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Reading and Interpreting
Weather Data
WxLive! Session 2
Copyright © 2012 Weather4Sailors
The material contained in this document is for the exclusive use of WxLive webinar participants and may not be shared
without the permission of the copyright holder.
Objectives For the Series
• How to get weather info onboard? – How do we decide which equipment to use?
• How to read and interpret marine weather data
FYI:
• How to apply weather data to your Newport – Bermuda Race strategy will be held in June
Objectives For this Session
• How do weather systems work?
• How do we gather and interpret marine weather data
to determine future weather conditions?
• What are the best weather data sources (publically-
available)
• What are the phases of planning? – What weather data do we use in each phrase?
“Some People Are Weather-wise,
but Most Are Otherwise” Benjamin Franklin
Hosts
• Bill Biewenga – Over 400,000 nm at sea
– Multiple speed records, numerous races and deliveries
– 39 Transatlantics as well as passages through virtually every ocean of the world
– Author & lecturer
• Lou Roberts – Co-owner Weather4Sailors.com
– Winner 2008 Marion to Bermuda Short Handed Trophy
– Corporate consultant in instructional media and training
Panelists
• Ken Campbell
– Commanders’
Weather
• Joe Sienkiewicz
– National Weather
Service’s Ocean
Prediction Center
(NOAA)
Weather Acumen Questions
• Use the Chat Room to answer the
questions.
Public vs. Private
Weather Forecasters
• What’s the role of public (government)
vs. private weather forecasting?
• What’s the difference between
human/machine forecasting and
machine forecasting?
Topics
• Weather Maps (OPC)
• Satellite Images
• Radar Images
• Local Conditions
Weather Maps
Surf Anal, N Atl, Valid 06 28 07, 12Z
The Difference Ship Obs Makes
Weather Map Symbols
Weather Routing Wizard –
“Weather Map Symbols” Tool
Fronts
Professionals analyze frontal lows & high pressure centers first: Note added surface
ship observations are used to better position fronts & pressure centers…
Cold Front, Side View
Warm Front, Side View
Weather Maps
Surf Anal, N Atl, Valid 06 28 07, 12Z
Weather Maps
24 Hr Frcst, W N Atl, Valid 06 28 07, 12Z
Weather Maps
48 Hr Frcst, N Atl, Valid 06 28 07, 12Z
Weather Maps
96 Hr Frcst, N Atl, Valid 06 28 07, 12Z
Weather Maps
Surf Anal, N Atl, Valid 06 28 07, 12Z
Weather Map Animations
• Animations allow you to see the
direction and movement of weather
patterns.
Ocean Prediction Center (OPC) website
Health Break
500 mb Chart &
What It Tells Us • Numbers refer to ALTITUDE not Pressure
– All the contours are 500 mb of pressure
– Altitude is measure in meters above sea level
• Helps predict
– Speed and direction of surface lows
– Intensity of surface lows
• Influence on surface lows
– Cut off lows
– Blocking ridges
– High amplitude jet stream
– Low amplitude jet stream
500 mb Chart
• How surface low pressure system works
with the 5640 line
• Refer to 2 static maps (surface and 500
mb for the same timeframe)
500 mb Chart Valid 06 01 03, 00Z
Surface Analysis Chart Valid 06 01 03, 00Z
500 mb Chart
Cut off Low
500 mb Chart
Blocking Ridge
N Hemisphere High
N Hemisphere Low
Satellite Images Sat Pic, IR, N Atl, Valid 06 28 07, 12Z
Satellite Images Surf Anal, N Atl, Valid 06 28 07, 12Z
Scatterometer QuikScat
Scatterometer (ASCAT)
Scatterometer (OSCAT)
OSCAT in OPC operations
OSCAT
ASCAT
OSCAT and ASCAT in operations ASCAT and OSCAT: 1200 UTC 13 Mar
GFS wind speeds: 1500 UTC 13 Mar
GOES Sea Surface Temp: 1800 UTC 13 Mar
ACSAT-GFS difference: 1500 UTC 13 Mar
Numerical Forecast Models
GLOBAL ATMOSPHERIC MODELS • GFS – U.S. NWS Global Forecast System
– 4 x’s daily, global
• ECMWF – EU Center for Medium-Range Weather Forecasting
– 2x’s daily, global
• CMC – Canadian Meteorological Center
– 2x’s daily, global
• NOGAPS – Navy Operational Global Atmos Prediction System
– 4x’s daily, global
• UKMET - UK METeorological Office
– 2x’s daily, global
REGIONAL MODELS
Weather Research Forecast (WRF) Model based • NAM – U.S. North American Mesoscale Model
– 12 km to 4 km (6 hour cycle) (output hourly thru 36 hrs, then 3 hourly to 84 hrs)
• RAP – U.S. RAPid Refresh (formerly RUC, Rapid Update Cycle) – 13 km (hourly cycle) (output to 18 hrs)
• NWW3 – NOAA WAVEWATCH III
Using ASCAT/OSCAT to
confirm buoy &ship reports
Satellite Imagery Interpretation
• The Weather Routing Wizard contains
many job aids
• These job aids help simplify the
process of apply the theory in this
course.
