Over the last 24 hours, Harvey degenerated into an open wave thanks to an area of strong wind shear that tore the system apart. That being said, Harvey’s remnants still have a good shot of redeveloping in a few days, especially as they move over the Bay of Campeche. Regardless, this system won’t have an impact on the United States.
Of more interest perhaps, is Invest 92L, which was located about 100 miles NNE of the Turks and Caicos Islands on Sunday evening. Odds of development are still on the low side, but it will be moving into a more favorable environment by mid-week as it near the Bahamas and Florida. Most models are still keeping this system an open wave ultimately, but it does bear watching. One thing’s for sure, central and south Florida can count on increased rain chances and perhaps locally heavy rainfall mid to late week.
As of Saturday evening, we’re still watching three separate disturbances in the Atlantic basin. Harvey has been battling with dry air today and has weakened to a tropical depression for the time being. Over the next 24 hours, it should be able to regain tropical storm status as it moves west-northwest toward Central America. Harvey will bring heavy rains to portions of Nicaragua and Honduras on Monday before moving into Belize and the Yucatan Peninsula on Tuesday. As of now, no tropical storm watches or warnings have been issued for those areas yet.
There are still two tropical waves riding in the wake of Harvey. Of most interest is Invest 92L; although, odds of development with this wave continue to drop. It will have to contend with quite a bit of wind shear in addition to pockets of dry air over the next few days as it moves towards the Bahamas. Even though development is not likely, it will likely bring periods of heavy rain to the islands; as well as increased rain chances for parts of Florida by mid-late week.
As we head towards the peak of the hurricane season (Sept 10th) we normally start to see more activity in the tropics. This year is no exception to that. Tropical Storm Harvey formed on Thursday and we will be closely watching Invest 92L over the weekend for more development. As of 11am NHC placed a 70% chance of development on Invest 92L.
Tropical Storm Harvey has been struggling with wind shear as it moves into the Caribbean. This has kept the center of circulation along the far eastern side of the storm and the upper level center has been noted by the Hurricane Hunter to be displaced to the SW due to wind shear. This makes for a poorly organized storm which will continue to struggle. Despite that the official forecast from the Hurricane Center shows slow strengthening over the weekend and winds increasing to a strong tropical storm next week as it moves over Central America.
At the same time Invest 92L is moving toward the WNW now and will track just to the north of the Caribbean. The majority of computer models move this over the Bahamas and near S. Florida by the middle of next week.
While this possible track by the various computer models may look troublesome, it also should be noted that some of the most reliable computers models (GFS and the ECMWF) do not show significant development with this area. In fact, the GFS shows this as an open tropical wave of moisture moving over the state next week. That will be the key to this system as we move into next week is just how much development we end up seeing with Invest 92L.
Hurricane Gert has maintained category 1 hurricane strength for 24 hours as of 5 PM Tuesday. The second hurricane of the 2017 Atlantic season formed about two weeks ahead of schedule. Climatologically, the second hurricane of the Atlantic season forms on August 28th. Gert strengthens some Tuesday afternoon. As of 5pm max sustained winds top out at 80 mph and pressure is down to 981 mph. Enhanced satellite imagery shows the hurricane is elongated some from north to south due to moderate north/northwesterly shear. Visible satellite imagery showed hints of an eye Tuesday afternoon. Gert passes between the U.S. and Bermuda Wednesday as a stronger category 1 hurricane. It will transition to post tropical system over cooler north Atlantic waters by Friday.
While Gert passes safely east of the eastern U.S., surf builds northward through mid-week. The risk for rip currents increases at Mid Atlantic and Northeast U.S. beaches.
Behind Gert are three areas of interest in the Atlantic. The African wave train is in full swing and there are a few areas to watch through next week. As of Tuesday afternoon there is a medium chance Invest 91L and Invest 92L develop over the next 5 days. Another tropical wave near Africa has a low chance of developing over the next 5 days.
The odds of tropical depression development have dropped some for Invest 91L. Computer models have back off some on development as there is some dry Saharan air nearby. The graphic below is courtesy NOAA/The University of Wisconsin. The 12Z European model suggests a weak tropical storm may approach the Lesser Antilles by Friday. The model shows the system weakening further as it moves westward through the Caribbean. The latest GFS shows a weak tropical storm will also form Wednesday or Thursday before it approaches the eastern Caribbean. This run is much further south than previous runs with a path through the Caribbean too. Model consensus is pretty good that Invest 91L will headed due west into the Caribbean.
Meanwhile confidence increases some that newly pinned Invest 92L will develop into a named storm. 12Z models take this disturbance more northwesterly. Some as a possible strengthening hurricane. As of now, this path is east of the U.S.. Stay tuned. The next named storms are Harvey, Irma and Jose.
Tropical Storm Gert strengthens Monday. The storm develops good outflow and convective banding. As of the 5 PM advisory max sustained winds are just shy of hurricane strength at 70 mph as it moves north at 8 mph. Pressure has dropped steadily throughout the day and Gert will likely become the 2nd hurricane of the 2017 Atlantic Hurricane season Monday night. Gert will strengthen through mid work week over warm waters before it transitions to an extratropical low in the North Atlantic by Thursday. It is no threat to the Eastern U.S., but waves and rip currents build northward over the next few days.
