Rossby Waves & Jet Stream Dynamics: How Upper-Tropospheric Meanders and Vorticity Advection Steer Synoptic Storm Tracks
1. Outdoor Observer Field Notes: The Cirrus Veil and the Whispering Tropopause
Stand on an exposed western headland or a high ridgeline in the temperate latitudes on an afternoon when the surface air is deceptively calm. At ground level, the leaves of the birch and oak barely tremble; a gentle breeze drifts lazily out of the south-southeast. Yet, if you cast your gaze nine to eleven kilometres upward toward the dynamic tropopauseβthe boundary separating the churning troposphere from the stratified calm of the stratosphereβthe sky tells an entirely different, intensely kinetic story.
Across the zenith, high-altitude ice crystals paint sweeping, fibrous white brushes against the deep blue vault: cirrus uncinus, colloquially termed "maresβ tails," their hooked heads and trailing virga streaks pointing like compass needles along an invisible aerial freeway. Within hours, these discrete filaments fuse into a diffuse, milky sheet of cirrostratus nebulosus. The afternoon sun dims into a pale, luminous disc, encircled by a crisp, glowing $22^\circ$ halo born of sunlight refracting through millions of hexagonal ice prisms tumbling through the upper troposphere.
SURFACE TO TROPOPAUSE: A CROSS-SECTION OF THE SYNOPTIC ENGINE
Altitude
(km)
11 |-------------------- TROPOPAUSE / JET CORE (150-250 km/h) --------------------
| >>> Cirrus Uncinus / Cirrostratus Veil >>>
9 |
|
6 | [ Upper-Tropospheric Trough: 500 hPa Vorticity Maximum ]
| \
3 | \---> Positive Vorticity Advection (PVA)
| \
0 |--- Gentle SE Breeze --- [ SURFACE LOW CYCLOGENESIS ] <--- Barometer Falls
To the untrained eye, this delicate optical veil appears serene. To the seasoned meteorologist and outdoor observer, it is an unmistakable herald of an imminent restructuring of the synoptic steering flow. If you monitor your tracking watch or pocket aneroid barometer over the ensuing six hours, you will detect the initial inflection: the atmospheric pressure begins its steady, inexorable slide, falling perhaps one, then two hectopascals every three hours.
The high-altitude cirrus sheet is drifting from the west-southwest at velocities exceeding 180 kilometres per hour, far outstripping anything felt in the surface boundary layer. You are standing directly beneath the forward diffluent exit region of an upper-tropospheric jet streak, embedded within a planetary-scale Rossby wave. Long before radar detects the first droplet of rain or ground stations record a freshening gale, the geometry of these high-altitude rivers of air has already sealed the fate of the surface weather below.
2. Physical Principles & Intuitive Science: Planetary Waves, Vorticity, and the Beta Effect
To understand why the cirrus moves with such ferocity and why the barometer falls, we must zoom out from the observer's ridge to the planetary scale. The fundamental driver of mid-latitude weather is the persistent thermal imbalance between the solar-bathed equator and the radiation-depleted poles. This meridional temperature gradient sets up a permanent northβsouth pressure slope in the upper troposphere, driving strong westerly winds via the thermal wind relation.
However, this eastward flow does not travel in a straight, laminar ring. It meanders in colossal, undulating planetary ribbons known as Rossby waves, named after the pioneering Swedish-American meteorologist Carl-Gustaf Rossby.
PLANETARY ROSSBY WAVE UNDULATION (NORTHERN HEMISPHERE)
Poleward Ridge (High Height)
^ +--> Anticyclonic Curvature (Negative Vorticity)
/ \ /
/ X
/ \
v v
Equatorward Trough (Low Height)
+--> Cyclonic Curvature (Positive Vorticity Maximum)
The Beta Effect and the Restoring Force
The physical genesis of a Rossby wave relies on a single geometric reality: the Earth is a rotating sphere. The local vertical component of planetary rotation is quantified by the Coriolis parameter, $f$, defined as:
$$f = 2\Omega \sin\phi$$
where $\Omega$ is the Earth's angular velocity ($7.292 \times 10^{-5}\text{ rad/s}$) and $\phi$ is the latitude.