• “How to Read Satellite Images” Tool
Animated Satellite maps
• NASA’s Global Hydrology website
shows animated and static near-real
time satellite images
NASA website
Health Break
GRIBs
• Gridded Binary files
• Based on computer models
• Common GRIB models include: • GFS – U.S. NWS Global Forecast System
• ECMWF – EU Center for Medium-Range Weather Forecasti
• CMC – Canadian Meteorological Center
• NOGAPS – Navy Operational Global Atmos Prediction System
• UKMET - UK METeorological Office
• NAM – U.S. North American Mesoscale Model
• RAP – U.S. RAPid Refresh (formerly RUC, Rapid Update Cycle)
• GFS model available at www.grib.us
Which model represents the
best forecast?
Therefore, how useful are GRIBs?
Radar
Animated Radar
• Animated radar is available on the web
• Shows rain, but not necessarily wind
• Shows clouds, but not height (vs.
satellite)
• Offshore constraints
– As a downloaded file - not practical for
offshore sailors with limited bandwidth
– Available through Sirius
• Using your radar to track fronts at night
Local Conditions
• Influences the larger, synoptic scale wx
• But CAN be the dominant weather
feature
Sea Breeze
• Weather Routing Wizard –
“Sea Breeze” Tool
Clouds & What They’re Telling Us
Weather Routing Wizard –
“Cloud Forecasting” Tool
Cloud Gallery Website –
“Cloud Gallery” website
Dealing With Islands
• Between island
– Convergent winds
– Divergent winds
• Circulation around / over islands
– Bermuda
• Night land breezes
– Topographical influences
Between Islands
Convergent and Divergent winds
Circulation around / over islands
Night land breezes
• Night land breezes are significantly influenced
by
– Topographical features
– Temp differential between land and sea
• Not a sea breeze in reverse
– Topography based:
• If cooling is taking place in adjacent mountaintops, the
cooler air at night time can roll down the mountain side
and accelerate the night breeze
– Generally weaker than sea breeze
Gulf Stream
Interaction between water and air TEMP.
• Formation of warm and cold eddies
• Resultant cloud formation.
The Planning Process
Before Departure… • The single most important decision for a successful voyage may well be prior
to your departure time.
– Know the forecast…ahead of time
– Know ahead of time what products or services you will use at sea
– Know how to work with your private weather routing service… Be
in a position to intelligently engage; they are an advisory service
only.
• The ultimate responsibility for weather forecasts and routing rests with
the skipper and his/her properly trained crew.
The Planning Process
While Underway • Monitor the weather as part of watch keeping/navigation
– Log wind speed & direction, barometric pressure, sea state
• Monitor the weather
– Near shore: VHF, Smartphone, Wifi
– Offshore: HF-SSB, Satellite
• Update the current forecast and routinely verifying it with the most
current analyses.
• Keep asking: “Is the weather evolving as planned?”
– If not…determine why and redefine routing options
Organize your Weather Files
Resources
• Contributed by all speakers
• How best to use them
– Links to recorded session
– Further Study
– Speakers’ Contact Information
– Tables, Calculators, Tools
• When they will be available
Upcoming Webinars
• NorthU Trim
– Bill Gladstone, Host
– March 24 (all day)
– March 27 and 29, 7p EDT
• Performance Software Featuring
EXPEDITION
– Peter Isler, Host
– April 23 and 25, 7p EDT
• Newport – Bermuda Race Strategy
– Bill Biewenga, Host
– June 4 and 11, 7 p, 2012 EDT
For Further Study
• Articles
– Mariner’s Guide to 500 mb charts
– Mariner’s Guide to Hurricanes
– Oceanography from Space
– Arctic Impact Study
• Books and CD’s
Contacts
• Ken Campbell, Commanders’ Weather
– Tel: 1-603-882 6789
– E-mail: [email protected]
– Website: www.commandersweather.com
• Joe Sienkiewicz
– E-Mail: [email protected]
• Lee Chesneau
– 206-949-4680
– www.weatherbylee.com
• Bill Biewenga
– E-mail: [email protected]
– Website: www.weather4sailors.com
• Lou Roberts
– E-mail: [email protected]
– Website: www.weather4sailors.com
Reading and Interpreting
Weather Data
WxLive! Session 2
The End
(Resources will be made available by email)