ATL: BERTHA - Post-Tropical - Discussion

[NDG]

12z Best Track position:

AL, 93, 2014072812, , BEST, 0, 100N, 325W, 20, 1011, DB, 34, NEQ

[NDG]

According to the latest HD GFS run:

http://www.tropicaltidbits.com/analysis/models/gfs/2014072806/gfs_pres_wind_93L_18.png

NDG - I can't seem to find that graphic on Tropical Tidbits. I'm looking at the high-res GFS on my workstation and don't see anything below about 1005 mb.

http://www.tropicaltidbits.com/analysis ... 014072800/

Edit: make sure you click on 93L's link on the upper right corner of the page.

[cycloneye]

12z Best Track position:

AL, 93, 2014072812, , BEST, 0, 100N, 325W, 20, 1011, DB, 34, NEQ

A little more south than the 06Z.

103N, 310W

[gatorcane]

Saved image - quite impressive as far the convection we are seeing:

[blp]

12z Best Track position:

AL, 93, 2014072812, , BEST, 0, 100N, 325W, 20, 1011, DB, 34, NEQ

A little more south than the 06Z.

103N, 310W

The Euro had the vorticity below 10. It looks like it could be consolidating below 10.

[northjaxpro]

12Z Best Track has the system now at 1011 mb, a drop of 2mb since the intialization by NHC of labeling this system an invest. Lots of time to watch 93L, but the big question other than track will be if 93L/potential Bertha runs into the shear zone in the coming days which is very evident across the Caribbean, as has been all season to this point. EURO is holding steadfast at this time of keeping this system rather weak, and EURO may be indicating the possible the hostile environment in a few days. I think eventually 93L will slowly gain latitude and it is possible the Leeward Islands may get impacted by this system. It will be a close call. Currently, 93L certainly has a very decent moisture envelope, with the aid of the ITCZ, and with the upper diffluence element, this will likely become a TD within the next 24 hours. Outside of EURO, most of the models are developing this system into a moderately strong TS within the next 60-72 hours. The critical point will be after 72 hours with regards to the upper level environment once the system reaches around 55-60 degrees longitude. Either it will be a sheared, weak mess of a cyclone which EURO is insisting to be at this time, or it will be in at least a marginally conducive area with regards to how the shear is for the system to at maintain itself. Also, should 93L become a weak, sheared storm after the next 72-84 hours, the system will more than likely traverse farther westward. Also, as some as pointed out, Long range EURO also shows the Bermuda High bulding back in by the end of the upcoming weekend and by the start of next week. This is where timing is everything. If 93L is a fast mover, the current trough which is in place across Eastern North America I think will pick up the system and carry it out to sea by this weekend. But, there is a chance the trough may either lift out or retrograde back to the west this upcoming weekend, and if that occurs and 93L is still intact, then things could get really interesting next week.

So folks, we finally have our true first decent CV system of the season and interesting days ahead monitoring it.
_______________________
Personal Forecast Disclaimer:
The posts in this forum are NOT official forecast and should not be used as such. They are just the opinion of this poster. For official information, please refer to the NHC and NWS products.

[ConvergenceZone]

If anything, it will further moisten up the Atlantic, making it much easier for the waves that follow 93L to develop....I don't think many of us think it will do much down the road, but we take it as a sign that things may be getting active....

[Blown Away]

By: Dr. Jeff Masters, 2:43 PM GMT on July 28, 2014

An area of disturbed weather located near 10°N, 33°W at 8 am EDT Monday, about 500 miles southwest of the Cape Verde Islands, was designated Invest 93L by NHC early Monday morning. This disturbance is a more serious threat than Tropical Depression Two of last week, and has the potential to develop into a strong tropical storm before reaching the Lesser Antilles Islands on Friday or Saturday. Visible satellite loops on Monday morning showed that the disturbance had only a modest amount of spin, but infrared satellite images showed that the system's heavy thunderstorm activity had increased significantly since Sunday. Wind shear was light, 5 - 10 knots, which should aid development. Ocean temperatures were decent for development, about 27.5°C. Water vapor satellite loops showed that the atmosphere was reasonably moist in the area, though a large area of dry air lay a few hundred miles to the north.

Figure 1. Analysis of the Saharan Air Layer (SAL) made at 8 am EDT Monday July 28, 2014 using data from the Meteosat-9 satellite. Dry, dusty air was present from the coast of Africa westwards across the tropical Atlantic, but was located well to the north of tropical disturbance 93L. Image credit: University of Wisconsin CIMSS/NOAA Hurricane Research Division.

Forecast for 93L
The 12 UTC Monday forecast from the SHIPS model predicted that wind shear will remain low to moderate, 5 - 15 knots, for the remainder of the week, aiding development. Sea Surface Temperatures (SSTs) will cool a bit to 27°C on Tuesday and Wednesday, which will tend to slow development. Two of our three reliable models for predicting tropical cyclone genesis, the GFS and UKMET models, predicted in their 00Z Monday runs that the disturbance would develop into a tropical depression by Thursday. Several of our less reliable models, the NAVGEM and Canadian models, also predicted development. The only reliable model that did not predict development was the European model, which historically has had the highest incidence of failing to predict development when development actually occurs. The fact that two out of three of the reliable genesis models predict development bolsters the odds that development will actually occur. In their 8 am EDT Monday Tropical Weather Outlook, NHC put the 5-day odds of development at 70%, up from their 40% forecast from Sunday.