At the equator ($\phi = 0^\circ$), $f = 0$; at the North Pole ($\phi = 90^\circ$), $f$ reaches its maximum. The rate of change of the Coriolis parameter with respect to northward distance ($y$) is known as the Rossby parameter, or the beta effect ($\beta$):
$$\beta = \frac{\partial f}{\partial y} = \frac{2\Omega \cos\phi}{R_E}$$
where $R_E$ is the mean radius of the Earth ($6.371 \times 10^6\text{ m}$).
The Conservation of Absolute Vorticity
In fluid dynamics, vorticity measures the local spin or rotation of an air parcel. We distinguish between: 1. Relative Vorticity ($\zeta$): The spin of the air relative to the Earth's crust, produced either by curvature in the streamlines or by horizontal wind shear ($\zeta = \frac{\partial v}{\partial x} - \frac{\partial u}{\partial y}$). 2. Planetary Vorticity ($f$): The background spin imparted by the rotating Earth beneath the air.
Together, they constitute Absolute Vorticity ($\eta$):
$$\eta = \zeta + f$$
Under frictionless, adiabatic, and horizontally non-divergent conditions in the mid-troposphere (around the 500 hPa level), absolute vorticity is conserved following the motion of the air parcel:
$$\frac{d\eta}{dt} = \frac{d(\zeta + f)}{dt} = 0 \implies \zeta + f = \text{Constant}$$
This conservation law provides the fundamental restoring mechanism for planetary waves: * Poleward Displacement: When a parcel of air is deflected northward toward higher latitudes, $f$ increases. To keep the sum $\zeta + f$ constant, its relative vorticity $\zeta$ must decrease, turning negative. Negative relative vorticity corresponds to anticyclonic (clockwise in the Northern Hemisphere) spin. This clockwise curvature forces the parcel to bend back southwards toward its original latitude. * Equatorward Displacement: As the parcel overshoots and travels south toward lower latitudes, $f$ decreases. Consequently, $\zeta$ must increase, becoming positive (cyclonic / counterclockwise). This counterclockwise curvature forces the parcel back northwards.
This perpetual overshooting and restoring force produces the great planetary waves that undulate continuously around the globe, as monitored by agencies such as the National Oceanic and Atmospheric Administration (NOAA) and the World Meteorological Organization (WMO).
CONSERVATION OF ABSOLUTE VORTICITY IN ACTION:
Latitude Increases (Poleward) --> f Increases --> zeta Decreases (Anticyclonic / Ridge)
Latitude Decreases (Equatorward) --> f Decreases --> zeta Increases (Cyclonic / Trough)
3. The Synoptic Engine: Positive Vorticity Advection (PVA) and Cyclogenesis
How does a high-altitude planetary wave carve out a storm at the Earth's surface? The connection lies in the spatial variation of vorticity and horizontal wind advection.
On a synoptic 500 hPa chart, the base of a southward-dipping wave is the trough (a region of low geopotential height, cold air, and maximum cyclonic relative vorticity, $\zeta > 0$). The crest of a northward-bulging wave is the ridge (high geopotential height, warm air, and anticyclonic vorticity, $\zeta < 0$).
500 hPa TROUGH-TO-RIDGE TRANSITION & DIVERGENCE
Upper Ridge Upper Trough
(Low zeta) (Max zeta)
\ /
\ /
\ /
\ REGION OF PVA /
\ <--------------------- /
[ Upper-Level Divergence ]
|
| (Compensating Vertical Updraft: w > 0)
v
[ Surface Cyclogenesis ]
(Rapid Pressure Drop)
Between the trough axis and the downstream ridge axis, the upper-level jet winds blow across the vorticity gradient, transporting air with high cyclonic vorticity into a region of lower vorticity downstream. This process is known as Positive Vorticity Advection (PVA).
According to the Quasi-Geostrophic (QG) Omega Equationβthe theoretical cornerstone of synoptic forecasting championed by the UK Met Officeβdivergence aloft is directly proportional to the rate of increase of positive vorticity advection with height:
$$\nabla \cdot \vec{V}_{\text{upper}} \propto \frac{\partial}{\partial z} (\text{PVA})$$
When air diverges in the upper troposphere (spreading outward faster than it arrives), it evacuates atmospheric mass from the vertical column. Because the total weight of the air column is reduced, the barometric pressure at the surface must fall.
