Tropical Wave in Central Atlantic (Is Invest 97L)

[george_r_1961]

it looks like thr tropics will get interesting but the east coast trough looks like it will protect us.

Remember you are looking at model runs that are way out there in the long-range with systems that haven't even formed yet.

Also that trough may not be enough to protect the Caribbean islands.

Depending on the position and orientation of the trough the east coast may not be safe.

[ouragans]

Isn't that the first time the NHC refers to a TW while still over W Africa? Overall giving a potental percentage for development?

[Florida1118]

Isn't that the first time the NHC refers to a TW while still over W Africa? Overall giving a potental percentage for development?

They've been doing such since they started the 5 day outlooks. They've mentioned systems for the EPAC that were still in Central America, but given a high chance by 5 days. Same thought process here

[HurricaneMaster_PR]

ECMWF 12z run similar to the GFS in terms of the track
http://www.meteo.psu.edu/~fxg1/ECMWFTRO ... ml#picture

[Gustywind]

Interesting discussions from San Juan. That's the second highlight in a row...


AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
334 PM AST SAT AUG 24 2013

A FOURTH TROPICAL WAVE IS CURRENTLY OVER WRN AFRICA AND IS
ASSOCIATED WITH AN MCS. GLOBAL MODELS HAVE BEEN VERY CONSISTENT
IN DEVELOPING THIS WAVE EVENTUALLY INTO A TROPICAL CYCLONE IN THE
DY5-7 TIME FRAME (THU AUG 29-SAT AUG 31) ALTHOUGH THEY ARE SHOWING
SIGNIFICANT SPEED DIFFERENCES. BASED ON OFFICIAL NHC/WPC MEDIUM
RANGE GUIDANCE THIS WAVE MAY HAVE A LOW PRES AREA ASSOCIATED WITH
IT OR MAY BECOME A TROPICAL CYCLONE NEXT FRI AND BE IN THE
VICINITY OF 14N AND 47W NEXT SAT AUG 31.

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
313 PM AST SUN AUG 25 2013

TROPICAL WAVE FCST TO EXIT THE AFRICAN CONTINENT TONIGHT IS
EXPECTED TO BECOME A TROPICAL CYCLONE BY THE END OF THE WEEK AND
REACH 55W BY 12Z SUN SEP 01.

[gatorcane]

Here is how the 12Z FIM model ends at 168 hours:

[HurricaneMaster_PR]

Here is how the 12Z FIM model ends at 168 hours:

Also appears to recurve the system as it reaches 50W

[USTropics]

Here is how the 12Z FIM model ends at 168 hours:

The FIM, just like its eventual predecessor the GFS, extends beyond 168 hours. You have to switch the resolution from 15km to 30 km though. FIM eventually shows the system recurving.

[gatorcane]

18Z GFS out through 87 hours, not quite as consolidated with the low so far on this run compared to 12Z GFS with multiple lows showing up.

[Gustywind]

Tropical Update

Dr. Greg Postel, Hurricane Specialist, The Weather Channel

Aug 25, 2013 1:45 pm ET

http://www.weather.com/newscenter/tropical/


- Atlantic could soon become active

Tropical Atlantic

A couple of mechanisms that exert some control over the development potential will soon phase together and try to set the table for tropical formation during the next 1-2 weeks. Overall, the wind shear is expected to decrease, and the atmosphere over the Main Development Region (the tropical region between 10?N and 20?N and 20?W to 85?W, between the coast of Africa and the Caribbean) will become a little more humid. In addition, we are seeing signs that the strength, or amplitude, of the tropical "waves" coming off Africa (they're not really waves in the atmosphere ... they're more like isolated disturbances) will increase as well. Add all of that up, and you get a pretty high chance -in my opinion- of development before too long.


Within a surrounding pattern that's apparently suiting up for development, there is already one tropical "wave" to keep an eye on closely. It's just coming off the coast of Senegal, and has a well-defined rotary motion aloft with thunderstorms embedded within. Many of the global weather models grow it into a tropical cyclone (some keep it a depression or storm, some make it a hurricane) within 10 days. I don't recall seeing this season the kind of model consensus we've got now on the Atlantic tropical risk. I imagine the National Hurricane Center (NHC) will highlight this region in a day or so, and make the disturbance an "invest" soon thereafter. We'll see.

