Alex approaching the coast

At 4:00 PM CDT, Hurricane Alex was located near 24.4N/96.8W, or about 105 miles southeast of Brownsville, Texas and about 50 miles east of the coast of Mexico. Maximum sustained winds are near 90 mph. Alex has been moving to the west around 12mph. After taking a jog towards the north-northwest this afternoon it looks like the upper level ridge is now influencing the cyclone and Alex is expected to continue moving west until landfall which could be in the next couple of hours.

Alex continues to have a very organized appearance on the latest high res visible sat imagery with a very well defined but small eye emerging as he nears the coast. Surface pressure has dropped once again and is currently at 959mb so it looks like Alex is really trying to complete the eye-wall replacement cycle which began late this morning. Latest radar data shows that the cyclone is once again developing a well defined inner eye which could mean that it is just about finished with the replacement cycle and a further increase in surface wind speeds are possible before landfall. Alex remains a very large storm with tropical storm force winds extending out up to 200 miles from the center. It looks like however, that the sustained hurricane force winds should remain south of the Brownsville area.

Local radars continue to show showers moving inland from the gulf as deep tropical moisture remains in place across the area. Rain chances will remain high through the weekend and even deeper moisture arrives later tonight. Locally heavy rainfall will remain the main threat; however there could be a very isolated tornado in any of the heavier convective bands that might develop and push onshore. Widespread 1-2 inches of rain with isolated 2-4 inches seem like a good bet through Friday evening.

KBRO Radar


KBRO Storm Total Precip

Alex North of Track

The latest satellite imagery shows that Alex is currently traveling to the north of the 10am NHC track forecast. This could be because the upper level ridge that computer models have been forecasting to start pushing the cyclone off to the west has been slower to build across the northern gulf coast. The storm does look like it could be starting to make that more west-northwest turn based on some of the latest radar data; however the storm is going to still be north of the current track. It would not surprise me to see the NHC adjust their 1pm track a bit further north up the coast.

Satellite and Track Overlay

Alex Continues to Strengthen

At 10:00 AM CDT, Hurricane Alex was located near 23.9N/95.4W, or about 185 miles southeast of Brownsville, Texas. Maximum sustained winds are near 80 mph. Alex has been moving to the northwest near 5 mph. Latest high resolution visible satellite imagery shows that Alex has been tracking north (or to the right) of the latest NHC track, likely in response to a continued upper level weakness to the north of the cyclone. Current thinking is that this weakness should start to be replaced by a ridge over the next few hours. As this occurs we should see the system resume more of a west-northwest track and head inland tomorrow morning in northern Mexico.

Alex has quite an impressive presentation on the latest satellite images which show a very well organized storm this morning with improved upper level outflow. The latest data from the Hurricane hunter aircraft indicate that the cyclone is currently going through an eye-wall replacement cycle and that the inner eye-wall has collapsed and the pressure has risen to 961mb, up 2mb from earlier this morning. The atmosphere around Alex is very moist to dry air entrainment does not look like it is going to be a limiting factor for increased strengthening today. Much like we saw with Ike, the storms central pressure is already that of a category 3 storm; however the storm is so large that the wind field will take some time to catch up with the pressures. I do not think that the storm will have enough time to fully complete its eye-wall replacement cycle and allow for the development of another strong inner eye-wall before landfall. Therefore it still looks like Alex will be a cat 2 hurricane with max sustained winds around 100-105mph as the storm reaches the coastline.

The main threats for southeast Texas will be the potential locally heavy rainfall due to a very tropical air mass in place over the region. Precip water values this morning are running in the 2.5-2.6'' range which is easily 2 standard deviations above normal for this time of year, meaning that any of the heavier convection will be capable of putting down 2-3'' per hour rainfall rates or greater. This will likely lead to some street flooding problems should we see training setup over the metro area. As of 11am, most of the activity has been confined to our coastal counties and offshore which is where the greatest risk of flooding should remain for the day. We will need to keep a close eye on the radar however to see if the heavier activity that has been over the gulf starts to move inland.

Winds across the region should remain out of the east-northeast 15-20mph through the day with some gusts to 30mph, especially in the heavier storms.

Alex Satellite Imagery

10am NHC Track

Models shift back south

Discussion..

