A strengthening tropical storm is brewing southeast of Hawaii this afternoon, and forecasters are worried that the storm may turn into a hurricane before possibly making landfall on the island chain this weekend. Here's what you need to know about Tropical Storm Ana.
What are the storm's current stats?
Tropical Storm Ana is churning about 900 miles southeast of Hilo at this hour with winds of about 50 MPH. The storm is slowly gathering strength and organization, and environmental conditions are favorable for the storm to grow into a hurricane as it tracks northwest towards Hawaii.
For a couple of days now the models have been showing this storm making a direct landfall on Hawaii, and the latest forecast from the Central Pacific Hurricane Center agrees with that general idea. For four forecasts now, the agency has drawn Ana's forecast path directly towards the Big Island.
How strong could Ana be when it approaches Hawaii?
The current forecast shows Ana packing 80 MPH with gusts to 100 MPH by the end of the forecast period at 2:00 AM HST on Sunday. Intensity forecasting with hurricanes is still imprecise, so it's possible for the storm to be much stronger (or much weaker!) by the time it approaches Hawaii.
Could the storm miss Hawaii? What about the cone of uncertainty?
The cone of uncertainty is always an important factor in hurricane forecasts, and it's especially important here since the cone is so large in these forecasts. The cone of uncertainty is the margin of error in a hurricane's projected path. On average, the center of a tropical cyclone stays within the cone of uncertainty 66% of the time.
Uncertainty grows with time, so longer-range forecasts have a higher margin of error, resulting in a larger cone. Tropical Storm Ana's cone is quite large, with the margin of error lying at about 340 miles at the end of the five-day period on Sunday. The center of the storm could go hundreds of miles to the north or south of Hawaii, or the storm could make a direct landfall.
Hawaii is relatively small, so it would be very easy for the future hurricane to miss the island chain altogether. However, based on current trends, meteorologists have reason to believe that Hawaii is at risk from this storm. Sunday is a long way away, so it's worth watching even if it does miss.
What are the similarities to Iselle?
First off, Hurricane Iselle approached the island chain from the east-southeast while Ana is coming in from the southeast. That seems trivial but it's an important distinction—if the storm stays on its projected course and indeed makes a direct landfall on the Big Island, whatever survives of the storm would likely travel over the more populated islands. Iselle's direction kept what was left of the storm south of the islands after it made landfall on the Big Island and moved west.
As we saw with Iselle, Mauna Kea and Mauna Loa completely destroyed the storm when it made landfall on the Big Island. Again, if Ana stays the course and hits the island, we could see a similar situation play out. It's too early to tell.
We just had "Iselle." Where did the name "Ana" come from?
Hurricane Iselle was unique because it formed in the eastern Pacific Ocean off the west coast of Mexico and traveled west into the central Pacific Ocean. These are two different storm basins (overseen by two different agencies), so the naming conventions are different.
In the Atlantic Ocean and eastern Pacific Ocean, we use yearly lists that recycle every six years. When the 2014 season ends, for instance, we'll move on to the a new list next year and won't use this year's names again until the 2020 hurricane season.
The central Pacific, on the other hand, has a list of 48 names that's used on a rolling basis. Years don't matter here. For instance, look towards the bottom of List 2—Oliwa was a tropical storm that formed in 1997. Between 1997 and today, we've gone from the bottom of List 2 to the top of List 4. There are so few storms that form in the central Pacific that they're able to use an endless, rolling list of names without having to worry about overlap or retirements.
However, when a tropical storm moves west into the central Pacific from the eastern Pacific, it keeps the name assigned to it by the National Hurricane Center in Miami.
Where can I find information on hurricane preparedness?
Hawaii News Now has a great checklist to help residents prepare for a potential tropical storm or hurricane. If you're in an area susceptible to flooding, mudslides, or storm surge, listen for evacuation notices from local authorities. Many Hawaii residents treated this advice with a resounding "HA!" when Iselle struck, but don't let arrogance get in the way of risking your life or the lives of those who may have to come rescue you.
Tourists anywhere on the island chain should listen to local authorities and evacuate if and when told to do so. Before anyone even thinks it—nobody cares how much money you spent on your vacation. Rare as hurricane strikes are in Hawaii, you knew the risks of traveling to the tropics during hurricane season. The remainder of your vacation is not worth risking your safety and the safety of those who may have to rescue or help you.
The Central Pacific Hurricane Center in Honolulu is responsible for issuing forecasts on Ana. Forecasts are released every six hours, with the interval dropping down to every three hours once the storm gets close to land.
Ana striking Hawaii is by no means a done deal, but the forecast path making a straight line for the Big Island should be enough to warrant concern for residents and tourists anywhere on the island chain. Hope for the best, but stay alert and prepare for the worst.
[Images: author, NASA, NHC]