• Member Statistics

    16,103
    Total Members
    7,904
    Most Online
    Christina
    Newest Member
    Christina
    Joined
WxWatcher007

Tropical Depression Gonzalo

Recommended Posts

Figured it was time to break out a thread, as Invest 99L continues to increase in organization. 

59198117.gif?0.4892467927181269

99L is one of the many vigorous waves we’ve seen come out of Africa, and is the closest to development in the MDR thus far. While the guidance is in better agreement that some form of development will occur, the WV loop above illustrates the forecast challenge ahead.

While shear is low, SAL is lurking to the north, and that may be enough to effectively choke off 99L in a few days. However, if 99L can create a small pocket of moisture that is more resistant to dry air intrusions, it may develop a bit more as it closes in on the islands. These small systems are difficult to forecast. Ceiling looks fairly low for now but I think we can get our first MDR TC out of this. 

XRmy8Xi.jpg

Latest ASCAT image courtesy of Pappin.

KHyT77n.jpg

  • Like 2

Share this post


Link to post
Share on other sites

Welp, nothing yet. Don't use me for bets. Still, I think for all intents and purposes, 99L is a depression now. Perhaps @ 5PM ADT.

  • Like 1

Share this post


Link to post
Share on other sites

I agree. I think 99L is a TD. Sometimes they slow walk these things.

The 12z guidance will be interesting. The small storms can ramp up and unwind rapidly. If this is able to develop a decent core, it would have a shot in the Caribbean. Wind shear is much lower than usual there. 

Even if this falls apart, we gotta watch the steering pattern and whether remnants get into a more favorable environment long term. We know the history there...

Share this post


Link to post
Share on other sites



Wind shear is much lower than usual there.

Even if this falls apart, we gotta watch the steering pattern and whether remnants get into a more favorable environment long term. We know the history there...


Yep...

  • Like 1

Share this post


Link to post
Share on other sites

I know it’s projecting, but that’s a disaster waiting to happen for someone should that kind of anomaly continue during the peak of the season with this kind of thermo profile. I mean just about everything is aligned for a nasty season.

2020202at.jpg

Share this post


Link to post
Share on other sites

The 06z HWRF did bring this to Cat 2 hurricane intensity in the ECARIB but this may be due to it wanting to take a much more southerly track. It still has a hypothetical Gonzo south of 15°N @ 9z Sunday. It also keeps the TC rather compact. This does two things. 1) Avoids the strong easterly SAL-mixed wind burst to its immediate north, preventing decoupling. 2) Allows the vortex to somewhat isolate itself within a pocket of moist mid-level airmass, feeding off the ITCZ and SA. Also a small vort might do better against advecting stable air from the NE when the sub 700 hPa easterly wind burst gets there.

 

Obviously take the HWRF with bags of salt. But it is interesting nonetheless to see why it wants Gonzo to be a stud, not a dud. The 12z run could just as easily squash it. I would be surprised at any consistency with such close proximity to a very unfavorable airmass so close with this developing TC.

10e22812e43023047ce5b4436690f536.jpg&key=e4e714896059a99d3dffee19225254a48abe54e120e48a20df6eae5b8fd70f7e

  • Like 2

Share this post


Link to post
Share on other sites
Special Tropical Weather Outlook
NWS National Hurricane Center Miami FL
1105 AM EDT Tue Jul 21 2020

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

Special Tropical Weather Outlook issued to update the status of the 
reconnaissance mission originally scheduled for the system near the 
Straits of Florida and to increase the formation chances for the 
system in the tropical Atlantic.

Updated:  A tropical wave is producing a large area of disorganized 
showers and thunderstorms over western Cuba, the northwestern 
Bahamas, southern Florida, and the adjacent Atlantic and Caribbean 
waters.  Gradual development of this system is possible while it 
moves west-northwestward during the next few days.  This system is 
expected to move over the southeastern Gulf of Mexico later today,
the central Gulf on Wednesday, and the northwestern Gulf on 
Thursday and Friday.  The Air Force Reserve Hurricane Hunter 
aircraft scheduled to investigate the system this afternoon has 
been canceled.
* Formation chance through 48 hours...low...30 percent.
* Formation chance through 5 days...medium...40 percent.

Updated:  Satellite imagery and recent satellite wind data indicate 
that the low pressure system located about midway between the west 
coast of Africa and the Lesser Antilles continues to get better 
organized.  If current trends continue, advisories could be 
initiated on this system as a tropical depression later today.  
Regardless of development during the next couple of days, less 
favorable conditions should limit additional development by the 
weekend.
* Formation chance through 48 hours...high...80 percent.
* Formation chance through 5 days...high...80 percent.

$$
Forecaster Beven
  • Like 2

Share this post


Link to post
Share on other sites

12z GFS really tries to keep 99L together into the eastern Caribbean. Levi hits on the possibility of survival in the tweet below. It’s a delicate dance. 
 

