SPC MD 1636



MD 1636 CONCERNING SEVERE POTENTIAL…WATCH POSSIBLE FOR PORTIONS OF THE LOUISIANA/MISSISSIPPI COASTAL AREAS EASTWARD TO THE MOBILE BAY VICINITY

MD 1636 Image

Mesoscale Discussion 1636
NWS Storm Prediction Center Norman OK
0401 AM CST Mon Nov 12 2018

Areas affected...portions of the Louisiana/Mississippi coastal areas
eastward to the Mobile Bay vicinity

Concerning...Severe potential...Watch possible 

Valid 121001Z - 121230Z

Probability of Watch Issuance...60 percent

SUMMARY...Risk for surface-based/severe storms -- including some
tornado potential -- will continue to spread gradually northward
into coastal portions of the central Gulf Coast region.  A tornado
watch may eventually be required.

DISCUSSION...Latest surface analysis depicts a weak low near PSX
(Palacios TX), along a wavy surface baroclinic zone that is now
returning northward as a warm front across the northern Gulf.  The
front remains just off the Louisiana coast in all areas, with the
exception of the southern tip of Plaquemines Parish at the mouth of
the Mississippi.  

A sharp thermal/moisture gradient exists from the coastal regions to
the northern Gulf, with east-northeast surface winds maintaining 50s
F temperatures/dewpoints inland, and 70s observed just offshore. 
While the aforementioned east to northeast surface winds, and inland
precipitation, will keep northward advance of the warm front
restrained, the slow/steady advance of Gulf air will continue, as
the upper trough advancing gradually eastward permits modest
deepening/northeastward movement of the weak Texas coast frontal
low.

Strongly veering/increasing flow with height is observed via WSR-88D
VWPs inland/north of the front, within the zone of low-level warm
advection.  Large/looping hodographs are thus observed, with 0-1KM
shear quite favorable for low-level rotation.  Though low-level
shear is obviously less pronounced within the warm sector,
sustained/rotating storms developing over the Gulf and moving
northward across the boundary may be capable of producing inland
tornadoes as the morning progresses.  We will continue to monitor
evolution of both the warm front, and of the offshore storms, with
an eye toward possible tornado watch issuance over the next couple
of hours.

..Goss/Edwards.. 11/12/2018

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...MOB...LIX...LCH...

LAT...LON   29589358 29869301 29969180 30219094 30389013 30628909
            30668834 30438765 30068670 29798660 29198701 28758881
            28689109 29129190 29429355 29589358 

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