For the first time since September 2016, the Atlantic has two investigative areas (known officially as invests) at once! Yesterday, a tropical wave was designated 92L in the central Atlantic. This morning, the National Hurricane Center (NHC) designated Invest 93L – a broad area of low pressure over the Northwestern Caribbean Sea. Both have a significant chance of developing into tropical cyclones over the next few days. The NHC gives 92L a 40 percent chance of development within 48 hours, and a 60 percent chance within five days (down from 70 percent this morning). The NHC gives 93L a 30 percent chance of development within 48 hours, and an 80 percent chance of development within five days.

Invest 92L: Currently lacks much deep convection, but still could develop

As of 18:00 UTC Saturday (2:00 PM EDT), Invest 92L was centered near 5.8°N 41.2°W. Maximum winds were estimated to be near 25 knots (30 mph) with an estimated minimum pressure of 1009 mb. 92L has struggled to gain latitude as expected. However, nearly all models show 92L being able to gain enough latitude to avoid crashing into South America.  The 12z Saturday GFS and ECMWF models both develop 92L into a small tropical storm by Monday. The CMC and UKMET models do not predict development. The GEFS and EPS ensembles also are somewhat bullish in developing 92L into a tropical cyclone southeast of the Windward Islands.

Invest 92L is not much to look at right now. Deep convection remains sparse and disorganized. In addition, based on this morning’s ASCAT pass, 92L continues to lack a well-defined circulation. NHC actually lowered their five-day development chances for 92L from 70% to 60% this afternoon since it has not improved in organization. Since both the ECMWF and GFS models still predict development and models predict 92L to clear South America, I continue to give it a 60 percent chance of development within five days. If 92L develops, it will be historic, as I noted in yesterday’s post.

92L is currently in a moderately moist environment with low wind shear. Wind shear should remain favorable for development through the next 48 hours. After that time, the shear will increase to over 25 knots (30 mph), as well as trade winds. Both the GFS and ECMWF models show 92L dissipating in the Eastern Caribbean. The Eastern Caribbean is known for being very hostile for tropical cyclones, especially early in the season. 92L still has about 48 hours to develop, so even with its current unimpressive appearance, development still could occur. The NHC has tentatively scheduled a reconnaissance mission for 92L on Monday afternoon, when it is expected to be near Trinidad. The southern Windward Islands as well as Northern South America should monitor the progress of 92L.

Invest 93L: A potential messy tropical storm for the Gulf Coast – but where?

A broad area of low pressure in the Northwestern Caribbean Sea was designated Invest 93L Saturday morning by the NHC.  This is the Caribbean low pressure system models have been predicting to develop for over a week. As of 18:00 UTC Saturday, 93L was centered near 17.5°N 86.5°W. Maximum sustained winds were estimated to be near 25 knots (30 mph), with an estimated minimum pressure of 1007 mb. 93L is given a high (80 percent) chance of development by the NHC within five days, and I think this is fair. Model support for 93L to develop into a tropical storm is strong. The 12z Saturday ECWMF, GFS and CMC models all predicted that 93L would develop into a tropical cyclone during the next five days. Many ensemble members from both the GEFS and EPS show develop as well.

While models are consistent that 93L will likely develop, they differ greatly on where they think it will go. The 12z Saturday GFS and CMC models are predicting landfall near the Florida-Alabama border, while the ECMWF model is predicting landfall in northern Mexico. The future track of 93L is largely dependent on the strength of the high pressure ridge over the south-central United States. A stronger ridge would favor a track farther west, while a weaker ridge would favor a turn to the north. It is way too soon to predict a track for 93L – residents from Northern Mexico all the way to the Florida Panhandle should continue to monitor the progression of this system. 93L is expected to emerge into the Gulf of Mexico by Tuesday. NHC has scheduled a reconnaissance mission for 93L for late tomorrow afternoon, if necessary.

93L is expected to be in a moist environment during the next few days as it emerges into the Gulf of Mexico. Shear is expected to be moderate, around 20 knots. The moderate wind shear, in addition to the broad nature of 93L, should limit it from strengthening significantly. The most likely scenario with 93L is a messy tropical storm with maximum sustained winds around 50 miles per hour.

I give an 85 percent chance of Tropical Storm Bret forming during the next five days, and a 30 percent chance of Tropical Storm Cindy forming as well. It is very likely that we will see our second named storm of the 2017 Atlantic hurricane season over the next few days. I will be back for another blog post on 92L and 93L.