS
--------------------
There are no coastal watches or warnings in effect.

Interests in the Leeward Islands and the Virgin Islands should
monitor the progress of Danny. Tropical storm watches will likely
be required for portions of the Leeward Islands and the Virgin
Islands later today.

[Nimbus]

Looking at the water vapor imagery the outflow is not being impinged by a "wall of shear" as many predicted.
First visible images it should be obvious there is an intact core.
End of the day there will still be a hurricane on track towards the north coast of PR.

The ridging is migrated WNW with the storm..