Hurricane Erin

[tornado examiner]

Erin’s eye still hasn’t fully eroded away on IR

 

[wx_guy]

At 11 PM, Erin is at 20.3N and 140 mph and 937 mb

 

[Kds86z]

 

[Kds86z]

 

[tornado examiner]

Remember, the larger the eye of a hurricane, usually the more stable it is.

 

[wx_guy]

For a few hours, it was logging west-northwest like it was supposed to. The past hour, it's been moving due west again.

 

[Kds86z]

 

[tornado examiner]

What is with this EWRC taking this long? Is it actually failing somehow?

 

[notsoencrypted]

I feel like questions about EWRCs are hard to answer while the storm is happening and usually get answered when folks are able to see the whole track/system. We won't really know if it's failing or succeeding until the storm pulls together or weakens. Which isn't a very helpful answer, unfortunately.

That said, it looks like there's still plenty of convection where the new eyewall is trying to form, so it seems like it's still trying.

I'm just afraid it's converting all that intensity it had into a big, spread-out storm, which is why it's taking longer. But that's just based on my casual observations over time, not any real expertise or solid knowledge. But without land, colder water, or shear in the way, there shouldn't be too much to cause it to hiccough. Dry air, maybe? But I always struggle with telling dry air intrusion vs weirdness of EWRC.

 

[wx_guy]

What is with this EWRC taking this long? Is it actually failing somehow?

I'm not totally sure, but you're right, it is taking a long time. The radar and recon don't show a new eye wall taking over that I can tell, so it might indeed be failing.

EDIT: Also it looks to be wobbling south of west now. Again.

EDIT2: 2 AM advisory is out and Erin is now a CAT 3 at 125 mph.

 

[Kds86z]

 

[wx_guy]

The track has shifted to the west again as of the 5 AM update, and now Tropical Storm Warnings have been issued for the Turks and Caicos Islands, and Tropical Storm Watches have been issued for parts of the Bahamas.

 

[notsoencrypted]

The discussion on Erin this morning talks quite a bit about its structure and how the weakening is related to it trying to reorganize, rather than due to environmental issues. It's a really informative discussion, IMO:

Satellite and Doppler Radar data from San Juan indicate that Erin is going through some notable structural changes. The hurricane still has a small eye in radar images with a tight and closed eyewall. Beyond the small core, there are numerous convective rainbands that are expanding in all quadrants, with some indication of an outer eyewall beginning to take shape. Data from the Air Force Hurricane Hunters a few hours ago indicated that the peak winds have been decreasing, and the initial intensity is set at 110 kt using a blend of the latest satellite estimates. The outer bands to the south of the center are still affecting portions of the Virgin Islands, Puerto Rico, and the Dominican Republic. These bands are producing gusty winds and locally heavy rains. The Air Force and NOAA Hurricane Hunters are scheduled to investigate Erin again later this morning, and their data will provide a better assessment of the hurricane's intensity and structure.

Erin has been wobbling around, but it appears to be moving a little to the south of the previous track. The hurricane is still moving west-northwestward at 12 kt on the south side of a subtropical ridge. This ridge is expected to break down later today due to a series of troughs moving across the northwestern Atlantic. In response to the pattern change, Erin should gradually turn toward the north and eventually the northeast. This motion should take the core of Erin to the east of the Bahamas on Monday and then roughly midway between Bermuda and the east coast of the U.S. around the middle of the week. The NHC track forecast has been nudged to the west in the short term based on the initial motion and latest model guidance.

The quick weakening over the past 6 to 12 hours is associated with Erin's structural changes and not environmental conditions. Since the large-scale environment is expected to be favorable for about another day, re-strengthening is possible during that time period. However, it should be noted that predicting the intensity evolution from internal dynamics are challenging, and models often provide little reliability in their solutions. Beyond 24 to 36 hours, a broadening of the wind field and some increase in shear should cause a gradual decay in the peak winds. Regardless of the details, there is high confidence that Erin will remain a powerful hurricane during the next several days.

Erin is growing in size, and that trend is expected to continue over the next few days. The expanding wind field will result in rough ocean conditions over much of the western Atlantic. Given the track adjustments and increasing size, the government of the Bahamas has issued a Tropical Storm Warning for the Turks and Caicos Islands and a Tropical Storm Watch for the Southeast Bahamas.

 

[wx_guy]

Some morning analysis.


The Official track at a 5-day error is only 120 miles off currently, so we'll see if that continues. We can also see the steady WNW track now in place.





It's now outside the NHC Cone from 2 days ago to the south, which is likely why the Turks and Caicos now have tropical storm warnings.





It is hugging the south edge of the cone from yesterday morning as well. I imagine additional westward jogs are possible.





For Alert Levels, Bermuda should still be watching trends in 4 days, and on Day 5, places like the Northeast U.S. and Atlantic Canada need to watch trends as well, but not any strong chance of a direct hit.








Finally, a new graphic I've been working on. In the vein of the Alert Level, I wanted this to convey top-quality information but without all the numbers and bells and whistles. So here's what I cooked up. It uses a statistical clustering procedure to analyze and group the possible Pathways the model depicts and also shows any model outliers. The result is mostly numberless and doesn't use numeric probabilities openly and instead just conveys the message. I think this is key to public messaging.

As shown here, through 72 hours, the models are in great agreement on the path now (unlike a day or two ago). We'll see if any westward jogs are needed.