2021 EPAC Season

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Ubuntwo
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Re: 2021 EPAC Season

#1061 Postby Ubuntwo » Thu Oct 07, 2021 6:21 pm

Should get an invest soon.

1. A tropical wave emerging over the Pacific coast of Central America
is producing disorganized showers and thunderstorms over portions of
Central America and the adjacent eastern Pacific waters.
Environmental conditions are forecast to be conducive for
development over the next several days, and a tropical depression is
likely to form over the weekend or early next week while the system
moves westward to west-northwestward.
* Formation chance through 48 hours...low...30 percent.
* Formation chance through 5 days...high...80 percent.
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Re: 2021 EPAC Season

#1062 Postby Yellow Evan » Thu Oct 07, 2021 6:43 pm

aspen wrote:So far the ceiling looks pretty high for Pamela. The GFS has consistently shown a favorable 200mb-level environment and RI on nearly all of its runs, and SSTs of 30-30.5C are capable of supporting a sub-900mb storm. However, this is a -ENSO year, and the GFS has hyped up plenty of EPac systems this year that fell way short of expectations.

Pamela will only become anything significant if:
—It organizes at the pace the GFS has shown it to
—The UL environment is indeed favorable like the GFS says it’ll be
—No pesky mid-level shear pops up
—The precursor disturbance isn’t too broad that it slows development and/or results in a large core that’s hard to tighten up
—The presence of a -ENSO somehow doesn’t impact it

If Pamela somehow overcomes or avoids all of those hurdles, watch out Mexico.


The setup is quite favorable with cold air damping triggering the gap event in the Gulf of Tehuantepec, which will enhance the vorticity over the upcoming days, plus the favorable trough interaction from an unseasonably strong trough off the West Coast. These events have help trigger several powerful hurricanes in this area before in the fall, most notably Patricia and Willa so I’d be a little surprised if the UL modeled by the GFS did not verify. The GFS does have issues in the medium and long range with moving the MJO too quickly across the Pacific and showing an American standing wave like pattern anytime MJO is in the Pacific yes but the GFS has shown this feature for several days now and has moved the timeframe earlier. There’s no CAG involved just a compact wave moving over the dry Atlantic so it’s not likely to be particularly broad. While at times the ECMWF was showing a setup that could invoke mid to upper level shear, it’s been trending away from that for several runs now, and global models in general have gotten better at predicting mid level shear. It’s also not impossible to get a strong recurving hurricane in a -ENSO (I believe October has had 4 -ENSO hurricane landfalls) though climo certainly isn’t on its side, and why I was skeptical of this back on Sunday. Given the impressive consistency and realism of the GFS and the fact that other models have at least been hinting (ICON, ECMWF) at sometimes showing a very similar setup, I’m fairly sure we get something formidable near the Mexican coast. It’s maximum strength will largely depend on how fast it gets going, which the GFS has previously been overdoing prior to yesterday, and to a lesser extent, depends on at what point does recurvature begin.
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Re: 2021 EPAC Season

#1063 Postby Yellow Evan » Thu Oct 07, 2021 6:48 pm

Weather Dude wrote:GFS peaks it at 970mb. Which means the next run will be back in the 940s :lol:

Back and forth back and forth 8-)


GFS back to its usual tricks with the vorticity and may be why the rate of strengthening was delayed this run. Considering the GFS can’t really handle inner core dynamics that are likely to control the intensity of potent systems, the difference between 940 mbar and 970 mbar is pretty small anyway.

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Re: 2021 EPAC Season

#1064 Postby Kingarabian » Thu Oct 07, 2021 8:35 pm

Maybe in a warmer ENSO regime. Not seeing it to be honest. This area has been a graveyard despite the models originally showing development.
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Re: 2021 EPAC Season

#1065 Postby Yellow Evan » Thu Oct 07, 2021 9:29 pm

Image

18z GFS showing as favorable of a sounding as you'll find tbh. Just can't go north of 20-21N.
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Re: 2021 EPAC Season

#1066 Postby Yellow Evan » Fri Oct 08, 2021 1:20 am

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Re: 2021 EPAC Season

#1067 Postby Yellow Evan » Fri Oct 08, 2021 1:31 am

ZCZC MIATWOEP ALL
TTAA00 KNHC DDHHMM

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
1100 PM PDT Thu Oct 7 2021

For the eastern North Pacific...east of 140 degrees west longitude:

1. A tropical wave moving offshore of the Pacific coast of Central
America is producing disorganized showers and thunderstorms over
portions of Central America and the adjacent eastern Pacific waters.
Environmental conditions are forecast to be conducive for
development over the next several days, and a tropical depression is
likely to form over the weekend or early next week while the system
moves westward to west-northwestward.
* Formation chance through 48 hours...low...30 percent.
* Formation chance through 5 days...high...80 percent.

