Minor Case Study #1: Buffalo, NY Lake Effect Snow AOS 453 1st Minor Case Study: November 17-­‐19, 2014 Buffalo, NY Lake Effect Snow (Due 3/24) In this minor case study, we will investigate the November 17-­‐19th, 2014 lake effect snow event in Buffalo, NY. We will focus our attention to the early morning hours of November 18th in this study. Instead of me giving you cool stats and information about the event, you will be required to provide a short intro in the paper you will turn in upon completion of this case study. You will be working alone for this case study. Follow the instructions carefully and make sure to answer the questions that are posed. Specifically, we will focus on the evolution of the boundary layer over Lake Eerie during the event. At the end of the paper, you will produce a conceptual model of the event in a concluding discussion. The paper you will turn in will be separated into 3 sections. The 3 sections are as follows and will be discussed in more detail below, 1.) Introduction 2.) Analysis 3.) Conclusion and Conceptual Model COMPONENTS OF THE PAPER INTRODUCTION (1 page of text, not including figures) The introduction should include a discussion about the event in a general sense to “introduce” your audience to what you are about to study. You must research this information on your own. Find and discuss things like a.) the surface water temperature of Lake Eerie b.) the synoptic setup (can find from NWS and other online case studies) c.) Facts about the event (snowfall totals, etc). It is always good to incorporate nice graphics for the introduction as well since your audience will be drawn to them. Bottom line: hook your reader! ANALYSIS (4-­‐5 pages including embedded figures) In this section, you will analyze the dynamics manifested in the figures you will produce. The figures you produce for this section will be produced in GEMPAK using RUC data and will be discussed in the “Figures” section of this hand out. In addition to introducing your figures to your audience in the text, you should answer the following questions in this section: 1.)
What is the height of boundary layer over lake Eerie at each location along the lake at 00Z? at 03Z? at 06Z? Minor Case Study #1: Buffalo, NY Lake Effect Snow 2.)
3.)
4.)
5.)
6.)
Are there any obvious circulations in the boundary layer over Lake Eerie at 00Z? At 03Z? At 06Z? o Draw them on your cross sections using dark, solid arrows to indicate the flow (can use powerpoint or some other graphics manipulation software…even Word will let you do this, come see me if you need some help or ideas) What is the surface temperature of the lake (compared to the atmospheric layer over the lake (within the boundary layer)? o Considering your circulations, what does this mean about precipitation at the surface? Discuss why the circulation(s) exist where they do. (i.e. where is warm (cold) air rising and/or sinking and why?) How does the top of the boundary layer compare to the top of the boundary layer circulation(s) you drew at each time? How does the boundary layer’s depth change along the long axis of Lake Eerie in your cross sections at 00Z? at 03Z? at 06Z? o Is there any relationship to the strength of the circulation(s) you’ve drawn? Make sure you refer to the figures you produce in your text with citations! CONCLUSION AND CONCEPTUAL MODEL (2-­‐3 pages including embedded figure) In this section, you will first summarize the results of your analysis in the previous section. Then, you will make (on your own) a conceptual diagram. You will discuss the details of your conceptual diagram to provide a summary of the event as you have come to realize it through scientific investigation. For information about these conceptual diagram, read the “Conceptual Diagram” section. End with a discussion on how your conceptual diagram compares to the conceptual model of Lake Effect precipitation as we’ve discussed in class. Is it wind, or shore, parallel? FIGURES You will be using GDCROSS to produce your figures in this case study. The GEMPAK data you will use is found in the following directory corresponding to the 18th of November, 2014: /weather/archive/daily/2014_11_18/gemdata/hds/ You will make 3 figures corresponding to data evaluated on 18 November, 2014 at 00Z, 03Z and 06Z, respectively. Each of the three figures will consist of three cross section images. Minor Case Study #1: Buffalo, NY Lake Effect Snow TIMES WE WILL USE THE ANALYSIS DATA, NOT THE FORECAST DATA. So your GDATTIM and GDFILE will look like: GDATTIM
= f00
GDFILE
= /weather/archive/daily/2014_11_18/gemdata/hds/141118
??_ruc40.gem
where the “??” indicates the part of the data filename you will need to change in order to evaluate the data at 00Z, 03Z and 06Z. So, if you were interested in plotting the data from the 00Z RUC, you would have: GDFILE
