Alex Becomes a Hurricane

By: Dr. Jeff Masters , 2:57 AM GMT on June 30, 2010

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Hi, Dr. Rob Carver filling in for Jeff on the late shift.

430AM EDT Update
The 400AM EDT advisory package has hit the wires. Alex' center of circulation is located at 23.3N, 95.1W, which is 175 miles east of La Pesca, MX and 235 miles southeast of Brownsville, TX. Alex is responding to a weakness in the ridge to it's north, the storm motion has shifted to WNW at 7 mph. The winds are unchanged from the 100AM advisory, they are still 80 mph. However, Alex continues to deepen it's pressure, the minimum central pressure is 961 mb. Hurricane force winds now extend to 30 miles away from the center, and tropical force winds extend to 200 miles from the center. Alex is currently over warm ocean waters and under weak vertical shear, so the winds are forecast to increase. However, given the strength of Alex's central pressure, there is a small possibility of a rapid intensification of an additional 35 mph.

I haven't changed my risk assessment with this advisory. Flooding from rain still remains the greatest hazard posed by Alex. Tropical storm force winds are expected to reach the coast later this morning. People should plan on finishing their outdoor preparations by this time.

150 AM Update As of the 100AM EDT advisory, Alex is at 23.1N, 94.8W. The minimum central pressure is 972 mb, and the winds have increased to 80 mph. Alex is slowly moving westwards at 5 mph in an "erratic" fashion.

As of the 11PM EDT advisory, NHC has upgraded Alex to a hurricane with maximum winds of 75 mph and a minimum central pressure of 973 mb. Alex's center is at 23.1N, 94.8W, which is 255 miles south of Brownsville, TX and 195 miles east-southeast of La Pesca, MX. Alex is moving westwards at 9 mph. Alex is expected to slightly alter it's course to the WNW before making landfall south of the Rio Grande. The winds are also forecast to pick up to 90 mph before landfall. In any event, mandatory evacuation orders have been issued for recreational vehicles and other high-profile vehicles in county parks on South Padre Island. A voluntary evacuation is in place for residents of South Padre Island and Port Isabel.

Threat from storm surge
NHC is forecasting a 3-5 foot storm surge north of the eye as Alex makes landfall.

Threat from wind
NWS forecasters expect that damage from Alex's winds will be limited to the southern counties of Cameron, Willacy, and Hidalgo. Hurricane force winds extend 15 miles from the storm center, but tropical storm force winds extend 175 miles from the center. This is a rather large circulation. The Storm Prediction Center is monitoring southern Texas for the threat of tornadoes in the outer rainbands as Alex makes landfall. I'd expect a tornado watch to be issued around noon CDT.

Threat from rain
This is the most significant impact from Alex. Rainfall totals of 6 to 12 inches are expected over northern Mexico/southern Texas with 20 inches possible in some locations. There will be flooding from this storm. If more than 5 inches fall in 6 hours, there will likely be flash flooding. The NWS office in Brownsville is advising people who were flooded out by Dolly in 2008 to evacuate to higher ground now.


Satellite-derived rainfall estimates for Alex's passage over the Yucatan peninsula on June 28, 2010. Data provided by the Climate Prediction Center.

Alex is the first Atlantic June hurricane since 1995's Allison. The storm tally for that season was 19 named storms, 11 hurricanes, and 5 major hurricanes. It will be interesting to see how this season compares to 1995.

Next update
I'll have an update Wednesday evening/night. Jeff will have an update sometime tomorrow morning.

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Quoting xcool:
huh nnw


what??
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589. xcool
Enhanced Water Vapor Satellite best update in 5mins
Member Since: September 26, 2009 Posts: 2 Comments: 15670
588. Asta
LSU EARTHSCAN GOES ANIMATED IR LINK
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587. xcool
huh nnw
Member Since: September 26, 2009 Posts: 2 Comments: 15670
Quoting txsweetpea:
Is it possible for Alex to go to "break thru " the ridge or whatecer alot of you said was guiding Alex and go north or are we SURE that Alex is going to make landfall in Mexico or south texas? Just wondering if Alex does become a cat 2-3 overnite could this happen?


