WPC Met Watch |
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Mesoscale Precipitation Discussion: #0830 (2020) |
(Issued at 1229 AM EDT Sun Oct 25 2020
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MPD Selection |
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Mesoscale Precipitation Discussion 0830
NWS Weather Prediction Center College Park MD
1229 AM EDT Sun Oct 25 2020
Areas affected...portions of the southeastern FL Peninsula
Concerning...Heavy rainfall...Flash flooding possible
Valid 250427Z - 251000Z
Summary...Heavy rain with rates near 3 in/hr will be found along
coastal locations of the southern FL Peninsula through at least
10Z. Given wet antecedent conditions and the urban nature of the
region impacted, flash flooding will be possible with localized
maxima between 3-6 inches.
Discussion...KAMX reflectivity showed slow moving heavy rain over
eastern Broward County at 04Z with radar estimated rates between 2
and 3 in/hr, supported by surface observations. The convection
appears to be focusing near a low level convergence axis which was
located near or just inland of the coast, with its northern end
possibly tied to an inferred low level circulation located 25-50
miles east of the coast of Martin County. An earlier northward
surge of moisture, seen in CIRA Layered PW imagery between the
surface and 700 mb, has helped increase precipitable water values
to 2.2-2.4 inches across the southern Peninsula and high wet bulb
zero heights over 15 kft will support efficient production of
rainfall via warm rain processes.
Modestly diffluent flow aloft will help to support lift throughout
the rest of the morning over FL as noted in short term RAP
forecasts. Meanwhile, a continued northward transport of tropical
moisture, emanating north from T.D. Twenty-Eight (located south of
western Cuba), will support waves of heavy rain with stalling of
cells at times given 850 mb flow near or in excess of average cell
movement to the north between 15-20 kt. Current thinking is that
potential for cell stalling will be greatest along the low level
convergence axis. Much of southeastern FL has seen 4-8 inches of
rain, locally in excess of 10 inches, over the past week which has
left the region more susceptible to flash flooding. An additional
3-6 inches (localized maxima) is expected through 10Z with rain
rates peaking near 3 in/hr.
Otto
ATTN...WFO...KEY...MFL...MLB...
ATTN...RFC...SERFC...NWC...
LAT...LON 27278023 27218002 26907987 26507981 26007986
25567998 25198029 25258057 25518063 25988050
26668042 27148034
Last Updated: 1229 AM EDT Sun Oct 25 2020
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