Download 2016 South Florida Winter Outlook and Forecast Tips - Miami

2016 South Florida
Winter Outlook and
Forecast Tips
Robert Molleda
Warning Coordination Meteorologist
National Weather Service
Miami/South Florida Forecast Office
South Dade Freeze Climatology
• Since 1948, 31 years have had freezing
temperatures (32F or colder). Return period
is slightly over 2 years.
• Longest stretch without freeze since 1948: 6
years (occurred twice 1971-1977 and 19891995)
• No widespread freezes the past three
winters
South Dade Freeze Climatology
• Since 1948, 47 years have had temperatures
of 35F or lower (near freeze or freeze). 70%
of years since 1948.
• Lowest recorded temperature in S. Dade ag
area: 25F at Coop office (Dec 1989). 26F at
Tamiami Airport on Jan 11, 2010.
Source Region of Very Cold Air
Masses Affecting Florida
Polar Region
Siberia
Cold Outbreak Indicators
High pressure from
Canada centered over
North Dakota/Minnesota
and moving due south
towards Gulf coast and
Florida, with low
pressure over NE U.S. or
eastern Canada.
Brown lines roughly
depict wind flow around
the two systems, in this
case NW over Florida.
Cold Outbreak Indicators
Snow cover
deep into
southern U.S
(shown in
blue here).
Arctic air
blowing over
snow cover
will not warm
as fast as it
moves south.
2016 Winter Outlook
NOAA/Climate Prediction Center
Temperature Outlook: Jan-Mar
• Equal chances of
near, above or
below normal
temperatures for
south Florida
• Cooler signal much
of southern US and
warmer signal
northern US
Long-range NOAA/CFS Model
Temperature Projections: Jan-Mar
Long-Range Atmospheric Indicators
• ENSO (El Niño Southern Oscillation). In other
words, El Niño/La Niña
• This winter, we are in a strong El Niño
phase
• Other factors play a big role in winter weather
pattern across N. America, such as North
Atlantic Oscillation and Pacific-North
American Pattern
Wintertime El Niño Impacts in
North America
North Atlantic Oscillation
Slide Courtesy:
NWS Melbourne, FL
Periodic Fluctuation of Pressure Patterns over the North
Atlantic Ocean – Scale of Weeks – Primary Impact on Florida Winter Temperature
Warm
Positive
Cold
Negative
El Niño/La Niña and
South Florida Freezes
• 31 freeze seasons since 1948
- Neutral – 12 of 25 (1 in 2)
- La Niña – 11 of 21 (1 in 1.9)
- El Niño - 8 of 21 (1 in 2.6)
• Less frequent freezes during El Niño due to
influence of Pacific jet stream in cutting off
or modifying polar air mass intrusions into
SE United States
January-April
Jet Stream
1950-2015 Mean
Strong El Niños
- Direct relationship between strong El Niño and increased winter
storminess in Florida, mainly due to a southward shift in the
position of the jet stream over North America
- Increased storminess brings a greater potential for severe weather
with significant societal impacts
Some Possible Impacts of El Niño
on Florida Weather This Winter
and Spring Include
 Greater number of storms
affecting the southern United
States and Florida
 Higher chance of tornadoes,
severe thunderstorms and
flooding
 More rainy winter and spring
days
Dashed red line is Pacific jet stream.
Typical track of low pressure systems
affecting Gulf coast and Florida during
active El Niño patterns which can lead
to severe weather in Florida
 Slightly below normal
temperatures
South Florida 2015-2016
Dry Season Outlook
Element
Outlook
Dec-Apr
Temperature
Below Normal
(NOTE: mainly as a result of
Long-Term
Normal
Values/Frequency
64-66F Interior/W
67-69F East
cooler daytime temperatures.
Overnight lows tend to be
milder)
Precipitation
Above Normal
Storminess/Severe
Weather
Above Normal
Freeze
Below Normal
(pacific jet stream cuts
off/modifies polar air mass
intrusions)
12-15” Interior/W
15-21” East
32-41 precip days
5-6 events per season
(wind/hail/tornado/flood)
At least one per season
More Rainy Winter Days Across
All of South Florida
2016 South Florida
Winter Precipitation Outlook
Likelihood of
wetter than
normal/more
storminess for
Florida
Forecast Tips
• Years of experience amongst many NWS
forecasters are behind the following tips
Types of Freezes
• “Advective Freeze”: driven primarily by
rush of cold air into state. Accompanied by
strong and gusty winds throughout the
night. Rare occurrence for far South Florida,
but when they occur, have potential for
devastating impacts (1977, 1989, 2010)
Types of Freezes
• “Radiation Freeze”: driven by light winds
and clear skies allowing for ground to
release heat into space and cools off
quickly. Most common South Florida
freeze.
Timing of Temperatures/Winds
• First night after front usually the windiest night
but NOT the coldest night. Depends on exact
timing of frontal passage.
• Second or third night usually the coldest (with
lighter winds but not totally calm the entire night).
• Overnight winds can be very fickle and tricky to
forecast. Winds can keep temps up, but a brief
calm period can drop temperatures several degrees
in a very short time. Normally occurs second or
third night.
