#308 Postby MississippiWx » Wed May 23, 2018 9:59 am
Kind of long, but here is an excellent discussion from NWS New Orleans with details about the system this weekend. They explain the differences between the GFS/Other models and why the GFS is a bit suspect, but still a possibility. Enjoy!
“A long wave trough over the open eastpac will dig today causing
the subtropical jet to buckle offshore of the Baha Pen. This will
also kick the large upper low over the innermountain west to the
NE. As the subtropical jet buckles southward over the eastpac, it
will buckle northward downstream over northern Mexico and southern
Texas by late today. This will be the first chance to get a good
sampling of these jet winds and get something concrete to injest
in the model solutions. This could occur as early as 00zThursday
or (7pm)today if we get a good set of RAOB out of northern Mexico.
So the evening model runs should tend to come into better
agreement. If not, we will need to wait on the 12zThursday run
when the subtropical jet has moved into southern Arizona, New
Mexico and Texas. The reaction to all this buckling upstream will
cause a strong buckling southward in the jet over the gulf digging
out a deep and eventually sharp upper trough. Relatively stronger
winds will continue to be brought down on the west side of this
trough causing it to become sharp and stand through the weekend
and well into next week. All models do this, but the GFS would
like to keep wind speeds the same width and equal across the
channel through the base of the trough. Although the wind speeds
do slow by 10kt as they accelerate in direction around the trough
base. This occurs even as the trough sharpens. This seems a little
suspect. The Euro has this belt of winds much narrower when
accelerating through the base of the trough which would seem more
accurate. The area this occurs is near over the Yucatan and the
time frame is SUN 06z, then again at 18z. But the GFS would be a
better case than the EURO, bringing the area around 3 to 6 inches
of rainfall through mid next week.
All other models have something in between or totally 180 from
this. The Euro wants to keep the broad sfc circulation and
attendant sfc low coupled while large convective blowups
repetitively cause their own small convective lows and
circulations. And it looks as if the EURO would like to keep the
larger sfc low moving into the areas of intense convection to
couple and become the new slightly stronger sfc low. This may be
why the Euro also deepens the system the most. This scenario
would also make sense, especially since the upper trough should
remain in place allowing for these intense bursts and transport of
the sfc low northward along the belt of deep moisture. If this
were to play out though, it would be the worst case scenario out
of all other model solutions by bringing the area rainfall totals
of 8 to 12 inches as the sfc low would wobble and lose stearing as
it reaches the coast.
So all in all, both these solutions are possible with only the GFS
being slightly questionable with the subtropical jet. But either
only one or something in between will eventually play out. Again,
the sampling of the subtropical jet late today or Thursday morning
will give much better clues to which or these scenarios will be
more accurate. But regardless of which solution wins, the area
will receive some relatively high totals of rainfall starting
Saturday and lasting into at least mid next week.”
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This post is not an official forecast and should not be used as such. It is just the opinion of MississippiWx and may or may not be backed by sound meteorological data. It is not endorsed by any professional institution including storm2k.org. For Official Information please refer to the NHC and NWS products.