 

  • Like 2

Share this post


Link to post
Share on other sites
The 06z HWRF did bring this to Cat 2 hurricane intensity in the ECARIB but this may be due to it wanting to take a much more southerly track. It still has a hypothetical Gonzo south of 15°N @ 9z Sunday. It also keeps the TC rather compact. This does two things. 1) Avoids the strong easterly SAL-mixed wind burst to its immediate north, preventing decoupling. 2) Allows the vortex to somewhat isolate itself within a pocket of moist mid-level airmass, feeding off the ITCZ and SA. Also a small vort might do better against advecting stable air from the NE when the sub 700 hPa easterly wind burst gets there.
 
Obviously take the HWRF with bags of salt. But it is interesting nonetheless to see why it wants Gonzo to be a stud, not a dud. The 12z run could just as easily squash it. I would be surprised at any consistency with such close proximity to a very unfavorable airmass so close with this developing TC.
10e22812e43023047ce5b4436690f536.jpg&key=e4e714896059a99d3dffee19225254a48abe54e120e48a20df6eae5b8fd70f7e

It may be an outlier but after Michael I will never discount it. If my memory serves me correct. It was showing (at that point) some 930’s before we had any idea what a monster was coming. It does have its quirks but, it has its place also.


.
  • Thanks 1

Share this post


Link to post
Share on other sites

The small circulation size gives this a good chance of over-performing in the short run.  I think 99l will be the first hurricane of 2020.   Don't think it survives far into the Caribbean though.  

 

Some recent storms in this region similar in size

Danny 2015 Cat3

Beryl 2018  Cat1

 

Share this post


Link to post
Share on other sites

I expect advisories to begin at 5pm.

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
200 PM EDT Tue Jul 21 2020

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

A tropical wave is producing a large area of disorganized showers 
and thunderstorms over western Cuba, the northwestern Bahamas, 
southern Florida, and the adjacent waters of the Atlantic, 
Caribbean Sea, and the Gulf of Mexico.  Gradual development of this 
system is possible while it moves west-northwestward during the 
next few days.  This system is expected to cross the southeastern 
Gulf of Mexico this afternoon and tonight, move over the central 
Gulf on Wednesday, and reach the northwestern Gulf on Thursday and 
Friday.  An Air Force Reserve Hurricane Hunter aircraft is 
scheduled to investigate the system on Wednesday, if necessary.
* Formation chance through 48 hours...low...30 percent.
* Formation chance through 5 days...medium...40 percent.

Showers and thunderstorms associated with the low pressure area 
located about midway between the west coast of Africa and the 
Lesser Antilles continue to get better organized, and a tropical 
depression appears to be forming.  If current trends continue, 
advisories could be initiated on this system this afternoon.  
Regardless of development during the next couple of days, less 
favorable conditions should limit additional development of the 
system by the weekend.
* Formation chance through 48 hours...high...90 percent.
* Formation chance through 5 days...high...90 percent.

$$
Forecaster Beven

 

38047412.gif?0.5494837155177894

  • Like 1

Share this post


Link to post
Share on other sites

The latest HWRF is really getting jiggy with this system... 967 mb going through the islands.  I'm not expecting that, but there is certainly potential for strengthening.

Share this post


Link to post
Share on other sites

Euro not enthused but I think the guidance across the board is playing catch-up. Wasn’t too long ago there wasn’t a signal for TC genesis. Next 24 hours are critical for the organization of 99L. 

Share this post


Link to post
Share on other sites

They'll probably name it a depression at 5pm. I think the bigger concern is what it could do later on in the Western Caribbean or Gulf, should it make it that far.

Share this post


Link to post
Share on other sites
Euro not enthused but I think the guidance across the board is playing catch-up. Wasn’t too long ago there wasn’t a signal for TC genesis. Next 24 hours are critical for the organization of 99L. 

Most EPS members and even the ECMWF op pooped the bed last year with Dorian. But even though the GEFS ens and GFS op did much better, none of them had much of a real clue on its long-term trend. It wasn't until we started seeing potential posturing north of PR and the insane synoptic setup that alarms started going off. Dorian was a weak (and struggling I might add) tropical storm at the time too. The HWRF had some wacky runs during that time frame though. Even quite a number of Cat 3/4 strikes in the Lesser Antilles. Of course that was wrong. Still, what we're seeing today may very well be what makes us gasp tomorrow or when this system gets better modeled in the 7-10 day range. That is probably not going to be until we actually have a TC and trajectory through the Windwards.

