Tropical Storm Emily Forms West of Tampa Bay; Heavy Rain Threat

Anytime an area low pressure sits over the Gulf of Mexico during the summertime tropical cyclone development can never be ruled out. Despite marginally favorable wind shear, the area of low pressure thrived off of the warm eastern Gulf waters and gained tropical characteristics early Monday. Tropical Depression 6 was quickly upgraded to Tropical Storm Emily at 8 AM. As of 8 AM max sustained winds are at 45 mph. Emily moves east at 8 mph. Tropical storm force winds extend out up to 60 miles for the center. As of 8:45 AM the center is less than 25 miles from the Sunshine Skyway Bridge. Tropical Storm Emily will cut across Central Florida Monday. Training/flooding is likely is spots, especially for Tampa Bay South near the coast. Winds 30-40 mph+ are possible in the strongest squalls. A Tropical Storm Warning is in effect for the Anclote River southward to Bonita Beach. Emily will weaken to a depression and move into the Atlantic early Tuesday.

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Heavy rain/the potential for flooding is the primary threat from Tropical Storm Emily. A Flood Watch is in effect for Hillsborough, Pinellas, Manatee, Sarasota, Hardee, Desoto and Highlands county until 8 PM Monday. 3-6″ of rain are likely. Some coastal areas will pick up well over 6 inches of rain Monday.

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At times it will be gusty, especially for Tampa Bay South Monday morning and afternoon. Wind gusts will be much lower than they are in a severe thunderstorm in the summertime. Gusts up 30-40 mph+ are possible through Monday afternoon. The strongest wind field is limited to an area around the center.

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Watching Frontal Boundary Near Florida and Atlantic Tropical Wave

A rare summer cold front settles into Central Florida Sunday and stalls late in the day. Low pressure will develop along this boundary in the Eastern Gulf and brings the threat for periods of heavy rain to Central Florida early this work week. Anytime low pressure sits over warm water temperatures in the upper 80s to near 90 it is worth watching for tropical development. The odds of this low gaining any tropical characteristics are low over the next 5 days. Wind shear is enhanced near this frontal boundary and upper level winds are only marginally favorable for tropical development.  Development or not, this feature is a rainmaker for parts of the Sunshine State.

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The Weather Prediction Center shows Central Florida, North Central Florida, and Southwest Florida will see the heaviest rainfall in the days ahead. The heaviest will fall where the frontal boundary stalls and lingers. 2-4″+ is expected in Tampa Bay, with isolated higher amounts near the coast. This will be spread out through mid-work week. Localized flooding is possible at times, especially when training sets up.

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We are also watching a tropical wave southwest of the Cabo Verde Islands. Convection is disorganized Sunday with some dry air nearby. Slow development is possible in the days ahead as the disturbance moves west at 10-15 mph.  Models aren’t too impressed with development of this feature. Officially as of Sunday morning there is a 30% chance of tropical cyclone development the next 5 days. The next name is Emily.

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Quiet in the Atlantic; Active in the East Pacific

It’s looking more and more likely that July 2017 will wrap up with no additional named storms in Atlantic Basin. Only one named storm formed this month, Don. It was shredded apart by wind shear in the Caribbean and dry air kept it short-lived and weak.  Dry air has a firm grip on the Caribbean and central Atlantic Tuesday, and there are no areas of interest for at least the next 5 days.

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A fresh batch of Saharan air is situated over the south central and eastern Atlantic near Africa. All four tropical waves between the Lesser Antilles and Africa will stay disorganized due to this feature. The graphic below is courtesy NOAA/the University of Wisconsin.

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Fast forward to the weekend and the Saharan Air Layer (SAL) remains quite active, especially in the Main Development Region. Dry, dusty stable air sticks around through at least next Sunday. Long-range computer models are pretty quiet. The 12Z Euro attempts to close off weak low pressure late next work week as a tropical wave approaches the eastern Caribbean. The latest GFS shows absolutely no tropical cyclone formation for the next 2 weeks+.  Activity will likely ramp up at some point in August.  Once dry air erodes, there is the potential for stronger storms to thrive off of warm sea surface temperatures.