Don't worry, that's physically impossible, no matter how strong Alex gets. Here's what's happening,

There is a large upper trough over the E United States, any standard upper trough in the mid-latitude westerlies has upper convergence on its west side and upper divergence on its east side. So, the upper convergent region of the ridge is N of Alex. Upper convergence leads to increasing pressures N of Alex, which means that Alex must now turn west in the face of rising surface pressures north of it. Alex cannot fight massive-scale upper air convergence and rising pressures to its N.
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Still don't see much movement. If you have movement loop, please post.
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583. Asta
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Quoting RecordSeason:
559:

Yes, I know, I've been watching since it left Africa, but where did the wave form before it hit Africa?


the wave did not hit Africa, lol.

Waves form over Africa. When you get a chance you can read these two blogs on tropical waves

Tracking Tropical Waves: Structure, Nature and Propagation

Tracking African Easterly Waves: Genesis

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Quoting Patrap:


Thats very kind indeed sarah.

Its been a good run here and I like sharing the info as well.

But Like Presslord...,

I may be going Up to the ether world here to the Portlight call.

Alex may be my last Live posting Storm.


Say it ain't so, Pat!
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Quoting Patrap:


Thats very kind indeed sarah.

Its been a good run here and I like sharing the info as well.

But Like Presslord...,

I may be going Up to the ether world here to the Portlight call.

Alex may be my last Live posting Storm.


Seriously? :(
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Quoting Unfriendly:


Say it ain't so!
ditto, Pat contributes some of the best stuff here.
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Quoting NCHurricane2009:


So I take it that the warm AMO and negative NAO this year make the ITCZ more north, and in general, reduce surface atmospheric pressure in the tropics.

In 2005, there were a lot of low pressure 'canes, and I know that year had a north ITCZ (Katrina's 905 mb pressure, and its 920 mb pressure at landfall lowest for a category 3 on record. Rita's 895 mb pressure. Wilma's 888 mb pressure). I am wondering if Alex's lower than normal pressure for cat 1 hurricane is a sign of more lower than normal pressure storms this year, and if the northward displacement in the ITCZ can be linked to this?


Yes and yes....1) the forecast for the 2010 hurricane season is lower than normal pressures (2-4 millibars below normal) which is significant. For much of June, pressures continue to be below normal for most parts of the ATL.

2) lower than normal pressures in the ATL (NH) as compared to the South Atlantic (SH) indicates that trades would have a tendency to converge further north (the ITCZ).
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Quoting txsweetpea:
Is it possible for Alex to go to "break thru " the ridge or whatecer alot of you said was guiding Alex and go north or are we SURE that Alex is going to make landfall in Mexico or south texas? Just wondering if Alex does become a cat 2-3 overnite could this happen?


The ridge is already starting to take control of Alex. Should steer the storm WNW, maybe due West. :)
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Quoting Patrap:


Thats very kind indeed sarah.

Its been a good run here and I like sharing the info as well.

But Like Presslord...,

I may be going Up to the ether world here to the Portlight call.

Alex may be my last Live posting Storm.


Say it ain't so!
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574. hercj
Quoting Gorty:
I am sure there will be another HH flight right?

0700Z
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573. 7544
hi all hmm nice wave about to come off of africa
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Quoting Patrap:


Thats very kind indeed sarah.

Its been a good run here and I like sharing the info as well.

But Like Presslord...,

I may be going Up to the ether world here to the Portlight call.

Alex may be my last Live posting Storm.
you will be missed around here. you do so many good things. guess it would be greedy to keep you all to ourselves:)
Member Since: September 10, 2008 Posts: 0 Comments: 1293
Is it possible for Alex to go to "break thru " the ridge or whatecer alot of you said was guiding Alex and go north or are we SURE that Alex is going to make landfall in Mexico or south texas? Just wondering if Alex does become a cat 2-3 overnite could this happen?
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Parallel GFS 156 hours

Nothing.

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Is it possible for Alex to go to "break thru " the ridge or whatecer alot of you said was guiding Alex and go north or are we SURE that Alex is going to make landfall in Mexico or south texas? Just wondering if Alex does become a cat 2-3 overnite could this happen?
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567. xcool
lol
Member Since: September 26, 2009 Posts: 2 Comments: 15670
566. Gorty
I am sure there will be another HH flight right?
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Quoting Drakoen:


Please refer to post 238 on page 5.


