Torrential rains from Harvey continue to produce catastrophic flooding in SE Texas, especially the Houston metro area. Thoughts and prayers go out to the residents there, as current rainfall totals could still be doubled during the next few days, and Harvey may not leave Texas until around Thursday. While it is still possible that Harvey will drift back over the Gulf of Mexico waters for a brief time, it is not expected to be long enough for significant reintensification of winds to occur. However, if it wasn’t clear by now, flooding is the primary threat to life and property. If you live in these areas experiencing flooding, avoid driving your vehicle, as the vast majority of flooding-related deaths are drivers being caught in water and having nowhere to escape. Please be safe everyone.
Elsewhere…Invest 92L, a disturbance which has been drifting near Florida for the last several days, is developing into a well-defined area of low pressure just NE of Jacksonville. The system is highly sheared out of the west due to upper-level outflow from Harvey, but low-level thermal gradients associated with a nearby front are helping to focus thunderstorm activity not far from the low center despite the shear. An ASCAT pass from earlier today indicated that the circulation is not yet well-defined enough to call the system a tropical depression, but 92L now has a high chance of becoming one over the next day or so, and the NHC has initiated advisories on Potential Tropical Cyclone Ten (PTC10). The system is expected to gradually move northward today and Monday, nearing the South Carolina coastline. Acceleration toward the northeast is then expected near coastal North Carolina, and then out into the NW Atlantic. Given the aforementioned shear, PTC10 is not expected to intensify much in the short term, but a Tropical Storm Watch has been issued for coastal North Carolina and a portion of the South Carolina coastline. Rain and gusty winds are expected in the area regardless of development. As the storm moves out into the NW Atlantic, it may intensify as a nontropical storm, but away from land. For further details, visit hurricanes.gov.
Harvey made landfall near Rockport, Texas late Friday night as a Category 4 hurricane. As the storm drifts inland, winds are diminishing, but remain dangerous, with hurricane force wind gusts still possible near the storm core today. The storm surge threat along the coast is not over, as strong onshore flow southeast of Harvey’s center could keep water levels well above normal for some time yet, and a Storm Surge Warning remains in effect for a portion of the Texas coastline.
While Harvey will weaken like any hurricane that moves over land, this unfortunately is only the beginning of the flooding threat for SE Texas. Hurricanes can drop copious rainfall for days after landfall, and in this case, Harvey is not expected to move much at all over the next several days. Current forecasts suggest that Harvey could be barely 100 miles from its current location by next Thursday. This is forecast to result in heavy rainfall of unprecedented magnitude for such a large area, with widespread storm totals of 15-30 inches, and isolated amounts up to 40 inches. This will likely result in catastrophic flooding in portions of SE Texas. Rainfall and flooding can vary greatly from place to place, and some locales will be luckier than others, but it’s not possible to know in advance which specific locations will see the worst problems. Don’t drive in your car if there is a flood warning for your area or it is raining heavily. The majority of flood-related fatalities are due to people getting stuck in their vehicles. You are vastly safer inside a structure.
Isolated tornadoes are also possible, especially in the outer bands north and east of Harvey’s center, and some tornadoes have indeed been reported in the Houston area since last night. These tornadoes are typically harder to see coming than “normal” tornadoes, as they are often moving quickly and wrapped in rain. Keep your weather radio on listening for tornado and flash flood warnings.
Do not assume that it’s safe to begin moving around and driving until your local officials say so. This is not a normal storm, and your local area could be hazardous for many days.
Hang in there and stay safe everyone. There is a long road ahead.
[Thursday Evening] Harvey Continuing to Strengthen – Devastating Flooding and Winds Expected in Texas Beginning Friday Night
[Thursday Morning] Harvey Intensifying Faster than Expected; Dangerous Flooding and Wind Event Forecast for Texas
[Wednesday Evening] Harvey Reforms – Likely to Become a Hurricane and Impact Texas with Dangerous Flooding
[Tuesday Evening] Ex-Harvey Likely to Reform and Approach Texas by Friday; Flooding Threat Anticipated
On Saturday, Tropical Storm Harvey lost its closed circulation due to a combination of fast forward motion and the weakening impact of vertical wind shear. Thus, the National Hurricane Center ceased advisories last night. However, the remnants of Harvey remain a well-defined wave axis, and concentrated deep convection has redeveloped over the system this morning. The strong wind shear that plagued Harvey over the last couple of days has begun to relax significantly, and low shear is expected while the system moves through the western Caribbean. Thus, Harvey could easily redevelop into a tropical storm during the next day or two. An air force hurricane hunter aircraft is scheduled to investigate the system later today. Regardless of redevelopment, (ex)-Harvey will bring heavy rain and gusty winds to Nicaragua and Honduras on Monday, and to Belize and the Yucatan Peninsula on Tuesday. If Harvey becomes a tropical storm again, strengthening could occur prior to landfall, though how much would depend on how soon the storm reforms, if it does so. (ex)-Harvey would then likely move into the Bay of Campeche later in the week, and if the track takes the storm over water for more than a day, restrengthening could occur there as well. Thus, interests in eastern Mexico should also monitor ex-Harvey if the storm reforms. The National Hurricane Center currently gives ex-Harvey a 60% chance of ultimately redeveloping into a tropical storm.