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The eastern Pacific is especially active. 5 named storms have formed over the past two weeks. On Tuesday there are three named storms: Hurricane Hillary, Hurricane Irwin and Tropical Storm Greg. All three will stay over the open Pacific waters. Greg could dissipate by Wednesday but Irwin and Hillary strengthen. Due to proximity, Hurricane Irwin and Hurricane Hillary will interact with, and possibly rotate around each other later this work week. This is called the Fujiwara Effect. Irwin may eventually be absorbed by Hillary southwest of the Cabo Peninsula over the weekend or early next week.

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July Winds Down; Quiet in the Atlantic

The second month of the 2017 Atlantic hurricane season winds down. On Saturday, dry African Saharan air keeps convection limited with a few tropical waves in the Atlantic and Caribbean. Saharan air outbreaks are very common in July. No tropical cyclone development is expected for at least the next 5 days.

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As we shift to August and September all eyes are on the Main Development Region between the Caribbean and Africa. Water temperatures run 1-1.5 C above average. This could aid in a more active period as we approach the peak of the season (September 10th). Most computer models keep the Atlantic basin quiet for the next week. On average, the first hurricane in Atlantic forms on August 10th, therefore, it’s pretty common for July to wrap up on a quiet note.

 

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Don Dissipates; A New Weak Wave on It’s Heels

Tropical Storm Don dissipated over the last 24 hours and it’s remnants are slowly moving through the southern Caribbean. With that system out of the way, we turn our eyes to a weak tropical wave (Invest 96L) in the Central Atlantic. As of Wednesday afternoon, the National Hurricane Center gives this only a 30% chance of development over the next few days as it moves west-northwest.

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Like Don, high wind shear and dry air aloft will ultimately keep Invest 96L from developing into anything of consequence, but nonetheless we’ll keep an eye on it through the rest of the week.

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It is still a bit early in the season for these Central Atlantic waves to develop into strong tropical systems, but as we head into the months of August and September, expect things to get more active. In fact, on average since 1950, 61% of named storms have formed over the next couple of months.

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Tropical Storm Don Forms; Headed for the Caribbean

Don becomes the 4th named storm of the 2017 Atlantic hurricane season Monday. On average, the 4th named storm of the Atlantic season forms on August 23rd, so this is about one month ahead of schedule.  Data from hurricane reconnaissance aircraft confirms a closed area of low pressure formed with winds up to 40 mph. Don is a tiny tropical storm. Winds only extend out 25 miles for the center. At 5 PM Don moves west at 17 mph. At this pace, tropical storm conditions will reach portions of the Windward Islands overnight Tuesday into Wednesday morning. A Tropical Storm Warning is in effect for Grenada. A Tropical Storm Watch is in effect for
Barbados, St. Vincent, the Grenadines, and St. Lucia. Only some strengthening is expected before landfall due to dry air in the mid levels of the atmosphere. Beyond landfall, Don will run into a wall of wind shear in the eastern Caribbean and dissipate mid-week.

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Water vapor imagery shows a pocket of dry African air directly in the path of the newly named storm. This is indicated by the red color.

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As mentioned above, dry air and increased wind shear should keep Don as a weak tropical storm. By Wednesday and Thursday it encounters strong westerly shear over the open Caribbean waters.

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Behind Don is an area of disturbed weather between Africa and the Lesser Antilles. Convection is disorganized Monday due to a bit of dry air. There is a low 30% chance of tropical development the next 5 days as the tropical wave moves west-northwest. It will battle dry African air and increased moderate wind shear in the days ahead.

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Continue to Monitor Former Tropical Depression Four & African Tropical Wave

Former Tropical Depression Four hasn’t given up yet. Convection has flared up yet again Monday morning, as the disturbance pulls away from a nearby upper level low. As it does so, moderate wind shear will drop some in the days ahead. The tropical wave approaches south Florida mid to late work week and enhances daily sea breeze showers and storms. Hurricane Hunters are scheduled to investigate the area of disturbed weather Tuesday, if necessary.

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The tropical wave southwest of the Cabo Verde Islands is worth keeping an eye on. While it is disorganized Monday and will battle dry African air over the next 5-7 days, some models still hint at tropical development. As of Monday morning the National Hurricane Center says there is a 20% chance a tropical depression/Tropical Storm Don forms over the next 5 days.

