ATL: DANNY - Post-Tropical - Discussion

[Shell Mound]

Why did the MSLP drop so quickly, from 1016 to 1009 mb, over the Gulf Stream despite negligible improvement in satellite presentation? Does this prove that a mesoscale vortex was involved? I suspect that aircraft merely found a mesoscale feature and upgraded on that basis. Additionally, should this system have been upgraded to begin with, given the above and the fact that surface data did not really support reconnaissance- or radar-derived measurements? At some point the distinction between a mere mesoscale complex and a tropical cyclone tends to disintegrate and we may as well end up naming mesoscale features and waterspouts.

[Hammy]

Why did the MSLP drop so quickly, from 1016 to 1009 mb, over the Gulf Stream despite negligible improvement in satellite presentation? Does this prove that a mesoscale vortex was involved? I suspect that aircraft merely found a mesoscale feature and upgraded on that basis. Additionally, should this system have been upgraded to begin with, given the above and the fact that surface data did not really support reconnaissance- or radar-derived measurements? At some point the distinction between a mere mesoscale complex and a tropical cyclone tends to disintegrate and we may as well end up naming mesoscale features and waterspouts.

All criteria was met and the satellite presentation, radar, organization, size, and intensity were about even with Arthur in 1996.

[EquusStorm]

From the official NHC definition...

A warm-core non-frontal synoptic-scale cyclone, originating over tropical or subtropical waters, with organized deep convection and a closed surface wind circulation about a well-defined center.

...Danny ticks every box and honestly should have been upgraded even earlier if the LLC had been clearly closed (which it definitely had today) via ASCAT on Sunday

NHC are the professionals and I trust their assessment. They're quite aware of small scale features that could impact the results, yet upgraded anyway, so they were pretty confident. If anything maybe closer to 35kt than 40, but the flight level and SFMR is enough for at least that.

[Sciencerocks]

[AlphaToOmega]

Danny was just Bertha reincarnated

[aspen]

Danny came in and out quickly…like a phantom.

[tolakram]

Why did the MSLP drop so quickly, from 1016 to 1009 mb, over the Gulf Stream despite negligible improvement in satellite presentation? Does this prove that a mesoscale vortex was involved? I suspect that aircraft merely found a mesoscale feature and upgraded on that basis. Additionally, should this system have been upgraded to begin with, given the above and the fact that surface data did not really support reconnaissance- or radar-derived measurements? At some point the distinction between a mere mesoscale complex and a tropical cyclone tends to disintegrate and we may as well end up naming mesoscale features and waterspouts.

Are you claiming that recon doesn't know how to find the center of a storm? The fact you mentioned water spouts is downright insulting.

[Shell Mound]

Why did the MSLP drop so quickly, from 1016 to 1009 mb, over the Gulf Stream despite negligible improvement in satellite presentation? Does this prove that a mesoscale vortex was involved? I suspect that aircraft merely found a mesoscale feature and upgraded on that basis. Additionally, should this system have been upgraded to begin with, given the above and the fact that surface data did not really support reconnaissance- or radar-derived measurements? At some point the distinction between a mere mesoscale complex and a tropical cyclone tends to disintegrate and we may as well end up naming mesoscale features and waterspouts.

Are you claiming that recon doesn't know how to find the center of a storm? The fact you mentioned water spouts is downright insulting.

I do believe that reconnaissance located the centre. There was clearly a closed circulation. My argument was that the TS-force winds were attributable to mesoscale thunderstorms and not to the circulation itself. For the record, I believe the professionals at the NHC and in the Air Force do excellent work. However, I do think that classification has become too liberal due to the improvement in detection. As scientific instrumentation has improved, the threshold for classification has become more unclear and “looser,” so to speak, than in the past.

[EquusStorm]

Looks like what's left of the center is gonna go directly overhead, that's pretty cool. Not much wind left but a pretty vigorous band on the west side just brought some heavy rain.

[tolakram]

I do believe that reconnaissance located the centre. There was clearly a closed circulation. My argument was that the TS-force winds were attributable to mesoscale thunderstorms and not to the circulation itself. For the record, I believe the professionals at the NHC and in the Air Force do excellent work. However, I do think that classification has become too liberal due to the improvement in detection. As scientific instrumentation has improved, the threshold for classification has become more unclear and “looser,” so to speak, than in the past.

I strongly disagree with this. Their mission statement is not to be consistent with the past, it's to provide the best possible product to warn people of the risk. I'll point again to the outrage when Sandy transitions to post tropical and they dropped it. They are free to act in a way that is unconcerned with storm and ACE counters.

[Ubuntwo]

Why did the MSLP drop so quickly, from 1016 to 1009 mb, over the Gulf Stream despite negligible improvement in satellite presentation? Does this prove that a mesoscale vortex was involved? I suspect that aircraft merely found a mesoscale feature and upgraded on that basis. Additionally, should this system have been upgraded to begin with, given the above and the fact that surface data did not really support reconnaissance- or radar-derived measurements? At some point the distinction between a mere mesoscale complex and a tropical cyclone tends to disintegrate and we may as well end up naming mesoscale features and waterspouts.

Are you claiming that recon doesn't know how to find the center of a storm? The fact you mentioned water spouts is downright insulting.

I do believe that reconnaissance located the centre. There was clearly a closed circulation. My argument was that the TS-force winds were attributable to mesoscale thunderstorms and not to the circulation itself. For the record, I believe the professionals at the NHC and in the Air Force do excellent work. However, I do think that classification has become too liberal due to the improvement in detection. As scientific instrumentation has improved, the threshold for classification has become more unclear and “looser,” so to speak, than in the past.

Mesovortex-induced fluctuations in intensity are pretty common in TCs. They're usually short term but can be quite intense. AFAIK, the NHC has always considered the intensity measured within them as the TC's max intensity if they are over the center. Of the top of my head some recent examples are Gordon '18 off the SW FL coast, Bertha '20 as it moved towards the SC coast, and Sally '20 during its first bout of intensification into a hurricane.

[AlphaToOmega]

The NHC has stopped posting advisories for the Remnants of Danny. Do we lock this thread?

[AJC3]

The NHC has stopped posting advisories for the Remnants of Danny. Do we lock this thread?

Never. These threads get moved to the archives once the discussion dies off, but are never locked.

[Audrey2Katrina]

I'd bet serious money that in 1960 a storm like Bill would have been upgraded. If a ship would have made contact it probably would have found a slightly stronger storm too then the nhc's estimates. I'd bet on it.

I also suspect that the nhc in 1960 would have upgraded Danny 24 hours earlier.

Claudette would have been upgraded off the east coast.

You'd LOSE that bet! Happy 4th Everyone-- Stay safe!