Well, the 18z suite of models has resulted in a major shift in the three models (GFS, CMC, and GFDL) that seemed to be the northern outliers but really got forecasters attention over the past couple of days. Now all of the major dynamic models with the exception of the HWRF are now predicting a landfall right around where the 4pm NHC track is currently positioned about 100 miles south of Brownsville, TX. It seems like as Alex has now moved into the gulf, the models are able to ingest better data and initialize better and have seemed to come into pretty good agreement with a ridge of high pressure forecast to build to the north of the storm and turn it more west-northwest, towards northern Mexico. It is still very possible due to the slow forward speed, that Alex could still move to the right of the current forecast and impact south Texas. Tomorrow is looking like the pivotal day in the track forecast because that is when Alex is currently forecast to make that more westward turn in response to the building ridge to its north-northeast. If that does not happen, then Alex could take more of a northerly track and head more towards the middle Texas coast.

Houston Impacts..

With the center of Alex currently forecast to remain well south of the area really strong winds do not look like an issue; however very deep tropical moisture with precip water values around 2 standard deviations above normal will continue to move into the region for the remainder of the week. This will likely produce periods of heavy showers and thunderstorms and the possibility of some localized flooding problems. The latest 5-day rainfall total forecast from HPC (Hydrometeorological Prediction Center) shows the potential for a widespread 1-3 inches with isolated 3-6 in totals if we see training setup. Depending on the future track of Alex, some outer rain bands may begin to affect areas south of I-10 as early as Wednesday afternoon or evening. Isolated tornadoes and gusty winds up to 40mph could be possible if we see some of the stronger squalls reach the coast later this week; however this will be highly dependent on the future track of Alex.

At this time I would expect to see winds at UH turn more east to northeast Wednesday and Thursday and increase into the 15-20mph range with gusts 25-30mph.

For UHCC, look for east winds increasing to the 20-25mph range with gusts 30-35mph Wednesday and Thursday.

4pm NHC Track


18z Tropical Models

TS Alex Possible Texas Threat?

Since the last time the blog was updated was for the approach of Hurricane Ike back in 2008, the potential threat from Alex seems to be a good place to start up again.

The first tropical cyclone of the 2010 season is presenting forecasters with anything but an easy forecast. As of 10pm Alex has re-emerged into the southern gulf and is centered at 19.4N/91.3W, or about 470 miles east-southeast of Tampico, MX. Maximum sustained winds are near 45 mph. Movement is to the west-northwest at 7 mph.

The forecast track over the next 36 hours or so looks pretty good with Alex expected to continue to generally move off to the northwest; however as we get into day 3 and beyond there remains a great amount of uncertainly in regards to the future track Alex will take. At this time the storm is expected to begin to interact with a ridge of high pressure forecast to be located across the northern Gulf of Mexico. The main question remains how strong the ridge across the northern gulf will be as we see a trough of low pressure drive south across the eastern US. A weaker ridge will allow for Alex to turn more to the northwest and north and head toward the middle to upper Texas coast. A stronger ridge, which the NHC forecast is currently based on will turn Alex more toward the west-northwest and then west into the northern Mexican coast about 150 miles south of Brownsville.

This uncertainty is reflected in the dynamic models, four of which (GFS, GFDL, HWRF, and CMC) calling for a Texas landfall while the NOGAPS and ECMWF take the storm into northern Mexico. Interestingly enough, the best preforming models at the 3-4 day range last season were the GFS and the CMC (Canadian) with these models forecasting a middle to upper Texas coast landfall Thursday or Friday of this week. The current NHC track is slightly further north but still takes Alex into the northern Mexican coastline; however, another item to consider is the right bias associated with land-falling gulf storms. It would not surprise me if we see the NHC continue a northward adjustment to future tracks if the dynamics models start to trend closer to the GFS and CMC which at this time remain the northern outliers.

Therefore having said all this, it would be a safe bet to start looking over your hurricane preparedness plans just to be on the safe side.

Below is the current NHC forecast track along with the 00z dynamic models and a link to Dr. Jeff Masters blog on Alex which is a very interesting read and has some more statistics regarding which models preformed the best last year.

10pm NHC Track


00z Models


http://www.wunderground.com/blog/JeffMasters/article.html