Tropical Storm Harvey finally moved into Louisiana on Wednesday after lingering for several days over the northwestern Gulf of Mexico. Harvey weakened to a tropical depression after it moved inland. At the same time a new tropical storm named Irma strengthened quickly over the eastern Atlantic Ocean. At 11:00 p.m. EDT on Wednesday the center of Tropical Depression Harvey was located at latitude 31.7°N and longitude 92.3°W which put it about 30 miles (50 km) north-northeast of Alexandria, Louisiana. Harvey was moving toward the north-northeast at 9 m.p.h. (15 km/h). The maximum sustained wind speed was 35 m.p.h. (55 km/h) and there were wind gusts to 45 m.p.h. (75 km/h). The minimum surface pressure was 998 mb.
After dropping record rainfall and causing destructive floods of parts of southeastern Texas and western Louisiana, Tropical Depression Harvey finally started to move steadily toward the north-northeast on Wednesday. Harvey was still producing heavy rain over parts of western Louisiana, but the fact that it was moving should limit the total rainfall at any location. Bands of showers and thunderstorms on the far eastern periphery of Harvey’s circulation were also dropping heavy rain. Some of those thunderstorms were strong enough to approach severe criteria. Tropical Depression Harvey is forecast to move toward the Ohio River Valley during the next several days and it will bring windy, wet weather to the Middle Mississippi and Ohio River Valleys. Rain associated with the circulation of Tropical Depression Harvey could also reach the Mid-Atlantic States later this week.
At 11:00 p.m. EDT on Wednesday the center of Tropical Storm Irma was located at latitude 16.4°N and longitude 32.2°W which put it about 545 miles (875 km) west of the Cabo Verde Islands. Irma was moving toward the west at 12 m.p.h. (19 km/h). The maximum sustained wind speed was 65 m.p.h. (105 km/h) and there were wind gusts to 80 m.p.h. (130 km/h). The minimum surface pressure was 999 mb.
The circulation of Tropical Storm Irma organized quickly on Wednesday. Numerous bands of showers and thunderstorms formed and began to revolve around a well organized center of circulation. Thunderstorms in the core of Irma generated well developed upper level divergence which pumped away mass in all direction. There were occasional satellite images which hinted that an eye could be forming at the center of Tropical Storm Irma.
Tropical Storm Irma will be moving through an environment that will be favorable for intensification. Irma will move over water where the Sea Surface Temperature is near 28°C. The upper level winds are weak and there is little vertical wind shear. Irma is likely to become a hurricane on Thursday and it could intensify rapidly if an eye forms. Tropical Storm Irma is forecast to become a major hurricane and it could become one of the big classic Cape Verde hurricanes.
A strong subtropical high to the north of Irma is steering the tropical storm toward the west and a general westerly motion is forecast to continue for the next few days. There is more divergence in the model guidance after a few days and the future track of Irma when it nears the Lesser Antilles is more uncertain. Tropical Storm Irma has the potential to become a big dangerous hurricane and it will need to be watched carefully.
The record setting rainfall from Tropical Storm Harvey continued over southeastern Texas and Louisiana on Tuesday morning. A rain gauge southeast of Houston near Mary’s Creek at Winding Road has measured 49.20 inches (125 cm) of rain from Tropical Storm Harvey as of 9:00 a.m. CDT on Tuesday. This total sets a new record for the most rainfall from a tropical cyclone over the contiguous 48 states of the U.S. The previous record was 48 inches (122 cm) dropped by Tropical Cyclone Amelia in 1978 over Medina, Texas.
At 11:00 a.m. EDT on Tuesday the center of Tropical Storm Harvey was located at latitude 28.4°N and longitude 94.3°W which put it about 115 miles (185 km) south-southwest of Cameron, Louisiana. Harvey was moving toward the north-northeast at 5 m.p.h. (8 km/h). The maximum sustained wind speed was 45 m.p.h. (75 km/h) and there were wind gusts to 60 m.p.h. (95 km/h). The minimum surface pressure was 997 mb.
