Tropical Storm Eta

[Normandy]

Eta is pounding Nicaragua.  I was sure it would be inland by now

[cptcatz]

Recon still finding impressive winds. 143 kts at 915 mb.

[JasonOH]

2 hours ago, Crocodile23 said:

This is from a post on twitter.
 

We can speculate (like I did above), but I don’t think that kid is a good source. It’s likely extreme turbulence made it unsafe, but I find it unlikely it went so far as stalling.

[cptcatz]

138 knots at surface.  That's category 5.

[JasonOH]

Based on flight level obs I think that’s just a gust. Flight level obs have never had a wind speed greater than 130kt this mission. Also, there is usually decrease in wind speed in the lowest 20mb and that isn’t the case in that sonde.  The only value that’s Cat 5 is the surface wind, nothing else. Mean wind in the lowest 150m is more useful in this case and that’s still Cat 4. 

[Orangeburgwx]

It went almost due SW on the fixes, could it miss the coast entirely?

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[eyewall]

Just now, Orangeburgwx said:

It went almost due SW on the fixes, could it miss the coast entirely?

Sent from my LML212VL using Tapatalk
 

Sure, so it turns back north and goes for Louisiana

[Moderately Unstable]

Wrt the hhunters, I agree it is good not to speculate and I'd really only buy that news from the nhc, their staff, the hunters, their staff, or a tropical met professor. I consider that report plausible but dramatized. As both a met an avgeek, I know enough about both to say that while wind shear can rocket you around, wings are built to handle 150% of their expected in-life stress load. In 1988, a mesovortex almost downed a P-3, with 200 mph winds causing a +5.8g and -3.7g stress that ripped off a propeller and brought the plane to within 1k feet of sea level. That was hurricane hugo.  Mesovortices are dangerous, the ever so slightly alarm tinged vdm they sent out stating many mesos circulating coupled with stopping outgoing data reporting and the other plane turning around do all point strongly to the safety threat. Speculation beyond that (stalling, structural integrity), are rumors and not things one can know unless explained by an official source. While I did mention stalling as a threat, they usually fly around 240 knots in the eyewall, and the nice thing with the C-130 is that it has a very low stall speed and high stability. Look at the hhunter personal Twitter pages for any comments on that. 

 

I agree with JasonOH on the probability for the surface winds to be gust driven. However it may also, itself, be due to a mesovortex. Last night and today we see low level wind fields potentially above the mid levels. This is not a typical presentation and can be due to mesovortex interaction which can raise wind speeds near the surface. Per a nasa paper https://svs.gsfc.nasa.gov/3377 , wind speeds in a mesovortex can be 10% higher than the rest of the eye. 

 

Pressures are up, wind speeds down a bit. Could be completion of an erc or erc nearing completion. Could also be that the shallow water near the coast which the eye is over has lower overall heat content and unwelling brought up slightly cooler water. Final possibility is that minimal land interaction is adversely affecting the storm. That's more likely if a secondary larger eye is taking over that may already have part of its circulation on the coast. This thing definitely made a valiant effort at cat 5, but appears it was not to be. I do wonder if the storm may have briefly attained cat 5 intensity at some point and we just didn't have the data point. Two things are now in my mind. First is how this affects Central America. 14-20 feet of storm surge. Phew. The location is south of most population centers however the flooding rain is going to hit the whole country. Some people will still also get impacted by the eyewall. Second it starting to look more at what the models are suggesting medium range, and comparing that against basic physics principles and figuring out what's likely and what's not.

 

 

[Moderately Unstable]

Also I did want to announce, user WeatherQ did win last night's contest. They predicted 931mb, 150mph winds. I didn't have the opportunity to verify the scores last night--44 members submitted entries--but wanted to officially acknowledge their win today now that the dust has settled haha. Good job!!

[Windspeed]

Last 12 hours of motion and fixes have been an absolute crawl. It may pick up westward motion but it sure is slow enough to cause some uncertainty and put down some insane rainfall totals.

[Windspeed]

That last vortex message was a little concerning. Closed eyewall at 8nm. It's over a shallow shelf, not sure if upwelling or participitable cooling could bring down shallow SSTs fast, but it leaves the door open for some possible restrengthening if it lingers too long off the coast. Might just hold its own through landfall, but we'll have to see if the satellite presentation responds and the eye can clear out. New outer band could also reinstate another ERC just as well too.

