Stability Analysis, Page 1 Synoptic Meteorology I
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A Local Large Hail Probability Equation for Columbia, Sc
EASTERN REGION TECHNICAL ATTACHMENT NO. 98-6 AUGUST, 1998 A LOCAL LARGE HAIL PROBABILITY EQUATION FOR COLUMBIA, SC Mark DeLisi NOAA/National Weather Service Forecast Office West Columbia, SC Editor’s Note: The author’s current affiliation is NWSFO Mt. Holly, NJ. 1. INTRODUCTION Skew-T/Hodograph Analysis and Research Program, or SHARP (Hart and Korotky Billet et al. (1997) derived a successful 1991). The dependent variable, hail diameter probability of large hail (diameter greater than or the absence of hail, was derived from or equal to 0.75 inch) equation as an aid in spotter reports for the CAE warning area from National Weather Service (NWS) severe May, 1995 through September, 1996. There thunderstorm warning operations. Hail of that were 136 cases used to develop the regression diameter or larger requires a severe equation. thunderstorm warning be issued by NWS offices. Shortly thereafter, a Weather The LPLH was verified using 69 spotter Surveillance Radar-1988 Doppler (WSR- reports from the period September, 1996 88D) radar probability of severe hail (POSH) through September, 1997. The POSH was became available for warning operations (Witt verified as well. Verification statistics et al. 1998). This study recreates the steps included the Brier score and the chi-square taken in Billet et al. (1997) to derive a local (32) statistic. probability of large hail equation (LPLH) for the Columbia, SC National Weather Service The goal of this study was to develop an Forecast Office (CAE) warning area, and it objective method to estimate the probability assesses the utility of the LPLH relative to the of large hail for use in forecast operations. -
Pressure Gradient Force Examples of Pressure Gradient Hurricane Andrew, 1992 Extratropical Cyclone
4/29/2011 Chapter 7: Forces and Force Balances Forces that Affect Atmospheric Motion Pressure gradient force Fundamental force - Gravitational force FitiFrictiona lfl force Centrifugal force Apparent force - Coriolis force • Newton’s second law of motion states that the rate of change of momentum (i.e., the acceleration) of an object , as measured relative relative to coordinates fixed in space, equals the sum of all the forces acting. • For atmospheric motions of meteorological interest, the forces that are of primary concern are the pressure gradient force, the gravitational force, and friction. These are the • Forces that Affect Atmospheric Motion fundamental forces. • Force Balance • For a coordinate system rotating with the earth, Newton’s second law may still be applied provided that certain apparent forces, the centrifugal force and the Coriolis force, are • Geostrophic Balance and Jetstream ESS124 included among the forces acting. ESS124 Prof. Jin-Jin-YiYi Yu Prof. Jin-Jin-YiYi Yu Pressure Gradient Force Examples of Pressure Gradient Hurricane Andrew, 1992 Extratropical Cyclone (from Meteorology Today) • PG = (pressure difference) / distance • Pressure gradient force goes from high pressure to low pressure. • Closely spaced isobars on a weather map indicate steep pressure gradient. ESS124 ESS124 Prof. Jin-Jin-YiYi Yu Prof. Jin-Jin-YiYi Yu 1 4/29/2011 Gravitational Force Pressure Gradients • • Pressure Gradients – The pressure gradient force initiates movement of atmospheric mass, widfind, from areas o fhihf higher to areas o flf -
Chapter 5. Meridional Structure of the Atmosphere 1
