ATL: DORIAN - Post-Tropical - Discussion

[DioBrando]

Not NHC as they didn't release a map JUST YET but you might get a ROUGH idea from this app. SO TAKE THIS WITH A GRAIN OF SALT.

[NDG]

They forecast 75 kt in the Caribbean? Skeptical of that

Why? it wont have any issues with flow since it is already an established system. only thing is shear.. and thats always iffy.

I don't see a problem with shear down the road and as long as it stays in a low latitude not much problem with the dry mid levels to the north.

[DioBrando]

Edit: the NHC did now upload a lil map. Forecast to become (Dorian?) tomorrow.

[Kazmit]

They forecast 75 kt in the Caribbean? Skeptical of that

I was surprised to see that too. Especially since they tend to be conservative.

[NDG]

Just 24 hours ago it only had a 20% chance of developing lol, like I said yesterday the Euro let the NHC down with this one.

[cycloneye]

Tropical Depression Five Discussion Number 1
NWS National Hurricane Center Miami FL AL052019
1100 AM AST Sat Aug 24 2019

The small low pressure system that the NHC has been tracking the
past several days across the tropical Atlantic Ocean has acquired
enough deep convection to be classified as a tropical depression,
the fifth tropical cyclone of the 2019 hurricane season. Two ASCAT
passes between 1200-1300Z this morning indicated that the system
had a closed circulation and surface winds of at least 30 kt, and
that is the intensity set for this advisory. Upper-level outflow
is fair to the northwest and restricted to the southeast due to
moderate easterly vertical wind shear.

The initial motion estimate is 280/10 kt. The NHC model guidance is
in very good agreement that the cyclone will move in a general
west-northwestward direction along the southern periphery of a
deep-layer ridge for the next 5 days, bring the system through the
central or northern Lesser Antilles on Tuesday, and into the
northeastern Caribbean Sea on Wednesday and Thursday. The official
forecast track is close to the consensus model TVCN, which is a
little north of the NOAA HCCA corrected-consensus model.

The small cyclone is currently experiencing easterly to
southeasterly shear of about 15 kt. The shear is forecast to
steadily decrease over the next 24 h and be around 5 kt in the
24-to-72-hour time period. Although the depression is expected to
remain embedded in a fairly dry mid-level environment, the small
overall circulation, small radius of maximum winds, low shear
regime, and warm SSTs of 28.0-28.5 deg C should allow for slow but
steady intensification through the 5-day period despite occasional
intrusions of dry air. The NHC intensity forecast is a blend of the
statistical-dynamical SHIPS and LGEM models, and the more robust
HWRF model.

FORECAST POSITIONS AND MAX WINDS

INIT 24/1500Z 10.4N 47.9W 30 KT 35 MPH
12H 25/0000Z 10.7N 49.4W 30 KT 35 MPH
24H 25/1200Z 11.0N 51.4W 35 KT 40 MPH
36H 26/0000Z 11.4N 53.5W 40 KT 45 MPH
48H 26/1200Z 12.0N 55.5W 45 KT 50 MPH
72H 27/1200Z 13.6N 59.3W 55 KT 65 MPH
96H 28/1200Z 15.2N 63.1W 65 KT 75 MPH
120H 29/1200Z 17.1N 66.7W 75 KT 85 MPH

$$
Forecaster Stewart

[Aric Dunn]

Tropical Depression Five Discussion Number 1
NWS National Hurricane Center Miami FL AL052019
1100 AM AST Sat Aug 24 2019

The small low pressure system that the NHC has been tracking the
past several days across the tropical Atlantic Ocean has acquired
enough deep convection to be classified as a tropical depression,
the fifth tropical cyclone of the 2019 hurricane season. Two ASCAT
passes between 1200-1300Z this morning indicated that the system
had a closed circulation and surface winds of at least 30 kt, and
that is the intensity set for this advisory. Upper-level outflow
is fair to the northwest and restricted to the southeast due to
moderate easterly vertical wind shear.

The initial motion estimate is 280/10 kt. The NHC model guidance is
in very good agreement that the cyclone will move in a general
west-northwestward direction along the southern periphery of a
deep-layer ridge for the next 5 days, bring the system through the
central or northern Lesser Antilles on Tuesday, and into the
northeastern Caribbean Sea on Wednesday and Thursday. The official
forecast track is close to the consensus model TVCN, which is a
little north of the NOAA HCCA corrected-consensus model.

