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WELCOME TO BASIC WEATHER FOR MARINERS PRESENTED BY: HANK POMERANZ, KIM CURRY Carolina Yacht Care, LLC (cYc) ORIENTAL, NC 7 FEBRUARY 2015 Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 1 • Hank and Kim each bring more than 30 years in Navy forecasting experience. - Includes operational forecasting and briefing for ships, aircraft and ground forces • Hank is a long time cruising sailor and Kim brings both USCG Aux crew and VE experience Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved Kim 2 Today’s Goal • Our goal: – Help improve your safety, confidence and selfreliance on the water by • Providing a basic understanding of: • the atmosphere, • the causes of weather impacting your experience on the water and • the foundation for anticipating significant weather (forecasting). • We call this last goal: developing a Seaman’s Eye. Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 3 Seminar Outline • Some Basic Meteorology and Definitions – – – – – – – • • Weather Maps Local Forecasting – – – – – • • A little about the structure and gasses making up our atmosphere Water Vapor and Clouds Scale of Weather Systems - from global to local Atmospheric pressure and frontal systems Weather reporting and reports Winds Atmospheric Stability Precipitation Thunderstorms Winds (shifts, direction and speed) Fog Seas Government and Commercial Sources of information Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved Exercises 4 Basic Meteorology DEFINITIONS OF WEATHER Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 5 Weather is: • …the short-term variation of the atmosphere. It includes changes in: – air pressure, – air temperature, – humidity, – wind, – clouds, – precipitation, and – visibility. Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 6 Weather happens in • The Troposphere – – The lowest layer of the atmosphere – Has 75% of our atmospheric molecules – Varies in height from ~5 miles at the poles to ~10 miles at the equator – Where our weather forms • In only rare instances does a thunderstorm “pierce” the Tropopause and they are extremely severe Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 7 Troposphere Structure Temperature generally decreases with altitude in the troposphere But not always. When temperatures are steady or warm with height we call it a temperature inversion. Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 8 Tropopause Troposphere International Space Station astronauts captured this photo of Earth's atmospheric layers on July 31, 2011, revealing the troposphere (orange-red), stratosphere and above. Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 9 The Atmospheric Makeup Although a very small percentage of the atmospheric gases, Water Vapor plays a key role in our weather. Miscellaneous Gasses Neon, Ne 0.0018 Helium, He 0.00052 Methane, CH4 0.0002 Krypton, Kr 0.00011 Nitrogen(I) oxide, N2O 0.00005 Hydrogen, H2 0.00005 Xenon, Xe 0.0000087 Ozone, O3 0.000001 Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 10 Basic Meteorology RADIATION – THE EARTH’S WEATHER DRIVER Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 11 Incoming Solar Radiation The Inter-Tropical Convergence Zone (ITCZ) March /September Unequal heating of the earth’s atmosphere is the engine that 12 Carolina Yacht Care, LLC, drives the weather Copywrite 2015, All rights reserved Global General Airflow Pattern Oriental Latitude 35.0deg N ~5 miles thick Jacksonville, FL Latitude 30.3deg N Ferrel Cell ~10 miles thick Ferrel Cell Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 13 The 5 Air Masses AIR MASS DEFINITION • • • • • • If a body of air moves slowly or stays over an extensive area that has fairly uniform temperature and moisture characteristics, the air takes on those characteristics and is called an air mass. Five main types of air masses ultimately influence U.S. weather: Continental Polar (cP): cold, dry Continental Arctic (cA): extremely cold, very dry Maritime Polar (mP): cool, moist Maritime Tropical (mT): hot, moist Continental Tropical (cT): hot, dry Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 14 Basic Meteorology ATMOSPHERIC MOISTURE Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 15 Water Vapor The atmosphere contains water vapor. Although small by percentage of the atmospheric gases (up to 4%*), it: • Is an important constituent contributing to water and ice clouds that produce various types of precipitation • Stores and releases great quantities of heat energy, that powers Thunderstorms and Hurricanes. *Water Vapor in the atmosphere varies from a trace (<1%) to 4%. Greatest over the tropics and least over the poles and deserts. Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 16 Water Vapor Distribution Almost half of all water vapor is found within the lowest three miles of the atmosphere, where amounts vary with region, elevation and season. Changes of water from liquid to gas or gas to liquid greatly affect the heating and Copywrite 2015, Carolina Yacht Care, LLC, cooling of the atmosphere. All rights reserved 17 Critical Term - Condensation • Condensation is the phase change of water from a gas to a liquid. Condensation adds heat energy to the environment and is thus a WARMING process in the atmosphere. • As this heat is released, it helps storms, including thunderstorms and hurricanes, to form and grow. Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 18 Critical Term - Evaporation • Evaporation is the phase change of water from a liquid to a gas. Evaporating water removes heat from the environment and is therefore a COOLING process in the atmosphere. • Evaporation adds moisture to the atmosphere. If enough moisture is added to the atmosphere by evaporation, dew, fog, clouds, and precipitationCopywrite can2015, form. Carolina Yacht Care, LLC, All rights reserved 19 The Hydrologic Cycle – What Goes Around, Comes Around These physical processes continually release and take in heat energy to/from the environment – helping to maintain the earth’s heat balance. Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 20 Soil Moisture Active Passive (SMAP) Satellite Helping scientists better understand the Hydrologic cycle and the effect on the earth’s well being Copywrite 2015, Carolina Yacht Care, LLC, Launch All rights reserved January 31, 201521 Basic Meteorology CLOUDS Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 22 What is a Cloud? • A cloud is composed of tiny water droplets or ice crystals that coalesce around tiny “hygroscopic nuclei”** and are suspended in the air. – A series of processes have to happen in order for these water droplets or ice crystals to form into clouds in the atmosphere, and – Different types of clouds form from different processes. **Particles in the atmosphere – including dust, sand, salt, pollutants, etc. that tend to attract and condense ambient water vapor Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 23 The Basics - “Changes of State” are Constantly in Progress Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 24 How Clouds Form (1) In addition to the hygroscopic nuclei, almost all cloud formation requires the cooling of air. Why? It’s all about condensation – atmospheric moisture as water vapor (a gas) condensing and becoming liquid or ice (a solid). So, how do we get condensation? Cool the water vapor! Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 25 How Clouds Form (2) We know now that air needs to cool. What are the general processes whereby air will be cooled? Catalysts causing air to rise and cool • • • • Surface heating Mountains and Terrain Fronts (cold and warm) Low pressure Catalyst causing air to cool without rising • Earth Surface cooling and cooling the air above it Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 26 Air Rising and Cooling Catalyst #1 - Surface Heating • The Sun heats the ground, which then heats the air. • Lighter and less dense than the surrounding air, it rises, expands and cools. • Cooler air means slower molecular movement and the water vapor particles start to coalesce into water droplets. • The higher the air parcel gets, the cooler it gets, and more moisture condenses out of it – eventually forming a cloud. • The types of clouds that form from the process of surface heating are cumulus type. Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 27 Air Rising and Cooling Catalyst # 2 - Mountains and Terrain • When air encounters a mountain range or other types of terrain the air rises and cools, and this slows molecularAir rises, cools and condenses motion and causes coalescing (condensation). Air warms and holds moisture • The types of clouds that form Precipitation (wet) side from encounters with mountains are cumulus clouds and lenticular clouds. Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved Dry Side 28 Air Rising and Cooling Catalyst # 3 - Low Pressure In a low pressure system, wind moves in towards the center from all directions because air moves from high to low pressure. When this air converges (meets) in the center, there is nowhere for the air to go but up. As air rises it cools, resulting in condensation. Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 29 Air Rising and Cooling Catalyst #4 - Cold and Warm Fronts Weather fronts can cause clouds to form. Fronts occur when two large air masses collide at the Earth's surface. • Cold fronts occur when heavy cold air displaces lighter warm air, pushing it upward. Cumulus clouds are the most common cloud types that are produced by cold fronts. They often grow into cumulonimbus clouds, which produce thunderstorms. • Warm fronts produce clouds when warm air replaces cold air by sliding above it. Many different cloud types can be created in this way: altocumulus, altostratus, cirrocumulus, cirrostratus, cirrus, cumulonimbus (and associated mammatus clouds), nimbostratus, stratus, and stratocumulus. Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 30 Earth Surface Cooling the Air Above it • In contrast to surface heating, the cooling of the Earth's surface may lead to the development of fog and stratus clouds. • Stratus clouds belong to the Low Cloud (surface-6,000’ up) group. They are uniform gray in color and can cover most or all of the sky. Stratus clouds can look like a fog that doesn't reach the ground. • Light mist or drizzle is sometimes associated with stratus clouds. Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 31 To summarize • 4 Mechanisms for lifting air and resultant cooling – Surface Heating – Mountains and Terrain – Low pressure centers – Frontal Systems • 1 mechanism for cooling from below – Earth’s surface cooling and cooling the air just above. Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 32 Main Groups of Clouds • FOUR main groups of clouds, based on their height, form and appearance: • (I) High Clouds (20,000’ to 40,000 ‘above sea level) • • • • (II) Medium Clouds (6000’ – 20,000’) • • • Altocumulus Altostratus (III) Low Clouds (below 6000’) • • • • Cirrus Cirrocumulus Cirrostratus Stratus Stratocumulus Nimbostratus (IV) Clouds With Great Vertical Extent (stretching from Surface – >30,000’) • • Cumulus Cumulonimbus Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 33 High Clouds (20,000’-40,000’) Cirrus clouds are ice-crystals. Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 34 Mid Clouds (6,000’ – 20,000’) Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 35 Low Clouds (Surface to 6,000’) Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 36 Clouds with Vertical Growth (Surface to >30,000’) Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 37 Other Clouds Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 38 Cloud Wonders in the Antarctic Sky Photo credit: NASA Project scientist Michael Studinger On Nov. 24, 2013, he took this photograph of a multi-layered lenticular cloud hovering near Mount Discovery, a volcano about 70 kilometers (44 miles) southwest of McMurdo Station on Antarctica’s Ross Island. Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 39 Basic Meteorology SCALES OF WEATHER SYSTEMS Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 40 From the Big Picture to Your Backyard • The largest weather features occur on the global scale. At this scale, forecasters are thinking about large patterns of winds, temperature, and pressure. • Weather patterns that affect one or several states are called synoptic scale events. Examples are circulations around high and low pressure areas, large snowstorms, large-scale droughts, and hurricanes. • Smaller and shorter-term weather events such as tornadoes, flash floods, and similar “local” events are called mesoscale phenomena. These events are often the most hazardous—and the most difficult to forecast. • All these scales are interrelated. – A mesoscale event will have its roots in global and synoptic patterns. – Likewise, a synoptic scale event will have a variety of consequences on the mesoscale. These complex connections explain why forecasting is so difficult. Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 41 The Global Scale Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 42 The Synoptic Scale • Traditionally, forecasters have been trained in synoptic scale meteorology. This type of meteorology deals with analyzing and forecasting meteorological features of scales in excess of 1200 miles. Features such as troughs, ridges, highs, lows and frontal boundaries are well understood. Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 43 The Synoptic Scale Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 44 The Mesoscale Small Scale events – Thunderstorms, fog, precipitation, etc.45 Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved The Mesoscale • As meteorologists and savvy boaters, our challenge is to predict what will happen at this scale based on our knowledge of the Synoptic Scale and local effects. Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 46 Basic Meteorology ATMOSPHERIC PRESSURE Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 47 Atmospheric Pressure Pressure is the force per unit area exerted on a surface by the weight of the air above it Units are “inches of mercury,” “pascals,” or most commonly: “millibars” When we talk about atmospheric pressure, we are really talking about the weight of all those air molecules above us at a given location At sea level, the average force exerted by all the molecules in a column of air resting on your head and extending up to the top of the atmosphere (at about 30 miles) is approximately 14.7 pounds per square inch (psi), 29.9 inches of mercury (in. Hg), or 1013.25 millibars (mb), the most common measure of pressure used by Copywrite 2015, Carolina Yacht Care, LLC, meteorologists. All rights reserved 48 Pressure Tidbits On average, a column of air, one square inch in cross section measured from sea level to the top of the atmosphere would weigh about 14.7 lbs. Mercurial barometer (84 cm in length) immersed in a bowl of mercury – weight of mercury causes a vacuum in the top of the tube. Atmospheric pressure on bowl causes mercury to rise Toricelli’s simple Mecurial Barometer in the graduated tube – measured as “in. Hg” The aneroid barometer consists of a closed sealed capsule with flexible sides. Any change in pressure alters the thickness of the capsule. Levers magnify these changes, causing a pointer to move on a dial, or numbers to change in a digital read-out device Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 49 Aneroid Barometer Pressure Tendency Perhaps more important than actual pressure reading is your awareness of the Pressure Tendency. Set the manually set needle to current pressure then a few hours later compare to current pressure reading to determine rise or fall Seaman’s Eye Note: Pressure falling rapidly (6 Mb per 3 hours) – look for deteriorating weather Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 50 HIGH VS LOW PRESSURE CENTERS Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 51 LOW PRESSURE GENERATION Extra-tropical Cyclone Development “Cyclogenesis” - normally associated with a weak frontal zone near the surface with an upper level trough. Extra-tropical – poleward of tropics, i.e. poleward of 23.5 Deg North (and South) Life cycle of traditional low pressure system. Many frontal wave low pressure centers never continue to develop to maturity Copywrite 2015, Carolina Yacht Care, LLC,52 All rights reserved Hatteras Low Approx. 12 hours earlier Copywrite 2014, Carolina Yacht Care, LLC, All rights reserved 53 Surface Reports Total Cloud Cover Temperature = 98 Deg F Pressure = 1012.4 Mb Winds = Southeast at 15 Kts Dew Point = 78 Deg F Pressure Trend = -3 Mb last three hours Clouds = Cumulus Bases at 2000’ Cirrus above Copywrite 2015, Carolina Yacht Care, LLC, 54 All rights reserved Basic Meteorology FRONTAL BOUNDARIES COLD / WARM / OCCLUDED SQUALL LINES / DRY LINES Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 55 FRONT An “air mass” is a large body of air that has similar moisture and temperature characteristics. A front is the transition zone between two air masses. As depicted on a surface weather chart Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 56 COLD FRONT As the cold front moves, warm, moist unstable air is usually replaced by cold, dry stable air. Blue triangles indicate direction of frontal movement Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 57 WARM FRONT A warm front typically replaces cool dry air with warm moist air. * Red half-circles indicate direction of frontal movement Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 58 OCCLUDED FRONT As central low pressure matures (lowering pressure), Cold front moves faster and overtakes the Warm front. Warm air is pushed aloft and the Occluded front is formed. Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 59 Squall Lines Squall Line Development Cold Front Warm Unstable Air Downdrafts Cold Front Cold Front Warm Unstable Air Downdrafts Large quantities of cold air from aloft descend in downdrafts along the front and form a wedge of cold air ahead of the front. The wedge of cold air then serves as a lifting mechanism for the warm, moist, unstable air; and a line of thunderstorms develops several miles in advance of the front Warm Unstable Air Downdrafts 30 to 100 miles Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 60 SQUALL LINES A narrow band or line of active thunderstorms that is well ahead of a cold front, and may contain heavy precipitation, hail, frequent lightning, dangerous straight line winds, and possibly funnel clouds, tornadoes and waterspouts.[ Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 61 Squall Line - Near Frontal Passage 4/25/14 • This squall line resulted in significant damage from tornado activity AND “straight-line” winds across NE NC. Courtesy: Intellicast.com Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 62 Dry Line Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 63 Basic Meteorology WIND Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 64 Basic Meteorology Wind is the movement of air across the Earth’s surface and is produced by differences in air pressure between one place to another. Within the atmosphere, there are several forces that impact the speed and direction of winds. The most important though is the Earth’s gravitational force. As gravity compresses the Earth’s atmosphere, it creates air pressure- the driving force of wind. Without gravity, there would be no atmosphere or air pressure and thus, no wind. Wind is a balance between three Forces – two real, one not so real Pressure Gradient Friction Coriolis Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 65 Pressure Gradient Think of Highs as mountains and Lows as valleys. The larger the difference between central pressures, the steeper the contours (packed isobars) – meaning stronger “pressure gradient” ----Resulting in stronger winds H H 1028 mb 1028 mb 1016 mb Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved L 1000 mb 66 Pressure Gradient Weak PGF Strong PGF On most surface weather charts produced by NOAA agencies, isobars (lines of equal pressure) are plotted at 4 mb intervals. It is difficult to accurately determine wind speeds by looking at a surface weather chart, but it is possible to identify areas where the wind is relatively stronger or weaker by examining the spacing Copywrite 2015, Carolina Yacht Care, LLC, of the isobars. All rights reserved 67 Coriolis Force Coriolis force is an “apparent” force resulting from the fact that the earth is constantly rotating. Coriolis always acts at a 90 Deg angle to the right of the motion of a parcel of air (Northern Hemisphere). A northbound parcel of air (winds from the south) would have a Coriolis force acting toward the east. Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 68 Friction Friction will always act In the opposite direction of flow Factor of surface roughness, height above the surface and wind speed Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 69 Streamline Analysis L H L H it is difficult to find a straight line among the many twisting and turning arrows covering the United States. And it is very evident that there isn't a wind arrow originating near the high in Virginia and ending in the low in eastern Nebraska. Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 70 Basic Meteorology Any resemblance to Kim is completely coincidental STABILITY Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 71 Stability • In a stable environment, air that is forced upward is cooler (shown in yellow) than its surroundings (shown in white) and will tend to sink or spread out. • Because the air resists being moved upward, clouds formation is limited, and those that do form will be more horizontal than those in in unstable atmosphere. Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 72 Stability • An unstable environment is one in which air parcels can maintain their upward motion. The rising air cools at a rate that is slower (shown in yellow) than the rate of the atmosphere (shown in white). • As long as the rising air remains warmer than its environment, it will continue to rise. The vertical motion will cease when it is cooler than the surrounding environment. • Instability is important because rising air is conducive to vertical cloud development that can result in severe storms. Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 73 Stability • A temperature inversion occurs when a layer of warmer air lies above colder air. In this graphic, the inversion layer lies where the environmental temperature (white line) warms from 48°F to 52°F. • Inversions are key factors in air pollution incidents and fog events because they act like lids, trapping the pollutants or fog. They are common early in the day, but if the atmosphere heats up enough, the inversion can be destroyed. If this happens, usually the fog will dissipate and/or air pollutants will disperse Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 74 Weather Maps KEY SYMBOLOGY/LABELS/COLORS Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 75 Weather Maps Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 76 Weather Maps Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 77 Local Forecasting Whether power or sail, as mariners we care about: • Precipitation • Thunderstorms • Winds (shifts, direction and speed) • Fog • Seas Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 78 Forecasting Precipitation • Since we need clouds for precipitation AND different types of clouds bring different types of precipitation (for example showers versus steady rain), our ability to predict precipitation is a matter of anticipating the arrival of clouds AND the type of cloud. Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 79 There’s More to it Than This Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 80 Forms of Precipitation • Precipitation exists in two forms: – Frozen (snow, sleet, hail, and ice pellets) – Liquid (drizzle and rain) • The type of precipitation that falls to the ground depends on the temperature of the air above. • If the atmosphere is entirely below freezing, all of the precipitation will fall as snow. • If it's above freezing, the precipitation will be rain. But if there are layers of warmer and colder air, forecasting the precipitation type can be tricky. Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 81 Seaman’s Eye for Precip from Clouds Associated with Fronts • A quick glance at forecast frontal positions provides our first hint of what to expect. • With or without looking at Weather Charts, we can frequently observe the changing nature of the clouds over time and anticipate an approaching front and potential precipitation. • Check radar for current precipitation locations and movement. Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 82 Cold Fronts – As Cloud and Precipitation Makers Analysis Valid Time 1800Z Tue 48 hr Valid Time 1200Z Thurs 24 Hr Valid Time 1200Z Wed 72 hr Valid Time 1200Z Fri Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 83 SEAMAN’S EYE – ADVANCING COLD FRONTAL CLOUDS 30 miles Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 84 Warm Fronts – As Cloud and Precipitation Makers Analysis Valid Time 1800Z Tue 48 hr Valid Time 1200Z Thurs 24 Hr Valid Time 1200Z Wed 72 hr Valid Time 1200Z Fri Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 85 Seaman’s Eye – Advancing Warm Frontal Clouds 370 miles Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 86 Local Forecasting THUNDERSTORMS Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 87 Critical Elements for Thunderstorm Formation 1. Lift – due to thermal, frontal, orographic or upper level effects In this picture we see lower layers heated by warm surface 2. Instability – allows for sufficient rise of air to form the cumulonimbus cloud. Unstable layer Moisture None of this is sufficient without the third ingredient – Warm Surface 3. Available moisture Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 88 Initial CUMULUS Stage Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 89 MATURE stage Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 90 Classic “Anvil” of Mature stage Anvil is formed as rising cumulonimbus cloud reaches a very stable upper level known as the “Tropopause” and upper level wind carries cloud top downwind - storm is at peak intensity Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 91 Dissipating stage Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 92 Limitations of Models to “Predict” Local Thunderstorms • The resolution of numerical models is defined by the space between grid points. • Local events such as Thunderstorms typically form between the grid points and are thus missed by the models Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 93 The Seaman’s Eye for Precip Not Associated With Fronts • The primary precipitation in this category comes from “air mass” thunderstorms. • We previously said that thunderstorms require – Moist, unstable air and – A lifting mechanism – Conditions in the upper atmosphere conducive to enhancing the “lift” Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 94 The Seaman’s Eye for Precip Not Associated With Fronts • In the Pamlico region, particularly in spring and summer, we frequently get plenty of moist, unstable, tropical air up from the Gulf of Mexico AND lifting from normal daytime heating. • In our area, heating is more pronounced further inland, west of here, or out over the Gulf Stream. Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 95 The Seaman’s Eye for Precip Not Associated With Fronts • While it is beyond this seminar to present upper atmospheric conditions conducive to thunderstorm development, a practiced Seaman’s Eye can keep you out of trouble. Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 96 The Seaman’s Eye for Precip Not Associated With Fronts • Be aware of wind direction and speed. – A long blowing (days) southerly breeze is pumping moisture laden air into the region. – Light winds are conducive to allowing lift from daytime heating. – If a sea breeze (onshore wind) kicks in during the afternoon you know there’s plenty of heating over land. Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 97 The Seaman’s Eye for Precip Not Associated With Fronts – Cumulus clouds indicate some level of moisture and instability. – The “taller” they get, the more instability is evident. – Fair weather cumulus, towering cumulus and Cumulonimbus (thunderstorms) are varying intensities of the same general cloud type – Cumulus Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved Increasing Instability • Watch the trend of cumulus cloud development over days 98 The Seaman’s Eye for Avoiding Thunderstorms • How do you know if you are on a collision course with a thunderstorm? – Constant Bearing – Site over your compass. If the bearing does not change with time, the storm is not crossing your path and is moving towards or directly away – Remember that First Gusts, downbursts can extend many Copywrite 2015, Carolina Yacht Care, LLC, miles from the storm center. All rights reserved 99 The Seaman’s Eye for Estimating Distance to Thunderstorms • If lightning is visible and thunder is audible… – Lightning arrives ~immediately – Thunder (sound) travels at 1/5 miles per second. – Divide the time between lightning and thunder by 5 = distance to thunderstorm in miles. Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 100 The Seaman’s Eye Critical Considerations - Lightning • Note in this image that the thunderstorm is about 10 miles across and that ground flashes originate anywhere inside the storm at a height of about 5 miles. • Further, lightning channels usually slant away from vertical and can even emerge from the side of the storm. Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 101 The Seaman’s Eye - Critical Considerations – Bolt out of the Blue • Boaters frequently underestimate the danger of being struck by lightning well outside the immediate area of the thunderstorm. The “bolt out of the blue” Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 102 Strike Probabilities Courtesy BoatUS – Seaworthy Magazine Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 103 Courtesy BoatUS – Seaworthy Magazine Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 104 And a few thoughts on “Grounding” Systems Ungrounded Boat Electrical charge exits through through hulls and will melt hull. Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved Grounded Boat Electrical charge is directed to hull mounted grounding plate and discharged into Water. 105 Lightning Protection Systems – Not Just for Sailboats Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 106 Local Forecasting WINDS Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 107 Winds – Synoptic Scale • Remember – Synoptic Scale is looking at the broader picture – in our case over the U.S. • Knowing current and forecast locations of highs, lows and fronts that dominate our region is key to knowing the near term general wind pattern. • Knowing the forecast movement of these systems is key to knowing long term changes to the general wind pattern. Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 108 Synoptic Scale Winds Analysis Current Analysis Our interpretation of Pamlico region winds from the current pattern • Flow is Clockwise around the high pressure to our east = Wind direction S to SW winds for Oriental region. • Isobars (lines of equal pressure) are loosely spaced indicating light winds = 5 to Copywrite 2015, Carolina Yacht Care, LLC, 109 All rights reserved 10 knots. Synoptic Scale Winds – 72 Hour Forecast 72 hour prognosis Our forecast for Pamlico region winds in 72 hours • Flow is still clockwise around the High to the East and ahead of the advancing cold front = Winds direction S to SE. • Isobars are closer spaced in 72 hours indicating increased wind speed. This pattern might indicate 10Copywrite 2015, Carolina Yacht Care, LLC, 110 All rights reserved 15 knots. Synoptic Scale Winds – 5 Day Forecast 5 Day prognosis Our forecast for Pamlico region winds in 5 days • Flow is clockwise around the High to the west, behind the cold front that is forecast to move offshore = Wind direction N to NW. • Isobars are slightly more closely spaced behind the front and winds can be gusty around the front = 10 to 15 knots with gusts to 20. Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 111 Synoptic Scale Winds – 7 Day Forecast 7 Day prognosis Our forecast for Pamlico region winds in 7 days • Flow is still clockwise around the High to the west, but the center is closer to the Pamlico/Neuse region = Wind direction is NE. • Isobars are loosely spaced indicating light winds = Winds speed 5 to 10 knots. Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 112 LOCAL SCALE WINDS THAT UPSET THE SYNOPTIC FLOW – LAND AND SEA BREEZES Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 113 Land and Sea Breezes Land and Sea breezes result from temperature differences between the land and local water bodies. During daytime the land heats up At night, the land looses heat more rapidly significantly more than the water and the relatively warm air over the water and the air over the land rises to rises to be replaced by air from over the be replaced by air from over the cooler land. 114 Copywrite 2015, Carolina Yacht Care, LLC, cooler water. All rights reserved Ideal Conditions • Sea Breeze – Spring and Summer (seasons with greatest temperature difference between land and sea) – Sunny day that allows for maximum heating. – Light prevailing (synoptic scale) winds. • Land Breeze – Clear night to allow for radiation cooling of the land thereby increasing the temperature difference between land and sea. Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 115 Ocean to Oriental Prevailing Summer Wind direction Nighttime cooling over land ~18 nm Land Breeze Daytime heating over land Sea Breeze July SST ~78-85 Deg F Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 116 November SST ~ 74o Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 117 January 2015 SST ~66o Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 118 July Southerly Wind SST ~82-84o Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 119 July 1st – Classic Light Southerly Winds SST ~82o Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 120 July 4th Gale SST ~82o Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 121 Race Courses Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 122 Sea Breeze and Thunderstorms • At the bend at MCAS Cherry Point, afternoon sea breezes and summer thunderstorms often converge. Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 123 LOCAL SCALE WINDS THAT UPSET THE SYNOPTIC FLOW – THUNDERSTORMS Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 124 Thunderstorm First Gust This sailboat Is heeling under bare poles In a first gust • One of the most significant weather hazards to boaters! • A rapid change in wind direction and speed many miles from the storm. • Results from the horizontal spreading of downdraft winds at the earth’s surface. • Normally the highest recorded speed for the storm and as much as a 180 degree change in direction. • Occur in ALL shower producing convective clouds and are predictable and expected Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 125 Thunderstorm Downbursts • In addition to the First Gust, other strong, violent and dangerous downdraft winds are associated with thunderstorms. • Macro bursts – – Large Scale, widespread damage similar to tornadoes – Can last 5-20 minutes with speeds up to 130 knots Note the lateral spreading as the downburst reaches the ground. The surface wind speed will greatly increase and the direction may change up to 180o • Micro bursts – – Small Scale, can last 2 to 5 minutes with speeds up to 130 126 Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved knots Local Forecasting FOG Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 127 Coastal Fog Formation Coastal Fog can take on many forms: Radiation Dynamically Forced Advection West Coast (obviously not stressed) Steam Fog (High Lat. – cold regions) Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 128 A closer look at Condensation • Fog is a cloud and is atmospheric moisture in a liquid state. • And we said: “Apply enough cooling to Water Vapor (Gas) and the molecules slow down, may coalesce and change state to Liquid (condensation) ” – “enough cooling” is the Dewpoint Temperature – the temperature at which some of the water vapor must condense into liquid water. • It is always equal to or lower than the air temp. – So…if the air temp cools to the dewpoint (OR CLOSE) or the dewpoint rises to the air temp, - fog, clouds or dew begin to Copyright 2015, Carolina form. Yacht we Care, LLC, All rights reserved • When they are equal have 100% Relative Humidity 129 Fog Radiation Fog - Radiation fog is a ground-based cloud caused by nocturnal cooling at and near the ground surface Advection Fog - Advection fog is a ground-based cloud caused by the cooling of an air mass as it moves over a colder surface - Typically occurs under clear skies and moist low-level conditions. - That surface may be cold ground, snow cover, water, or ice. Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 130 Radiation Fog . Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 131 Seaman’s Eye for Conditions Favorable for Radiation Fog • As learned, Radiation Fog results from a cool earth’s surface, cooling the air above it to the point that the molecules slow down enough to coalesce – forming water droplets. • The point at which condensation occurs is called the “dew point” (the point at which dew forms due to condensation) and it is expressed as “Dew Point Temperature”. – If Dew Point equals the air temperature = full saturation = 100% Relative Humidity (RH) – Simple approximation - For each 1.8 degrees F the Dew Point temperature is less than the air temperature = 5% lower RH • Examples: Air temperature = 75F and Dew Point = 73.2F then RH = 95%. Similarly, Air temperature = 75F and Dew Point – 71.4F then RH = 90%, etc… Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 132 Seaman’s Eye for Conditions Favorable for Radiation Fog • So, we need – Plenty of moisture in the air near the ground – Moist ground also helps (such as after a rain) - adding to moisture availability. • Swamps also provide significant moisture to the lower atmosphere – Clear skies AT NIGHT (to allow for the earth’s heat to escape into the upper atmosphere (Radiation) and therefore cool the ground and the air in contact with it – Calm winds • Then, if all is right, and the air cools to its Dew Point (usually early morning when there’s been maximum cooling) we have a strong probability for fog. Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 133 Seaman’s Eye for Conditions Favorable for Radiation Fog • For the Pamlico region, moist air generally results from a southerly flow (mT) bringing in moist tropical air. • Then, if the wind dies at night and the sky becomes clear all night, allowing the air temperature to lower to the dew point and become saturated, we have a strong fog potential. • But it can be spotty here because: Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 134 Seaman’s Eye for Conditions Favorable for Radiation Fog Our local topography, where raw land (which cools faster) is interwoven with water bodies and can go from forest to farm, swamp to pavement quickly, 135 canLLC,make fog formation quite localized. Copywrite 2015, Carolina Yacht Care, All rights reserved Seaman’s Eye for Dissipation of Radiation Fog • When will it dissipate? Depends heavily on: – Depth of the fog. • Typically depth is 3’ to about 1000’ • If your visibility is near zero and you cannot see a lighter shade of gray as you look up, chances are the layer is quite deep and will be slow to burn off – Strength of the sun - to provide warming at the top of the layer • Winter sun’s rays are more oblique and thus weaker = slower for “burnoff” – Wind strength – Calm winds mean slower to dissipate. Stronger winds = more atmospheric turbulence and mixing of warmer and cooler air. Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 136 Advection Fog So, when do we have warm moist air moving over a colder surface? Copyright 2015, Carolina Yacht Care, LLC, All rights reserved 137 Current NWS Surface Analysis Copywrite 2015, Carolina Yacht Care, LLC, 4, 2014 (1PM local) Valid 1800Z Thursday December 138 All rights reserved Advection FOG Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 139 Seaman’s Eye for Advection Fog • We said that advection fog is a ground-based cloud caused by the cooling of an air mass as it moves over a colder surface • When do we have those conditions in our region? Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 140 Seaman’s Eye for Advection Fog • When the land mass is cold – Typically Late Fall, Winter, Early Spring • When we have an onshore flow of relatively warm, moist One Scenario air from over the Gulf Copywrite 2015, Carolina Yacht Care,Stream. LLC, 141 All rights reserved Local Forecasting SEAS – WIND WAVES AND SWELL Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 142 Some Definitions • Fetch – the distance over which the wind blows and imparts energy to the sea. • For a given wind speed a minimum fetch and duration is required to generate a “fully arisen sea”. • Thus, we seek shelter in the lee of a weather shore. Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 143 Ripples, Waves and Swell Ripples - the instant effect of wind on water and they die down as quickly as they form. Wind Waves - If a wind blows steadily across a large enough patch of water for a few hours then the ripples become waves and these will not be dampened so easily. Swell - When strong winds blow for longer than a few hours, it gives the water sufficient energy that it then takes on a character of its own. It will march across open areas of water independent of the wind and typically has longer periods and an undulating/rolling type motion . . Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 144 Significant Wave Height Commonly Referred to as Seas in the Marine Forecast The average of the highest one-third (33%) of waves (measured from trough to crest) that occur in a given period Statistically, if forecast Hs = 6 ft • H (most probable) = 0.6 times Hs = 3.6 ft • H1/10 (10% highest waves) = 1.27 times Hs = 7.6 ft • H1/100 (1% highest waves) = 1.67 times Hs = 10 ft • Hmax (highest wave you should be on the alert for) = approximately 2 times Hs = 12 ft! Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 145 Wind Wave versus Swell Wave – Impacts to our Transit Possible impacts: Seas higher than forecast Confused seas Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 146 Seaman’s Eye for Wave Height and Direction • Look at the weather map and consider the direction and speed of winds generating local waves. • Look at the weather map for major storms up to 1000 to 1500 miles away! • Anticipate wind waves coming from the direction of the wind with a shorter period. • Anticipate swell waves coming from the direction of the storm with a longer period. – If wind and swell waves are from same direction – the result will be higher. – If wind and swell waves are from opposite or perpendicular directions – they will be “confused” and more choppy. Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 147 Tides As the moon rotates around the Earth, its gravitation pulls the water on the nearest side of the Earth outward into a bulge. The earth’s spin results in a second bulge on the opposite side. These two bulges travel around the globe, producing 2 high tides each lunar day. During time of the new moon and full moon, when the sun and moon are in a straight line, their gravitational pulls combine and produce spring tides; high tides are very high and low tides are very low. When sun and moon are at right angles from the Earth, during the quarter phases of the moon, the gravitational pull on the oceans is less producing a smaller difference between high and low tide known as a neap tide. Copywrite 2015, Carolina Yacht Care, LLC, 148 All rights reserved Seaman’s Eye for Depth / Currents on the Neuse (1) • First, a bit about the Neuse The Neuse River is a Coastal plain estuary, or drowned river valley, and was formed when rising sea levels flooded the area. It is a shallow estuary with a mean depth of 12’, mean width of 4 miles, and length of 43 miles. • And the Pamlico Sound It is the largest Sound on the East Coast. A Sound is a Saltwater Lagoon (Separated from the sea by a sandy barrier). Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 149 Seaman’s Eye for Depth / Currents on the Neuse (2) We are fond of saying that the Neuse River has no astronomical tidal flow. It is more correct to say that: (1) Astronomical tides constitute less than 2% of the variation in both water level and current velocity. (2) Water exchange is dominated by winds for periods of days. (3) Fresh water discharge dominates water exchange for periods of days to weeks. (4) Less known is that significant cross river circulation occurs and exhibits side to side sloshing. Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 150 Ocean Currents Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 151 Information Sources NATIONAL WEATHER SERVICE Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 152 NOAA/NWS ILM Office http://www.weather.gov/ilm/ Choose overlays Such as winds, seas, sea water temperature etc. Offshore Buoy observations Links to Near and Offshore forecasts, Tides, Hurricane info, etc. Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved Your portal to local marine information 153 Local NOAA Broadcast WX1 on your VHF Radio Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 154 Other NWS Operational Centers • The Ocean Prediction Center (OPC) http://www.opc.ncep.noaa.gov/ – GRIB data • surface (10-m) wind speeds with direction (KT) – surface (10-m) wind gusts (KT) – significant wave heights (FT) – marine hazards – Marine Graphic and Text Analyses and Forecasts Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 155 Other NWS Operational Centers • National Hurricane Center (NHC) http://www.nhc.noaa.gov/?atlc – All tracks, advisories, forecasts • Graphical and Text – This is the horses mouth on everything tropical! Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 156 Other NWS Operational Centers • Storm Prediction Center (SPC) – responsible for prediction of severe weather across the country. • http://www.spc.noaa.gov/ Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 157 Information Sources COMMERCIAL Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 158 Commercial Websites WEB • Oriental area Land and Marine Weather, Seas and Tides – www.towndock.net (Nice job Keith) – www.intellicast.com/Marine/Boating.aspx – www.passageweather.com – Excellent source for animated wind/wave/ pressure charts Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 159 EXERCISES Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 160 Review Questions 1. Which of the following is not required for precipitation to occur? a. condensation nuclei b. source of lifting c. moisture d. southerly winds 2. Sleet and freezing rain are caused by a cold layer of air aloft (True or False)? 3. Which one of these clouds can produce heavy showers? a. Stratocumulus b. Cumulonimbus c. Altostratus d. Nimbostratus Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 161 Review Questions 7. What is the surface temperature? 8. What is the surface visibility? 78 068 9. What is the surface wind direction and speed? 07 05 10. What is the type of low cloud? 72 15 11. What has been the pressure tendency over the last three hours? Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 162 Review Questions 12. Which type of cloud begins as a middle layer cloud, but as it develops the base of the cloud lowers into the low-level clouds? a. Altostratus b. Stratus c. Cumulonimbus d. Nimbostratus 13. The best clue that this is mid-level Altostratus and not high-level Cirrostratus is the lack of? a. precipitation b. other cloud types c. halo Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 163 Review Questions 14. Moist air weighs less than dry air. (True or False) 15. At night, temperatures will normally be higher under cloudy skies than under clear skies. (True or False) 16. Your aneroid barometer indicates that pressure has been decreasing rapidly over the past three hours. The type of weather that would normally be expected to occur would be? a. Fog b. Thunderstorms c. Drizzle d. Clearing 17. A thunderstorm is approaching your anchorage, but rain has not started – it is safe to assume that lightning will not affect your area Copywrite 2015, Carolina Yacht Care, LLC, (True or False) All rights reserved 164 Review Questions 4. An easterly wind means that air is moving towards the east (True or False) ? 5. A high level cloud that forms in a layer would be called? a. Cirrus b. Cirrocumulus c. Cirrostratus d. Altostratus 6. The force that results from the rotation of the earth is known as the… a. Pressure Gradient b. Coriolis c. Frictional d. Convergence Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 165 Weather Exercise Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 166 Weather Exercise Copywrite 2015, Carolina Yacht Care, LLC, All rights reserved 167