Thread by @althecat

[#CentralAmerica #ExtremeWeather #ClimateChangeNOW update THREAD (ongoing coverage - initiated October 2 - storms #Julia #Karl]

With #Karl now dissapated the next disturbance has now been designated by @NHC_Atlantic.

The situation remains complex and unpredictable with many significant variables at play which could alter the outcome. The latest complete GFS run shows the next hurricane landfalling in Mexico 24 Oct. & remnants forming into a Gulf cyclone on 26 Oct.

The latest GFS run (incomplete) does not see the storm reforming into a tropical storm in the Gulf, but the synoptic scenario here - with this storm forming and crossing Mexico has been fairly stable for some time - as indicated in previous #KARL #TSKarl updates.

Sticking with the 18.00 GFS run here in the PWAT presentation the variables become apparent.
1. The strength of a 3rd Tehuantepec wind gap event
2. The formation and development of #roslyn
3. The strength & timing of an Arctic air blast sth ove the US.

Given these complex variables the latest GFS run understandably has a different outcome - and a much stronger impact from a southerly arctic blast.

Ominously it also shows the development of a new tropical storm off the northern Coast of South America heading into the Carribean.

Here is a 24 hour animation over Southern Mexico and the Eastern Pacific where this stituation is currently developing. Yesterday and overnight it shows spectacular convection over Southern Mexico - which is presumably causing flash flooding.

The convective storms are developing along the coastal and inland mountain ranges of Mexico. and extend up the East coast of Mexico up to the US Border.

Here is a closeup 12 hour animation of these #Mexico rain storms which shows the development so far. This extreme weather rain event is ongoing.

This is providing another variable to the complex #ExtremeWeather synoptic situation - introducing mass water vapour to the Gulf.

Here is the full 18-06 IWVT run from GFS3 which provides additional perspective on this ongoing #ExtremeWeather event. In particular revealing the simulated origin of the storm which we can see in the forecast forming over the Carribean towards the end of the 16 day period.

This storm is simulated to form in the Pacific off the coast of Panama around 22nd-24th October. This clip of part of the full GFS IWVT forecast begins on the 24th and runs till the end on November 3rd.

At this point probably distraction - but it illustrates the complexity.

Completing this long range set up picture of the evolution of this #ExtremeWeather event, here is a North America PWAT simulation from the 18.06 run for the next 16 days.

It appears this persistent pattern over the US may be weakening at long last which, accompanied by the southwards progression of the ICTZ (Equatorial Tropical Water flow) ought to eventually bring an end to this.

The overall causes of this #CentralAmerica #ExtremeWeather event are this pattern of southerly arctic blasts (originating over Canada) and an equinox (sun crossing the equator) boost of tropical water flow from the West African/Tropical Atlantic Monsoon through the Carribean.