Special Marine Warning 289, NWS Mobile, AL

Area Forecast Discussion...UPDATED
National Weather Service Mobile AL
637 AM CDT Fri Aug 27 2021

.UPDATE...Did a quick update to grids and forecast for the early
part of the extended term, specifically for the Monday and Monday
night period. Bumped up PoPs to likely and categorical for that
time frame to better match surrounding offices. Still high moisture
levels indicate a continued threat of widespread rain. Otherwise,
no changes to previously released morning forecast package. /12

&&

.PREV DISCUSSION... /issued 614 AM CDT Fri Aug 27 2021/

NEAR TERM UPDATE /Now Through Saturday/...Upper level ridging
slowly builds in to the southeastern U.S. through Saturday as weak
upper level troughing begins to dig into the north-central U.S.
Saturday. At the surface, high pressure resides over the eastern
U.S. and what is currently Tropical Storm Ida will have transmitted
Cuba and entered the central Gulf of Mexico through Saturday
evening. In the mean time, weak upper level disturbances round the
southern periphery of our upper level ridge, and will continue to
bring us heightened rain/storm chances through the near term period.

A very convectively active marine zone early this morning will
gradually transition northwest into coastal counties over the next
few hours, resulting in a scattered to numerous coverage of showers
and thunderstorms. Forecast guidance seems most enthused about
coverage over southeastern MS into far southwestern AL through early
afternoon. Coverage should gradually diminish as we go into the
evening hours as showers and storms propagate inland.
We get a brief break in convection Friday night into Saturday
morning before the moisture surge with Ida starts to stream in,
enhancing shower and thunderstorm coverage through Saturday
afternoon and evening. Given high PWATs in the 2.2 to 2.4 inch
range, very heavy rainfall can be expected with any thunderstorms.
Some nuisance flash flooding can not be ruled out in thunderstorms
today and Saturday. MM/25

AVIATION...
12Z issuance...Showers and thunderstorms presently offshore should
move onshore by mid morning. VFR conditions prevail outside of
this activity, but expect temporary reductions in ceilings and
visibility to MVFR/IFR as these pass through the afternoon hours.
By tonight, showers and storms decrease in coverage and should
remain at best isolated. This will allow for VFR conditions to
once again prevail for the region. MM/25

PREV DISCUSSION... /issued 544 AM CDT Fri Aug 27 2021/

NEAR TERM UPDATE /Now Through Saturday/...Upper level ridging
slowly builds in to the southeastern U.S. through Saturday as weak
upper level troughing begins to dig into the north-central U.S.
Saturday. At the surface, high pressure resides over the eastern
U.S. and what is currently Tropical Storm Ida will have transmitted
Cuba and entered the central Gulf of Mexico through Saturday
evening. In the mean time, weak upper level disturbances round the
southern periphery of our upper level ridge, and will continue to
bring us heightened rain/storm chances through the near term period.

A very convectively active marine zone early this morning will
gradually transition northwest into coastal counties over the next
few hours, resulting in a scattered to numerous coverage of showers
and thunderstorms. Forecast guidance seems most enthused about
coverage over southeastern MS into far southwestern AL through early
afternoon. Coverage should gradually diminish as we go into the
evening hours as showers and storms propagate inland.
We get a brief break in convection Friday night into Saturday
morning before the moisture surge with Ida starts to stream in,
enhancing shower and thunderstorm coverage through Saturday
afternoon and evening. Given high PWATs in the 2.2 to 2.4 inch
range, very heavy rainfall can be expected with any thunderstorms.
Some nuisance flash flooding can not be ruled out in thunderstorms
today and Saturday. MM/25

SHORT TERM /Saturday night Through Sunday night/...Tropical Storm
Ida is going to be the main focus of the short term period. Ida is
presently located just north of Grand Cayman, moving northwest
towards the southwestern portion of Cuba. Ida will be transiting
the central Gulf of Mexico at the beginning of the short term period
Saturday night, likely as a hurricane. The track of Ida has become
clearer, and generally south-central into southeastern LA looks to
be the favored region for a landfall. There remains the potential
for additional shifts in track as Ida's near-term intensity,
strength of the upper level ridge, and strength of the eventual
north-central U.S. trough will play key roles in Ida's future. These
details should be figured out today with the assistance of hurricane
hunter reconnaissance data in their low level and upper air missions
this morning and afternoon. It is extremely important to NOT focus
on the exact path of the storm as impacts will reach far away from
the hurricane and outside of the forecast cone. These impacts will
be discussed below in detail for our area:

Tropical Storm Watch: A Tropical Storm Watch remains in effect for
the potential of tropical storm conditions during the short term
period. This is in place for far southeastern MS into far
southwestern AL and the marine waters. These will likely be upgraded
to warnings later today.

