We are continuing to closely monitor the development and progression of Hurricane Harvey, which is currently located over the southwestern Gulf of Mexico.
...Current Trends of the System and Expected Coastal Impacts...
Since the early morning update today, the center of Harvey has moved more toward the Northwest vs. West/Northwest. The system has also intensified rapidly, and has since reached hurricane strength. The system is forecast to continue in a general West/Northwest to Northwest direction and make landfall generally between 1am and 7am on Saturday somewhere in the vicinity of Rockport, TX. The system will likely be a "major" hurricane at landfall, with extensive impacts from wind, storm surge and fresh water flooding across much of the Texas coastal bend.
...Expected Movement of the System Once Inland...
Based on present indications, once the system makes landfall...the center is expected to drift Northwestward and come to a stop somewhere approximately 40-60 miles to the Southeast of San Antonio on Saturday night or early Sunday morning. The system is then expected to remain nearly stationary during most of the day on Sunday before turning back toward the Southeast toward the coastal waters late Sunday into Monday. Assuming the stall-out and then Southeast recurve occurs as described above, the center of the system would remain to the East and/or Southeast of the local area at all times - and therefore the tendency for the most significant, widespread rainfall would also generally be to the Southeast of the local area - closer to I-10 and East of I-35.
...Local Rainfall Forecast and Potential Flooding Impacts...
Based on the above assumptions, we are currently forecasting widespread average rainfall of 3-6 inches across most of the local area from later Friday evening into Sunday. As per the map at the top of this bulletin, the lower end of the range would be in the Northwest part of the area, and the higher end toward the Southeast part of the area. Locally higher amounts are also possible in spots.
Rainfall of the amount currently forecast for the local area would mostly occur in the form of numerous showers and some scattered thunderstorms (thunderstorms are actually less dominant in tropical systems vs. regular showers). Some of the showers, however, are likely to produce periods of locally heavy downpours. It will be these downpours that are likely to result in flooding of especially low lying and poor drainage areas in at least some parts of the local region during the Advisory period, and especially during the day on Saturday into Saturday night and Sunday morning. Any parts of the area that receive repeat episodes of locally heavy downpours would be particularly vulnerable to such flooding, especially at low water crossings and similar areas.
With the above in mind, at this time, we continue to forecast that the potential for significant creek, stream and/or river flooding would mainly exist further to the East of I-35 - to the East of the local area - and further to the South, closer to I-10 and Southward. Much higher rainfall totals in excess of 6 inches appear likely in those areas...and possibly over a more prolonged time period as well.
...Important Note on Potential Changes to the Rainfall and Flooding Impact Portion of the Forecast...
It is very important to note that should the center of Harvey shift significantly West/Northwestward vs. what is currently expected, and/or should the system stall out just to the Southeast of the local area instead of turning back toward the coast as is currently anticipated, then the threat of more significant rainfall would potentially shift deeper into the local area, and increased flooding potential could occur as a result (also, the flooding potential could then be extended into Monday and possibly even Tuesday if such a scenario were to occur). Present indications suggest that it will be difficult for us to confidently express whether or not such a change in movement is possible until the system has already made landfall and has progressed inland for a number of miles. This would most likely be sometime during the day on Saturday, based on present indications.
...Local Wind Impacts...
During the period from 6am Saturday through 12 Noon on Sunday, look for East-Northeast winds of 20-25 mph on a sustained basis, with frequent gusts of 25-35 mph. Some peak gusts of 35-40 mph are also possible at times, especially on Saturday afternoon and/or evening. This forecast is again based on the expected current track of the center of the system once it moves inland, as described in detail above.
...Important Note on Potential Changes to the Wind Impact Portion of the Forecast...
It is very important to note that should the center of Harvey shift significantly West/Northwestward vs. what is currently expected once it has moved inland, then the threat of more significant wind gusts may develop locally over the weekend. Under such a scenario, sustained winds of around 30 mph with several gusts of 35-45 mph would be possible in some parts of the area, mainly on Saturday afternoon or evening. It will be difficult to tell whether or not this scenario is possible until we've been able to track the inland progression of the system on Friday night into early Saturday. At this time we will continue with the current "most likely" scenario described in the "Local Wind Impacts" section noted above. If changes in the track appear likely to occur, we will update the forecast accordingly as soon as those conditions appear probable.
We will continue closely monitoring the progression of this system and issue updates as conditions warrant.
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