Sep 10, 2017 0600 UTC Day 1 Convective Outlook
Updated: Sun Sep 10 05:33:04 UTC 2017 (20170910 1200Z Day 1 shapefile | 20170910 1200Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20170910 1200 UTC Day 1 Outlook Graphic
Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
ENHANCED 13,852 7,094,429 Miami, FL...Hialeah, FL...Fort Lauderdale, FL...Pembroke Pines, FL...Hollywood, FL...
SLIGHT 16,875 4,450,297 Jacksonville, FL...Orlando, FL...West Palm Beach, FL...Lakeland, FL...Deltona, FL...
MARGINAL 14,455 3,887,127 Tampa, FL...Cape Coral, FL...Savannah, GA...Gainesville, FL...Charleston, SC...
Probabilistic Tornado Graphic
20170910 1200 UTC Day 1 Tornado Probabilities Graphic
Probability of a tornado within 25 miles of a point.
Hatched Area: 10% or greater probability of EF2 - EF5 tornadoes within 25 miles of a point.
Day 1 Tornado Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
10 % 13,935 7,027,399 Miami, FL...Hialeah, FL...Fort Lauderdale, FL...Pembroke Pines, FL...Hollywood, FL...
5 % 16,860 4,542,567 Jacksonville, FL...Orlando, FL...Lakeland, FL...Deltona, FL...The Hammocks, FL...
2 % 14,455 3,953,290 Tampa, FL...Cape Coral, FL...Savannah, GA...Gainesville, FL...Charleston, SC...
Probabilistic Damaging Wind Graphic
20170910 1200 UTC Day 1 Damaging Wind Probabilities Graphic
Probability of damaging thunderstorm winds or wind gusts of 50 knots or higher within 25 miles of a point.
Hatched Area: 10% of greater probability of wind gusts 65 knots or greater within 25 miles of a point.
Day 1 Wind Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
5 % 45,220 15,403,284 Jacksonville, FL...Miami, FL...Tampa, FL...Hialeah, FL...Orlando, FL...
Probabilistic Large Hail Graphic
20170910 1200 UTC Day 1 Large Hail Probabilities Graphic
Probability of hail 1" or larger within 25 miles of a point.
Hatched Area: 10% or greater probability of hail 2" or larger within 25 miles of a point.
Day 1 Hail Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
No Risk Areas Forecast
   SPC AC 100533

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1233 AM CDT Sun Sep 10 2017

   Valid 101200Z - 111200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS TODAY ACROSS
   INTERIOR AND ATLANTIC COASTAL AREAS OF THE FLORIDA PENINSULA BETWEEN
   THE GREATER MIAMI METROPOLITAN AREA AND ORLANDO/MELBOURNE...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS SURROUNDING
   AREAS OF EASTERN AND SOUTHERN FLORIDA...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS WESTERN
   PORTIONS OF THE FLORIDA PENINSULA AND GEORGIA/SOUTH CAROLINA COASTAL
   AREAS...

   ...SUMMARY...
   Hurricane Irma will impact much of the Florida Peninsula into
   northeastern Florida today and tonight.  Among the potential
   hazards, associated thunderstorm activity will be accompanied by a
   risk for tornadoes, particularly across interior and coastal areas
   between Miami and Orlando.

   ...Synopsis...
   As upper troughing progresses east of the northern Atlantic Coast,
   models indicate that the mid-latitude westerlies will become
   generally confined to areas near and north of the Canadian/U.S.
   border during this period.  To the south, a much weaker but more
   amplified belt of subtropical westerlies will prevail, with one
   embedded closed low remaining more or less stationary west of the
   southern California coast.  More significantly, a downstream impulse
   is in the process of digging across the central/eastern Gulf Coast,
   and this is contributing to the gradual north/northwestward
   acceleration of Hurricane Irma, toward the lower Florida Keys.  Irma
   is expected maintain hurricane strength through today and tonight
   while  continuing to migrate north of the Keys, near the west coast
   of Florida, into Florida's Nature Coast by late tonight.

   ...Florida and adjacent south Atlantic coastal areas...
   The northward forecast track of Irma, along (near and just west of)
   Gulf coastal areas, could allow for an appreciable risk for
   longer-lived supercells across at least the interior peninsula and
   Atlantic coastal areas, with northward/northwestward storm motions
   tending to be aligned with the major axis of the peninsula.  North
   through east of the center of Irma, lower/mid tropospheric
   hodographs are forecast to be large to extreme in size, with
   considerable clockwise curvature, more than supportive of potential
   for sustained low-level mesocyclones, and the risk for tornadoes
   within the more moist and potentially unstable boundary layer air. 
   The extent of this potential will considerably hinge on boundary
   layer warming between the stronger convective bands pivoting around
   the circulation center of Irma.  This remains unclear at the present
   time, but at least a few tornadoes appear possible, particularly
   during the daytime hours within a corridor between the Greater Miami
   metro area and Orlando/Melbourne.

   Continuing tornado potential late this evening into daybreak Monday
   becomes more unclear farther to the north, particularly across and
   inland of Georgia/Carolina coastal areas, where near-surface wind
   fields may maintain a northerly component, emanating from a
   dry/potentially cool environment associated with expansive surface
   ridging centered over the lower Great Lakes region.

   ..Kerr/Picca.. 09/10/2017

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