ATL: DORIAN - Post-Tropical - Discussion

[beoumont]

Classic spiral banding, reminds me of Hurricane Hugo but obviously not the same intensity.

Hugo Images:

[tolakram]

16:45Z

[Dean4Storms]

Yeah, Dorian is going to keep us up late a many of nights coming up that's for sure. The weakness is strong enough on those latest 12Z runs to enable Dorian to curve and just miss the U.S. East Coast. But, this is still a long way out and I am certain there will be several other changes with the models with time. Definitely must pay close attenion the next 7-10 days with my obvious understaement!

If that weakness fails to develop, it keeps going west?

If the ridge builds back in stronger, then Dorian will head more west, and possibly be a threat to the Bahamas, Florida, and maybe the EGOM. It is going to be a close call as there will be a trough developing cross the Eastern CONUS going into this weekend. However, if the trough lifts out early next week and the ridge builds back in, then all of us really will have to really pay attention. It is all about timing as always with forecasting the track of tropical cyclones.

Just have to watch closely. More changes I am certain are going to come in the coming days from the models.

It's actually another trough swinging barely into the upper Great Lakes and southern Canada down to just barely the Southern Appalachians that creates the weakness in the 12z GFS run come the 2nd of Aug.

Going to be interesting!

[Blown Away]

12z GFS run was much slower than previous runs, maybe giving the trough more time break down ridge and allow recurve...12z thinks it will take 10 days from now for Dorian to be in NW Bahamas.

[gatorcane]

12Z GEM 168 hour position:

[artist]

Classic spiral banding, reminds me of Hurricane Hugo but obviously not the same intensity.

Hugo Images:

the one on the left looks like a whale with his mouth open or a smile on his face.

Hopefully this thing doesn't continue at the rate it seems to have this morning.

[beoumont]

Hopefully this thing doesn't continue at the rate it seems to have this morning.

I believe the picture on the bottom right is just after Hugo's central pressure fell 55 mb. in a 24 hour period. Cat. 5 !!

[Blown Away]

@200 hours seems to be the time when Dorian feels the weakness and turns NW. The models seem to keep Dorian under the ridge on a WNW path until the 190-200 hour range, so it will depend on forward speed...12z GFS slowed down Dorian and that's why the recurve well east of SE CONUS. JMHO

[tolakram]

Looks to me like more ensemble members want it to recurve sooner, rather than later.

hour 204 spread

[GCANE]

Anti-cyclone has now shifted to the east of the LLC.

Dorian is tracking away from it.

Intensification may start to level off or at least slow down.

Still clear on 200mb PV, so nothing really to weaken it however.

[TheStormExpert]

Yeah, Dorian is going to keep us up late a many of nights coming up that's for sure. The weakness is strong enough on those latest 12Z runs to enable Dorian to curve and just miss the U.S. East Coast. But, this is still a long way out and I am certain there will be several other changes with the models with time. Definitely must pay close attenion the next 7-10 days with my obvious understatement!

Does the overall pattern look similar to the pattern of the last 3 seasons?

[TheStormExpert]

12z GFS run was much slower than previous runs, maybe giving the trough more time break down ridge and allow recurve...12z thinks it will take 10 days from now for Dorian to be in NW Bahamas.

Yeah it really slowed down just north of the NE Caribbean islands. Something I noticed right away that looked different from previous runs.

[Blown Away]

NHC 120 hour position...


12z GFS 120 hour position...

NHC position is about 350 West

[Gustywind]

Dr. Jeff Masters latest on TS Dorian.


Tropical Storm Dorian Forms

http://www.wunderground.com/blog/JeffMa ... rynum=2471

The season's fourth named storm, Tropical Storm Dorian, is here. Born from a strong tropical wave that moved off the coast of Africa on Monday, Dorian formed unusually far east for so early in the season, at longitude 29.9°W. Only Hurricane Bertha of 2008, which became a tropical storm at 22.9°W longitude on July 3, formed farther to the east so early in the year. Satellite images show that Dorian is a small but well-organized system with a moderate amount of heavy thunderstorms. A large area of dry air lies to Dorian's west, as seen on water vapor satellite images, but Dorian has moistened its environment enough that this dry air should not interfere with development for the next day. Dorian is under a low 5 - 10 knots of wind shear, which will tend to allow slow development. Ocean temperatures are barely adequate for maintaining strength of a tropical storm, about 26.5°C.

Forecast for Dorian
The SHIPS model predicts that wind shear will stay in the low range through Thursday, then rise to the moderate range Friday through Monday. Ocean temperatures will fall to 25 - 26°C Wednesday night through Thursday night, which may induce some weakening of Dorian. Thereafter, ocean temperatures will rise again, but wind shear will rise. This increase in wind shear will be capable of causing weakening, since there will still be a large area of dry air to Dorian's west that the shear may be able to bring into Dorian's core. Given its small size, Dorian is capable of relatively large changes in intensity in a short amount of time, and it would not surprise me if the storm dissipated by the end of the week--or became a Category 1 hurricane. However, the official NHC forecast of a tropical storm passing just north of the Lesser Antilles on Sunday is the most likely outcome; the 11 am wind probability forecast from NHC gave Dorian a 6% chance of being a hurricane at that time. Dorian should maintain a west-northwest track through the week, and spread heavy rains and gusty winds to the northern Lesser Antilles Islands beginning on Sunday. The usually reliable European model (ECMWF) has Dorian passing several hundred miles to the north of the Lesser Antilles Islands, while the other models show Dorian passing closer, within 100 miles. It currently appears that Dorian will be a potential threat to the Bahama Islands, Bermuda, and the U.S. East Coast next week. There will be a trough of low pressure capable of recurving Dorian out to sea before the storm reaches the Bahamas and U.S., but this trough is currently depicted as being fairly weak, reducing the chances of Dorian missing the Bahamas and U.S. East Coast.

[Hurricaneman]

The GFS tends to be a little on the slow side compared to other models especially the Euro but based on what I'm seeing with the ridge and stuff the GFS is too slow

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[TheStormExpert]

I buy the NHC's position over the 12z GFS right now.

[hurricaneCW]

It's a close call and the western Atlantic ridge has verified stronger than modeled so far this season so that's interesting.

You would thing this would recurve fairly quickly given how far north it is already but with more subtropical ridging thus far, I wouldn't be surprised if it made it all the way west.

[TheStormExpert]

Just goes to show you how easily these environmental impacts can change the intensity of such small storms rather quickly.

[blazess556]

Through 36 hrs, 12z ECMWF is much more defined at 500mb with Dorian compared to 00z run.

[Gustywind]

2 PM TWD.

...SPECIAL FEATURE...

TROPICAL STORM DORIAN IS LOCATED NEAR 14.3N 29.9W ABOUT 356 NM
WSW OF THE CAPE VERDE ISLANDS ON 24/1500 UTC. ITS PRESENT
MOVEMENT IS WNW AT 18 KT WITH MAXIMUM SUSTAINED WINDS OF 45 KT
GUSTING TO 55 KT. MINIMUM CENTRAL PRESSURE IS 1002 MB. SOME
SLIGHT STRENGTHENING IS POSSIBLE TODAY...FOLLOWED BY GRADUAL
WEAKENING ON THURSDAY AS DORIAN MOVES OVER COOLER WATER.
SCATTERED MODERATE CONVECTION IS FROM 13N-16N BETWEEN 28W-31W.