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Aug
25
2017

Tropical Cyclone Activity Report – Atlantic Ocean / Caribbean Sea / Gulf of Mexico

Tropical Cyclone 09L (Harvey) is located about 45 miles southwest of Port Connor, Texas

PDC Disaster Alert, displaying PDC Active Hazards, Tropical Cyclone segments, positions, and the TAOS model for Tropical Cyclone Harvey…and a tropical disturbance with a low chance of developing

Hurricane Harvey is a Category 4 hurricane at the time of this writing…as it nears the Texas coast

Here’s a NASA satellite image of Hurricane Harvey…taken today – close up satellite image of Harvey as it impacts the Texas coast

Here’s the radar image coming out of Corpus Christi, Texas

Hurricane Harvey was “dangerously approaching the Texas Coast” Friday morning, expected to drop as much as 35 inches of rain and usher in “life-threatening” storm-surge flooding upon landfall late today or early Saturday, the National Hurricane Center said.

The combination of heavy rain, storm surge, flooding and strong winds could leave wide swaths of South Texas “uninhabitable for weeks or months,” the National Weather Service in Houston said.

“All indications from the hurricane center are that this is going to be the first major hurricane the nation has dealt with since 2005,” FEMA Director Brock Long said.

“Texas is about to have a very significant disaster,” Long, the FEMA chief, said, stressing that people need to heed evacuation warnings. Those who stay should “elevate and get into a structure that can withstand potentially Category 4 winds from a hurricane,” he said.

Here’s a current satellite image…and what the computer models are showing

Here’s a looping satellite image of this system

Here’s a graphic showing the current radar and wind speeds across Texas

Here’s a graphic showing the rainfall outlook

The NHC advisory #21, shows sustained winds are 95 knots…with gusts to near 115 knots.

According to the National Hurricane Center (NHC), multiple observing platforms indicate that Harvey’s structure is evolving. The hurricane has developed concentric eyewalls, as observed in data from the WSR-88D Doppler radars in Brownsville and Corpus Christi, and an Air Force Reserve Hurricane Hunter plane reported double wind maxima with diameters of 12 and 28 n mi.

The aircraft data indicate that the central pressure has continued to fall–now down to 947 mb–but the maximum winds have not increased further. This discrepancy is not surprising given hurricane’s current structure. Intensity forecasts become complicated once a hurricane develops concentric eyewalls, and fluctuations in intensity become more likely.

If an eyewall replacement occurs, then Harvey’s intensity could decrease a bit while at the same time the overall wind field increases in size. However, the hurricane remains in an environment for intensification, and strengthening beyond the current intensity is still possible before the center reaches land.

But in the end, the hurricane’s exact intensity at landfall does not change the fact that catastrophic flooding due to a prolonged period of heavy rainfall and/or storm surge is expected at the coast and well inland across much of southern and southeastern Texas. Slow weakening is expected after Harvey crosses the coast since the center is not expected to move very far inland, and the cyclone is likely to maintain tropical storm status through Wednesday.

Harvey has not quite begun to slow down, and the initial motion estimate is 315/9 knots. Strong mid-level ridging building over the western United States is still expected to impede Harvey’s forward motion in the coming days, and the track guidance continues to show the hurricane meandering or stalling near or just inland of the Texas coast in 36-48 hours.

Harvey could begin moving slowly eastward on days 4 and 5 due to the influence of a mid-level shortwave trough digging southward over the upper Midwest, but at this time it is too early to say whether the center will definitely re-emerge over the northwestern Gulf of Mexico.

Current Warnings

A hurricane warning has been issued for a portion of the Texas coast, from north of Port Mansfield to Sargent, including the city of Corpus Christi. A hurricane warning means hurricane conditions are likely within the watch area. In this case, hurricane conditions are likely within 12 to 24 hours.

Importantly, tropical storm-force winds may begin to affect the hurricane-warned area above as soon as late this morning, making final preparations difficult.

Tropical storm warnings are in effect from north of Sargent to High Island, Texas, including the cities of Houston and Galveston. Tropical storm warnings are also in effect from north of Port Mansfield to the mouth of the Rio Grande River.

Here’s a graphic showing current advisories along the Guff coast of Mexico

HAZARDS AFFECTING LAND

RAINFALL: Harvey is expected to produce total rain accumulations of 15 to 25 inches and isolated maximum amounts of 35 inches over the middle and upper Texas coast through next Wednesday. During the same time period Harvey is expected to produce total rain accumulations of 5 to 15 inches in far south Texas and the Texas Hill Country over through southwest and central Louisiana. Rainfall of this magnitude will cause catastrophic and life-threatening flooding.

STORM SURGE: The combination of a dangerous storm surge and the tide will cause normally dry areas near the coast to be flooded by rising waters moving inland from the shoreline. The water is expected to reach the following heights above ground if the peak surge occurs at the time of high tide…

N Entrance Padre Island Natl Seashore to Sargent…6 to 12 ft Sargent to Jamaica Beach…5 to 8 ft Port Mansfield to N Entrance Padre Island Natl Seashore…5 to 7 ft Jamaica Beach to High Island…2 to 4 ft Mouth of the Rio Grande to Port Mansfield…2 to 4 ft High Island to Morgan City…1 to 3 ft

The deepest water will occur along the immediate coast near and to the northeast of the landfall location, where the surge will be accompanied by large and destructive waves. Surge-related flooding depends on the relative timing of the surge and the tidal cycle, and can vary greatly over short distances.

WIND: All last-minute preparations should be rushed to completion since tropical storm conditions are likely just beginning in portions of the hurricane and tropical storm warning areas. Hurricane conditions are likely to begin within the hurricane warning area later today or tonight. Tropical storm conditions are likely to persist along portions of the coast through at least Sunday.

SURF: Swells generated by Harvey are affecting the Texas, Louisiana, and northeast Mexico coasts. These swells are likely to cause life-threatening surf and rip current conditions. Please consult products from your local weather office.

TORNADOES: A few tornadoes are possible later today through Saturday near the middle and upper Texas coast.

>>> Meanwhile, a broad area of low pressure located near the west-central coast of the Florida peninsula is producing a large area of disorganized cloudiness and thunderstorms over southern and central Florida and the adjacent waters.

This system is forecast to move northeastward and emerge over the western Atlantic over the weekend where some development is expected through early next week before it merges with a front.

Regardless of development, very heavy rain and flooding is possible over portions of southern and central Florida, and the northwestern Bahamas during the next few days.

In addition, this system is expected to cause increasing northeast winds and rough surf along the coast of Georgia and the Carolinas through early next week.

This disturbance is being referred to as Invest 92L, here’s a satellite image…along with what the computer models are showing.

Here’s the NWS Florida looping radar image

* Formation chance through 48 hours…low…20 percent
*
Formation chance through 5 days…medium…50 percent

 

Atlantic Ocean

There are no current tropical cyclones

NOAA satellite image of the Atlantic

Caribbean Sea

There are no current tropical cyclones

NOAA satellite image of the Caribbean Sea

Gulf of Mexico

Tropical cyclone 09L (Harvey)

NHC textual forecast advisory
NHC graphical track map
NOAA satellite image

Latest satellite image of the Gulf of Mexico

 

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