Chapter 5. Meridional structure of the atmosphere 1. Radiative imbalance 2. Temperature • See how the radiative imbalance shapes T 2. Temperature: potential temperature 2. Temperature: equivalent potential temperature 3. Humidity: specific humidity 3. Humidity: saturated specific humidity 3. Humidity: saturated specific humidity Last time • Saturated adiabatic lapse rate • Equivalent potential temperature • Convection • Meridional structure of temperature • Meridional structure of humidity Today’s topic • Geopotential height • Wind 4. Pressure / geopotential height • From a hydrostatic balance and perfect gas law, @z RT = @p − gp ps T dp z(p)=R g p Zp • z(p) is called geopotential height. • If we assume that T and g does not vary a lot with p, geopotential height is higher when T increases. 4. Pressure / geopotential height • If we assume that g and T do not vary a lot with p, RT z(p)= (ln p ln p) g s − • z increases as p decreases. • Higher T increases geopotential height. 4. Pressure / geopotential height • Geopotential height is lower at the low pressure system. • Or the high pressure system corresponds to the high geopotential height. • T tends to be low in the region of low geopotential height. 4. Pressure / geopotential height The mean height of the 500 mbar surface in January , 2003 4. Pressure / geopotential height • We can discuss about the slope of the geopotential height if we know the temperature. R z z = (T T )(lnp ln p) warm − cold g warm − cold s − • We can also discuss about the thickness of an atmospheric layer if we know the temperature. RT z z = (ln p ln p ) p1 − p2 g 2 − 1 4. -
Pressure Gradient Force
2/2/2015 Chapter 7: Forces and Force Balances Forces that Affect Atmospheric Motion Pressure gradient force Fundamental force - Gravitational force Frictional force Centrifugal force Apparent force - Coriolis force • Newton’s second law of motion states that the rate of change of momentum (i.e., the acceleration) of an object, as measured relative to coordinates fixed in space, equals the sum of all the forces acting. • For atmospheric motions of meteorological interest, the forces that are of primary concern are the pressure gradient force, the gravitational force, and friction. These are the • Forces that Affect Atmospheric Motion fundamental forces. • Force Balance • For a coordinate system rotating with the earth, Newton’s second law may still be applied provided that certain apparent forces, the centrifugal force and the Coriolis force, are • Geostrophic Balance and Jetstream ESS124 included among the forces acting. ESS124 Prof. Jin-Yi Yu Prof. Jin-Yi Yu Pressure Gradient Force Examples of Pressure Gradient Hurricane Andrew, 1992 Extratropical Cyclone (from Meteorology Today) • PG = (pressure difference) / distance • Pressure gradient force goes from high pressure to low pressure. • Closely spaced isobars on a weather map indicate steep pressure gradient. ESS124 ESS124 Prof. Jin-Yi Yu Prof. Jin-Yi Yu 1 2/2/2015 Balance of Force in the Vertical: Pressure Gradients Hydrostatic Balance • Pressure Gradients – The pressure gradient force initiates movement of atmospheric mass, wind, from areas of higher to areas of lower pressure Vertical -
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Environmental Conditions Producing Thunderstorms with Anomalous Vertical Polarity of Charge Structure Donald R. MacGorman Alexander J. Eddy NOAA/Nat’l Severe Storms Laboratory & Cooperative Cooperative Institute for Mesoscale Meteorological Institute for Mesoscale Meteorological Studies Studies Affiliation/ Univ. of Oklahoma and NOAA/OAR Norman, Oklahoma, USA Norman, Oklahoma, USA [email protected] Earle Williams Cameron R. Homeyer Massachusetts Insitute of Technology School of Meteorology, Univ. of Oklhaoma Cambridge, Massachusetts, USA Norman, Oklahoma, USA Abstract—+CG flashes typically comprise an unusually large Tessendorf et al. 2007, Weiss et al. 2008, Fleenor et al. 2009, fraction of CG activity in thunderstorms with anomalous vertical Emersic et al. 2011; DiGangi et al. 2016). Furthermore, charge structure. We analyzed more than a decade of NLDN previous studies have suggested that CG activity tends to be data on a 15 km x 15 km x 15 min grid spanning the contiguous delayed tens of minutes longer in these anomalous storms than United States, to identify storm cells in which +CG flashes in most storms elsewhere (MacGorman et al. 2011). constituted a large fraction of CG activity, as a proxy for thunderstorms with anomalous vertical charge structure, and For this study, we analyzed more than a decade of CG data storm cells with very low percentages of +CG lightning, as a from the National Lightning Detection Network throughout the proxy for thunderstorms with normal-polarity distributions. In contiguous United States to identify storm cells in which +CG each of seven regions, we used North American Regional flashes constituted a large fraction of CG activity, as a proxy Reanalysis data to compare the environments of anomalous for storms with anomalous vertical charge structure. -
