Mainland South Florida Tropical Briefing

Mon Sept 27 10 AM

Rob Molleda

National Weather Service

Miami/South Florida

Forecast Office

Area of Disturbed Weather in Caribbean Sea

Remnant of

Matthew

Deep Moisture

EXTREMELY HIGH atmospheric moisture content

• Low pressure south of Keys moving northward.

• Caribbean moisture surges northward

• Purple and red colors indicate high 6-hour rainfall amounts of over 3 inches

Model Forecast: 8 AM Wednesday

Model Forecast:8 PM Wednesday

• Low moves north of area.

• Moisture lingers over area, although heaviest rainfall begins to shift north of region.

Rainfall Forecasts

8 AM Tuesday – 8 AM Wednesday

• Average of 3-4 inches over much of South Florida.

• Isolated areas typically could see as much as twice that amount.

Rainfall Forecasts

8 AM Wednesday – 8 AM Thursday

• Average of 2-3 inches over eastern half of South Florida.

Summary

• Tropical (or subtropical) system may or may not develop south of Florida.

• Regardless of what type of system impacts our area, the main threat is for torrential rainfall and potential for significant flooding.

Rainfall Forecasts

• Model forecasts and human-adjusted forecasts suggest 2-day average rainfall amounts of 5-8 inches over parts of South Florida from 8 AM Tue to 8 AM Thu.

• This type of weather pattern favors development of heavy rain bands which could produce even higher rainfall values.

Impacts• Flooding: Significant flooding entering

structures is possible, especially in historically flood-prone areas.

• Timing: Late Tuesday through Wednesday night.

• Too early to pin down with high confidence areas most likely to receive worst flooding.

• Present indications are that the SE Florida metro areas may be more likely to see greatest flood potential.

Impacts

• Flood Watch may be issued early tomorrow. This means that the potential exists for significant flooding affecting property.

• Tornado threat may be higher than normal, but right now not our primary concern.

Questions?

Thank you for your time!

National Weather Service

Miami/South Florida Forecast Office