ATL: THREE - Remnants - Discussion

[Nancy Smar]

AL, 94, 2019072100, , BEST, 0, 235N, 689W, 25, 1014, DB, 0, , 0, 0, 0, 0, 1016, 120, 50, 0, 0, , 0, , 0, 0, GENESIS007, , 0, , 0, 0, 0, 0, genesis-num, 007, SPAWNINVEST, al782019 to al942019,
AL, 94, 2019072106, , BEST, 0, 235N, 702W, 25, 1014, DB, 34, NEQ, 0, 0, 0, 0, 1016, 120, 50, 0, 0, L, 0, , 0, 0, INVEST, S, 0, , 0, 0, 0, 0, genesis-num, 007,

[Nancy Smar]

000
ABNT20 KNHC 210546
TWOAT

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
200 AM EDT Sun Jul 21 2019

For the North Atlantic...Caribbean Sea and the Gulf of Mexico:

A tropical wave located about 300 miles east of the Central Bahamas
is producing disorganized showers and a few thunderstorms. Although
environmental conditions are currently unfavorable for development,
they are expected to become a little more conducive over the next
few days while the disturbance moves westward at 10 to 15 mph.
Interests in the Central and Northwest Bahamas, and the southern
Florida peninsula and the Florida Keys should monitor the progress
of this system.
* Formation chance through 48 hours...low...10 percent.
* Formation chance through 5 days...low...20 percent.

$$
Forecaster Stewart

[CyclonicFury]

This came out of nowhere. It doesn't appear to have any model support.

[northjaxpro]

Well now, NHC really did throw us a bone to munch on uh??? Wow. I did not anticipate this from NHC, given the lack of model support. Well, it is in area in which we definitely must monitor and it is a vigorous vorticity signiture shown at 850 mb. Apparently, conditions appear to have moisture returning for the system to possibly get going as it approaches South Florida in the next 48 hours.

[AtlanticWind]

Looks like it has some spin, wonder if it has any support from the ensembles

[northjaxpro]

Looking at IR Satellite and WV imagery early this morning, it does appear that some convection is beginning to fire on the eastern side of the LLC . This may be a sign that the dry air, which had been so pronounced around the system, may be loosening its grip and conditions may be improving for Invest 94L to possibly get going. This is probably why NHC pulled the trigger to upgrade this to an invest early this morning, especially given its proximity to the Bahamas and later Florida, and being in an area currently notorious for spawning tropical cyclones quickly i.e. Katrina... Let's see if the increase in convection is the kick start boost this system needed. This will get the Storm2K forum jumping real quick, whenever the rest of you all wake up to this development this morning

[AtlanticWind]

* ATLANTIC 2019 SHIPS INTENSITY FORECAST * * IR SAT DATA AVAILABLE, OHC AVAILABLE * * INVEST AL942019 07/21/19 06 UTC * TIME (HR) 0 6 12 18 24 36 48 60 72 84 96 108 120 V (KT) NO LAND 25 26 28 30 33 40 47 53 60 63 62 59 55 V (KT) LAND 25 26 28 30 33 40 47 53 60 63 62 59 55 V (KT) LGEM 25 25 26 26 27 30 33 37 42 47 52 53 50 Storm Type TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP SHEAR (KT) 14 10 8 8 12 5 13 9 6 18 31 35 40 SHEAR ADJ (KT) -2 -6 -5 -3 -3 -5 -3 -3 -1 -1 2 4 -3 SHEAR DIR 266 276 289 291 315 320 309 351 290 229 239 241 254 SST (C) 28.8 28.9 29.0 29.2 29.4 29.6 30.5 29.8 29.5 28.4 27.5 26.6 25.6

[northjaxpro]

Wow. 94L continues to fire convection on the eastern flank of the LLC. Dry air is still impairing the western flank, but overall, definitely 94L is pulsating rather nice early this morning. Big developments in the past 6-12 hours for sure! 06Z GFS currently running.

