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Cristobal slowly lumbers toward Gulf Coast

By Skip Rigney

Pearl River County is under a flood watch as tropical cyclone Cristobal is expected to spread heavy rain across southern portions of Louisiana, Mississippi, and Alabama.
The eventual wind intensity and exact track are not the main story with Cristobal. Instead, forecasters are keeping an eye on the large plume of moisture streaming northward ahead of the storm. The heaviest and most widespread rains in south Mississippi and southeast Louisiana will probably be Sunday, Sunday night, and/or Monday, but there’s a chance that some of today’s widely scattered showers could also be heavy.
June got off to a relatively dry start in the southern one-third of the county where most locations received less than one-quarter of an inch of rain Monday through Thursday. It was a different story in a swath running from north of Carriere to northwest of Poplarville where heavy showers on Tuesday and Thursday afternoons dumped one to three inches of rain.
Our historical average total rainfall for the entire month of June in Pearl River County is just under five and one-half inches. Some locations may exceed that amount in just the next several days as widespread three to six inch totals are expected by the National Weather Service. Clouds in tropical weather systems can be very efficient rain producers leading NWS forecasters in Slidell to warn that as much as two to four inches could fall in just an hour’s time.
As I write this on Friday morning, Cristobal is only at tropical depression strength with winds of 35 mph. That’s the weakest of tropical cyclone categories.
However, the National Hurricane Center in Miami is forecasting that as Cristobal moves northward across the warm waters of the Gulf of Mexico it could intensify to tropical storm strength. A tropical storm means that the highest sustained wind speeds in at least one location in the cyclone’s circulation are between 39 and 73 miles per hour. “Sustained” means not just a brief gust, but the average wind speed over one minute.
All indications from the computer models for several days now is that the center of Cristobal will come ashore somewhere in Louisiana, and as of Friday morning that is still reflected in the official projected path from the National Hurricane Center. However, whereas for hurricane-strength cyclones the worst weather is usually very near the eye, in relatively weak, poorly organized tropical systems the worst conditions can be displaced a hundred or more miles from the storm’s center. As noted by NHC on Friday morning, “Regardless of its exact track and forward speed, Cristobal is expected to have a broad and asymmetric wind field as it approaches the northern Gulf coast. The strongest winds, highest storm surge, and heaviest rains could be well removed from the center of circulation. Therefore, it is important that users do not focus on the exact forecast path of the center of the cyclone.”
Also keep in mind that even if Cristobal has tropical storm force winds over water, those winds will be significantly reduced in strength by the time they move inland over Pearl River County.
For the latest forecast of winds and rain locally, check out the NWS Slidell Forecast Office’s website at https://www.weather.gov/LIX/