Chapter 8 Atmospheric Statics and Stability
Chapter 8 Atmospheric Statics and Stability 1. The Hydrostatic Equation • HydroSTATIC – dw/dt = 0! • Represents the balance between the upward directed pressure gradient force and downward directed gravity. ρ = const within this slab dp A=1 dz Force balance p-dp ρ p g d z upward pressure gradient force = downward force by gravity • p=F/A. A=1 m2, so upward force on bottom of slab is p, downward force on top is p-dp, so net upward force is dp. • Weight due to gravity is F=mg=ρgdz • Force balance: dp/dz = -ρg 2. Geopotential • Like potential energy. It is the work done on a parcel of air (per unit mass, to raise that parcel from the ground to a height z. • dφ ≡ gdz, so • Geopotential height – used as vertical coordinate often in synoptic meteorology. ≡ φ( 2 • Z z)/go (where go is 9.81 m/s ). • Note: Since gravity decreases with height (only slightly in troposphere), geopotential height Z will be a little less than actual height z. 3. The Hypsometric Equation and Thickness • Combining the equation for geopotential height with the ρ hydrostatic equation and the equation of state p = Rd Tv, • Integrating and assuming a mean virtual temp (so it can be a constant and pulled outside the integral), we get the hypsometric equation: • For a given mean virtual temperature, this equation allows for calculation of the thickness of the layer between 2 given pressure levels. • For two given pressure levels, the thickness is lower when the virtual temperature is lower, (ie., denser air). • Since thickness is readily calculated from radiosonde measurements, it provides an excellent forecasting tool. -
Comparison Between Observed Convective Cloud-Base Heights and Lifting Condensation Level for Two Different Lifted Parcels
AUGUST 2002 NOTES AND CORRESPONDENCE 885 Comparison between Observed Convective Cloud-Base Heights and Lifting Condensation Level for Two Different Lifted Parcels JEFFREY P. C RAVEN AND RYAN E. JEWELL NOAA/NWS/Storm Prediction Center, Norman, Oklahoma HAROLD E. BROOKS NOAA/National Severe Storms Laboratory, Norman, Oklahoma 6 January 2002 and 16 April 2002 ABSTRACT Approximately 400 Automated Surface Observing System (ASOS) observations of convective cloud-base heights at 2300 UTC were collected from April through August of 2001. These observations were compared with lifting condensation level (LCL) heights above ground level determined by 0000 UTC rawinsonde soundings from collocated upper-air sites. The LCL heights were calculated using both surface-based parcels (SBLCL) and mean-layer parcels (MLLCLÐusing mean temperature and dewpoint in lowest 100 hPa). The results show that the mean error for the MLLCL heights was substantially less than for SBLCL heights, with SBLCL heights consistently lower than observed cloud bases. These ®ndings suggest that the mean-layer parcel is likely more representative of the actual parcel associated with convective cloud development, which has implications for calculations of thermodynamic parameters such as convective available potential energy (CAPE) and convective inhibition. In addition, the median value of surface-based CAPE (SBCAPE) was more than 2 times that of the mean-layer CAPE (MLCAPE). Thus, caution is advised when considering surface-based thermodynamic indices, despite the assumed presence of a well-mixed afternoon boundary layer. 1. Introduction dry-adiabatic temperature pro®le (constant potential The lifting condensation level (LCL) has long been temperature in the mixed layer) and a moisture pro®le used to estimate boundary layer cloud heights (e.g., described by a constant mixing ratio. -
How Appropriate They Are/Will Be Using Future Satellite Data Sources?