To satisfy mass continuity, air from the lower troposphere is sucked upward to replace the evacuated mass. As this low-level air ascends, it cools adiabatically; water vapor condenses into expansive cloud decks, releasing latent heat that further fuels the rising motion. At the surface, the converging air spins up via the Coriolis force into a potent mid-latitude depression (cyclogenesis).
4. The Four-Quadrant Jet Streak Model
Within the broader band of the jet stream, there exist distinct, localized cores of maximum wind speed known as jet streaks. While a typical 300 hPa jet stream might blow at 120 km/h, a jet streak embedded within it can scream along at 250 to over 350 km/h.
When air parcels enter and exit these intense velocity maxima, they experience extreme horizontal accelerations and decelerations that disrupt geostrophic balance (the exact equilibrium between the horizontal pressure gradient force and the Coriolis force). This disequilibrium forces the creation of an ageostrophic wind ($\vec{v}_{ag}$), establishing transverse vertical circulation cells across the jet axis.
THE FOUR-QUADRANT JET STREAK MODEL
(Plan View - Northern Hemisphere)
POLEWARD (Cold Air)
|
RIGHT ENTRANCE | LEFT ENTRANCE
[ Thermally Direct ] | [ Thermally Direct ]
Convergence Aloft | DIVERGENCE ALOFT
Subsidence / High Pressure | Ascent / Cyclogenesis
|
============================== JET CORE ==============================>
(Entrance Region) [MAX SPEED] (Exit Region)
======================================================================>
|
RIGHT EXIT | LEFT EXIT
[ Thermally Indirect ] | [ Thermally Indirect ]
DIVERGENCE ALOFT | Convergence Aloft
Ascent / Cyclogenesis | Subsidence / High Pressure
|
EQUATORWARD (Warm Air)
We divide every jet streak into four distinct quadrants relative to the wind direction:
1. The Entrance Region (Accelerating Flow)
As an air parcel enters the rear of the streak, it accelerates rapidly ($du/dt > 0$). Because its real velocity temporarily exceeds the velocity corresponding to the Coriolis force, the pressure gradient force overpowers the Coriolis deflection. The parcel is accelerated across the height contours toward lower geopotential heights (to the left in the Northern Hemisphere). * Left-Entrance: Convergence aloft $\rightarrow$ Sinking air (subsidence) $\rightarrow$ Surface high pressure, fair weather. * Right-Entrance: Divergence aloft $\rightarrow$ Strong vertical ascent $\rightarrow$ Surface pressure falls, frontal precipitation. This forms a thermally direct circulation (warm air rises on the right, cold air sinks on the left).
2. The Exit Region (Decelerating Flow)
As an air parcel shoots out the front of the streak, it decelerates ($du/dt < 0$). The Coriolis force temporarily overpowers the relaxing pressure gradient force, deflecting the parcel toward the right (toward higher geopotential heights). * Right-Exit: Convergence aloft $\rightarrow$ Sinking air $\rightarrow$ Surface anticyclogenesis and clearing skies. * Left-Exit: Intense Divergence aloft $\rightarrow$ Vigorous vertical ascent $\rightarrow$ Explosive surface cyclogenesis, heavy precipitation, and severe convection. This forms a thermally indirect circulation (forcing cold air to rise and warm air to sink, driven entirely by kinetic inertial dynamics).
SUMMARY OF JET STREAK DIVERGENCE DYNAMICS:
* LEFT EXIT QUADRANT --> Maximum Upper Divergence --> Potent Storm Hatchery
* RIGHT ENTRANCE QUADRANT --> Secondary Upper Divergence --> Frontal Bands & Rain
* RIGHT EXIT QUADRANT --> Maximum Upper Convergence --> Stable, Fair Weather
* LEFT ENTRANCE QUADRANT --> Secondary Upper Convergence --> Stable, Clear Skies
When the Left-Exit quadrant of an upper-level jet streak aligns directly over an area of Positive Vorticity Advection ahead of a 500 hPa trough, the two divergence mechanisms superimpose. Meteorologists call this a coupled synoptic engine, capable of producing rapid storm intensification, often termed "bombogenesis."
5. Accessible Mathematical Foundations: Rossby Wave Dispersion and Atmospheric Blocking
How fast do these massive planetary waves move across continents and oceans? To answer this, we turn to the Rossby Wave Dispersion Relation.