With all of that said, there is so much atmosphere it will have to move through before it could ever threaten our interests in the Caribbean or United States, with lots of time for other factors ... those associated with the daily "weather" that are yet determined by the forecast models ... to interfere with, or even terminate, its progress. Tough call, so stay tuned. It's hard to lose sight of the fact that the tropical Atlantic is an historically rough place to grow up if you want to be a tropical cyclone.

[gatorcane]

Weaker an a touch more west on the 18Z GFS than the 12Z...now out through 114 hours...

Edit: Out through 126 hours and much weaker and more west on this run than 12Z...

[gatorcane]

18Z GFS 165 hours. Big difference from 12Z. Weak low impacting Leewards, nowhere near as strong as the 12Z was showing during the same timeframe and significantly further west:

[TropicalAnalystwx13]

Pay no attention to the 18z GFS. It missed a majority of critical satellite data.

[gatorcane]

228 Hours 18Z GFS, the low passes through Puerto Rico and is heading WNW:

[ninel conde]

Tropical Update

Dr. Greg Postel, Hurricane Specialist, The Weather Channel

Aug 25, 2013 1:45 pm ET

http://www.weather.com/newscenter/tropical/


- Atlantic could soon become active

Tropical Atlantic

A couple of mechanisms that exert some control over the development potential will soon phase together and try to set the table for tropical formation during the next 1-2 weeks. Overall, the wind shear is expected to decrease, and the atmosphere over the Main Development Region (the tropical region between 10?N and 20?N and 20?W to 85?W, between the coast of Africa and the Caribbean) will become a little more humid. In addition, we are seeing signs that the strength, or amplitude, of the tropical "waves" coming off Africa (they're not really waves in the atmosphere ... they're more like isolated disturbances) will increase as well. Add all of that up, and you get a pretty high chance -in my opinion- of development before too long.


Within a surrounding pattern that's apparently suiting up for development, there is already one tropical "wave" to keep an eye on closely. It's just coming off the coast of Senegal, and has a well-defined rotary motion aloft with thunderstorms embedded within. Many of the global weather models grow it into a tropical cyclone (some keep it a depression or storm, some make it a hurricane) within 10 days. I don't recall seeing this season the kind of model consensus we've got now on the Atlantic tropical risk. I imagine the National Hurricane Center (NHC) will highlight this region in a day or so, and make the disturbance an "invest" soon thereafter. We'll see.

With all of that said, there is so much atmosphere it will have to move through before it could ever threaten our interests in the Caribbean or United States, with lots of time for other factors ... those associated with the daily "weather" that are yet determined by the forecast models ... to interfere with, or even terminate, its progress. Tough call, so stay tuned. It's hard to lose sight of the fact that the tropical Atlantic is an historically rough place to grow up if you want to be a tropical cyclone.

pretty much talking climo.

[ninel conde]

18Z GFS 165 hours. Big difference from 12Z. Weak low impacting Leewards, nowhere near as strong as the 12Z was showing during the same timeframe and significantly further west:

best to wait till 0Z run of GFS and euro. will the GFS be stronger and will the euro show a storm?

[gatorcane]

Here is how the 18Z GFS ends. This system combines with another system and creates this below recurving east of the United States:

[Alyono]

Pay no attention to the 18z GFS. It missed a majority of critical satellite data.

what in the world are you talking about? Seriously... did you just say 18Z runs do not have satellite data?

I guess we have not had any GOES and polar orbiting data since 12Z then. I just learned something

[gatorcane]

18Z GFS 165 hours. Big difference from 12Z. Weak low impacting Leewards, nowhere near as strong as the 12Z was showing during the same timeframe and significantly further west:

best to wait till 0Z run of GFS and euro. will the GFS be stronger and will the euro show a storm?

That is a big change from the 18Z from the 12Z even in the medium range. I wonder if this is a one-run thing or if it is the beginning of a trend away from developing this now?

If this one doesn't develop somehow, I can't imagine the "season cancel" posts that will spread across this board like wildfire!

[alienstorm]

This system has weakened as it exits Africa - so this may take awhile to get its act together if at all.