12.4: Alternative Text Descriptions for Investigation 12

Figure 12.1.1: Tracks of all tropical cyclones on record. 

Map-based tool showing that tropical cyclones have historically formed across multiple ocean basins, with the highest concentration in the Atlantic, Caribbean, Gulf of Mexico, and western Pacific. The tracks illustrate how storms often cluster in warm, tropical regions and can travel across large portions of the ocean. The map also shows fewer storms in the South Atlantic and eastern South Pacific, highlighting that those areas rarely experience cyclones. The tool includes filters for storm categories, options for printing and downloading, and labels for major ocean basins and continents.

Figure 12.2.1: Michael advisory at 7pm CDT on October 7, 2018. 

This forecast product was issued by the National Hurricane Center on Sunday, October 7, 2018, at 7 PM CDT for Tropical Storm Michael.

• Current storm details: At issuance, the center of Michael was located at 19.9°N, 85.4°W with maximum sustained winds of 60 miles per hour. The storm was moving north at 5 miles per hour.
• Forecast track and timing:
  • By late Sunday night and Monday, the system was expected to move northward over the northwestern Caribbean and strengthen.
  • By Tuesday afternoon, Michael was forecast to approach the Gulf Coast as a hurricane.
  • By Wednesday and Thursday, the storm was predicted to track inland across parts of the southeastern United States.
  • By Friday, the system was expected to move off the U.S. East Coast and into the Atlantic Ocean.
• Intensity forecast: The advisory indicated that Michael would strengthen from a tropical storm into a hurricane before reaching land, with sustained winds projected to exceed 74 miles per hour.
• Hazard notes: The forecast emphasized that the cone represents the probable path of the storm’s center but does not account for the full size of the system. Hazardous conditions such as wind, rain, and storm surge could extend beyond the cone.
• Watches and warnings: At the time of the forecast, both tropical storm and hurricane watches and warnings had been issued for parts of the affected region, alerting coastal and nearby inland areas to prepare for possible impacts.

Figure 12.2.2: Michael advisory at 1am CDT on October 9, 2018.

This advisory was issued by the National Hurricane Center early on Tuesday, October 9, 2018, for Hurricane Michael.

• Current storm details: At the time of issuance, the storm center was located at 23.6°N, 85.7°W with maximum sustained winds of 90 miles per hour. Michael was moving north-northwest at 12 miles per hour.
• Forecast track and timing:
  • By Tuesday evening, Michael was predicted to intensify into a hurricane with maximum winds exceeding 110 miles per hour as it continued toward the Gulf Coast.
  • By Wednesday morning, the storm was expected to make landfall along the Gulf Coast as a major hurricane.
  • By Wednesday evening and Thursday, the storm center was projected to move inland across the southeastern United States, weakening but still bringing strong winds and heavy rainfall.
  • By Friday and Saturday, the system was forecast to move off the U.S. East Coast into the Atlantic Ocean.
• Intensity forecast: Michael was expected to strengthen from a hurricane into a major hurricane before landfall, producing winds well above 110 miles per hour.
• Hazard notes: The cone of uncertainty depicts the probable path of the storm’s center, not its full size. Impacts such as wind, rainfall, and storm surge could extend beyond the cone.
• Watches and warnings: Hurricane and tropical storm watches and warnings were in effect for portions of the Gulf Coast at the time of this advisory, highlighting the potential for life-threatening conditions.

Figure 12.2.3: Michael advisory at 7am CDT on October 10, 2018.

This is an official forecast graphic for Hurricane Michael, issued by the National Hurricane Center at 7 AM Central Daylight Time on Wednesday, October 10, 2018 (Advisory 15A). The map outlines the projected path and intensity forecast for the storm, along with watch and warning areas and a shaded region known as the “cone of uncertainty.” A note clarifies that the cone shows only the probable track of the storm center, and hazardous weather can occur outside the cone.

Current Storm Information:

• Storm Name: Hurricane Michael
• Storm Type: Major Hurricane
• Advisory Time: 7 AM CDT
• Center Location: Latitude 29.0° North, Longitude 86.3° West
• Maximum Sustained Winds: 145 miles per hour
• Movement: North at 13 miles per hour

Watches and Warnings:

• Hurricane warnings are in effect for parts of the Gulf Coast, including areas near where landfall is expected.
• Tropical storm warnings extend inland and along portions of the southeastern U.S. coastline.
• These designations indicate where hurricane- and tropical-storm-force winds and storm surge are expected or possible within the next 12–48 hours.

Forecast Path and Timing:

• Landfall is expected later on Wednesday, with Michael still at major hurricane strength (wind speeds greater than 110 mph).
• By 1 AM Thursday, the storm is forecast to weaken slightly but remain a hurricane as it moves inland.
• By 1 PM Thursday, the system is expected to weaken to a tropical storm as it progresses further across the southeastern U.S.
• By 1 AM Friday, the storm is forecast to move off the East Coast, continuing as a tropical storm.
• Between Saturday and Monday, the system is forecast to transition to a post-tropical cyclone as it moves over the open Atlantic Ocean, away from North America.

Each forecast position along the track includes a symbol to indicate the predicted intensity of the storm at that point:

• M = Major hurricane (>110 mph winds)
• H = Hurricane (74–110 mph winds)
• S = Tropical Storm (39–73 mph winds)
• D = Tropical Depression (<39 mph winds)
• O = Potential or post-tropical cyclone

The forecast cone expands over time, indicating increased uncertainty in the storm’s future position beyond the first 72 hours. Forecast points are labeled at 24-hour intervals up through 1 AM Monday, five days after the advisory issuance.

Figure 12.3.1: Air Pressure and Wind Speed graph for Hurricane Michael

This image is a time series graph showing how Hurricane Michael’s maximum sustained wind speed and minimum central pressure changed over time. The graph covers the period from October 6 to October 12, 2018, with time shown in Coordinated Universal Time (UTC).

The horizontal axis displays the date and time in regular intervals. The graph includes two separate sets of data:

• Wind speed, measured in miles per hour,
• Central pressure, measured in millibars (mb).

Wind speed values range from 0 to 160 mph, and pressure values range from 880 mb to 1020 mb.

Summary of the Data:

• In the early part of the timeline, wind speed remains low, around 30 mph, while central pressure is relatively high, above 1000 mb.
• Over the next couple of days, wind speed increases steadily, reaching a peak of over 140 mph around October 10. At the same time, central pressure drops to below 925 mb.
• This period of increasing wind and decreasing pressure represents the rapid intensification phase of Hurricane Michael.
• Following the peak, wind speed gradually decreases and pressure increases, marking the weakening phase of the storm as it moves inland or loses organization.
• By the end of the timeline, wind speed falls to around 60–70 mph, and pressure returns to values near 980–990 mb.

The data shows a clear inverse relationship between wind speed and central pressure: as pressure decreases, wind increases, which is typical behavior for strengthening tropical cyclones.