The small cyclone is currently experiencing easterly to
southeasterly shear of about 15 kt. The shear is forecast to
steadily decrease over the next 24 h and be around 5 kt in the
24-to-72-hour time period. Although the depression is expected to
remain embedded in a fairly dry mid-level environment, the small
overall circulation, small radius of maximum winds, low shear
regime, and warm SSTs of 28.0-28.5 deg C should allow for slow but
steady intensification through the 5-day period despite occasional
intrusions of dry air. The NHC intensity forecast is a blend of the
statistical-dynamical SHIPS and LGEM models, and the more robust
HWRF model.

FORECAST POSITIONS AND MAX WINDS

INIT 24/1500Z 10.4N 47.9W 30 KT 35 MPH
12H 25/0000Z 10.7N 49.4W 30 KT 35 MPH
24H 25/1200Z 11.0N 51.4W 35 KT 40 MPH
36H 26/0000Z 11.4N 53.5W 40 KT 45 MPH
48H 26/1200Z 12.0N 55.5W 45 KT 50 MPH
72H 27/1200Z 13.6N 59.3W 55 KT 65 MPH
96H 28/1200Z 15.2N 63.1W 65 KT 75 MPH
120H 29/1200Z 17.1N 66.7W 75 KT 85 MPH

$$
Forecaster Stewart

Luckily Stewart was on shift this morning lol

[Hypercane_Kyle]

I do have some doubts about that NHC forecast verifying. I don't think the intensity models are really taking into account its size and how much dry air/wind shear TD5 will be facing.

[northjaxpro]

Will it avoid the shredder aka Hispaniola? That is always the BIG BIG ? about potential big tropical cyclones threatnening the Caribbean. We will find out in a few days in subsquent model runs.

[wxman57]

I would forecast it to be dissipating in the NE Caribbean, not a hurricane. Using HWRF for intensity guidance????

East Caribbean looks quite hostile this week:

[Aric Dunn]

I would forecast it to be dissipating in the NE Caribbean, not a hurricane. Using HWRF for intensity guidance????

East Caribbean looks quite hostile this week:
https://www.tropicaltidbits.com/analysis/models/gfs/2019082406/gfs_shear_watl_20.png

probably because that TUTT is moving west with it..... 06z gfs has it moving less west then previous runs.....

[wxman57]

Well, we're forecasting it to dissipate in the NE Caribbean, not intensify. Looks like I'm working today...

[psyclone]

I'm definitely surprised at the NHC's aggressive intensity forecast. It seems like the first forecast on a system is subject to big changes (at least that's been my past impression) so future projections will be interesting. maybe the system will have a better shot if it can escape to areas north of the greater Antilles. No matter what becomes of this one...we probably won't need to wait too long for something else. We're in the hot zone now and if this season is going to do something...it's time to dance..

[SoupBone]

Well, we're forecasting it to dissipate in the NE Caribbean, not intensify. Looks like I'm working today...

Mother Nature will not be denied.

[PTrackerLA]

The forecast caught me by surprise as well, given the most bullish model (GFS) has backed off intensity the last few runs. Interesting times ahead...

[USTropics]

Intensity has always been the most difficult aspect to forecast. Just a personal observation, but due to the likely impact on the islands, it's best to use the upper spectrum of the intensity forecast blend and gradually decrease if models continue to show a weaker system. Also, while the GFS was able to forecast genesis consistently, the models haven't been great past 96 hours (including with the position of upper-level features).

[Frank2]

My guess the NHC wants to err on the side of caution especially for the islands, small and large, since the track brings it across many of them. P.S. The 12Z GFS is running now, though the 6Z run had it heading directly for the Carolinas (not via Florida) as a weak system...

It's still early...

[abajan]

I'm definitely surprised at the NHC's aggressive intensity forecast. It seems like the first forecast on a system is subject to big changes (at least that's been my past impression) so future projections will be interesting. maybe the system will have a better shot if it can escape to areas north of the greater Antilles. No matter what becomes of this one...we probably won't need to wait too long for something else. We're in the hot zone now and if this season is going to do something...it's time to dance..

Yep. There's even something near Texas now. Won't likely amount to anything. But still ...

[wxman57]

My guess the NHC wants to err on the side of caution especially for the islands, small and large, since the track brings it across many of them. P.S. The 12Z GFS is running now, though the 6Z run had it heading directly for the Carolinas (not via Florida) as a weak system...

It's still early...

Everything I'm looking at says dissipation as it enters the Caribbean. Stewart is generally very aggressive on upgrading systems and with intensification. I would never trust the HWRF for anything. It just hasn't proven to be very reliable. Still forecasting it to dissipate once it crosses into the Caribbean. I think you'll see future NHC forecasts inching the intensity forecast downward.

[AtlanticWind]

Seems like a tough intensity forecast. The global models all weaken TD 5 as it enters the carribean and that's
hard to discount. On the other hand ships and Hwrf are more aggressive . On top of that small systems
are more sensitive to small variations in the environment.