WPC Met Watch |
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Mesoscale Precipitation Discussion: #0309 (2020) |
(Issued at 1034 AM EDT Sun Jun 07 2020
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MPD Selection |
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Mesoscale Precipitation Discussion 0309
NWS Weather Prediction Center College Park MD
1034 AM EDT Sun Jun 07 2020
Areas affected...Central Gulf Coast
Concerning...Heavy rainfall...Flash flooding likely
Valid 071433Z - 072033Z
Summary...Spiraling rain bands associated with T.S. Cristobal will
move onshore this morning. Hourly rain totals in excess of 1.5"
are expected. Totals through 19Z of 2-4" are expected with some
locally higher amounts possible. This is likely to lead to some
instances of flash flooding.
Discussion...Spiraling rain bands from T.S. Cristobal are
beginning to move onshore portions of central Gulf Coast, with
current radar imagery showing one band over the western/central FL
Panhandle and another closer to the center over southeastern LA
and southern MS. Radar estimates indicate hourly rates are in
excess of 1.5" in places.
As the storm center approaches the coast, expect an increase in
the low level flow and convergence, maximized over LA/MS/AL later
this morning, and a surge in the 850 mb moisture transport on the
heels of 35 to near 50 kt winds. This will continue to push very
anomalous tropical moisture into the outlook area, characterized
by PWs of 2 to 2.4 inches. Instability, currently tied to the
immediate coast (SBCAPE 500 J/kg) will be on the increase as the
system moves further north, and is expected to reach 1500-2000
J/kg by late morning and early afternoon. The combination of the
tropical air mass (warm cloud depths near 5 km), high PWs, maximum
low level convergence, and sufficient instability should yield
highly efficient and training rain bands over the area. Hourly
totals 1.5-2" will be likely at times and total amounts through
19Z of 2-4" are expected. Some of the latest hi-res guidance shows
the possibility of higher amounts 4-5" in this time frame. The
National Water Model near term streamflow response shows near much
above normal to high flows by this afternoon. Additional rainfall
with T.S. Cristobal will further saturate the grounds. As such,
some instances of flash flooding will become increasingly likely
today.
Taylor
ATTN...WFO...JAN...LIX...MOB...TAE...
ATTN...RFC...LMRFC...SERFC...NWC...
LAT...LON 31468747 31408590 31088518 30278500 29558502
30208625 30258709 30148807 29908878 29038908
29169080 30639027 31418876
Last Updated: 1034 AM EDT Sun Jun 07 2020
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