[olafminesaw]

4 minutes ago, Windspeed said:

That last vortex message was a little concerning. Closed eyewall at 8nm. It's over a shallow shelf, not sure if upwelling or participitable cooling could bring down shallow SSTs fast, but it leaves the door open for some possible restrengthening if it lingers too long off the coast. Might just hold its own through landfall, but we'll have to see if the satellite presentation responds and the eye can clear out. New outer band could also reinstate another ERC just as well too.

Looks like maybe a bit of shear though, on the south side of the circulation? May prevent the eye from organizing very fast. Motion definitely seems more south than west right now

[JasonOH]

I think the reported 8 mile eye was the decaying inner eyewall. Based on satellite imagery you can see the old eye rotating around the eyewall.

[TPAwx]

Nope.  Would be on brand for 2020 tho.

[Amped]

1 hour ago, TPAwx said:

Nope.  Would be on brand for 2020 tho.

Euro finally bringing ETA across Cuba. Took it longer than just about every other model.  It has not been great with TC tracks this year.

[Amped]

This was supposed to be inland a long time ago.  It's running around in circles offshore.

[wkd]

4 hours ago, JasonOH said:

We can speculate (like I did above), but I don’t think that kid is a good source. It’s likely extreme turbulence made it unsafe, but I find it unlikely it went so far as stalling.

He said it NEARLY stalled.

[turtlehurricane]

This reminds me of Hurricane Mitch https://en.wikipedia.org/wiki/Hurricane_Mitch

[TPAwx]

1 hour ago, Amped said:

Euro finally bringing ETA across Cuba. Took it longer than just about every other model.  It has not been great with TC tracks this year.

12z GFS has landfall in the Keys, up the spine and then out off Tampa Bay, and then landfall in the Panhandle.  OK

[PSLwx]

19 minutes ago, TPAwx said:

12z GFS has landfall in the Keys, up the spine and then out off Tampa Bay, and then landfall in the Panhandle.  OK

This is so #2020.

[olafminesaw]

Is it possible that the reason Eta was weaker than satellite suggested because of how far south it is? I don't know much about the physics of hurricanes, but I ask because I was wondering if the coriolis effect only played a role in development or also in maintaining intensity

[Amped]

Just now, TPAwx said:

12z GFS has landfall in the Keys, up the spine and then out off Tampa Bay, and then landfall in the Panhandle.  OK

Anything but yesterdays 12z euro which had it ducking under the troff.    That was a practically impossible stunt.

[JasonOH]

2 hours ago, wkd said:

He said it NEARLY stalled.

I even find that unlikely.  I don’t think that dude is a good source at all. If that was the case I would have heard about it by now.

[olafminesaw]

Oof. Still stalled out too

 

[Derecho!]

42 minutes ago, olafminesaw said:

Is it possible that the reason Eta was weaker than satellite suggested because of how far south it is? I don't know much about the physics of hurricanes, but I ask because I was wondering if the coriolis effect only played a role in development or also in maintaining intensity

No, not at all. In other basins extremely powerful tropical cyclones occur closer to the equator than Eta. Haiyan was 4 degrees closer to the equator than Eta, for example. 

And even the development thing is a myth - the Atlantic is the oddball basin in having so little development close to the equator - and that's because the ITCZ is so far north in the Atlantic during tropical season  not a  "lack of Coriolis." 

[Amped]

3 minutes ago, olafminesaw said:

Oof. Still stalled out too

 

It's been making more progress west the past few hours.   It stalled just long enough to bust my prediction that the new eyewall would not have a chance to takeover. 

[wxmx]

Just now, Amped said:

It's been making more progress west the past few hours.   It stalled just long enough to bust my prediction that the new eyewall would not have a chance to takeover. 

It's even gaining some latitude in the short term, that enhances the probability of Puerto Cabezas/Bilwi being in the northern eyewall, plus the highest surge.

[Windspeed]

Definitely an improving satellite presentation before landfall.

[the ghost of leroy]

11 minutes ago, Windspeed said:

Definitely an improving satellite presentation before landfall.

What’s the raw T?

[JasonOH]

10 minutes ago, the ghost of leroy said:

What’s the raw T?

5.1