A certain kind of unease settles over Hawaii when weather forecasters use words like “uncertain track” and “potential for multiple systems.” Indeed, that is the current situation. Two different tropical cyclones, Tropical Storm Lowell and Category 4 Hurricane Karina, are both moving through the Pacific, and the Hawaiian Islands are in the path of both of them. Things aren’t really bad yet. It’s not nothing, though.
Hurricane Karina was moving west at a slow 9 mph as of early Monday morning, about 1,055 miles west-southwest of the southern tip of Baja California. The strongest sustained winds had slowed down a bit to about 130 mph, which put it firmly in Category 4 territory on the Saffir-Simpson scale. By Tuesday, the hurricane is expected to slowly move toward the west-northwest, and around the same time, forecasters at the National Hurricane Center think it will start to slowly weaken. Still, the storm’s lowest central pressure was 950 millibars, which is a very high number for anyone who has seen hurricanes act in ways that were not expected.
Karina is worth keeping a close eye on for more than just how intense it is right now. The things that lie ahead of it. According to the National Hurricane Center, short-term environmental conditions are still pretty good, and Karina might develop what meteorologists call “annular characteristics.” This means that Karina’s inner structure will become more stable and symmetrical, which makes it less likely that it will weaken. After 72 hours, dry air is likely to become a big problem, and the rate of decay could speed up once Karina moves over cooler ocean water. But the word “could” does a lot in that sentence. These storms tend to go against what most people think.
For Hawaii, Lowell is the more important issue right now. Monday at 5 a.m. HST, the storm was 785 miles southeast of Hilo and moving west at about 14 mph. It’s interesting and a little scary that the storm is expected to get worse quickly over the next 48 hours. Forecasters think that Lowell will become a major hurricane by Wednesday. It already has winds of a tropical storm that reach 90 miles from the center. Around midweek, swells will start to affect parts of the Hawaiian Islands, bringing with them the risk of life-threatening surf and dangerous rip currents.
For people in Hawaii, wind will be the bigger problem until the middle of the week. As Lowell moves south of the islands from Thursday to Friday, the trade winds that are already blowing lightly will likely get much stronger. In some places, wind gusts of over 50 mph are possible. The National Weather Service said there was a moderate risk of fire during this window. This isn’t because fuel conditions are very bad, but because the wind picks up where the rain leaves off. On Thursday, a pocket of dry air could move in and bring the humidity down to the mid-40s in some leeward areas. In the past few weeks, it has rained, which has helped lower some of the risk. However, this only helps so much when wind speeds reach 50 mph.
The bigger question about the forecast, which is harder to answer, has to do with Labor Day weekend and what will happen when Karina and Lowell might be close to the state at the same time. Forecasters are being smart about how they use words here, which is a good thing. At that range, there is real track uncertainty. Models get off track, steering patterns change, and the speed of a storm changes where it goes in every way. Some of the faster, more southerly track solutions for Lowell have come from the HCCA and Google DeepMind guidance. The official NHC forecast, on the other hand, is somewhere between the middle and higher end of the intensity envelope.
Watching all of this happen makes me think that people in Hawaii would be smart to start getting ready early this week instead of waiting to see which way the models break. That’s not alarmism; it’s just the reality of following two systems across an ocean at the same time, where the forecast window gets smaller as you move farther away. Even if neither storm hits directly, the waves, wind, and lack of certainty are reason enough to pay attention. Every year on Labor Day weekend, people go to the beach. The ocean doesn’t look at the time, though.