EDIT: Latest 06Z GFS run just out shows 94L as a surface trough/tropical wave next 48 hours. A very unusually strong front for July is dropping down and absorbing 94L on Tuesday as 94L approaches the Florida East Coast. However, I am sure that the 12Z GFS and other model runs later today will probably be a bit more assertive in their display of 94L, given the trends early this morning. I talked about the strong frontal system coming down in the Surface Trough east of Bahamas Thread earlier.

[drezee]

Visible is pretty compelling. I would guess it has a broad but closed LLC.

[USTropics]

First visible images of this morning, certainly has evident rotation at the low-levels:


Confirmed by the CIMSS 850mb vort products as well, although noticed what appears to be a small eddy that rotated north a few hours ago that seems to has since caused some elongation:


Main issue remains this dry air entrainment, as evident on the GFS 06z initialization:


A closer look reveals a low-shear environment (under 10kts) but relative humidity values under 40%:


This has left 94L struggling to sustain any mid-upper level identity:

[northjaxpro]

Dry air is still affecting the invest right now, but the fact that convection is firing up closer to the LLC tells me that the environment is gradually moistening around 94L. Some westerly shear with convection displaced to the east of LLC. SHIPs showing a good 48-72 hour window of relatively low wind shear around 94L. I think we may have a pretty decent chance of seeing Chantal in the next couple of days.

Remember, this is in an area notorious for quickly spinning up tropical cyclones if conditions are reasonably conducive for developmenty, which right now gradually seems to be the case for 94L.

[cycloneye]

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
800 AM EDT Sun Jul 21 2019

For the North Atlantic...Caribbean Sea and the Gulf of Mexico:

A tropical wave located a couple of hundred miles east of the
Central Bahamas is producing disorganized showers and a few
thunderstorms. Some slight development is possible over the
next few days while the disturbance moves westward to
west-northwestward at 10 to 15 mph.
* Formation chance through 48 hours...low...10 percent.
* Formation chance through 5 days...low...20 percent.

$$
Forecaster Pasch

[TheStormExpert]

There is about 20kts. of westerly shear, hence why the convection keeps getting displaced to the east of the circulation.

[NDG]

NHC must be bored like us j/k
But we know how sometimes these small TWs that reach the northern Bahamas/FL Straights organize all the sudden without much model support.

[USTropics]

Shear should be decreasing later today:


It'll be interesting to see if the low-level circulation can pump out convection today and build a mid-level core. With such a tiny core, it's possible models are having resolution issues (i.e. a difficult time even identifying an LLC).

[northjaxpro]

SHIPs showing only 10kts of shear in the next 48-72 hours. When you add toasty ssts and a moistening atmosphere in the mid levels, this could be a recipe for modest intensification.

In this region 94L is in right now, as NDG and yours truly have noted, we do not have to look very far back at all in the analog s on how quickly a few tropical cyclones have rapidly developed ....

[Dylan]

 https://twitter.com/DylanFedericoWX/status/1152914118388719616

[USTropics]

Of some impact, the models were overdoing the speed and impact of the EC trough.

ECMWF current analysis (in blue) show quite a bit more ridging compared to its 144 hr forecasts (in red):


WPC Model Diagnostic discussion:

The 00Z Non-NCEP suite has all slowed with its eastern CONUS
trough development, which is reasonable based on the intensity of
the ridge preceding it. The CMC which was a fast outlier is now in
line with the ensemble means, and the ECMWF/UKMET look similar to
the NAM with the slower frontal progression and trough axis
position. While small differences exist in shortwave impulses
moving atop the ridge the first 36 hours, as well as the
wavelength of the ridge building northward from the Four Corners,
a general model blend should be sufficient until the finer scale
details can be resolved.

[Aric Dunn]

Like I said.. as it approaches the bahamas.. dont count it out.

[northjaxpro]

Yeah I noticed that as well.The latest WPC Analysis holds the ridge longer to extend west to about South Florida into the middle of this week. The East Coast trough not nearly as amplified as it was being shown on the reliable models even 12 hours ago. This would move 94L farther west across South Florida and possibly into the Southeast Gulf of Mexico over the next 72 hours.