Invest 91L bears watching southwest of the Cabo Verde Islands. The disturbance rolled off the coast of Africa over the weekend. The elongated area of low pressure could gradual organize in the days ahead. As of Monday afternoon there is a 60% chance a tropical depression forms over the next 5 days. Until this feature gets a chance to consolidate, computer models will continue to struggle with the long range-track. There has been a lot of run to run inconsistency, which is often the case with a developing tropical disturbance.
Wind shear near Invest 91L is low to moderate and the area of low pressure is in a moist environment as it moves west at 15 mph. Drier air in the mid levels of the atmosphere is nearby to its west and north, so development will be a gradual process. Invest 91L will likely moisten that path ahead of this dry air.
Computer models show a west and eventually west-northwest track through Saturday. This puts a possible tropical depression near the Leeward Islands early Saturday. Beyond the weekend there are even more question marks. The latest Euro is less impressed with Invest 91L down the road and brings a weak tropical storm (Harvey) through the Caribbean through early next week. The GFS also shows a weak system/eventual open wave but suggests a more northwesterly track near Turks and Caicos early next week. Stay tuned as there will likely be more big changes in the models in the days ahead.
Behind Invest 91L may be another area of interest in the Atlantic, according the ECWWF. The Atlantic Basin heats up.
On Sunday afternoon, Tropical Storm Gert formed about 350 miles NE of the Bahamas. At 5pm Sunday, max sustained winds were at 40 mph and Gert was moving NNW at 10 mph. Gert is expected to strengthen further as it moves north and eventually northeast, shooting the gap between the U.S. mainland and Bermuda. It is not a threat to land at this point.
As we head toward the peak of hurricane season the Atlantic basin is heating up. A new wave (Invest 91L) has emerged off the coast off Africa; and while it is a long way away, it bears watching as it moves westward over the next week and a half. This wave should have a pretty favorable environment for development at times as it makes its way across the Atlantic. It is far too early to speculate what may become of Invest 91L, but we’ll be watching it closely.
Tropical Depression 8 combats some drier air aloft early Sunday. As of 11 AM max sustained winds are 35 mph and it moves NNW at 13 mph. It will strengthen to Tropical Storm Gert by Sunday afternoon or evening under favorable upper level winds as it moves northward. The future 7th named storm of the 2017 Atlantic season will strengthen some through early work week. A trough across the East coast will guide it out to sea. It is the no threat to the U.S. or Bermuda, but future Gert will enhance swells and rip currents at some East coast beaches through mid work week.
A healthy African tropical wave is pinned Invest 91L Sunday morning. This is one to watch in the long-run. Gradual development is expected over the next few days as it moves west or west-northwest into the Main Development Region at about 10-15 mph. At this pace it will approach the Eastern Caribbean on Friday. Here are early 12Z computer models showing the general westward track through the work week.
While the GFS is pretty aggressive on tropical cyclone development (Harvey) in the days ahead, the ECMWF is a little more bullish. It puts a tropical storm north of Puerto Rico by next Sunday morning. We’ll have to watch the positioning of the Bermuda high in 7-10 days for possible U.S. impacts. There is plenty of time to watch Invest 91L.
Tropical wave activity will increase in the weeks ahead as the Main Development Region moistens up. By next weekend the ECWMF suggest there are 3 areas worth watching in the Atlantic. Now is the time to update your hurricane kits and stay tropical weather aware. The climatological peak of hurricane season is less than one month away on September 10th.
Tropical Depression 8 has formed east of the Bahamas late this evening. At 11pm Saturday, sustained winds were at 35 mph and TD 8 was moving NNW at 13 mph. The system is expected to become our 7th named storm of the season, Gert by early Sunday morning. The good news is that Gert should stay well east of the U.S. mainland, moving just west of Bermuda before moving into the north Atlantic by the middle of next week.
The rest of the Atlantic basin remains quiet for now.
Invest 99L shows signs of life early Saturday. Wind shear in the vicinity has dropped and the area of low pressure organizes some east of Turks and Caicos and the Bahamas. Convection increases over warm Atlantic waters, but there is still some dry air in its path. Invest 99L has a high chance of becoming a tropical depression over the next couple of days. If it reaches tropical storm strength it will become Gert.
A northwest/northerly track is expected through early Monday. A trough will safely guide it east of the U.S. early this work week. Swells and an increase in rip currents are possible at some East coast beaches early in the week.
Elsewhere the Atlantic is quiet overall. A new tropical wave coming off of Africa is worth watching. There is some model support for development. This is the time of year that low pressure can spin up quickly. All eyes are on the ITCZ in the coming weeks. This is where the strongest storms of the season often originate in August and September.
Some of the remnants of Franklin crossed over into the East Pacific Basin Friday and became Tropical Storm Jova. It will stay a minimal tropical storm and dissipate due to a combination of drier air and cooler waters in a few days.
We’ve had Invest 99L on the map for a while now as it has made its way across the Atlantic over the last week and a half or so. It’s a disturbance that refuses to give up, but has never been able to gain any ground due to an on & off battle with wind shear and dry air.
On Friday afternoon, it was a couple hundred miles north of Puerto Rico. There have been flare-ups of convection at times, but still no indication of a closed circulation. Upper level winds are becoming a little more favorable for development as we head into the weekend, but it will still have to contend with some pockets of dry air. The National Hurricane Center currently has development odds at 50% over the next 5 days. However, our latest model runs still aren’t too excited about any development with system… keeping it an open wave through the rest of its journey.
Whether or not a tropical depression, or even Gert, forms; steering flow should keep this well offshore as it moves north and northeast up the eastern seaboard.