On August 12, a tropical wave moved off the west coast of Africa, accompanied by a large area of convection.
The National Hurricane Center (NHC) began to track the wave the next morning, just before the convective mass dissipated.
The tropical wave was expected to merge with a broad area of low pressure located southwest of Cape Verde and slowly consolidate, with the NHC giving a low chance of tropical cyclogenesis over the next five days.
The merger failed to complete, however, with the two areas of disturbed weather remaining separate despite being contained by the same area of low pressure.
The two systems eventually split again on August 15, with the original low-pressure area continuing westwards towards the Caribbean Sea while the tropical wave moved farther north.
Conditions in the Caribbean Sea though were not forecast to be conducive for development.
Convection around the low began to increase that same day as a Kelvin wave passed through the area, but remained disorganized amid strong upper-level winds.
However, the NHC noted that the low could experience a slight reprieve near the Lesser Antilles.
On August 17, satellite imagery revealed that the system had become much more organized, with the circulation becoming better defined.
Assessing it as having a high chance of tropical cyclogenesis over the next two days, the NHC began issuing advisories at 15:00 UTC on Potential Tropical Cyclone Nine roughly 295 mi (475 km) east of Barbados; this allowed tropical cyclone warnings and watches to be issued for the Lesser Antilles.
Post-analysis revealed that a tropical depression had already formed by 06:00 UTC while located 505 mi (815 km) east of Barbados.

An Air Force Reserve Hurricane Hunter aircraft investigating the disturbance from 18:00—21:00 UTC on August 17 detected a well-defined circulation center with strong convection sheared to the west.
With the system already producing maximum sustained winds near 40 mph (65 km/h), the disturbance was immediately upgraded to a tropical storm and given the name Harvey.
With Harvey moving due west at 18 mph (29 km/h) in an environment of moderate easterly vertical wind shear, the intensity forecast remained challenging; statistical and hurricane models called for Harvey to near or reach hurricane intensity, while the global models, most notably the ECMWF and the GFS, showed Harvey degenerating to a tropical wave within the next few days.
Meanwhile, on August 18, Harvey's center passed over Barbados at 10:00 UTC and over Saint Vincent at 15:00 UTC with winds of 45 mph (75 km/h) and a central pressure of 1,004 mbar (hPa; 29.65 inHg); both islands received little impact as Harvey's strongest winds were located well to the north.
The latter scenario eventually played out as Harvey remained disorganized, with the low- and mid-level circulations becoming misaligned.
In fact, a reconnaissance aircraft flying through Harvey on the next day was unable to find a closed mid-level circulation, although the low-level circulation remained intact.
By 12:00 UTC on August 19, Harvey had degraded to a tropical depression.
The weakening circulation opened up into a wave six hours later.
Despite subsiding vertical wind shear ahead, Harvey's quick motion and proximity to dry air were expected to hinder reintensification for the time being.
However, the NHC noted the possibility of Harvey regenerating near the Yucatán Peninsula or in the Bay of Campeche.
On August 12, a tropical wave moved off the west coast of Africa, accompanied by a large area of convection. The National Hurricane Center (NHC) began to track the wave the next morning, just before the convective mass dissipated. The tropical wave was expected to merge with a broad area of low pressure located southwest of Cape Verde and slowly consolidate, with the NHC giving a low chance of tropical cyclogenesis over the next five days. The merger failed to complete, however, with the two areas of disturbed weather remaining separate despite being contained by the same area of low pressure. The two systems eventually split again on August 15, with the original low-pressure area continuing westwards towards the Caribbean Sea while the tropical wave moved farther north. Conditions in the Caribbean Sea though were not forecast to be conducive for development. Convection around the low began to increase that same day as a Kelvin wave passed through the area, but remained disorganized amid strong upper-level winds. However, the NHC noted that the low could experience a slight reprieve near the Lesser Antilles. On August 17, satellite imagery revealed that the system had become much more organized, with the circulation becoming better defined. Assessing it as having a high chance of tropical cyclogenesis over the next two days, the NHC began issuing advisories at 15:00 UTC on Potential Tropical Cyclone Nine roughly 295 mi (475 km) east of Barbados; this allowed tropical cyclone warnings and watches to be issued for the Lesser Antilles. Post-analysis revealed that a tropical depression had already formed by 06:00 UTC while located 505 mi (815 km) east of Barbados.
An Air Force Reserve Hurricane Hunter aircraft investigating the disturbance from 18:00—21:00 UTC on August 17 detected a well-defined circulation center with strong convection sheared to the west. With the system already producing maximum sustained winds near 40 mph (65 km/h), the disturbance was immediately upgraded to a tropical storm and given the name Harvey. With Harvey moving due west at 18 mph (29 km/h) in an environment of moderate easterly vertical wind shear, the intensity forecast remained challenging; statistical and hurricane models called for Harvey to near or reach hurricane intensity, while the global models, most notably the ECMWF and the GFS, showed Harvey degenerating to a tropical wave within the next few days. Meanwhile, on August 18, Harvey's center passed over Barbados at 10:00 UTC and over Saint Vincent at 15:00 UTC with winds of 45 mph (75 km/h) and a central pressure of 1,004 mbar (hPa; 29.65 inHg); both islands received little impact as Harvey's strongest winds were located well to the north. The latter scenario eventually played out as Harvey remained disorganized, with the low- and mid-level circulations becoming misaligned. In fact, a reconnaissance aircraft flying through Harvey on the next day was unable to find a closed mid-level circulation, although the low-level circulation remained intact. By 12:00 UTC on August 19, Harvey had degraded to a tropical depression. The weakening circulation opened up into a wave six hours later. Despite subsiding vertical wind shear ahead, Harvey's quick motion and proximity to dry air were expected to hinder reintensification for the time being. However, the NHC noted the possibility of Harvey regenerating near the Yucatán Peninsula or in the Bay of Campeche.
Meteorological history of Hurricane Harvey