2020 Global Model Runs Discussion (Out thru day 16)

[crownweather]

Maybe or not? This is 12z GFS on days 10-12.

https://i.imgur.com/uOuLGe7.gif

Nada on the 12Z Canadian. We await the Euro to see what its day 10 prog looks like.

[Astromanía]

Be careful with early model runs, especially if it's GFS, most of them are just ghosts

[cycloneye]

Maybe or not? This is 12z GFS on days 10-12. 12z ECMWF has something on day 9 in NGOM but goes inland to the northeast.

https://i.imgur.com/uOuLGe7.gif

https://i.imgur.com/SrUA7E9.png

Quoting myself.

[cycloneye]

Very interesting about the lack of planes that may have something to do with this big fall in the models.

 https://twitter.com/RyanMaue/status/1244989136450306048

[cycloneye]

Something to watch.

 https://twitter.com/AliciaMBentley/status/1245058874182373377

[crownweather]

The first 384 hr GFS tropical system of the season. In a way though, it makes sense as conditions may be favorable during the second half of May for a early season tropical system.

[Ivanhater]

The first 384 hr GFS tropical system of the season. In a way though, it makes sense as conditions may be favorable during the second half of May for a early season tropical system.

https://i.imgur.com/ID3btPl.png

I was just about to post this. An early season system would make sense. If anything, it is a sign the tropics are waking up.

[cycloneye]

Plenty of time to watch as the MJO makes it's way by mid May into the GOM / Caribbean / West Atlantic.

[chaser1]

Looks like the mid range GFS is also painting some fairly low SLP's in the W. Caribbean. I could easily see the Eastern extension of the EPAC ITCZ bulging up and into the southwest Caribbean beginning around the 2nd week of May. Still, my bet would be for something sloppy in the GOM to start things off.

[TheStormExpert]

With the return of the East Coast trough this month I could see there being some weak/messy Tropical or Subtropical mischief occurring anywhere from the Eastern GoM or just off the SE U.S. coast mid-late May.

[TheAustinMan]

This far out, I wouldn't use the operational model guidance to make judgements at the 2 week range. It'll show just one scenario out of many during a transitional period as we head towards the early summer pattern. Ensembles probably offer the most useful guidance that far out. Climatologically, May-June is the first of two periods favorable to the formation of the Central American Gyre (CAG), a broad cyclonic circulation that often develops over Central America. They are probably the Atlantic's equivalent to the monsoonal gyres most commonly found in the Northern Indian Ocean. There are about 1-2 CAGs annually, with one typically in May-June and the other between September and November.

Importantly, these gyres can be quite persistent, and can provide an influx of moisture and vorticity that could lead to the formation of a tropical cyclone. This provides a focusing mechanism for storm development within the Atlantic's most favorable region of this time of year. Sometimes its the gyre itself that slowly evolves into a tropical cyclone, while other times it's a low that develops on the gyre's periphery that develops within the favorable conditions. Tropical cyclone developments on Central American Gyres, if they do happen, are most common on the gyre's northeastern flanks. The most recent example of a CAG-developed system in the early season was Tropical Storm Alberto in May 2018. These sorts of storms are often associated with the disorganized, broad, and ugly variety, but ultimately it's the path of these storms and the surrounding conditions that dictate their development (for instance...). Alongside stalled fronts over the ocean, CAGs probably offer the best opportunity for tropical cyclogenesis in June and July.

Looking at the GEFS ensemble, we see some signs of a potential CAG developing in about 10-12 days (note the cyclonic flow centered over Costa Rica in the 850hPa wind/vorticity image below, with westerlies and northerlies in the EPAC and easterlies and southerlies in the Caribbean). Even with ensembles I would caution "looking too far", but at least on the May 1/06z run it appears that this CAG could persist through May 17. Unsurprisingly, this modeled CAG is accompanied by enhanced precipitation over the western Caribbean and a general lowering of pressures in the region.

Of course, CAGs do not guarantee the development of tropical cyclones in the Caribbean/Gulf/East Pacific, but they remain important to monitor due to their production of favorable conditions and their potential for flooding rainfall in Central America. As cycloneye mentioned earlier, this modeled gyre appears to be aligned with a modeled increase in upper-air divergence, supportive of rising motion in the atmosphere that could lead to enhanced convection. If this gyre persists in the model guidance, Philippe Papin at UAlbany runs an excellent site for visualizing the model CAG on both the operational GFS and ECMWF. Here's a guide on how to interpret his maps.

271 KB. Wind flow and rotation at the 850mb level modeled by GEFS for May 12. Source: Tropical Tidbits

[Dean4Storms]

Did note the ECM Ensembles Precip forecast out 15 days places much of the southern half of the Gulf, NW Carib. Sea across South Florida and up the East Coast with above normal precip. With the MJO and all the other factors mentioned an early season development is not out of the question.

[Steve H.]

In season's that were continuously busy throughout the season, 1995's Allison I believe kicked it off right in the first week of June forming in the western Caribbean and moving up in the Eastern GOM as I remember as a Cat 1. That kicked off a crazy busy hurricane season that hadn't been seen in decades, and hordes of new born storm trackers

[Kingarabian]

The Euro has a weak retrograding feature in the BOC starting around hour 192.


GFS continues to try spinning something up in the EPAC.

Bottom line, it's still far out but I think this upcoming MJO passage will open up a window for development on both sides of the EPAC and ATL basins.

[chaser1]

The Euro has a weak retrograding feature in the BOC starting around hour 192.
https://i.imgur.com/kXUlIaf.gif

GFS continues to try spinning something up in the EPAC.

Bottom line, it's still far out but I think this upcoming MJO passage will open up a window for development on both sides of the EPAC and ATL basins.

ICON also suggesting falling pressures in the BOC as well towards the end of it's 10 day range.

[cycloneye]

Is after the 15th north of Puerto Rico so let's wait a few days to see the real picture but the MJO will be around by that time.

[JetFuel_SE]

Is after the 15th north of Puerto Rico so let's wait a few days to see the real picture but the MJO will be around by that time.

It also looks like that EPAC system tries to regenerate in the WCAR

[cycloneye]

12z GFS on long range has this. Plenty of time to see if it occurs and if other models join later.

[toad strangler]

Don't know much about this guy at all but first impressions are not good. He swings back and forth between yelling at those using 240 hr plus maps and then uses them himself

 http://twitter.com/DaDaBuh/status/1257388274852782086

[cycloneye]

A reminder that the season is approaching when you begin to see the models hinting different scenarios.

 https://twitter.com/webberweather/status/1257444277635989506