ATL: ZETA - Post-Tropical - Discussion

[underthwx]

Zeta moving NNE at 31 mph....does a cyclone moving that fast once inland, have some higher wind gusts as a result of a fast forward motion?...

[Steve]

Word Patrick. You already know it’s not real windy here except in the winter or during thunderstorms. This went a good 45 minutes (rain for about 3 hours) or so then we had the eye for maybe 20 minutes then the other side for maybe 15 minutes. It’s still the other side but just low clouds feeding in from the west and maybe 10mph.

[CrazyC83]

Zeta moving NNE at 31 mph....does a cyclone moving that fast once inland, have some higher wind gusts as a result of a fast forward motion?...

Yes on the right (in this case south/east) side of the storm.

[underthwx]

Zeta moving NNE at 31 mph....does a cyclone moving that fast once inland, have some higher wind gusts as a result of a fast forward motion?...

Yes on the right (in this case south/east) side of the storm.

Thankyou for your reply CrazyC83...

[wx98]

That was fun. I heard about 20 transformers explode and power is out around us but not on my block. I rode the eyewall on my back steps which face west and then the backside on my front porch when the SW/W winds kicked in. Backside had some higher gusts, but the frontside had the rain and sustained winds. Lots of small limbs are down, and we have about 9 roof shingles in the yard. All of my siblings (Lockport, Mandeville, west Metairie and Mid-City are all without power. My daughter in Metairie lost it too. I just chilled back and marveled at everything, and I’m happy about that. It never got terrible, but it was for sure tropical storm level. As others have said, it was orange in the eye. I saw a flock of egrets and then some ducks and other birds flying around in it. Zeta was a trip because it was serious but not so extreme that it made anyone panic here. Turned out to easily be the best storm of the 6 or 7 we got rain from and certainly the most exciting (for me) of the 6 we were in the cone for. Final thought is that not all baby boomers are climate denying idiots. Y’all can’t forget that we invented science.

That was a novel experience, even over here. Something different about that one, maybe because it was so quick moving. Montgomery, Atlanta, you're on the clock.

Just from observing and not being in the path, it seems like it went by too fast. It was just coming off the Yucatán and now it’s in Alabama. Usually a Cat 2/3 will bring large scale evacs but I don’t even think there was time to think about any.

[CrazyC83]

I'll do a full best track tomorrow, but here are my thoughts on the peak intensity of Zeta.

* Surface observations were quite significant. There were unofficial reports of sustained winds over 100 mph in southern Lafourche Parish and a gust to 136 mph. The strongest winds would have been over Grand Isle and into Plaquemines Parish where there were no observations. Even in southern Mississippi, sustained winds were well into hurricane territory. (New Orleans, where the eye went through, had relatively modest winds in comparison - likely a low-end category 1 or a strong tropical storm impact. That was because of the fast motion moving the strongest winds east.) All that data suggests winds of at least 90 kt.

* The highest flight-level winds were 119 kt, which would ordinarily support winds of 107 kt at the surface using a 90% reduction factor. Using an 80% reduction factor to account for the nearby trough interaction, however, would result in winds of 95 kt at the surface.

* The highest SFMR reading was 106 kt, but it was flagged and in very shallow water with shoaling issues. I would disregard all SFMR readings near landfall, or at least weigh them a lot less.

* The highest radar velocities were around 126 kt at 10,000 feet around the time of landfall. Using the same caveats as the flight-level winds would translate to winds of 101 kt at the surface.

* The minimum pressure at landfall I estimate was 967 mb, based on a combination of dropsondes (often misplaced, one would translate to 964 mb while the lowest eye drop was 970 mb), inland pressure observations (971 mb in New Orleans) and extrapolated pressures (about 967 mb). Based on that, using the KZC that would translate to about 95 kt when considering the fast motion I believe.

* The satellite signature was fast improving at landfall. From what I could see it was a T5.5 which would equate to 102 kt.

