Post by SKYSUMMIT on Sept 19, 2019 9:22:31 GMT -6
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Mesoscale Precipitation Discussion 0869
NWS Weather Prediction Center College Park MD
1111 AM EDT Thu Sep 19 2019
Areas affected...Southeast TX...Far western LA
Concerning...Heavy rainfall...Flash flooding likely
Valid 191509Z - 192109Z
Summary...Life-threatening flash flooding will continue across
portions of southeast Texas associated with Tropical Depression
Imelda. Extremely heavy rainfall will persist and drop south
toward Galveston Bay and the Houston metro.
Discussion...Tropical Depression Imeda is positioned 55 north of
Houston and is migrating north. As a result, expect heavy rainfall
to continue across portions of southeast TX into far west LA.
However, do anticipate the axis of heaviest rainfall to slowly
migrate south over the Houston metro area.
Over the next few (1-3) hours rain rates will remain very high
across this region. However, it is expected that the overall rain
rates will start to decrease by mid-afternoon. This is likely due
to the transition of the mid-level low position and forcing edging
northward which will aid in migrating the moisture flux/transport
away from the instability axis closer to the coast. Anticipate the
axis of heaviest rain/highest rain rates to shift toward Trinity
and Galveston Bay and the Houston metro area. This shift is
associated with the surface and boundary layer convergence
gradient which is farther south of the apparent low circulation.
Another factor that is contributing to the higher rainfall totals
is the training/backbuilding of convection oriented northwest to
southeast toward Hamshire, TX. This moisture feed is expected to
continue with the unidirection flow in place, though the position
should sag south.
Rainfall totals over the next couple of hours will be around 3 to
6 inches with locally higher amounts expected. Rain rates of over
3 inches per hour are still plausible as HREF probabilities are
still upwards of 50% for this threshold. Given heavy rain is
moving into areas already saturated from previous rainfall during
yesterdays activity, expect vulnerable soils to become iundated
rather quickly, especially across urban areas. Therefore, we are
continuing to message signicant to life-threatening flash flooding
across this region through mid-afternoon.
Pagano
Mesoscale Precipitation Discussion 0869
NWS Weather Prediction Center College Park MD
1111 AM EDT Thu Sep 19 2019
Areas affected...Southeast TX...Far western LA
Concerning...Heavy rainfall...Flash flooding likely
Valid 191509Z - 192109Z
Summary...Life-threatening flash flooding will continue across
portions of southeast Texas associated with Tropical Depression
Imelda. Extremely heavy rainfall will persist and drop south
toward Galveston Bay and the Houston metro.
Discussion...Tropical Depression Imeda is positioned 55 north of
Houston and is migrating north. As a result, expect heavy rainfall
to continue across portions of southeast TX into far west LA.
However, do anticipate the axis of heaviest rainfall to slowly
migrate south over the Houston metro area.
Over the next few (1-3) hours rain rates will remain very high
across this region. However, it is expected that the overall rain
rates will start to decrease by mid-afternoon. This is likely due
to the transition of the mid-level low position and forcing edging
northward which will aid in migrating the moisture flux/transport
away from the instability axis closer to the coast. Anticipate the
axis of heaviest rain/highest rain rates to shift toward Trinity
and Galveston Bay and the Houston metro area. This shift is
associated with the surface and boundary layer convergence
gradient which is farther south of the apparent low circulation.
Another factor that is contributing to the higher rainfall totals
is the training/backbuilding of convection oriented northwest to
southeast toward Hamshire, TX. This moisture feed is expected to
continue with the unidirection flow in place, though the position
should sag south.
Rainfall totals over the next couple of hours will be around 3 to
6 inches with locally higher amounts expected. Rain rates of over
3 inches per hour are still plausible as HREF probabilities are
still upwards of 50% for this threshold. Given heavy rain is
moving into areas already saturated from previous rainfall during
yesterdays activity, expect vulnerable soils to become iundated
rather quickly, especially across urban areas. Therefore, we are
continuing to message signicant to life-threatening flash flooding
across this region through mid-afternoon.
Pagano