All of the models predict that the disturbance will continue due west or west-northwest at 10 - 15 mph for the next five days. The UKMET is the fastest of the models, predicting that the disturbance will arrive in the Lesser Antilles Islands on Friday evening. The GFS is slower, predicting a Saturday morning arrival in the islands. Once the disturbance crosses west of about 55°W longitude on Thursday, ocean temperatures will warm to about 28°C, which should aid development. Dry air to the north will likely interfere with development late in the week, and we will have to see if the moderate levels of wind shear forecast to occur over the tropical Atlantic will be capable of driving this dry air into the core of the system, disrupting formation. The disturbance may also have trouble disentangling itself from the Intertropical Convergence Zone (ITCZ), the band of heavy thunderstorms that circles the globe in the tropics, which lies just to the south of the disturbance. Clusters of thunderstorms in the ITCZ may compete for moisture and energy, slowing development of the disturbance.

The long-range fate of 93L remains highly uncertain, and will depend upon exactly how far south the center ends up consolidating when the storm develops. Most of the 20 members of the 06Z Monday run of the GFS ensemble model (which runs the GFS model at low resolution 20 times with slightly different initial conditions to show a range of possible outcomes) showed the disturbance missing the U.S. East Coast and recurving out to sea next week; four of the members showed 93L hitting the Southeast U.S. coast. Most of the members of the 00Z Monday run of the European ensemble model showed 93L moving into the Eastern Caribbean on a more southerly trajectory without recurving.

Jeff Masters

Makes sense to me...

[dixiebreeze]

By the way, floater is up since 6z

http://www.ssd.noaa.gov/PS/TROP/floater ... oater.html

Haven't been able to access NOAA satellite link all day. Anyone else having this problem?

[meriland23]

Hmm to recurve or not to recurve ...that is the question.

[gatorcane]

It should be pointed out that we are still about 2 weeks from when we would expect development out in the Central Tropical Atlantic based on climatology as the Cape Verde season generally kicks off in mid August.

The fact we are seeing a large system like this making a run at development this early is quite impressive and could mean the MDR will be favorable for development for the Cape Verde season.

It also shows just how quickly things can change in the tropics. About a week or ago, the MDR was a war zone as far as allowing any development. Totally different atmospheric environment now.

Saved image showing the wide Atlantic view for perspective. 93L is quite large and looking more and more impressive:

[meriland23]

It should be pointed out that we are still about 2 weeks from when we would expect development out in the Central Tropical Atlantic based on climatology as the Cape Verde season generally kicks off in mid August.

The fact we are seeing a large system like this making a run at development this early is quite impressive and could mean the MDR will be favorable for development for the Cape Verde season.

It also shows just how quickly things can change in the tropics. About a week or ago, the MDR was a war zone as far as allowing any development. Totally different atmospheric environment now.

A lot of people were under the assumption of a very weak almost non existent season based on the fact we were forcasted a strong El Nino. First system in the Atlantic ended up being a cat 2 hurr .. just.. never know what mother nature has planned.

[wxman57]

Hmm to recurve or not to recurve ...that is the question.

I think that if it develops then it will recurve east of the U.S. If it doesn't develop (as per the ECMWF), then it will continue moving west through the Caribbean.

[TheStormExpert]

It should be pointed out that we are still about 2 weeks from when we would expect development out in the Central Tropical Atlantic based on climatology as the Cape Verde season generally kicks off in mid August.

The fact we are seeing a large system like this making a run at development this early is quite impressive and could mean the MDR will be favorable for development for the Cape Verde season.

It also shows just how quickly things can change in the tropics. About a week or ago, the MDR was a war zone as far as allowing any development. Totally different atmospheric environment now.

Saved image showing the wide Atlantic view for perspective. 93L is quite large and looking more and more impressive:
http://i58.tinypic.com/33lf1ow.jpg

I wouldn't say totally different, but it has improved a good deal to allow systems like TD #2 and 93L to have potential.

[cycloneye]

Off-Topic=Speaking of El Nino,the area Nino 3.4 continues to get cold. See the update at the ENSO Updates thread.

[Sanibel]

Looks like we have a curler. Slightly sheared by the easterlies.

[wxman57]

Tropical Atlantic is still relatively stable for this time of year. Instability is way down, due primarily to sinking (dry) air in the mid levels. Shear isn't too high in the Tropical Atlantic, however.

[TheStormExpert]

Yeah, despite 93L's moist envelope the Tropical Atlantic still remains quite dry and deserted.

[blp]

Tropical Atlantic is still relatively stable for this time of year. Instability is way down, due primarily to sinking (dry) air in the mid levels. Shear isn't too high in the Tropical Atlantic, however.

http://www.ssd.noaa.gov/PS/TROP/TCFP/da ... t_THDV.gif[/img]

You got to think that graphic is going to spike up soon. With TD#2 last week and this thing I expect a change once that graphic updates.

[KBBOCA]

A tiny bit off topic..., but is this the wave that was over Mali last Wed night and may have contributed to the crash of the Air Algeria flight? I haven't had a chance to go back and track this and compare with the time of the crash...