Typical “First
Night”
temperature
pattern.
“Advection”
Steady
temperature drop
through the night
with rather even
temperature
distribution.
Typical “Second
or Third Night”
temperature
pattern.
“Radiation”
Uneven
temperature drop
with large
difference
between inland
and metro/coast.
Timing of Temperatures/Winds
• Low dewpoints/dry air during afternoon leads to rapid
temperature drop after sunset and increases freeze
potential.
• Watch for very low relative humidity values during the late
morning/early afternoon (below 35 percent) coupled with
temperatures struggling to reach 60F despite full sun.
• Freezing temperatures can occur as early as Midnight, then
steady or rising afterward. Official forecast graphs have
very difficult time depicting the fast temperature drop
• Can sometimes get a second drop to freezing temperatures
just before sunrise
Where to Get Reliable
Weather Data
NWS Forecasts on the
Internet
• Miami-South Florida National Weather
Service (local weather forecasts and
warnings, video weather briefings, model
data, forecaster reasoning, etc.)
http://weather.gov/miami
• Climate Prediction Center (long range
outlooks – 2 weeks to one year)
www.cpc.noaa.gov
NWS Miami Web Site
Click on
second
map to
get
forecast
for a
specific
area.
http://weather.gov/miami
NWS Miami Web Site
You can also
enter
city/state/zip
at top left
Caution:
green box
may not
point to
right area.
Always
confirm with
map on right
weather.gov/miami
NWS Miami Web Site
Forecast Discussion
provides meteorologist
thinking behind forecast
Jump to Radar & Satellite
Images by clicking on
corresponding images
Hourly Weather Graph
gives hour-by-hour detailed
forecast for that location
weather.gov/miami
Forecast Database gives a
graphical representation of
forecast conditions.
Hourly Weather Graphs
Very useful for
hour-by-hour
breakdown of
forecast weather
conditions
Go here for
more
information:
http://www.nws
.noaa.gov/com/
weatherreadynat
ion/hourly_weat
her_graph.html
NWS Mobile Web Site for
Tablets and Smartphones
mobile.weather.gov
Also contains
hourly/3-hourly
breakdown of weather
conditions
Add to your device’s homescreen:
To add the widget to your mobile
device...
iOS: In Safari, click the "add to
home screen" link and it will place
an icon on your device.
Android: Choose which
homescreen view you want the icon
to appear on before creating the
shortcut. Then save page as a
bookmark to "create a shortcut to
homescreen" for the icon to appear.
VERY IMPORTANT Notes on NWS
Temperature Forecasts
• NWS forecast temps are for standard height of 6
feet above ground with good exposure.
• Temps near ground (2 ft or below) are frequently
a few to several degrees colder, especially on
nights with light winds.
• Be familiar with your particular area and “lay of
the land”.
• Temperatures in the field are usually several
degrees colder than at reporting stations.
Good Websites for Monitoring Local
Temperatures...Check Frequently on
Cold Nights
DO NOT RELY ON NWS
REPORTING SITES ALONE!
• Mesowest: http://mesowest.utah.edu/
• Weather Underground/Wundermap:
http://www.wunderground.com/wundermap/
• MADIS: https://madis-data.ncep.noaa.gov/MadisSurface
• IFAS Extension Weather Stations:
http://data.locherenv.com:8080/index.html
Make sure to monitor these sites on a regular basis (15-30
minutes) on potential freeze nights.
NWS Sites Only
Mesowest: All Networks (NWS +
Supplemental Sites
mesowest.utah.edu
Click on Florida
Select ALL NETWORKS to
get full data set
Weather Underground (Circled sites only
show up on this webpage)
Wunderground.com
IFAS ExtensionWeather Stations
http://data.locherenv.com:8080/index.html
NOAA Climate Prediction Center:
Good for long-range planning
www.cpc.noaa.gov
6-10 day and 8-14 day
outlooks give indication of
above/below normal
temperatures for that time
frame.
Updated each afternoon
Interactive Display link
gives additional detail
Anticipating Freeze Events
• About 5-7 days out, forecast confidence can
be quite low. Area forecast discussions are
good to assess level of confidence:
Link to Area Forecast Discussion
• Also check Hazardous Weather Outlook
• If trends hold, we will send out a freeze
outlook as early as 3-5 days before an event
a freeze outlook is issued. Continue to
monitor forecast discussion and hazardous
weather outlook.
Anticipating Freeze Events
• Continue to monitor up to
day before event
• Forecast graphics give good
areal perspective
• http://graphical.weather.gov
/sectors/mfl.php
Point forecasts derived from these data
Final (VERY IMPORTANT) Note on
NWS Temperature Forecasts
• NWS forecast temps are for standard height of 6
•
•
•
•
feet above ground with good exposure.
Temps near ground (2 ft or below) are frequently
a few to several degrees colder, especially on
nights with light winds.
Be familiar with your particular area and “lay of
the land”.
Temperatures in the field are usually several
degrees colder than at reporting stations.
Check field and area temperatures on a regular,
frequent basis on cold nights (at least every 15/30
minutes
Thank You!
Email:
[email protected]
Frost on car: NWS Miami parking lot
Dec 28th, 2010