ATL: DANNY - Remnants - Discussion

[ronjon]

May be close to hurricane as others have mentioned. Need a plane in there to confirm. Looks to be turning to the W-NW now.

[AJC3]

Yesterday I mentioned that Ryan Maue posted what I thought was an insightful tweet about the SAL likely causing the convection in Danny to collapse precipitously.

https://twitter.com/RyanMaue/status/634105591678566400

"Ryan Maue ‏@RyanMaue 14h14 hours ago NASA GEOS-5 dust extinction shows TS #Danny eaten by Saharan Air Layer (SAL). Soon more favorable conditions"

Well, it appears to me that this is coming to fruition. Both the CIMSS SAL as well as this morning's visible imagery (visible haze bounded by yellow) bear this out. It appears the westward thrust of the SAL is far outpacing Danny's slower forward speed. So it seems being pokey paid off for Danny in the short term.

http://tropic.ssec.wisc.edu/real-time/s ... litE5.html

[AJC3]

Wasn't this supposed to be a 2 by now? It isn't even a 1 yet.

No. Forecast from Advisory 1.

INIT 18/1500Z 10.6N 36.5W 30 KT 35 MPH
12H 19/0000Z 11.0N 37.9W 35 KT 40 MPH
24H 19/1200Z 11.3N 39.5W 40 KT 45 MPH
36H 20/0000Z 11.6N 40.9W 50 KT 60 MPH
48H 20/1200Z 12.1N 41.9W 60 KT 70 MPH
72H 21/1200Z 13.2N 44.2W 70 KT 80 MPH
96H 22/1200Z 13.7N 47.8W 80 KT 90 MPH
120H 23/1200Z 14.0N 52.4W 85 KT 100 MPH

edit: OK, it looks like there was one forecast for Danny to reach 65kt by 8 AM today and another to reach 70kt (below). Low end Cat 1, My bad.

INIT 19/0300Z 11.2N 38.8W 45 KT 50 MPH
12H 19/1200Z 11.6N 40.2W 55 KT 65 MPH
24H 20/0000Z 11.9N 41.7W 60 KT 70 MPH
36H 20/1200Z 12.3N 42.9W 70 KT 80 MPH
48H 21/0000Z 12.8N 44.1W 75 KT 85 MPH
72H 22/0000Z 13.5N 47.5W 85 KT 100 MPH
96H 23/0000Z 14.5N 51.5W 90 KT 105 MPH
120H 24/0000Z 15.0N 56.5W 85 KT 100 MPH

[Dean4Storms]

Despite the paucity of convection, Danny maintains a small, tightly wound core. Still, it's a tiny system and as such will be very susceptible to intrusions of dry air in the short term, and a combination of dry air plus shear down the road.

I've always understood that smaller size storms have less of the wind field pulling in the dry air and thus able to travel through the dry air less impeded as large storms that pull in air from much greater distances.

[tailgater]

I was thinking that maybe it's best chance to survive the next couple days is to remain small and compact. We saw what happened when it was larger it started pulling in more dry air. Pro mets please weigh in.

Here is a loop that shows MID level moisture.
http://tropic.ssec.wisc.edu/real-time/s ... vmid5.html

Dean beat me to it.

[SouthDadeFish]

Since Danny is so small, it might only take one intrusion of dry air to completely collapse inner core convection. This is quite an interesting storm and a terribly challenging intensity forecast.

[AJC3]

Despite the paucity of convection, Danny maintains a small, tightly wound core. Still, it's a tiny system and as such will be very susceptible to intrusions of dry air in the short term, and a combination of dry air plus shear down the road.

I've always understood that smaller size storms have less of the wind field pulling in the dry air and thus able to travel through the dry air less impeded as large storms that pull in air from much greater distances.

I think we saw 24 hours ago that wasn't necessarily the case. As long as there s a substantial envelope of dry air around a system, a smaller one would likely wind down more quickly. What Danny had going for it is that it was still attached to the ITCZ and wasn't fully involved with the SAL.

[SouthDadeFish]

Also, Danny appears to be gaining some latitude this morning, moving away from the ITCZ.

[tailgater]

24 hr. MIMIC of Danny tightening up at the end. Tiny little storm.

http://tropic.ssec.wisc.edu/real-time/m ... splay.html

[AJC3]

0942 UTC M/I pass....

[northjaxpro]

It sure looks to me that an eyewall is trying to form in that image. What a tiny, but well formed inner core Danny has right now.

[USTropics]

A few shots of the first visible imagery of the day:

[Gustywind]

Latest from SSD...