= /weather/archive/daily/2014_11_18/gemdata/hds/14111800_ruc40.gem
LOCATIONS OF CROSS SECTIONS: The locations you should use for each cross section image in the three figures will not be strictly enforced, but they should be oriented such that they are perpendicular to the long axis of Lake Eerie at three locations along the lake with the lake centered in the cross section. For example, Number your cross sections such that the first cross section is furthest from Buffalo, the second is toward the middle of the lake, and the third is closest to Buffalo. Minor Case Study #1: Buffalo, NY Lake Effect Snow You will notice that there are not sounding stations at these locations, so you can use www.latlong.net to find the start and end points of your cross sections as latitude and longitude pairs that you can feed into the CXSTNS argument in your GEMPAK script. For instance, one of my cross sections has the following line of code: CXSTNS
= 44.388785;-80.639648>40.666195;-77.717285
Note that the syntax is as follows: CXSTNS
= lat1 ; lon1 > lat2 ; lon 2
Where lat1 and lon1 will be positioned on the left side of your cross section and lat2 and lon2 will be positioned on the right side of your cross section. VERTICAL DOMAIN SETUP For these cross sections, we will want to limit our domain to the first few kilometers of the atmosphere. Recall that lake effect snowstorms are typically shallow convective events! We will limit our domain to the 1000-­‐650mb layers. To do this, copy the following line of code into your GEMPAK script for your gvcor, ptype
and yaxis arguments: GVCORD
= pres
PTYPE
= log
YAXIS
= 1000/650/10
This enforces that we will use log-­‐pressure as our vertical coordinate from 1000mb to 650mb at 10mb intervals. WHAT TO PLOT IN EACH CROSS SECTION IMAGE OF EACH FIGURE Please plot the following in each cross section image for each of the three figures: -­‐
BLACK contours (not fill) of Potential Temperature o Contoured every 1K o ALSO: To provide a proxy for the boundary layer’s top, draw: ONE SOLID, THICK BLACK LINE of the: § 272K Pot. Temp. surface/contour (1st cross section) § 274K Pot. Temp. surface/contour (2nd cross section) § 276K Pot. Temp. surface/contour (3rd cross section) -­‐
RED contours (not fill) of TOTAL WIND CONVERGENCE o Contoured every 2 units (inverse seconds in this case) from a magnitude of 2 to a magnitude of 12. -­‐
BLUE contours (not fill) of TOTAL WIND DIVERGENCE o Contoured every 2 units (inverse seconds in this case) from a magnitude of 2 to a magnitude of 12. -­‐
DASHED, BROWN CONTOURS of temperature in Celsius o Contoured every -­‐5OC from 0OC to -­‐20OC. Minor Case Study #1: Buffalo, NY Lake Effect Snow WHAT YOU SHOULD END UP WITH When all is said and done, you should end up with 3 figures as follows: FIGURE 1: 18 November, 2014 at 00Z a.) First cross section (furthest from Buffalo) b.) Second cross section (toward middle of lake) c.) Third cross section (closest to Buffalo) FIGURE 2: 18 November, 2014 at 03Z a.) First cross section (furthest from Buffalo) b.) Second cross section (toward middle of lake) c.) Third cross section (closest to Buffalo) FIGURE 3: 18 November, 2014 at 06Z a.) First cross section (furthest from Buffalo) b.) Second cross section (toward middle of lake) c.) Third cross section (closest to Buffalo) AS ALWAYS…MAKE SURE YOUR FIGURES HAVE CAPTIONS!!! CONCEPTUAL DIAGRAM This will be the final figure of your paper. You must make sure it is clear and easy to understand. The goal of conceptual diagrams is to provide your audience with a snapshot of everything you have discussed in such a way that they can understand everything in one, passing glance. This is where you get to be creative! However, a good rule of thumb is: LESS IS MORE! WHAT YOU NEED TO SHOW The evolution of the boundary layer associated with the lake-­‐effect convection. You will do this with two figures stacked on top of eachother and labeled (a) and (b). Both are cross sections with the same orientation, but the first figure will show the boundary layer at an earlier (before or around the 18, November 00Z data you evaluated) and at a later time (after or around the 18, November 06Z data you evaluated). Minor Case Study #1: Buffalo, NY Lake Effect Snow HOW As a vertical cross section at 00Z and 06Z oriented ALONG the long axis of the lake. So the cross section should be LOOKING FROM THE SOUTHEAST TO THE NORTHWEST at the long axis of Lake Eerie: WHAT TO INCLUDE IN EACH FIGURE OF YOUR CONCEPTUAL DIAGRAM -­‐
The boundary layer height across your whole cross section -­‐
Boundary layer convection with arrows indicating vertical motion (if any) -­‐
Region(s) of precipitation -­‐
Normal wind vectors (so magnitude into/out-­‐of board) AS ALWAYS…MAKE SURE YOUR DIAGRAM HAS A CAPTION!!!