Forecaster Latto/Papin
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Re: 2021 EPAC Season

#1068 Postby Yellow Evan » Fri Oct 08, 2021 4:18 am

Image

0z GFS came in stronger and a little further left, with genesis occurring in 48 hours. Will say this run has a little more southwesterly shear on Wednesday than the 18z run

Image

0z ECMWF back to normal. One thing to keep an eye on is the fact that the ECMWF moves this faster than the GFS especially in the day 2-3 which could mean less time over optimal conditions.
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Re: 2021 EPAC Season

#1069 Postby cycloneye » Fri Oct 08, 2021 6:35 am

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
500 AM PDT Fri Oct 8 2021

For the eastern North Pacific...east of 140 degrees west longitude:

A tropical wave is producing disorganized showers and thunderstorms
a few hundred miles south of the coasts of El Salvador, Guatemala,
and southern Mexico. Environmental conditions are forecast to be
conducive for development, and a tropical depression is likely to
form late this weekend or early next week while the system moves
westward to west-northwestward at about 15 mph south of the coast
of Mexico.
* Formation chance through 48 hours...medium...40 percent.
* Formation chance through 5 days...high...80 percent.

$$
Forecaster Berg
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Re: 2021 EPAC Season

#1070 Postby aspen » Fri Oct 08, 2021 6:44 am

We should get an invest soon, but seeing how hesitant they are to declare EPac invests, it could be a while. The first HWRF runs should be very interesting given the mostly favorable setup the GFS and Euro are agreeing on.
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Re: 2021 EPAC Season

#1071 Postby aspen » Fri Oct 08, 2021 8:15 am

06z GFS is the strongest run yet - 935mb before landfall on Wednesday afternoon.
Image
Image

Shear remains very low (<10 kt) until later on Wednesday. The environment is very moist with 30-31C SSTs and good outflow, however.
Image
Image

SSTs are ridiculously high for a -ENSO October. The track I marked is the 06z GFS track from 72-144 hours, with approximate uncertainty ranges based on other runs.
Image
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Re: 2021 EPAC Season

#1072 Postby Iceresistance » Fri Oct 08, 2021 8:42 am

aspen wrote:We should get an invest soon, but seeing how hesitant they are to declare EPac invests, it could be a while. The first HWRF runs should be very interesting given the mostly favorable setup the GFS and Euro are agreeing on.

You spoke too soon :lol:

viewtopic.php?f=59&p=2950970#p2950970
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Re: 2021 EPAC Season

#1073 Postby WiscoWx02 » Fri Oct 08, 2021 10:31 am

Really beginning to think the whole idea that La Nina and -PDO making it unlikely to spawn a powerful Pacific hurricane is about to bust majorly...literally in the sense of 91E likely becoming a major hurricane at this point. Has busted before, with the most recent example being Seymour in 2016.
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Re: 2021 EPAC Season

#1074 Postby Ubuntwo » Fri Oct 08, 2021 10:54 am

WiscoWx02 wrote:Really beginning to think the whole idea that La Nina and -PDO making it unlikely to spawn a powerful Pacific hurricane is about to bust majorly...literally in the sense of 91E likely becoming a major hurricane at this point. Has busted before, with the most recent example being Seymour in 2016.

Nothing is absolute and of course the Pacific pumps out canes during -ENSO events. The atmosphere has yet to respond to the Nina pattern & even with generally unfavorable conditions at least a couple storms will find a good environment. 1992 was an El Nino year and we all know what happened in the Atlantic. It only takes one, right?

IIRC updated EPAC climo is for 4 majors/year.
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Re: 2021 EPAC Season

#1075 Postby Yellow Evan » Fri Oct 08, 2021 11:17 am

:uarrow: 1992 was not an El Niño year.
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Re: 2021 EPAC Season

#1076 Postby Yellow Evan » Fri Oct 08, 2021 12:14 pm

Image

Looking less favorable on Thursday’s 45 day EPS run for additional post-91E late season activity and more favorable for Caribbean activity.
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Re: 2021 EPAC Season

#1077 Postby WiscoWx02 » Fri Oct 08, 2021 1:43 pm

Ubuntwo wrote:
WiscoWx02 wrote:Really beginning to think the whole idea that La Nina and -PDO making it unlikely to spawn a powerful Pacific hurricane is about to bust majorly...literally in the sense of 91E likely becoming a major hurricane at this point. Has busted before, with the most recent example being Seymour in 2016.

Nothing is absolute and of course the Pacific pumps out canes during -ENSO events. The atmosphere has yet to respond to the Nina pattern & even with generally unfavorable conditions at least a couple storms will find a good environment. 1992 was an El Nino year and we all know what happened in the Atlantic. It only takes one, right?

IIRC updated EPAC climo is for 4 majors/year.


I wasn't going to use this against the Atlantic actually....I was more alluding to the fact that a lot of people are in doubt of this happening because we are heading to La Nina again. Yeah, La Nina should mean little activity this time of year in the east Pacific, but that doesn't mean something is impossible.
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Re: 2021 EPAC Season

#1078 Postby Ubuntwo » Fri Oct 08, 2021 2:06 pm

Yellow Evan wrote::uarrow: 1992 was not an El Niño year.

You’re right. 1992 saw a rapid transition from Nino to cool neutral. I think the gist of my point still stands :P
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Re: 2021 EPAC Season

#1079 Postby Ubuntwo » Sat Oct 16, 2021 10:14 pm

Moderate ensemble support beyond day 5:
Image
Image
Some op. models onboard but only the GFS has more than a depression. Convective feedback? Time will tell...

The MJO state favors increasing TC formation potential over the East Pacific in the near-term, and Caribbean Sea later in the forecast period. The ECMWF model forecasts a pair of atmospheric Kelvin waves to have their suppressed phase cross the East Pacific and Atlantic during Week-2 though, which through destructive interference with the favorable MJO environment may limit TC genesis potential to brief windows. For the East Pacific, that genesis window appears to be late in the week of the 17th, with the moderate confidence for TC formation area along 10N during Week-2 maintained from the initial outlook.
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Re: 2021 EPAC Season

#1080 Postby Yellow Evan » Sun Oct 17, 2021 1:59 am

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