Different Convective Indices - - - How appropriate they are/will be using future satellite data sources? Ralph A. Petersen1 1 Cooperative Institute for Meteorological Satellite Studies (CIMSS), University of Wisconsin – Madison, Madison, Wisconsin, USA Will additional input from Steve Weiss, NOAA/NWS/Storm Prediction Center ✓ Increasing the Utility / Value of real-time Satellite Sounder Products to fill gaps in their short-range forecasting processes Creating Temperature/Moisture Soundings from Infra-Red (IR) Satellite Observations A Conceptual Tutorial All level of the atmosphere is continually emit radiation toward space. Satellites observe the net amount reaching space. • Conceptually, we can think about the atmosphere being made up of many thin layers Start from the bottom and work up. 1 – The greatest amount of radiation is emitted from the earth’s surface 4 - Remember, Stefan’s Law: Emission ~ σTSfc 2 – Molecules of various gases in the lowest layer of the atmosphere absorb some of the radiation and then reemit it upward to space and back downward to the earth’s surface - Major absorbers are CO2 and H2O 4 - Emission again ~ σT , but TAtmosphere<TSfc - Amount of radiation decreases with altitude Creating Temperature/Moisture Soundings from Infra-Red (IR) Satellite Observations A Conceptual Tutorial All level of the atmosphere is continually emit radiation toward space. Satellites observe the net amount reaching space. • Conceptually, we can think about the atmosphere being made up of many thin layers Start from the bottom and work -
MSE3 Ch14 Thunderstorms
Chapter 14 Copyright © 2011, 2015 by Roland Stull. Meteorology for Scientists and Engineers, 3rd Ed. thunderstorms Contents Thunderstorms are among the most violent and difficult-to-predict weath- Thunderstorm Characteristics 481 er elements. Yet, thunderstorms can be Appearance 482 14 studied. They can be probed with radar and air- Clouds Associated with Thunderstorms 482 craft, and simulated in a laboratory or by computer. Cells & Evolution 484 They form in the air, and must obey the laws of fluid Thunderstorm Types & Organization 486 mechanics and thermodynamics. Basic Storms 486 Thunderstorms are also beautiful and majestic. Mesoscale Convective Systems 488 Supercell Thunderstorms 492 In thunderstorms, aesthetics and science merge, making them fascinating to study and chase. Thunderstorm Formation 496 Convective Conditions 496 Thunderstorm characteristics, formation, and Key Altitudes 496 forecasting are covered in this chapter. The next chapter covers thunderstorm hazards including High Humidity in the ABL 499 hail, gust fronts, lightning, and tornadoes. Instability, CAPE & Updrafts 503 CAPE 503 Updraft Velocity 508 Wind Shear in the Environment 509 Hodograph Basics 510 thunderstorm CharaCteristiCs Using Hodographs 514 Shear Across a Single Layer 514 Thunderstorms are convective clouds Mean Wind Shear Vector 514 with large vertical extent, often with tops near the Total Shear Magnitude 515 tropopause and bases near the top of the boundary Mean Environmental Wind (Normal Storm Mo- layer. Their official name is cumulonimbus (see tion) 516 the Clouds Chapter), for which the abbreviation is Supercell Storm Motion 518 Bulk Richardson Number 521 Cb. On weather maps the symbol represents thunderstorms, with a dot •, asterisk , or triangle Triggering vs. Convective Inhibition 522 * ∆ drawn just above the top of the symbol to indicate Convective Inhibition (CIN) 523 Trigger Mechanisms 525 rain, snow, or hail, respectively. -
Effect of Deep Convection on the TTL Composition Over the Southwest Indian Ocean During Austral Summer
https://doi.org/10.5194/acp-2019-1072 Preprint. Discussion started: 22 January 2020 c Author(s) 2020. CC BY 4.0 License. Effect of deep convection on the TTL composition over the Southwest Indian Ocean during austral summer. Stephanie Evan1, Jerome Brioude1, Karen Rosenlof2, Sean. M. Davis2, Hölger Vömel3, Damien Héron1, Françoise Posny1, Jean-Marc Metzger4, Valentin Duflot1,4, Guillaume Payen4, Hélène Vérèmes1, 5 Philippe Keckhut5, and Jean-Pierre Cammas1,4 1LACy, Laboratoire de l’Atmosphère et des Cyclones, UMR8105 (CNRS, Université de La Réunion, Météo-France), Saint- Denis de la Réunion, 97490, France 2Chemical Sciences Division, Earth System Research Laboratory, NOAA, Boulder, 80305, CO, USA 3National Center for Atmospheric Research, Boulder, 80301, CO, USA 10 4Observatoire des Sciences de l’Univers de La Réunion, UMS3365 (CNRS, Université de La