DATE/TIME LAT LON CLASSIFICATION STORM
20/1145 UTC 12.4N 44.2W T3.0/3.0 DANNY
20/0545 UTC 12.0N 43.1W T2.5/3.0 DANNY
19/2345 UTC 11.9N 42.3W T3.0/3.0 DANNY
19/1745 UTC 11.6N 41.4W T2.5/2.5 DANNY
19/1145 UTC 11.0N 40.6W T2.5/2.5 DANNY
19/0545 UTC 11.3N 39.2W T2.5/2.5 DANNY
18/2345 UTC 11.0N 38.3W T2.5/2.5 DANNY
18/1745 UTC 11.1N 37.0W T2.0/2.0 04L
18/1145 UTC 10.2N 35.9W T2.0/2.0 96L
18/0545 UTC 9.5N 34.4W T1.5/1.5 96L
18/0000 UTC 9.3N 33.2W T1.0/1.0 96L
17/1745 UTC 9.8N 32.8W T1.0/1.0 96L
17/1145 UTC 9.6N 31.0W T1.0/1.0 96L
17/0545 UTC 9.8N 29.9W T1.0/1.0 96L

[Alyono]

3.0 when there is an eye? really?

[Gustywind]

Tropical Storm Danny Better Organized, May Become a Hurricane Later This Week; Potential Threat to Lesser Antilles Next Week
Published Aug 20 2015 08:13 AM EDT

weather.com
http://www.weather.com/storms/hurricane ... antic-2015

•Tropical Storm Danny was located about 1,200 miles east of the Windward Islands in the eastern Atlantic Ocean as of 5 a.m. EDT Thursday.
•Maximum sustained winds remained at 50 mph with higher gusts.
•The tropical storm is forecast to gradually strengthen as it moves west-northwest over the next several days. Danny is forecast to become a hurricane later this week.
•It will be until early next week before Danny reaches the longitude of the Lesser Antilles.
•Danny is expected to weaken in the eastern Caribbean Sea.

Tropical Storm Danny continues to spin and hold its own, well to the east of the Lesser Antilles in the central Atlantic Ocean.

Microwave satellite imagery indicates Danny's convection looks to be more solidly organized around its center of circulation Thursday morning than it was Wednesday, notes hurricane specialist, Michael Lowry.

Small circulations such as Danny are prone to sudden changes in intensity, and this may be a sign Danny is finally on its long-anticipated strengthening.

Dry air will be a continual challenge to Danny over the next several days, as water vapor imagery indicates an ample reservoir of dry air north of Danny extending westward into the Caribbean Sea.

Dry air hampers tropical cyclones by encouraging the development of stronger thunderstorm downdrafts, which then either squelch nearby thunderstorms from forming or push them away.

This dry air is also stable, meaning it suppresses upward vertical columns of air needed to maintain or form new thunderstorms.

Wind shear, namely, the change in wind speed with height either in speed and/or direction, can blow convection away from the center from a tropical cyclone. If strong enough, this can rip apart existing tropical cyclones.

Despite what had been a rather hostile atmosphere featuring record mid-July through mid-August Caribbean wind shear, Danny will remain far enough south over the next couple of days to remain in an environment of rather light wind shear.

So, assuming the atmosphere immediately surrounding Danny remains somewhat moist, Danny is forecast to strengthen to the first hurricane of the 2015 Atlantic hurricane season possibly as soon as Friday night or Saturday.

Danny will move generally toward the west-northwest the next several days. Computer model forecast guidance shows that it may not reach the longitude near the eastern Caribbean Sea (about 61 degrees West longitude) until Monday.

result, we have plenty of time to monitor its progress.

Given the aforementioned dry air and wind shear in place over the eastern Caribbean Sea, it's possible that this system will be weakening once it reaches the vicinity of the Lesser Antilles.

In summary, it's far too early to know if this system will bring any significant impacts to those islands in the long-term future. Interests in the Lesser Antilles, the Virgin Islands and Puerto Rico should monitor the progress of Danny.

Stay tuned to The Weather Channel and check back with weather.com for updates on this system.

[TheStormExpert]

Possible Eye peeking out?

[Gustywind]

Michael Lowry ‏@MichaelRLowry ·

Hurricane Specialist @WeatherChannel. Formerly Nat'l Hurricane Center, Florida DEM, Dept of Defense.

New SSMIS pass showing deep convection in organizing eyewall around a very small #Danny

https://twitter.com/MichaelRLowry

[Siker]

Up to 60kts:

AL, 04, 2015082012, , BEST, 0, 123N, 444W, 60, 992, TS

[abajan]

Up to 60kts:

AL, 04, 2015082012, , BEST, 0, 123N, 444W, 60, DANNY

Not surprising, considering the appearance of what certainly looks like an eye in the last frame of the visible loop posted by TheStormExpert a couple posts earlier. Interesting days ahead.

[Gustywind]

Up to 60kts:

AL, 04, 2015082012, , BEST, 0, 123N, 444W, 60, DANNY

Not surprising, considering the appearance of what certainly looks like an eye in the last frame of the visible loop posted by TheStormExpert a couple posts earlier. Interesting days ahead.

Agree Abajan, and us in the EC should continue to monitor closely the situation.