Severe Thunderstorm Warning 55, NWS Miami, FL

Area Forecast Discussion
National Weather Service Miami FL
254 PM EDT Mon Jun 22 2020

.Discussion...

Short Term (Today and Tuesday):

There is a weak 500mb ridge, that is weakening though the
afternoon, ahead of a 500mb trough. The main trough moving in is
centered in the Great Lakes Region. There is also a weak Bermuda
high maintaining the easterly flow in the lower levels. The other
player in the weather is the SAL. The SAL is not necessarily going
to move directly over the area, but may be along the periphery.
Depending on exactly where it sets up. Today, it may be a little
more over the area that thought, as any convection has so far been
hampered from developing today. We are still carrying chances of
active weather this afternoon, but models have back off of
PoPs,and continued to push the best chances to the western
interior.

However, this afternoons update has not made many changes to the
previous forecast, except to adjust PoPs to the current models.
The sea breezes along both coasts are set to develop in progress
inland this afternoon. With the Bermuda high given the overall
flow out of the east, the Atlantic sea breeze should dominate
today. However, weak ridging aloft, with the area under the
western side, has the steering flow out of the west. So, much like
the past couple of days, the convective cells will probably move
west at first, then back to the east in the evening.

Looking at this mornings sounding, there is plenty of CAPE, before
modifying the sounding. The sounding shows 2633 J/Kg. The modified
sounding for a high of around 89 F, shows CAPE values nearing 5000
J/kg. The sfc to 3km lapse rates were not too impressive once
again, coming in at 4.8 C/Km. the mid level rates are much better,
coming in at 6.7 C/Km. The NCAPE this morning was already at .24,
and the modified sounding should almost .4, which is extremely
high for South Florida. The 500mb temps should be around -9C, This
all adds up to any convective cells will have the ability to grow
tall, and holding a decent cold pool aloft. While the low level
shear is weak, st only 6, the Effective Bulk shear is 22,
basically moderate. The wind aloft is not particularly strong,
only around 20kts, but should be enough to keep many cells from
having their updraft killed by the downdraft. The freezing level
is a bit high, at over 15k ft, so, hail is not a significant
concern today. There is one other factor to mention, and that is
the SAL. Currently, the Saharan dust is still quite aways away on
the satellite feeds, and may move towards the area late this
afternoon or evening. It may even not get here until tomorrow.
But, even when it does, South Florida looks to remain on the
fringe, which typically causes the area to see enhanced convection
along the boundary. So, this is something to keep in mind for the
next few days, how the dust layer sets up around the area.

So, given all the different dynamics, the main concern, besides
typical frequent lightning, will be strong down-bursts, which may
produce locally damaging wind. Flooding of roadways, mainly in
urban areas is also possible today.

A very similar pattern looks to remain in place tomorrow, with
possibly a little more of the trough digging south. However, the
SAL may once again hamper any convective development. So, there is
a large amount of uncertainty with tomorrows forecast.

Long Term (Tuesday night through Sunday night):

Latest mid and long range model solutions depict broad high pressure
in control of the western Atlantic, with the edge of a sfc ridge
extending into the northern half of the peninsula, and keeping
prevailing ESE flow across SoFlo through much of the work week.
Meanwhile, a low and associated trough aloft will move into the Ark-
LA-Mis region Tue night, along with an associated sfc boundary
stretching across much of the SE CONUS.

The high/ridge north of SoFlo will provide enough blockage to
keep the aforementioned low and front well north of the area and
allow daytime heating and afternoon sea breezes to become the main
mechanisms for generating convection each day. But with the
prevailing easterly flow, much of the more significant convective
activity should develop towards the interior and Gulf coast areas
during the afternoon and early evening hours. The Atlantic side,
however, could still experience a few showers or storms late at
night as the warmer Atlantic waters provide enough BL instability,
and the easterly flow pushes those marine showers inland.