Storm Surge Watch: Ida will bring a high storm surge with it,
necessitating storm surge watches for the Mississippi Sound and
Mobile Bay for a 3 to 5 foot storm surge. This will likely be
upgraded to a storm surge warning later today. East of the watch
area through the Florida Panhandle, a coastal flood advisory is in
effect for up to two feet of anticipated water rise.

A High risk of Rip Currents goes into effect late Saturday evening
through late Monday night. Large swell height and periods will
foster the development of rip currents, along with strong onshore
winds.

Heavy rainfall is expected Sunday into Sunday night, and will
continue into the extended period. While it is too early at the
moment to issue a flash flood watch, one will likely become
necessary for southeastern MS into southwestern AL. Generally
anticipating storm total rainfall to be between 4 to 8 inches,
locally higher. This is particularly the case for southeastern MS.

The tornado threat will also begin to increase Sunday across
southeastern MS and far southwestern AL as the right front quadrant
outerbands of Ida begin to move into the area. The exact extent of
this threat will become clearer as we move forward in time.

In summary, a multitude of hazards will impact the area during the
short term period as Ida moves into Louisiana. Variations in the
track and intensity of Ida will have implications on the extent of
impacts to southeastern MS and southwestern AL/FL panhandle. Pay
close attention to any updates from the National Hurricane Center.
MM/25

EXTENDED TERM /Monday Through Thursday/...Conditions during the
beginning of the period will continue to be driven by IDA, which per
the latest NHC track is expected to have made landfall along the
northern Gulf late Sunday night. The system is expected to track
further inland through Tuesday and begin lifting slowly to the
northeast, with very high amounts of tropical moisture remaining
over the forecast area. This situation will continue to support
likely to categorical PoPs through Tuesday, then PoPs trend downward
to chance to good chance by Thursday as a typical summertime diurnal
convective cycle returns to the area. A potential for locally heavy
rainfall will continue through at least Monday, and mainly over the
western half of the area, although this is highly dependent on the
eventual track of IDA. A Flash Flood Watch will likely be necessary
for at least a portion of the forecast area early next week. A high
risk of rip currents will continue for Monday. Highs on Monday will
be moderated by the anticipated high coverage of precipitation, and
range from the lower 80s over southeast Mississippi to the mid to
upper 80s further to the east. Daytime highs then trend toward the
lower 90s by Thursday. Lows will be in the lower to mid 70s, with
the warmer overnight temperatures typically near the coast. /12

MARINE...Moderate southeast to east flow is expected to persist
into the weekend. Small craft exercise caution conditions will
continue through today, at least for the Gulf waters. Southeast
winds will then increase this weekend to be strong due to the
approach of Ida. Seas will gradually build through Friday, then
increase rapidly this weekend in response to Ida. Please visit
the National Hurricane Center's page for further details on Ida.
MM/25

&&

.MOB WATCHES/WARNINGS/ADVISORIES...
AL...Tropical Storm Watch for ALZ261>266.

     High Rip Current Risk from Saturday evening through late Monday
     night for ALZ265-266.

     Storm Surge Watch for ALZ263>266.

FL...High Rip Current Risk from Saturday evening through late Monday
     night for FLZ202-204-206.

     Coastal Flood Advisory from 7 PM Saturday to 7 PM CDT Monday for
     FLZ202-204-206.

MS...Tropical Storm Watch for MSZ078-079.

GM...Small Craft Advisory from 7 PM Saturday to 7 PM CDT Monday for
     GMZ634>636-655.

     Tropical Storm Watch for GMZ630>633-650-670-675.

&&

This product is also available on the web at:
http://weather.gov/mob

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MOBILE AL
214 AM CDT FRI AUG 27 2021

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0155 AM     MARINE TSTM WIND 3 E ORANGE BEACH        30.28N 87.53W
08/27/2021  M39 MPH          GMZ633             AL   AWOS

            ORANGE BEACH TEMPEST WEATHER STATION
            MEASURES WIND GUST TO 39MPH.

&&

MM

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MOBILE AL
224 AM CDT FRI AUG 27 2021

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0215 AM     MARINE TSTM WIND 3 E ORANGE BEACH        30.28N 87.53W
08/27/2021  M44 MPH          GMZ633             AL   AWOS

            ORANGE BEACH TEMPEST WEATHER STATION
            MEASURES WIND GUST TO 38KTS.

&&

MM