Réunion, Météo-France), Saint- Denis de la Réunion, 97490, France 5LATMOS, Laboratoire ATmosphères, Milieux, Observations Spatiales-IPSL UMR8190 (UVSQ Université Paris-Saclay, Sorbonne Université, CNRS), Guyancourt, 78280, France Correspondence to: Stephanie Evan ([email protected]) 15 Abstract. Balloon-borne measurements of CFH water vapor, ozone and temperature and water vapor lidar measurements from the Maïdo Observatory at Réunion Island in the Southwest Indian Ocean (SWIO) were used to study tropical cyclones' influence on TTL composition. The balloon launches were specifically planned using a Lagrangian model and METEOSAT 7 infrared images to sample the convective outflow from Tropical Storm (TS) Corentin on 25 January 2016 and Tropical Cyclone (TC) Enawo on 3 March 2017. 20 Comparing CFH profile to MLS monthly climatologies, water vapor anomalies were identified. Positive anomalies of water vapor and temperature, and negative anomalies of ozone between 12 and 15 km in altitude (247 to 121hPa) originated from convectively active regions of TS Corentin and TC Enawo, one day before the planned balloon launches, according to the Lagrangian trajectories. -
Basic Features on a Skew-T Chart
Skew-T Analysis and Stability Indices to Diagnose Severe Thunderstorm Potential Mteor 417 – Iowa State University – Week 6 Bill Gallus Basic features on a skew-T chart Moist adiabat isotherm Mixing ratio line isobar Dry adiabat Parameters that can be determined on a skew-T chart • Mixing ratio (w)– read from dew point curve • Saturation mixing ratio (ws) – read from Temp curve • Rel. Humidity = w/ws More parameters • Vapor pressure (e) – go from dew point up an isotherm to 622mb and read off the mixing ratio (but treat it as mb instead of g/kg) • Saturation vapor pressure (es)– same as above but start at temperature instead of dew point • Wet Bulb Temperature (Tw)– lift air to saturation (take temperature up dry adiabat and dew point up mixing ratio line until they meet). Then go down a moist adiabat to the starting level • Wet Bulb Potential Temperature (θw) – same as Wet Bulb Temperature but keep descending moist adiabat to 1000 mb More parameters • Potential Temperature (θ) – go down dry adiabat from temperature to 1000 mb • Equivalent Temperature (TE) – lift air to saturation and keep lifting to upper troposphere where dry adiabats and moist adiabats become parallel. Then descend a dry adiabat to the starting level. • Equivalent Potential Temperature (θE) – same as above but descend to 1000 mb. Meaning of some parameters • Wet bulb temperature is the temperature air would be cooled to if if water was evaporated into it. Can be useful for forecasting rain/snow changeover if air is dry when precipitation starts as rain. Can also give -
DEPARTMENT of GEOSCIENCES Name______San Francisco State University May 7, 2013 Spring 2009
DEPARTMENT OF GEOSCIENCES Name_____________ San Francisco State University May 7, 2013 Spring 2009 Monteverdi Metr 201 Quiz #4 100 pts. A. Definitions. (3 points each for a total of 15 points in this section). (a) Convective Condensation Level --The elevation at which a lofted surface parcel heated to its Convective Temperature will be saturated and above which will be warmer than the surrounding air at the same elevation. (b) Convective Temperature --The surface temperature that must be met or exceeded in order to convert an absolutely stable sounding to an absolutely unstable sounding (because of elimination, usually, of the elevated inversion characteristic of the Loaded Gun Sounding). (c) Lifted Index -- the difference in temperature (in C or K) between the surrounding air and the parcel ascent curve at 500 mb. (d) wave cyclone -- a cyclone in which a frontal system is centered in a wave-like configuration, normally with a cold front on the west and a warm front on the east. (e) conditionally unstable sounding (conceptual definition) –a sounding for which the parcel ascent curve shows an LFC not at the ground, implying that the sounding is unstable only on the condition that a surface parcel is force lofted to the LFC. B. Units. (2 pts each for a total of 8 pts) Provide the units used conventionally for the following: θ ____ Ko * o o Td ______C ___or F ___________ PGA -2 ( )z ______m s _______________** w ____ m s-1_____________*** *θ = Theta = Potential Temperature **PGA = Pressure Gradient Acceleration *** At Equilibrium Level of Severe Thunderstorms € 1 C. Sounding (3 pts each for a total of 27 points in this section).