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Tropical Tropical Storm Bret

Model run down (as of 6z) for 92L... As is often the case w/ small tropical cyclones (for ex Danny (2015)), there's an unusually large amount of non-linearity and inherent instability amongst various NWP and potential solutions, and thus it's not going to take much for 92L to intensify into a bonafide "vortcane" or remain an open tropical wave once it reaches the southern Antilles on Tuesday.

HWRF: 80 KT category 1 hurricane
hwrf_mslp_wind_92L_25.png


GFDL: 60 KT Tropical Storm
gfdl_mslp_wind_92L_12.png


GFS Operational: 60 KT Tropical Storm
gfs_mslp_wind_92L_13.png

GFS Parallel: 50 KT Tropical Storm
gfsp_mslp_wind_watl_12.png


ECMWF: 45 KT Tropical Wave axis
ecmwf_mslp_uv850_watl_4.png

CMC: 35 KT Tropical Wave Axis
gem_mslp_uv850_watl_11.png
 
Model run down (as of 6z) for 92L... As is often the case w/ small tropical cyclones (for ex Danny (2015)), there's an unusually large amount of non-linearity and inherent instability amongst various NWP and potential solutions, and thus it's not going to take much for 92L to intensify into a bonafide "vortcane" or remain an open tropical wave once it reaches the southern Antilles on Tuesday.

HWRF: 80 KT category 1 hurricane
View attachment 600


GFDL: 60 KT Tropical Storm
View attachment 601


GFS Operational: 60 KT Tropical Storm
View attachment 602

GFS Parallel: 50 KT Tropical Storm
View attachment 603


ECMWF: 45 KT Tropical Wave axis
View attachment 604

CMC: 35 KT Tropical Wave Axis
View attachment 605
Lot of uncertainty yet, but well deserves close watching ... ;)

Thanks for the update, Webb!
 
NHC Update:
A tropical wave located about 1300 miles east-southeast of the
southern Windward Islands is producing disorganized cloudiness and
showers. Some development of this system is possible during the
next few days before environmental conditions become less favorable
for tropical cyclone formation. This system is forecast to move
to the west or west-northwest at 15 to 20 mph toward the Windward
Islands and northeastern South America during the next several days.
* Formation chance through 48 hours...medium...40 percent.
* Formation chance through 5 days...medium...60 percent.
 
92L is finally showing signs of organization, with a marked increase in convection over the northern semicircle of the disturbance as it begins to enter an area characterized by higher TCHP and SSTs. If recent trends were to persist for the 18-24 hours or so, we would likely see it become a tropical depression... The relative vorticity is still somewhat elongated and stretched along the axis of the ITCZ but it has consolidated and intensified considerably over the past few hours after this convection went up.
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Convection has consolidated around the meridionally oblong, but closed circulation associated w/ 92L and if organizational trends continue for the next 12 hours or so, a tropical depression will likely develop.
avn-animated.gif

WMBds101.png
 
Webb - Thanks! That's actually the system of interest IMHO.
Sneaky little thing ...
Might be ringing the doorbell in the middle of the night, so to speak ... ;)
Best!
Phil
 
While it's not clear which NWP model has performed the best thus far with 93L, it's no secret that the GFS and HWRF have been absolutely rock solid on this disturbance from the get go and have spanked the ECMWF.
 
Here's the first public advisory and discussion for potential tropical cyclone two. Tropical Storm warnings have been hoisted for Barbados, St. Vincent, and the Grenadines.
Screen Shot 2017-06-18 at 4.58.25 PM.png
Screen Shot 2017-06-18 at 4.59.35 PM.png
Screen Shot 2017-06-18 at 5.00.01 PM.png
 
I have never seen "Potential tropical cyclone" before, but I saw them mentioning it in the 2017 updates for the NHC.

Yeah, the NHC is allowed to issue advisories, watches, and warnings for storms they think have a very good chance of becoming a tropical cyclone to allot individuals more time to prepare for and remain more alert to oncoming tropical cyclones...
 
The satellite presentation of Potential TC Two has continued to improve over the last several hours, and while the NHC is awaiting an ASCAT pass to confirm that a closed, well defined low level circulation exists, I suspect one is already in place with what appears to be the precursor to a central dense overcast and some banding developing near/over where the center is likely forming/has formed. Certainly an impressive storm and one worth watching as it's small size and relatively favorable environment could allow it to undergo rapid intensification into a strong tropical storm or perhaps a hurricane the next 24-36 HR.
Screen Shot 2017-06-18 at 9.36.12 PM.png
 
Latest ATCF message still labels Two as a potential tropical cyclone, but with maximum sustained winds of 35 knots (40 mph) & a minimum central pressure of 1005mb. The ascending ASCAT pass barely missed the storm but hopefully the descending pass will capture the circulation
 
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