A Tropical Storm Warning is in effect for the portion of the coast from Port O’Connor, Texas to Morgan City, Louisiana. A Tropical Storm Watch is in effect for the portion of the coast from Morgan City to Grand Isle, Louisiana.
The center of Tropical Storm Harvey moved back over the Gulf of Mexico late on Monday and it is currently over the northwestern Gulf. Harvey is still producing heavy rain over southeastern Texas and parts of Louisiana. There is still a well defined center and strong counterclockwise rotation in the lower levels of the atmosphere. Dry air wrapped around the circulation of Harvey and there are mainly lighter showers near the center of the tropical storm. There are several stronger bands of thunderstorms on the eastern periphery of the circulation. Those bands are dropping heavier rain over eastern Louisiana and parts of Mississippi. The strong counterclockwise rotation is transporting moist air over land. Increased friction over the land is causing more convergence which is pushing the air upwards. Stronger rising motion is generating areas of heavier rain over southeast Texas and southern Louisiana. In addition, the land is warming during the day, which is making the lower atmosphere more unstable and contributing to the heaver rain.
Flood Watches and Warnings are in effect from Northwest Florida to Southeast Texas because of the potential for more heavy rain. Tropical Storm Harvey is finally starting to move slowly toward the north-northeast. It should make a landfall on the coast of Louisiana early on Wednesday. Tropical Storm Harvey will weaken as it moves farther inland and it should move over the Lower Mississippi River Valley as a tropical depression late this week. The rain over southeastern Texas and southern Louisiana should end once Harvey moves farther inland.
Elsewhere, a low pressure system designated Potential Tropical Cyclone Ten was bringing gusty winds and higher waves to portions of the Mid-Atlantic coast. At 11:00 a.m. EDT on Tuesday the center of Potential Tropical Cyclone Ten was located at latitude 34.4°N and longitude 77.2°W which put it about 35 miles (60 km) west-southwest of Cape Lookout, North Carolina. It was moving toward the northeast at 17 m.p.h. (28 km/h). The maximum sustained wind speed was 40 m.p.h. (65 km/h) and there were gusts to 50 m.p.h. (80 km/h). The minimum surface pressure was 1006 mb. A Tropical Storm Warning was in effect from Cape Lookout to Duck, North Carolina including Pamlico and Albemarle Sounds. Potential Tropical Cyclone Ten is forecast to merge with a front and become a strong extratropical cyclone over the western Atlantic Ocean.
Slow moving Tropical Storm Harvey was causing record flooding in Houston and other places in southeast Texas. At 2:00 p.m. EDT on Sunday the center of Tropical Storm Harvey was located at latitude 29.0°N and longitude 97.2°W which put it about 25 miles (40 km) northwest of Victoria, Texas. Harvey was moving toward the southeast at 2 m.p.h. (3 km/h). The maximum sustained wind speed was 40 m.p.h. (65 km/h) and there were wind gusts to 50 m.p.h. (80 km/h). The minimum surface pressure was 1000 mb.
A Tropical Storm Warning was in effect for the portion of the coast from Port O’Connor to Sargent, Texas.
The center of Tropical Storm Harvey is drifting back toward the Gulf of Mexico. A significant portion of the eastern side of Harvey is over water and the strongest winds are occurring in rainbands over the Gulf of Mexico. Those winds are the reason Harvey is still a tropical storm and why there is still a tropical storm warning for a portion of the coast. The circulation around Harvey is circulating over the water and it is transporting large amounts of moisture over southeast Texas. Strong convergence into the center of Harvey is lifting the air and it is producing prolonged periods of heavy rain when rainbands move inland.
The extremely heavy rain in Harvey is causing record flooding in parts of Houston and other locations in southeastern Texas. The Buffalo Bayou is currently at 67.46 feet (20.56 m). The previous record water level was 61.2 feet (18.65 m).