Vertical profiles on model soundings remain relatively humid despite
the fact of having SAL dust intrusion at the mid levels, which
should persist through the end of the long term. Thus, it is
reasonable to keep at least scattered afternoon showers and storms
in the forecast, and even an isolated strong storm or two enough to
produce damaging winds and brief periods of localized flooding. But
the drier conditions aloft should at least limit a little the
overall coverage of potential rain and storms.

The SAL event may also provide the atmospheric conditions for
experiencing hazy skies, warm temperatures and high heat indices.
Thus, expect temperatures to reach upper 80s to mid 90s each day,
along with heat index values hitting the 105-110F range. The highest
heat index values will likely happen over some of the interior
areas.

&&

.Marine...
No significant weather is forecast for the South Florida waters. A
bermuda high to the east is the main surface feature controlling
the wind pattern for at least the next few days. Seas should
remain benign through the week. The main concern will be localized
adverse weather due to heavy showers or thunderstorms, which could
potentially bring localized hazardous conditions such as rough
seas, strong wind, torrential rain, and waterspouts.

&&

.Aviation...
The weather has been unexpectedly quiet today. The Atlantic sea
breeze has developed and should be west of the east coast metro
areas by around 18z. This helps to affirm no mention of weather in
the east coast TAFs. However, even though it is currently quiet,
there is still a potential for TS to develop through the evening
hours. Tomorrow, it may be a repeat of today, with high
uncertainty of convection, mainly due to the Saharan dust that
may suppress convection through the day.

&&

.Preliminary Point Temps/PoPs...
West Palm Beach  77  91  77  90 /  10  20   0  40
Fort Lauderdale  79  89  79  89 /  10  20   0  40
Miami            78  91  78  91 /  10  10   0  40
Naples           76  91  77  91 /  20  20  10  30

&&

.MFL WATCHES/WARNINGS/ADVISORIES...
FL...None.
AM...None.
GM...None.

&&

Marine...13
Aviation...13
Short Term...13
Long Term...17

Hazardous Weather Outlook for South Florida
National Weather Service Miami FL
1057 AM EDT Mon Jun 22 2020

AMZ610-630-650-651-670-671-FLZ063-066>075-168-172>174-GMZ656-657-676-
230300-
Lake Okeechobee-Biscayne Bay-
Coastal waters from Jupiter Inlet to Deerfield Beach FL out 20 NM-
Coastal waters from Deerfield Beach to Ocean Reef FL out 20 NM-
Waters from Jupiter Inlet to Deerfield Beach FL from 20 to 60 NM-
Waters from Deerfield Beach to Ocean Reef FL from 20 to 60 NM
excluding the territorial waters of Bahamas-Glades-Hendry-
Inland Palm Beach-Metro Palm Beach-Coastal Collier-Inland Collier-
Inland Broward-Metro Broward-Inland Miami-Dade-Metro Miami-Dade-
Mainland Monroe-Coastal Palm Beach-Coastal Broward-Coastal Miami-
Dade-Far South Miami-Dade-
Coastal waters from Chokoloskee to Bonita Beach FL out 20 NM-
Coastal waters from East Cape Sable to Chokoloskee FL out 20 NM-
Waters from Chokoloskee to Bonita Beach FL from 20 to 60 NM-
1057 AM EDT Mon Jun 22 2020

...Strong to Severe Thunderstorms Possible Today and Tuesday...

This hazardous weather outlook is for South Florida.

.DAY ONE...TODAY AND TONIGHT

Thunderstorms: Scattered thunderstorms are forecast today into this
evening over South Florida and the adjacent waters. Strong to severe
thunderstorms will be possible, along with frequent lightning and
torrential rainfall. The greatest coverage of storms is likely to be
across interior sections of South Florida, though there is some
possibility for this activity to affect the Atlantic and Gulf coastal
and metro areas.

Waterspouts: There is a slight chance for waterspouts in association
with showers and thunderstorms over the waters of South Florida.

Wind: Thunderstorms wind gusts of 45 to 60 mph are possible this
afternoon. Some of these gusts could produce localized wind damage.

