2018 EPAC Season

[cycloneye]

00z Euro is with GFS with the open waters development.

[cycloneye]

From those scattered areas of convection is what the models develop the first Tropical Cyclone of 2018.

[Shell Mound]

We're very likely to see Aletta emerge out of this. A precursive low-pressure area is already present, the EPS/GEFS means indicate development, and the operational ECMWF/GFS depict a future tropical storm. Based on the cross-section, vertical wind shear is not going to be a significant factor, while dry air and (relatively) lower SSTs will impinge on the system at or above ~15°N. But a fairly symmetric cyclone should emerge due to the negligible shear values expected to be in place. I would not be surprised to see a stronger-than-expected tropical storm, perhaps 50 to 60 knots at its peak, so models could adjust toward a more aggressive solution over time, but we shall see. As has been mentioned, the existing +PMM is going to be of assistance to future systems as the sun angle increases.

[cycloneye]

It should be Invest 90E in the next day or two.

[cycloneye]

From NHC EPAC discussion.

Active convection between 110W and 120W, mentioned in the
monsoon trough section above, is associated with a westward
propagating trough/wave interacting with a convectively coupled
Kelvin wave. This area of active convection will be one to watch
with interest the next several days as there is the potential for
further organization into a tropical low by the middle of the
week, further intensifying as it tracks northwest late in week.

[gatorcane]

Kinda of rare to get something that far west in the EPAC so early right?

[cycloneye]

Kinda of rare to get something that far west in the EPAC so early right?

Is not common to have something form in May well away from land.The close to Central-America or Mexican coasts are the ones that generally form early like last year with Adrian that formed on May 9.

[cycloneye]

12z EC a little bit stronger than past runs.

[weathaguyry]

With the possibility of development this far west, it further reinforces my thought that the activity will be west based this year, and that there may be a sizable amount of development in the CPAC.

[Kingarabian]

With the possibility of development this far west, it further reinforces my thought that the activity will be west based this year, and that there may be a sizable amount of development in the CPAC.

In the EPAC, western based activity is a function of favorable eastern based activity. So if the western side of the EPAC and the CPAC can maintain or induce activity, then that means the eastern portion of the EPAC is more than favorable. If the eastern portion of the EPAC is not favorable then the rest of the basin is not favorable as well.

[NotSparta]

With the possibility of development this far west, it further reinforces my thought that the activity will be west based this year, and that there may be a sizable amount of development in the CPAC.

In the EPAC, western based activity is a function of favorable eastern based activity. So if the western side of the EPAC and the CPAC can maintain or induce activity, then that means the eastern portion of the EPAC is more than favorable. If the eastern portion of the EPAC is not favorable then the rest of the basin is not favorable as well.

Not so much when the eastern EPAC gets filled with shear from those TCs

[Kingarabian]

With the possibility of development this far west, it further reinforces my thought that the activity will be west based this year, and that there may be a sizable amount of development in the CPAC.

In the EPAC, western based activity is a function of favorable eastern based activity. So if the western side of the EPAC and the CPAC can maintain or induce activity, then that means the eastern portion of the EPAC is more than favorable. If the eastern portion of the EPAC is not favorable then the rest of the basin is not favorable as well.

Not so much when the eastern EPAC gets filled with shear from those TCs

From which TCs?

[NotSparta]

In the EPAC, western based activity is a function of favorable eastern based activity. So if the western side of the EPAC and the CPAC can maintain or induce activity, then that means the eastern portion of the EPAC is more than favorable. If the eastern portion of the EPAC is not favorable then the rest of the basin is not favorable as well.

Not so much when the eastern EPAC gets filled with shear from those TCs

From which TCs?

The ones from the west based activity you were talking about. If the CPAC and western EPAC were active, the outflow from the TCs formed would shear the EPAC further east and maybe the Caribbean

[Ntxw]

If CPAC was active then its a good chance the EPAC is also active. There is some correlation of big seasons when systems survive the trek between the two and rack up sig ACE. This is from observations of seasons the past decade or so. CPAC has good correlation to +PDO and/or +ENSO

[Kingarabian]

Not so much when the eastern EPAC gets filled with shear from those TCs

From which TCs?