The slow movement of Tropical Storm Harvey is exacerbating the flooding. The winds are the steering level are weak and Harvey is now drifting back toward the southeast. Harvey is drifting back over places it moved over on Saturday. The center of Tropical Storm Harvey could drift back over the Gulf of Mexico. If the center of Harvey moves back out over water, it would likely maintain its intensity. Tropical Storm Harvey is forecast to continue to drop heavy rain over southeastern Texas and southwestern Louisiana during the next several days.
Tropical Storm Harvey was intensifying rapidly on Thursday morning and a Hurricane Warning was issued portions of the coast of Texas. At 11:00 a.m. EDT on Thursday the center of Tropical Storm Harvey was located at latitude 24.0°N and longitude 93.3°W which put it about 365 miles southeast of Corpus Christi, Texas. Harvey was moving toward the north-northwest at 10 m.p.h. (16 km/h). The maximum sustained wind speed was 65 m.p.h. (105 km/h) and there were wind gusts to 80 m.p.h. (130 km/h). The minimum surface pressure was 982 mb.
A Hurricane Warning was in effect for the portion of the coast from Port Mansfield to Matagorda, Texas. A Hurricane Watch was in effect for the portion of the coast from the mouth of the Rio Grande River to Port Mansfield. A Tropical Storm Warning was in effect for the portion of the coast from the mouth of the Rio Grande River to Port Mansfield and from Matagorda to High Island, Texas. A Tropical Storm Watch was in effect for the portion of the coast from Boca De Catan, Mexico to the mouth of the Rio Grande River.
Tropical Storm Harvey intensified very rapidly on Thursday morning. An eye with a diameter of 18 miles (29 km) formed at the center of circulation. The eye was surrounded by a ring of very strong thunderstorms. Additional bands of strong thunderstorms were revolving around the core of Tropical Storm Harvey. The thunderstorms were generating very strong upper level divergence which was pumping away large amounts of mass in all directions from the tropical storm. The strong upper level divergence was causing the surface pressure to decrease rapidly. The minimum surface pressure decreased from 1002 mb to 982 mb in 12 hours. The rapid decrease in pressure was increasing the pressure gradient force and the winds speeds were increasing accordingly.
Tropical Storm Harvey is in an almost perfect environment for rapid intensification. Harvey is moving over water where the Sea Surface Temperature is near 31°C. The upper level winds are very weak and there is almost no vertical wind shear. Tropical Storm Harvey should continue to intensify rapidly for another 24 to 36 hours. Harvey will become a hurricane later today and it will likely become a major hurricane before it makes landfall. Tropical Storm Harvey has the potential to intensify to a Category 4 hurricane on the Saffir-Simpson Scale.
Harvey is being steered toward the north-northwest by a subtropical ridge to the east of the tropical storm. A general northwesterly motion is forecast continue for another 36 to 48 hours. On its anticipated track the center of Harvey will approach the coast of Texas on Friday night. The steering currents are forecast to weaken as Harvey nears the coast. Some models are forecasting that Harvey drifts slowly toward the west. Other models stall Harvey and then turn it northeastward. There is a large degree of uncertainty about the future track of Harvey after it nears the coast.
Based on current projections the forecast Hurricane Intensity Index (HII) for Harvey at landfall is 22.1. The forecast Hurricane Size Index (HSI) is 18.0 and the forecast Hurricane Wind Intensity Size Index (HWISI) at landfall is 40.1 Those indices indicate that Harvey could cause regional major damage in Texas. The indices may be conservative if Harvey continues to intensify rapidly up until it makes landfall. Harvey would be stronger, but a little smaller, than Hurricane Ike was when Ike made landfall in Texas in 2008. The HII for Ike was 19.2, the HSI was 22.5 and the HWISI was 41.7.
Harvey will bring strong damaging winds to Texas. Harvey will also cause a dangerous storm surge at the coast. The storm surge could approach 12 feet (4 meters) in some locations. Harvey will also drop very heavy rain, if it stalls after it moves inland. Serious fresh water flooding is possible under that scenario.