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While the European model does not develop this feature, the GFS is consistent that a tropical storm may form as it nears the Lesser Antilles Friday and Saturday. The GFS is however extremely inconsistent on a long-range track. Each 6 hour run has varied greatly the past couple of days. At this point, model trends are worth watching for at least the next couple of days.

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Watching the Remnants of TD 4 and Tropical Wave Near Africa

On Sunday, officially the National Hurricane Center expects no tropical cyclone development over the next 5 days. We are however, keeping an eye on a couple of features. The remnants of Tropical Depression Four is moving west-northwestward north of the Lesser Antilles. Convection has flared up some since the disturbance degenerated into a tropical wave Friday. Wind shear is elevated with an upper level TUTT low nearby, but wind shear will be dropping in the days ahead as the disturbance approaches the Bahamas and eventually Florida later this work week. It will encounter some dry air over the next couple of days.

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The European model shows low wind shear Thursday and Friday near Florida, the Bahamas and the southwest Atlantic. The 0Z Euro tries to regenerate Tropical Depression Four over the warm Atlantic waters near the Carolinas early next work week.

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A tropical wave that emerged off of Africa Saturday is worth watching. There is plenty of dry Saharan air in its path early this work week. The European model has backed off on tropical cyclone development the past few days. The GFS is back and forth, but is more insistent on development in recent model runs. The next named storm is Don.

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The 06Z GFS develops Tropical Storm Don between the Lesser Antilles and Africa mid-work week. At this pace tropical storm conditions could reach the islands late Friday. Stay tuned.

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In the east Pacific, Hurricane Eugene rapidly intensifies and becomes a major hurricane south of the Baja peninsula. It will steadily weaken over cooler waters this work week. It is no threat to land.

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Watching Invest 94L in the Atlantic; Could Become Don This Work Week

On Monday, Invest 94L is still  disorganized.  The broad area of low pressure is nearly stationary with scattered pockets of showers and storms. Wind shear is marginally favorable for gradual organization by Thursday and Friday. The disturbance is separated from the most of the intense dry, Saharan air nearby. The NHC ups the odds of tropical depression/Tropical Storm Don development to 70% over the next 5 days.

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Computer models suggest a west-northwest path over the next 4 or 5 days. A few bring it close to the northeast Caribbean this weekend. As of Monday afternoon, most intensity models develop Tropical Storm Don by Wednesday or Thursday. It’s still too early to say if it stays out to sea as a stronger system or heads further west towards the Caribbean as a shallow/weaker one (and possible dissipate).

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Dry air could hinder long-term organization and development. Water vapor imagery shows dry air east of the Lesser Antilles and north of the Caribbean.

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Both the ECMWF and the GFS show Tropical Storm Don a few hundred miles east of the Lesser Antilles by late Thursday/early Friday. The Euro takes future Don further west and dissipates it southeast of the Bahamas by Monday. The GFS has been all over the place with track and intensity. The 12Z run suggests a recurve east of the U.S. through next work week. Stay tuned.

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Second Month of Atlantic Hurricane Season Begins; Watching Tropical Wave Near Africa

The second month of the 2017 Atlantic hurricane season begins Saturday. In July, we watch the Gulf Mexico, western Atlantic and the western and eastern Caribbean for tropical development. Climatologically, the first name storm of the season forms on July 9th. In 2017, two named storms, Bret and Cindy, formed in June. Arlene formed in April.

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On Saturday, a weak tropical wave southwest of the Cape Verde Islands bears watching. It produces widely scattered, disorganized showers and storms as it moves westward at about 10-15 mph. While wind shear in the vicinity will stay pretty light the next few days, there is plenty of dry air in its path. Upper level winds increase as this the tropical wave approaches the Caribbean late next week. Nonetheless, gradual development is possible. As of Saturday morning, The NHC puts those odds at 20% over the next 5 days.

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Water vapor imagery shows the weak tropical wave has dry, Saharan air in its path towards the Caribbean.

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The 06Z GFS continues to hint that a weak tropical storm may form east of the Lesser Antilles by Thursday or Friday. The 0Z Euro also suggests a closed low may form by Thursday, but is a bit slower to approach the Caribbean. It’s something to keep an eye on the next few days. It’s way too early to talk about the long-term strength/path of this potential tropical system.

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