Hail: Hail will be possible today. While any hail would most likely
be small in size, very isolated hail reaching near quarter-size
cannot be ruled out with the strongest storms.

Flooding: Localized flooding will be possible over urban and poor-
drainage areas where thunderstorms repeatedly move over the same
locations.

Temperatures: Afternoon heat-index readings could reach 105 degrees
over interior sections of South Florida.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

Scattered thunderstorms, some strong to severe and with heavy
rainfall and frequent lightning, are forecast for Tuesday afternoon
and evening. Otherwise, isolated to scattered showers and
thunderstorms will be possible each day for the remainder of this
week into the upcoming weekend. Maximum heat-index readings are
forecast to reach 105 to 107 degrees each afternoon across southwest
Florida, with the highest of these readings across interior sections.

.SPOTTER INFORMATION STATEMENT...

Widespread spotter activation is not anticipated, however individual
spotters are encouraged to report high wind, hail, and flooding to
the National Weather Service Forecast Office in Miami. Please relay
any information about observed severe weather to the NWS while
following all local, state, and CDC guidelines.

For more information...visit the National Weather Service in
Miami website at www.weather.gov/miami.

Special Weather Statement
National Weather Service Miami FL
335 PM EDT Mon Jun 22 2020

FLZ067-068-222015-
Inland Palm Beach County FL-Metro Palm Beach County FL-
335 PM EDT Mon Jun 22 2020

...SIGNIFICANT WEATHER ADVISORY FOR NORTHEASTERN PALM BEACH COUNTY
UNTIL 415 PM EDT...

* At 335 PM EDT, National Weather Service meteorologists were
  tracking a strong thunderstorm near Canal Point, moving northeast
  at 15 mph.

* Winds in excess of 45 mph and funnel clouds possible with this
  storm.

* Locations impacted include...
  West Palm Beach, Palm Beach Gardens, Pahokee, Canal Point, North
  County Airport, The Acreage, Loxahatchee Groves and Caloosa.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

This activity was also developing in an environment favorable for the
formation of funnel clouds. Stay tuned to NOAA weather radio and
local media for additional updates and possible warnings.

To report severe weather, contact your nearest law enforcement
agency. You can also share your report with NWS Miami on Facebook and
Twitter.

&&

LAT...LON 2671 8058 2693 8070 2696 8069 2699 8062
      2696 8061 2696 8022 2675 8012
TIME...MOT...LOC 1935Z 239DEG 13KT 2685 8057

CWC

Special Weather Statement
National Weather Service Miami FL
417 PM EDT Mon Jun 22 2020

FLZ069>071-073-075-222100-
Coastal Collier County FL-Inland Broward County FL-
Inland Collier County FL-Mainland Monroe FL-Inland Miami-
Dade County FL-
417 PM EDT Mon Jun 22 2020

...SIGNIFICANT WEATHER ADVISORY FOR SOUTHEASTERN COLLIER...NORTHERN
MAINLAND MONROE AND NORTHERN MIAMI-DADE COUNTIES UNTIL 500 PM EDT...

* At 417 PM EDT, National Weather Service meteorologists were
  tracking a strong thunderstorm over Loop Road Ee Center, or 21
  miles east of Chokoloskee, moving northeast at 15 mph.

* Small hail, funnel clouds, and winds in excess of 45 mph possible
  with this storm.

* Locations impacted include...
  Shark Valley Obs Tower, Loop Road Ee Center, Dade-Collier Training
  Airport, Fortymile Bend and Big Cypress National Preserve.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

This activity was also developing in an environment favorable for the
formation of funnel clouds. Stay tuned to NOAA weather radio and
local media for additional updates and possible warnings.

To report severe weather, contact your nearest law enforcement
agency. You can also share your report with NWS Miami on Facebook and
Twitter.

&&

LAT...LON 2558 8103 2590 8127 2601 8078 2562 8055
TIME...MOT...LOC 2017Z 246DEG 14KT 2577 8099

CWC