Tropical Storm Harvey weakened to a tropical wave on Saturday. At 11:00 p.m. EDT on Saturday the center of Tropical Wave Harvey was located at latitude 14.3°N and longitude 71.8°W which put it about 765 miles (1230 km) east of Cape Gracias a Dios. The wave was moving toward the west at 22 m.p.h. (35 km/h). The maximum sustained wind speed was 35 m.p.h. (55 km/h) and there were wind gusts to 45 m.p.h. (75 km/h). The minimum surface pressure was 1007 mb.
An upper level ridge east of Harvey produced northerly winds that blew toward the top of the former tropical storm. A subtropical high over the Atlantic Ocean produced strong easterly winds in the lower levels of the atmosphere. The combination of northerly winds in the upper levels and easterly winds in the lower levels produced strong vertical wind shear which disrupted the vertical structure of Harvey. A reconnaissance plane was unable to locate a low level center of low pressure on Saturday evening and the National Hurricane Center reclassified the system as a tropical wave.
Tropical Wave Harvey will continue to move west across the Caribbean Sea during the next several days. It will move over water where the Sea Surface Temperature is near 30°C. So, there will be sufficient energy in the ocean to support a tropical cyclone. When the tropical wave moves under the core of the upper level ridge, the wind shear will decrease. If the tropical wave moves into a more favorable environment and slows down, a new center of circulation could redevelop. Models are not forecasting significant redevelopment of the tropical wave at the current time, but the National Hurricane Center will continue to monitor the wave for possible redevelopment.
A reconnaissance plane found that a center of circulation and winds to tropical storm force had developed in a tropical wave previously designated as Invest 91L and Potential Tropical Cyclone Nine. Based on data collected by the recon plane the National Hurricane Center named the system Tropical Storm Harvey on Thursday afternoon. At 5:00 p.m. EDT on Thursday the center of Tropical Storm Harvey was located at latitude 13.0°N and longitude 55.8°W which put it about 250 miles (400 km) east of Barbados. Harvey was moving toward the west at 18 m.p.h. (30 km/h). The maximum sustained wind speed was 40 m.p.h. (65 km/h) and there were wind gusts to 50 m.p.h. (80 km/h). The minimum surface pressure was 1004 mb.
A Tropical Storm Warning is in effect for Martinique, Barbados, St. Vincent and the Grenadines, and St. Lucia. A Tropical Storm Watch is in effect for Dominica.
The circulation of Tropical Storm Harvey became better organized on Thursday. A low level center of circulation developed and bands of showers and thunderstorms began to revolve around the center. Intermittent bursts of thunderstorms occurred near and to the west of the center of circulation. The circulation of Tropical Storm Harvey is asymmetrical. Most of the stronger thunderstorms are occurring in the western half of the circulation. The bands in the eastern half of the circulation consist primarily of showers and low clouds. Thunderstorms near the core of Harvey were generating some upper level divergence which was pumping mass away to the south and west of the tropical storm.
Tropical Storm Harvey will be moving through an environment that will be somewhat favorable for intensification. Harvey will move over water where the Sea Surface Temperature is near 29°C. An upper level ridge northeast of Puerto Rico is producing northeasterly winds which are blowing toward the top of Tropical Storm Harvey. Those winds are producing moderate vertical wind shear which is probably the cause of the asymmetrical distribution of thunderstorms. Tropical Storm Harvey is likely to get better organized on Friday and it could strengthen. The intensity guidance is mixed. Some guidance forecasts that Harvey will become a hurricane as it moves over the Caribbean Sea, while other guidance weaken the tropical storm back to a tropical wave. So far, the guidance has underpredicted the strength of Tropical Storm Harvey and so strengthen would seem more likely.
Tropical Storm Harvey is being steered quickly toward the west by the subtropical high over the Atlantic Ocean. A general westerly or west-northwesterly track is forecast for the next few days. On its anticipate track Tropical Storm Harvey could reach Barbados in about 12 hours. Harvey could also reach Martinique, St. Lucia, St. Vincent and the Grenadines on Friday. Tropical Storm Harvey will bring gusty winds and locally heavy rain to those islands when it moves over them.