The Conceptual Foundation
Imagine walking briskly forward on a moving passenger walkway at an airport. Your speed relative to the terminal floor is your walking speed plus the walkway's speed. Now imagine turning around and walking backward against the walkway's motion. If you walk backward at 4 km/h while the walkway moves forward at 4 km/h, someone standing in the terminal sees you hovering perfectly stationary in space.
A Rossby wave operates on an identical principle: 1. The background westerly wind ($\bar{u}$) carries the entire wave pattern eastward (downstream). 2. The beta effect ($\beta$) acts as an internal phase engine that tries to propagate the wave westward (retrograde) relative to the moving air.
The net speed at which the wave crests and troughs move relative to the Earth's surfaceβthe phase speed ($c$)βis the difference between these two opposing forces.
ROSSBY WAVE PROPAGATION: THE BALANCE OF TWO OPPOSING SPEEDS
[ Eastward Advection by Mean Flow (+uΜ) ] --->
================> Net Phase Speed (c)
<--- [ Westward Intrinsic Wave Propagation (-Ξ²/kΒ²) ]
Step-by-Step Derivation of the Dispersion Formula
For an idealized, barotropic, one-dimensional horizontal flow, linearized perturbation analysis of the absolute vorticity equation yields the famous Rossby Wave Phase Speed Formula:
$$c = \bar{u} - \frac{\beta}{k^2}$$
Where: * $c$ = Zonal phase speed of the wave (m/s). Positive ($c > 0$) means moving eastward; negative ($c < 0$) means moving westward (retrograde). * $\bar{u}$ = Mean zonal background westerly wind speed (m/s). * $\beta$ = The Rossby parameter ($\partial f / \partial y \approx 1.6 \times 10^{-11}\text{ m}^{-1}\text{s}^{-1}$ at $45^\circ\text{N}$). * $k$ = Zonal wavenumber, defined by the wavelength ($L$) of the wave: $k = \frac{2\pi}{L}$.
Substituting $k = \frac{2\pi}{L}$ into the formula gives:
$$c = \bar{u} - \frac{\beta L^2}{4\pi^2}$$
Notice the decisive role of wavelength ($L$): the westward retarding term is proportional to the square of the wavelength ($L^2$)!
Real-World Mathematical Demonstrations
Let us test this formula under typical mid-latitude conditions at $45^\circ\text{N}$, assuming a representative upper-tropospheric westerly steering flow of $\bar{u} = 20\text{ m/s}$ (approx. 72 km/h), with $\beta = 1.6 \times 10^{-11}\text{ m}^{-1}\text{s}^{-1}$.
Wavelength Class | Wavelength (L) | Propagation Speed (c) | Synoptic Behavior
-----------------|----------------|-----------------------|-----------------------------------
Short Wave | 3,000 km | +16.35 m/s (Fast East)| Fast progressive frontal storms
Medium Wave | 5,000 km | +9.87 m/s (Slow East) | Typical weekly weather cycles
Stationary Wave | 7,025 km | 0.00 m/s (STALLED) | Persistent Omega / Rex Blocks
Super-Long Wave | 9,000 km | -12.83 m/s (WESTWARD) | Massive retrograde pattern shift
Case 1: The Short Synoptic Wave ($L = 3,000\text{ km}$)
Shortwaves are the fast-moving ripples associated with individual low-pressure systems and cold fronts. 1. Convert wavelength: $L = 3 \times 10^6\text{ m}$. 2. Calculate the retarding term: $$\frac{\beta L^2}{4\pi^2} = \frac{(1.6 \times 10^{-11}\text{ m}^{-1}\text{s}^{-1}) \times (3 \times 10^6\text{ m})^2}{4 \times (3.14159)^2} = \frac{1.6 \times 10^{-11} \times 9 \times 10^{12}}{39.478} \approx \frac{144}{39.478} \approx 3.65\text{ m/s}$$ 3. Compute phase speed $c$: $$c = 20\text{ m/s} - 3.65\text{ m/s} = +16.35\text{ m/s} \approx 58.9\text{ km/h}$$ * Result: Because $L$ is small, the beta retardation is negligible ($3.65\text{ m/s}$). The shortwave races swiftly eastward at nearly 59 km/h, sweeping cold fronts across the continent every 24 to 48 hours.