 

So here we go. Will potential Gonzalo take a southerly track through the deep or central Caribbean? There will be shear, but far less shear than typical of late July. Probably not enough to kill a well-developed TC. Weaken? Sure. The worry is what may come when it reaches the NW Caribbean. The pattern might become dangerous then.

Share this post


Link to post
Share on other sites

Yeah. Dorian was a massive miss by the Euro op and EPS, and the rest of the guidance struggled for a while. We’re really just in wait and see mode right now. Part of the reason tropical is so fascinating.

Share this post


Link to post
Share on other sites
11 minutes ago, WxWatcher007 said:

Yeah. Dorian was a massive miss by the Euro op and EPS, and the rest of the guidance struggled for a while. We’re really just in wait and see mode right now. Part of the reason tropical is so fascinating.

Yes over the Antilles and Virgin Islands.   After that it did better, and it was the first model to have Dorian missing Florida.

Irma was the exact opposite, The Euro did good with the track until Cuba, then it crapped the bed and took it into the FL panhandle while every other model had it going into Naples.  

Share this post


Link to post
Share on other sites
14 minutes ago, Amped said:

Yes over the Antilles and Virgin Islands.   After that it did better, and it was the first model to have Dorian missing Florida.

Irma was the exact opposite, The Euro did good with the track until Cuba, then it crapped the bed and took it into the FL panhandle while every other model had it going into Naples.  

 

Right but the NHC weighed way too heavily on the GFS with Irma. The EURO consistently showed a landfall in the Florida Keys and a threat to SW Florida. The GFS kept showing Irma heading into SE Florida and the Miami region. Both models completely missed the stronger ridge that interacted Irma with Cuba, thus weakening it atleast 20-40 mph before the Keys landfall. Irma's 130 mph landfall would have been much worse at 150 or 160 mph.

Share this post


Link to post
Share on other sites

Well then. Forecasted to become a strong TS but low confidence forecast.

Tropical Depression Seven Discussion Number   1
NWS National Hurricane Center Miami FL       AL072020
500 PM AST Tue Jul 21 2020

Satellite imagery and scatterometer data indicate that the low 
pressure area located over the central tropical Atlantic has a 
well-defined circulation and sufficient organized convection to be 
designated a tropical depression.  Thus, advisories are being 
initiated on Tropical Depression Seven.  The initial intensity is 
set at 30 kt in best agreement with the subjective satellite 
intensity estimate from TAFB.

The initial motion is 300/7.  The depression is south of a strong 
subtropical ridge over the central Atlantic, and over the next 
several days it should turn generally westward and accelerate as it 
encounters the easterly flow associated with the ridge.  The ECMWF, 
GFS, and UKMET models are in reasonably good agreement on their 
track forecasts, and the NHC official forecast is close to them and 
the various consensus models.

The intensity forecast is lower confidence.  The GFS, ECMWF, and 
UKMET models forecast the cyclone to be dissipated or be a weak low 
by the 120 h point, likely due to to some vertical shear and dry 
air entrainment.  On the other hand, the SHIPS-based guidance and 
the HWRF forecast the system to be a hurricane at 120 h, shrugging 
off the shear and dry air.  The NHC intensity forecast will be a 
compromise between these extremes, showing a peak intensity of 55 
kt in 60-72 h followed by some weakening based on the global models. 
The cyclone is small in size, and as a result it could change 
intensity - both up and down - faster than what is currently 
forecast.


FORECAST POSITIONS AND MAX WINDS

INIT  21/2100Z  9.8N  40.4W   30 KT  35 MPH
 12H  22/0600Z 10.1N  41.7W   35 KT  40 MPH
 24H  22/1800Z 10.3N  43.9W   40 KT  45 MPH
 36H  23/0600Z 10.3N  46.3W   45 KT  50 MPH
 48H  23/1800Z 10.4N  49.0W   50 KT  60 MPH
 60H  24/0600Z 10.6N  51.6W   55 KT  65 MPH
 72H  24/1800Z 11.0N  54.7W   55 KT  65 MPH
 96H  25/1800Z 12.0N  61.0W   50 KT  60 MPH
120H  26/1800Z 13.5N  68.5W   45 KT  50 MPH

$$
Forecaster Beven

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...

  • Recently Browsing   0 members

    No registered users viewing this page.