AG/Energy AM Update: Harvey Strengthening & Expected to Become a Hurricane

Good morning! This is a special morning update on Harvey in the Western Gulf of Mexico. Harvey became a tropical storm overnight and continues to strengthen this morning, as convection increased and deepened around the center. As of the 8am advisory from the National Hurricane Center, the storm has maximum sustained winds of 60mph, minimum central pressure has dropped to 986mb and the storm moving north-northwest at 10mph. Further strengthening is likely today, as the storm continues to move over very warm waters in the Western Gulf of Mexico and the atmospheric environment becomes more favorable. Harvey is now expected to become a hurricane by tonight or Friday. Thus a Hurricane Warning has been issued for Port Mansfield to Matagorda along the South Texas coast. Hurricane Watches and Tropical Storm Warnings are now in effect for other parts of Texas and Northeast Mexico coast.

Model guidance overnight has come into better agreement that Harvey will make landfall along the Lower Texas Gulf coast sometime Friday night or Saturday morning as a hurricane. Harvey will be steered north-northwest around a western extent of ridge over the Eastern Gulf of Mexico until Saturday morning. Then steering currents will weaken over the Western Gulf of Mexico later in the weekend, as mid-upper troughs bypass Harvey to the north. This will cause Harvey to slow down and meander either along or just inland of the South Texas or Northeast Mexico coast, producing prolific rainfall and significant flooding, over those regions, for rest of the weekend.

An upper-level low over the northwest Gulf of Mexico that has been producing more shear and dry air on the western side of Harvey now appears to be weakening this morning and will likely disspate by Friday. Forecast models show an upper-level anticyclone building on top Harvey over the next couple days, which will allow the storm to become more symmetric with convection and outflow expanding in all quadrants. There is potential for Harvey to rapidly intensify into a stronger Category 2, 3 or even 4 hurricane before making landfall. If this occurs, there will be higher risk for damaging hurricane force winds and destructive storm surge for the South Texas coast. Storm surge watches and warnings have also been issued for parts of the South Texas coast.

A breakdown of the current synoptic setup reveals that uncertainty regarding the initial landfall is quickly decreasing. The upper level height pattern strongly suggests, as we mentioned, that strengthening is likely to occur. It also strongly suggests that the tug-of-war between two distinct upper level features will allow Harvey to drift northwest toward the Texas coast before slowing down tremendously near landfall. The storm system may reach incredibly slow speeds upon landfall and this could create an extremely dangerous situation near the landfall point.

The uncertainty increases afterward. Some models show Harvey moving back into the Gulf of Mexico early next week, and re-intensifying again, as a ridge strengthens over the Southwest US and another upper-level trough digs into the Mississippi River Valley next week.  If this trough digs far south, Harvey could eventually pulled more north-northeastward and make landfall again over the Upper Texas Gulf Coast or Louisiana by the middle of next week. However, if Harvey remains further west or the trough is more progressive, Harvey will remain further south and continue to dump heavy rainfall over South Texas into the middle of next week.

Regardless of this exact track, forecast models continue to suggest the potential for rainfall, including dangerous flooding, is quite high near the systems track. As mentioned, the eventual outcome of any re-emergence into the Gulf of Mexico will be heavily modulated by the ridging around the system and a trough to its north. However, rainfall appears likely as tropical moisture surges northward and the system slows to a near-crawl during and after landfall. The GEFS and ECMWF both suggest the potential for prolific rainfall amounts in the short period of time when the system comes ashore, and additional rainfall amounts over the 5-Day period that follows.

These rainfall totals could present big problems for many residents near Southern Texas, not only near the coast but even inland where rainfall amounts over 10″ in a short period of time are simply not common. Residents in all of these regions should be preparing for the potential of a significant flooding event. All interests should have a flood plan in place and should be checking with local authorities in regards to the latest emergency information.

Stay tuned for more updates on Harvey through the weekend. We will continue to monitor Harvey closely for any significant changes More details on flooding, wind and storm surge impacts will be provided in future updates later today and tonight.

Clients should be able to access their latest personalized documentation and briefings via their inboxes this morning.

Forecast compiled by Miguel Pierre and John Homenuk.