Case 2: The Stationary Planetary Wave ($c = 0$)
What happens when the wavelength grows so large that the westward beta propagation exactly balances the eastward background wind? We set $c = 0$:
$$0 = \bar{u} - \frac{\beta L_s^2}{4\pi^2} \implies L_s = 2\pi \sqrt{\frac{\bar{u}}{\beta}}$$
Plugging in our values ($\bar{u} = 20\text{ m/s}$, $\beta = 1.6 \times 10^{-11}\text{ m}^{-1}\text{s}^{-1}$):
$$L_s = 2\pi \sqrt{\frac{20}{1.6 \times 10^{-11}}} = 2\pi \sqrt{1.25 \times 10^{12}} = 2\pi \times (1.118 \times 10^6) \approx 7.025 \times 10^6\text{ m} \approx 7,025\text{ km}$$
- Result: A planetary wave with a wavelength of approximately 7,000 km becomes stationary ($c = 0$). It ceases to move across the globe.
The Anatomy of Weather Disasters: Atmospheric Blocking
When a Rossby wave reaches this critical stationary scale ($L \approx L_s$), or when the background wind $\bar{u}$ weakens (common during summer or periods of low Arctic-equator temperature gradient), the wave stalls. If the amplitude of the wave grows excessively large, the wave can break like an ocean breaker on a beach, creating atmospheric blocks:
THE OMEGA BLOCK CONFIGURATION (Ξ©)
Warm Ridge / High
.---.
/ \
| H |
\ /
Cut-Off / \ Cut-Off
Low / \ Low
( L ) ' ' ( L )
===============================> Jet Flow Splitting
- Omega Blocks ($\Omega$): A massive, high-amplitude warm ridge flanked by two cut-off cold lows, resembling the Greek letter $\Omega$. The jet stream splits around the block, diverting rain-bearing depressions thousands of kilometres to the north and south. Under the central high, skies remain cloudless for weeks, causing severe heatwaves and droughts.
- Cut-Off Lows: An equatorward trough deepens to such an extent that the main jet stream pinches off and rejoins to the north, leaving an isolated cold-core vortex spinning autonomously over lower latitudes. These systems, frequently analyzed by the European Centre for Medium-Range Weather Forecasts (ECMWF), remain parked over regions for days, unleashing catastrophic flooding and unrelenting rainstorms.
6. Practical Weather Forecasting & Field Guidance: Reading the Upper-Air Atmosphere
Armed with an understanding of Rossby waves and jet streaks, an outdoor enthusiast, mariner, or amateur meteorologist can decipher professional upper-air charts and satellite feeds with precision.
3-STEP SYNOPTIC CHART ANALYSIS FOR FIELD FORECASTING
Step 1: Check 300 hPa Isotachs --> Locate Jet Core (>100 kt) & Left-Exit Quadrant
Step 2: Check 500 hPa Vorticity --> Locate PVA Ahead of Troughs (Ascent / Divergence)
Step 3: Check Visible / IR / WV --> Spot Water Vapor Dark Dry Intrusions & Cirrus Bands
1. Decoding Synoptic 300 hPa and 500 hPa Charts
- 300 hPa Isotach Charts (Jet Level): Look for elongated isotach contours (lines of equal wind speed) shaded in dark blue, purple, or red (winds exceeding 100 to 160 knots).
- Identify the wind direction through the streak.
- Draw an imaginary cross through the streak center to delineate the four quadrants.
- If your region lies under the Left-Exit or Right-Entrance quadrants, anticipate strong surface pressure drops, active storm formation, and wind shear.
- 500 hPa Geopotential Height & Absolute Vorticity Charts:
- Solid black lines represent geopotential height contours (e.g., the critical 552 dam or 540 dam lines). Deep southward loops indicate troughs; northward arches indicate ridges.
- Color-shaded "bullseyes" represent maximum absolute vorticity ($\eta$).
- Locate areas where the height contours blow out of a vorticity maximum toward lower vorticity. This is your PVA zone. Directly below this zone, expect cloud cover to thicken and surface storms to intensify within 12 to 24 hours.
TYPICAL 500 hPa UPPER AIR CHART INTERPRETATION
576 dam ----------------------------------------------------
_ . - - - - - . _ (Ridge Axis)
' ' .