* Conclusion: I believe the landfall intensity was 95 kt, which was the operational intensity. It was difficult to decide between 95 kt and 100 kt. However, I'm not fully convinced that 100 kt would be accurate since the radar may have been transient. The 106 kt SFMR reading could be a deciding point except it was literally at the edge of the marsh. A case could be made for a category 3 landfall, but it is not convincing enough for me.

[Willow333]

Hope I'm doing this correctly. My first post, been reading for years. I would like to thank ya'll for the information you share. We are still cleaning up from Sally and now this. My son just hooked my generator up, purchased a month ago due to Sally. Just know ya'll help many people out here. Thank you.

[EquusStorm]

Off the surface this hasn't weakened one bit. Just insane levels of trough interaction. Some of this could make it down in gusts... one of the nastiest inland wind events in recent memory across AL

[SconnieCane]

Satellite presentation on approach actually looked a lot like that of Michael, albeit with the deepest convection not fully wrapped around the eye. Absolutely perfect trough interaction (in terms of enhancing the TC) yet again; the only saving grace was the comparatively reduced SSTs in the NGOM vs. two years ago.

[EquusStorm]

Mesonet site in Grove Hill just reported a gust to 80 as wind shifted from SE to SSW; still packing hurricane force gusts even at the surface. Solid 130mph still at ~12kft from KMOB.

[us89]

It is dead calm in Atlanta right now. Plenty wet and humid, and a couple weaker showers and rainbands have started making their way through this evening, but as of now there is no wind at all. Zero.

Especially eerie when I look at the radar and see Alabama getting slammed, knowing that's going to be us in a few hours.

[ScottNAtlanta]

I just came in from outside and the breeze is starting to pick up. It is insane how humid it is outside (even by Atlanta standards). Its been showery on and off but looking at the radar we should be getting steady rain here soon. It is starting to look like we will be on the SE side of this where the winds are highest.

[EquusStorm]

HWRF very correct on the strength of the mid-level part of this thing racing across AL. Wind core nearly halfway across and still showing 130+ at beam height

[ElectricStorm]

Down to TS

...ZETA WEAKENS TO A TROPICAL STORM OVER CENTRAL ALABAMA...
...STRONG WINDS CONTINUE ACROSS PORTIONS OF ALABAMA AND THE FLORIDA
PANHANDLE


SUMMARY OF 100 AM CDT...0600 UTC...INFORMATION
----------------------------------------------
LOCATION...32.9N 87.4W
ABOUT 25 MI...40 KM SSE OF TUSCALOOSA ALABAMA
MAXIMUM SUSTAINED WINDS...70 MPH...110 KM/H
PRESENT MOVEMENT...NE OR 40 DEGREES AT 31 MPH...50 KM/H
MINIMUM CENTRAL PRESSURE...985 MB...29.09 INCHES

[Shell Mound]

 https://twitter.com/pppapin/status/1321641073677115394



 https://twitter.com/webberweather/status/1321630714408873984



 https://twitter.com/DylanFedericoWX/status/1321600127656669184



 https://twitter.com/burgwx/status/1321660525370105857



 https://twitter.com/burgwx/status/1321563748818178055

[LarryWx]

Conditions now deteriorating on westside of Atlanta area from what I'm reading and from looking at a sudden increase in outages.

[kevin]

The term 'baroclinic forcing' has been mentioned a lot in this thread with regards to Zeta's strengthening close to landfall. But unfortunately I couldn't really find a good explanation online of what it is and why it can result in RI near landfall. Could anyone explain this phenomena to me?

[SouthernBreeze]

The term 'baroclinic forcing' has been mentioned a lot in this thread with regards to Zeta's strengthening close to landfall. But unfortunately I couldn't really find a good explanation online of what it is and why it can result in RI near landfall. Could anyone explain this phenomena to me?

Until someone more knowledgeable replies with details, I just know that it's the mixing of the cold front with the warmer tropical system. I've been through it here on SC coast with past Oct storms. This interaction can definitely spin up some nasty gusts, that seem way higher than the overall storm itself

[Buck]

Winds howling in Acworth, GA right now. Power has flickered but not gone out yet.

[jlauderdal]

Heavy rains and wind going in lake toxaway,nc..300,000 without power in Atlanta and we are downstream from that