Tropical Weather Discussion...This Monday evening all eyes continued to look at Alex. The first named storm of the season continues to dominate the weather headlines. The latest information from the National Hurricane Center is now available.
Tropical Storm Alex
4p.m. CDT Monday, June 28, 2010
...Alex holding steady for now, strengthening into a hurricane expected over the next 24 hours...Additional watches issued for the Texas Gulf Coast...
Latitude: 20.5 N
Longitude: 91.8 W
This position is about 410 miles ESE of Tampico, Mexico & 520 miles SE of Brownsville, Texas.
Winds: 60 mph. Some strengthening is expected through Tuesday, and Alex could become a hurricane late tonight or Tuesday. Tropical Storm force winds extend outward to 70 miles from the center of circulation, the wind field will continue to expand as Alex strengthens.
Movement: NNW or 330 degrees at 5 mph. An increase in forward speed, and a turn back to the NW is expected on Tuesday, followed by a turn to the WNW by Wednesday. An increase in forward speed is also expected through Wednesday. On this track, Alex will continue moving through the open waters of the Gulf of Mexico, and approach the coastline in the hurricane watch area by Wednesday night into Thursday. Landfall is expected Thursday.
Pressure: 29.23" or 990 mb. The pressure has leveled off this afternoon, but should begin to fall once again later tonight as the strengthening process resumes.
Watches/Warnings...No change to the hurricane watch that was issued this morning. It remains in effect for portions of the Gulf coast of Mexico and Texas from La Cruz to the Mouth of the Rio Grande River on the U.S./Mexico border & from the U.S./Mexico border to Baffin Bay, Texas. Portions of this area could be upgraded to a hurricane warning tonight. A hurricane watch means that hurricane conditions are possible in the watch area. A watch is typically issued 48 hours before the first occurrence of tropical storm force winds are expected to occur. These are the conditions that make outdoor preparations dangerous and difficult.
Discussion...There really isn't much change to the forecast philosophy with Alex compared to the last forecast package. The model suite is clustered in the Rio Grande Valley on both sides of the border, and the current forecast track is a consensus of the models. The steering currents in the Southern Gulf are very weak at this time, and this is the reason for the slow movement of Alex today. However, the steering currents are expected to strengthen over the next couple of days. Alex has been steered around the periphery of an anticyclone over the SE United States. The ridge was in place across much of the Gulf coast over the weekend, but has now weakened. The presence of the persistent Bermuda high over the Eastern Gulf still exists. A weakness has developed over the Western Gulf, and Alex's more Northerly motion today has been a result of this weakness. All models are insistent on a new ridge developing over the Central U.S. from the Great Plains t the Mid West by mid-week, and this could lead to future ramifications of Alex. There is also one other key player on the field that could factor into the equation. An advancing summer trough and associated weakening cold front is sliding towards the Gulf Coastal Plain. This frontal zone could set up along the Gulf Coast later this week, and create stronger SW winds out ahead of it over the Gulf. It remains to be seen how far down into the Gulf, if it all, this frontal zone will progress, and if will have any effect at all on Alex. If the previously mentioned secondary ridging processes don't take shape then Alex could remain on a more Northerly course, and then have a chance to be influenced by the summer trough. This would cause Alex to make landfall at a point further North along the Gulf coast, but this scenario is an outlier at this point in time. This scenario would likely produce a landfall closer to SW Louisiana, and would certainly increase the threat for hurricane conditions in our part of the world, but again this is not anticipated at this time.
The NHC's didn't deviate a whole lot from their previous advisory for the official track on this advisory. It is still aimed at the general vicinity of the Rio Grande. I see no reason to deviate from my original forecast either. I am sticking to the idea that landfall will be in the U.S. with this occurring between the Rio Grande and Corpus Christi on Thursday. The possibility still exist as well that Alex could attain major hurricane status before making its ultimate landfall in the latter half of the week. The current forecast shows Alex making landfall on the Mexican side of the Rio Grande as a strong category 2 storm on Thursday. Alex's strengthening trend today has been temporarily impeded by a bit of shear to the North of the storm, but this is forecast to lift out by Tuesday morning, thus the strengthening process should resume. I fully expect Alex to become a hurricane Tuesday. While it remains to be seen who will endure the brunt of the storm, effects will felt over a wide area. Alex is a large tropical cyclone. Tropical rain bands are being experienced all the way to the Florida Panhandle. These are the outer rain bands, and the usual afternoon sea breeze along the Gulf coast is helping to enhance rainfall with the super tropical air mass in place. The effects of Alex across this forecast area will be enhanced chances for rainfall through the work week, and an increase in tides along the coast. Some coastal flooding will likely occur from Jefferson County in SE Texas over to the Atchafalaya Region. Strong Southerly winds will cause tidal backup along the coast, and into the lower end of area rivers. Winds and seas will increase in the offshore waters, but tropical storm conditions should remain over water. No tropical storm force conditions are expected over land areas in the forecast area at this time unless the forecast track changes. Right now in the oil spill zone, conditions are expected to be quite rough with seas around 10-11'. The strong onshore flow will likely unfortunately send more oil towards the Louisiana coast, but it is unclear at this time if it will move closer to SW Louisiana. Heavy rainfall is expected from time to time across the entire region. Rainfall totals through Friday should be on the order of 2-4" with some areas receiving in excess of 6". These totals are subject to revisions based on revisions to track and intensity of Alex. This is a good time to point out again that it is not important to focus simply on the black line displayed on the forecast track. This black line only indicates the center of the storm. Alex is a large storm, and his effects will be felt over a wide region as illustrated above. Stay tuned for any possible further revisions to the forecast track and intensity. Another Air Force Hurricane Hunter Aircraft is en route to Alex at this time, and we'll have more information available this evening. The graphics suite follows.
That's all for this update. An intermediate advisory will be issued at 7p.m. CDT by the National Hurricane Center followed by the next complete advisory at 10p.m. CDT. My next update on Alex will come shortly after that. I will also post a regular forecast discussion in a couple of hours. Of course, with Alex keeping us meteorologists busy, the blog is in short form. The forecast package until further notice will consist of the discussion, preliminary numbers, zone forecast, the 7 day forecast, and the marine forecast. All tropical information will be inserted into a different entry to keep it from being so cluttered. If my machine cooperates, I will also post the latest advisory on Alex in audio format. The audio blogs will only contain information Alex until further notice.
Have a good evening and God bless!
-DM-
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