564 dam ---- / ----------------------- \ -------------------
/ \
/ PVA INTENSIFICATION \
552 dam --/------ [Upper Divergence] -----\-----------------
/ \
| [ VORTICITY MAXIMUM ] |
540 dam -\--- [ Cyclonic Spin ] --------/----------------
'. .' (Trough Axis)
' - . _ _ . - '
528 dam ------------ ' - - - - - - '------------------------
2. Satellite Imagery Interpretation
Modern geostationary weather satellites offer specialized spectral bands that make high-altitude dynamics visible: * Water Vapor Channel (6.2 $\mu\text{m} - 7.3 \mu\text{m}$): This channel measures moisture in the middle-to-upper troposphere (see guidance on NOAA National Weather Service JetStream). * Dark / Jet-Black Ribbons: Represent extremely dry, descending air originating from the lower stratosphere (the "dry intrusion"). The sharp boundary between dark dry air and bright moist air marks the exact core of the jet stream. * Bright White Cloud Shields: Reveal regions of powerful ascent and upper-level divergence, often outlining the classic "comma head" of a maturing cyclone. * Visible & Infrared Imagery: A sharp, linear northern edge to an expansive cirrus cloud shield indicates the strong transverse shear along the poleward side of a jet streak.
3. Field Signs for the Skywatcher (No Internet Connection)
If you are trekking in the backcountry or sailing offshore without access to digital synoptic charts, apply these observational rules: 1. The Cirrus Speed & Vector Rule: Observe the motion of high cirrus against a static landmark (e.g., a mountain peak or your boat's mast). Rapid cirrus movement from WSW to ENE crossing at an angle to lower-level cumulus confirms strong vertical wind shear and the presence of an active upper jet. 2. Backing vs. Veering Winds (Buys Ballot's Law in 3D): * Stand with your back to the surface wind. In the Northern Hemisphere, low pressure is to your left. * If the wind is veering (shifting clockwise over time, e.g., from SE to S to SW), warm air advection is occurring, typically placing you in the warm sector ahead of a cold front. * If the wind is backing (shifting counterclockwise, e.g., from S to SE to E), cold air is being drawn in, indicating the cyclone center will pass south of you, frequently heralding prolonged, heavy stratiform precipitation. 3. The Halo Progression: A $22^\circ$ solar or lunar halo that gradually becomes obscured as the sky turns from milky white to uniform grey (altostratus) indicates an advancing warm conveyor belt forced upward by upper-level jet streak divergence. Expect steady precipitation within 12 to 18 hours.
+----------------------------------------------------------------------------------------------------+
| METEOROLOGICAL RULE OF THUMB |
+====================================================================================================+
| 1. THE JET STREAK QUADRANT HEURISTIC |
| * Left-Exit & Right-Entrance = DIVERGENCE ALOFT --> Air Rises --> STORMS & PRESSURE FALLS |
| * Right-Exit & Left-Entrance = CONVERGENCE ALOFT --> Air Sinks --> CLEAR SKIES & HIGH PRESSURE|
| |
| 2. THE WAVELENGTH DISPERSION CRITERION (c = uΜ - Ξ² / kΒ²) |
| * Shortwaves (L < 4,000 km) --> Move RAPIDLY EASTWARD (~40-70 km/h); bring transient fronts. |
| * Longwaves (L β 7,000 km) --> STALL & FORM BLOCKS (c β 0); bring weeks of uniform weather. |
| * Ultra-long (L > 8,000 km) --> RETROGRADE WESTWARD (c < 0); induce radical seasonal shifts. |
| |
| 3. SKYWATCHER'S 24-HOUR CYCLOGENESIS SEQUENCE |
| Mares' Tails (Cirrus Uncinus) --> 22Β° Solar Halo (Cirrostratus) --> Watery Sun (Altostratus) |
| --> Backing/Freshening Winds + Falling Barometer (>1.5 hPa/3h) = STEADY PRECIPITATION IMMINENT. |
+----------------------------------------------------------------------------------------------------+
Authoritative Meteorological References
- World Meteorological Organization (WMO) - Global Weather Systems
- National Oceanic and Atmospheric Administration (NOAA) - Jet Stream Dynamics
- UK Met Office - Synoptic Meteorology & Mid-Latitude Dynamics
- ECMWF - Numerical Weather Prediction & Upper-Air Diagnostics
- Wikipedia: Rossby Wave & Atmospheric Dynamics
- NOAA NWS JetStream - Online School for Weather: Upper Air Charts