Chapter 20 Lab Activity B Hurricane Andrew

Working Through the Hurricane Andrew Lab

Chapter 20 Lab Activity B Hurricane Andrew

You open the worksheet and stare at a grid map with pressure readings scattered across Florida. The instructions say to draw isobars every four millibars and then answer eight questions about storm structure. It sounds straightforward until you get to the part where the data points are messy. I remember spending twenty minutes on a single isobar line because two nearby stations read 996 and 1004 and the terrain between them isn't flat — it's Miami, and elevation changes matter more than the lab manual admits. The core task is contour mapping. You take raw station data — barometric pressure at specific points — and connect areas of equal pressure. That gives you a visual of where the low center sits and how tightly packed the isobars are. Tight packing means stronger winds. Loose spacing means weaker gradient. That's the whole principle. What most students miss is the direction you draw your isobars. They curve around the low, not straight lines. You sketch them like ripples in water, and each ring represents the same pressure value. Get one ring wrong and everything downstream of it is off. I learned this the hard way during a midterm where I drew a cross-isobar flow instead of a circular pattern around the center. Professor marked it wrong and said something about Coriolis deflection, which I should have known but didn't. Still do sometimes when I'm tired.

For Hurricane Andrew specifically, the 1992 landfall data shows a central pressure around 922 millibars near Miami-Dade. The isobars tighten dramatically as you move inward. Your job is to replicate that from the provided dataset. Use a light hand at first. Graphite pencil, not pen. You'll erase a lot. Here's the edge case nobody warns you about: when two pressure values sit on opposite sides of an isobar threshold — say 988 and 992 — and there's no reading in between, you still draw the 992 line. Don't skip it because you think the gap means the line doesn't exist. The atmosphere doesn't care about your data points. It interpolates between them whether you acknowledge it or not. I spent an entire lab period once trying to justify omitting a line because "there was no station data." My lab partner just pointed at the map and said, "it's right there." She was right. The questions after the map usually ask about wind speed, storm surge potential, and damage path. Wind speed correlates inversely with isobar spacing. Closer lines, faster winds. For Andrew, that meant Category 5 conditions over parts of the Florida coast before weakening to Category 4 at second landfall near Camacho, Louisiana. Students often confuse the two landfalls and attribute Louisiana damage to the Florida track. Just make sure you're reading the timeline correctly.

Storm surge modeling in this lab is simplified. You're not running SLOSH simulations. You're looking at the relationship between forward speed, basin shape, and onshore wind direction. Andrew moved northwest at about 22 miles per hour. That speed matters because slower storms push water longer in one area. Faster storms sweep it along. Andrew was on the slower side for a major hurricane, which contributed to the serious surge in South Florida. The lab probably asks you to connect these dots. If you're stuck on the actual isobar drawing, here's what I do. Start from the outside and work inward. Draw the 1000 millibar ring first as a loose circle around all the points above that value. Then 996, then 992, and so on. Each successive ring gets smaller and more irregular. Never let lines cross. If you feel like they might need to cross, you've made a mistake somewhere earlier in the process. Stop and check your baseline readings against the original table. The data tables in these labs sometimes have typos. I've seen missing decimal points and transposed numbers multiple times across different textbook editions. When your isobars come out wrong and you can't find the error, go back to the source table and verify each number against the printed page. Don't trust your memory or a peer's copied values.

For the written questions, be specific with numbers. Saying "the wind was very strong" gets partial credit. Saying "sustained winds reached 165 miles per hour with gusts near 180, consistent with Category 5 intensity on the Saffir-Simpson scale" gets full credit. The grader wants to see that you can read the data and translate it into proper terminology. Sometimes the lab includes a satellite imagery section alongside the isobar map. If yours does, pay attention to the eye structure. Andrew had a well-defined eye during peak intensity over the Florida Bay area. That tight, circular eye corresponds to the most densely packed isobars on your map. If your isobar map doesn't show a concentrated center matching the eye location in the satellite image, something is off. The two should align. One more thing about the aftermath questions. Andrew caused roughly $26.5 billion in damage in 1992 dollars. That's about fifty thousand homes destroyed or severely damaged. The lab might ask you to discuss preparedness failures. South Florida had expanded rapidly in the decades before the storm, and building codes weren't updated until after Andrew exposed the weaknesses. This is factual history, not opinion. Stick to what the textbook presents unless the question explicitly asks for your analysis.

If you finish the map early, don't rush the questions. Most errors happen in the writing portion where students skim and miss qualifiers in the prompt. "Explain how" is different from "Describe what." "Evaluate" means something else again. Read each question once before you start writing. Then read it again. The whole activity usually takes forty-five to sixty minutes if you work methodically. Rushing the isobar drawing costs you more time later when you have to redo it. Go slow on the map, go fast on the answers. That's been my pattern every time I've done this lab. Good luck with it. It's a standard exercise and nothing tricky about the concept itself. Just pay attention to the details and don't second-guess yourself unnecessarily.