The ones from the west based activity you were talking about. If the CPAC and western EPAC were active, the outflow from the TCs formed would shear the EPAC further east and maybe the Caribbean

How TC genesis generally works in the EPAC, is that you have disturbances off of CA or SW Mexico in the eastern portion of the EPAC. They develop as they move west or recurve towards Baja or central Mexico. It's rare that isolated disturbances develop close to 140W or the CPAC unless it's monsoon trough activity. Let's not forget the EPAC basin is quite large. We've seen numerous times that this basin can have a train (up to 3 or 4) of tropical cyclones ranging from the far EPAC to the CPAC.

So to get TC induced shear from the CPAC or western based activity to affect the EPAC is almost impossible because 1, the activity is coming from the eastern Pacific so conditions are automatically favorable, and 2, the basin is large enough to maintain a number amount of TC's. It's like saying that hurricanes originating in the western Caribbean are going to cause enough shear to shut down the entire Atlantic MDR and tropical Atlantic.

[Yellow Evan]

With the possibility of development this far west, it further reinforces my thought that the activity will be west based this year, and that there may be a sizable amount of development in the CPAC.

In the EPAC, western based activity is a function of favorable eastern based activity. So if the western side of the EPAC and the CPAC can maintain or induce activity, then that means the eastern portion of the EPAC is more than favorable. If the eastern portion of the EPAC is not favorable then the rest of the basin is not favorable as well.

Not sure I agree. We often see seasons that are more west based especially in west based el Ninos (although when we do get storms more east, they're often strong). 2004, 2009, and 2015 are good examples of this. In neutral years or when the EPAC is in its quiet phase, the center of activity shifts east, even in hyperactive years like 2014.

[Yellow Evan]

https://www.esrl.noaa.gov/psd/cgi-bin/d ... Timeseries

April EPAC SST's 2nd highest on record after 2015.

[NotSparta]

From which TCs?

The ones from the west based activity you were talking about. If the CPAC and western EPAC were active, the outflow from the TCs formed would shear the EPAC further east and maybe the Caribbean

How TC genesis generally works in the EPAC, is that you have disturbances off of CA or SW Mexico in the eastern portion of the EPAC. They develop as they move west or recurve towards Baja or central Mexico. It's rare that isolated disturbances develop close to 140W or the CPAC unless it's monsoon trough activity. Let's not forget the EPAC basin is quite large. We've seen numerous times that this basin can have a train (up to 3 or 4) of tropical cyclones ranging from the far EPAC to the CPAC.

So to get TC induced shear from the CPAC or western based activity to affect the EPAC is almost impossible because 1, the activity is coming from the eastern Pacific so conditions are automatically favorable, and 2, the basin is large enough to maintain a number amount of TC's. It's like saying that hurricanes originating in the western Caribbean are going to cause enough shear to shut down the entire Atlantic MDR and tropical Atlantic.

Ah, I see. I thought you meant mostly activity from the CPAC/western EPAC but not the eastern EPAC. That makes more sense

[Kingarabian]

With the possibility of development this far west, it further reinforces my thought that the activity will be west based this year, and that there may be a sizable amount of development in the CPAC.

In the EPAC, western based activity is a function of favorable eastern based activity. So if the western side of the EPAC and the CPAC can maintain or induce activity, then that means the eastern portion of the EPAC is more than favorable. If the eastern portion of the EPAC is not favorable then the rest of the basin is not favorable as well.

Not sure I agree. We often see seasons that are more west based especially in west based el Ninos (although when we do get storms more east, they're often strong). 2004, 2009, and 2015 are good examples of this. In neutral years or when the EPAC is in its quiet phase, the center of activity shifts east, even in hyperactive years like 2014.

Other than 1994, the rest of the most recent western based El Nino's technically behaved just like traditional El Nino's:

1992:


2002:


In neutral or La Nina years, activity remains east due to unfavorable conditions west. It's an illusion. During non El Nino years, it seems that there is more activity bunched and focused east, but it's just the same amount of systems that you would normally see during an El Nino but-minus the disturbances that got killed when they moved west.

[Kingarabian]

I think some are getting the wrong idea that if we see long tracking storms and more CPAC development than average, then that means the far eastern Pacific is in a La Nina state and there wont be excessive shear over the Caribbean. That's not true, unless we get a true Modoki El Nino and Nino 1+2 sustains level at or below -1C. Remember that even in western based El Nino events like recently 2009, and 2015 (warmer SST anomalies in the CPAC), the Atlantic hurricane season was pretty quiet.