Do you really think I want to work that hard....j/k thanks for the info
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There is also the composite AHIPS 24 hr precipitation estimates. This one is valid 2010-06-29-12Z centered on TX.

I am out, good night all.
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Quoting Weather456:


The position of the ITCZ is normally determine by 1) the forcing of either trade winds (in 2009 the NE trades were stronger than the SE trades which resulted in a low lat ITCZ) and 2) surface pressures particularly in the NH. During a negative NAO the subtropical ridge is weaker than normal and so surface pressures are lower than normal, attracting the ITCZ (which is a low pressure trough) northwards. During warm AMOs, warmer than normal SSTs result in lower than normal pressures again, attracting the ITCZ northwards.


So I take it that the warm AMO and negative NAO this year make the ITCZ more north, and in general, reduce surface atmospheric pressure in the tropics.

In 2005, there were a lot of low pressure 'canes, and I know that year had a north ITCZ (Katrina's 905 mb pressure, and its 920 mb pressure at landfall lowest for a category 3 on record. Rita's 895 mb pressure. Wilma's 888 mb pressure). I am wondering if Alex's lower than normal pressure for cat 1 hurricane is a sign of more lower than normal pressure storms this year, and if the northward displacement in the ITCZ can be linked to this?
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Quoting help4u:
hwrf just soth of texas as a 118 mph hurricane.
NHC working without HH and storm 24-48 from landfall. If I ran that org it would never happen.
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old GFS is garbage!

About to get a big cell in SETX
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Quoting sarahjola:
well your observation is appreciated, and even though your not a met. you are still good with info and observations. i have noticed this over the time i have been on this site.:)


Thats very kind indeed sarah.

Its been a good run here and I like sharing the info as well.

But Like Presslord...,

I may be going Up to the ether world here to the Portlight call.

Alex may be my last Live posting Storm.
Member Since: Posts: Comments:
Quoting RecordSeason:
546:

My theory about 93L (now Alex,) is that it probably formed in the EPAC 3 or 4 months ago and circled the globe. It takes a long time to make a wave that big, after all.


double what?

Alex formed from a wave that emerged June 12.
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Quoting sarahjola:
well your observation is appreciated, and even though your not a met. you are still good with info and observations. i have noticed this over the time i have been on this site.:)


ditto
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The Top of the CoC is seen now on Brownsville Long Range if ya squint at the Lower Right around 5 o'clock on the circle edge.

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hwrf just soth of texas as a 118 mph hurricane.
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Quoting Patrap:


Hard to say as Im not a Met.



So I watch and observe what I see in Laymans terms mostly here.

well your observation is appreciated, and even though your not a met. you are still good with info and observations. i have noticed this over the time i have been on this site.:)
Member Since: September 10, 2008 Posts: 0 Comments: 1293
Quoting firecane:
Drak,

What are your thoughts on the earlier discussion of the weakness to the north possible contributing to a slow or stall in motion over the last few hours...


Please refer to post 238 on page 5.
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Quoting centex:
Hum I don't remember "col between the two" explanation for W turn than slow motion after ridge builds in.


What?
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549. hercj
Quoting Skyepony:
centex~ Oh.. why didn't the next scheduled flight leave early? They may a little but you just can't rip up the POD. I feel your frustration..only like 4 more hrs. That's a nap.

Ok I got that now. I was wondering how they would upload 4 hrs.
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548. Skyepony (Mod)
Quoting hercj:

Sky did they get out of BIX early is that what your saying?


I thought he asking why did they leave the storm early even if there was problems..
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GFS 00z

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Quoting NCHurricane2009:


You know, I was thinking the same too. I know in 2005 and warm AMO years that the ITCZ is displaced northward in general. Is the generally low surface pressures in tropical cyclones a sign of northward ITCZ pressure field? Does that mean more voriticity and hence more tropical cyclone potential?


The position of the ITCZ is normally determine by 1) the forcing of either trade winds (in 2009 the NE trades were stronger than the SE trades which resulted in a low lat ITCZ) and 2) surface pressures particularly in the NH. During a negative NAO the subtropical ridge is weaker than normal and so surface pressures are lower than normal, attracting the ITCZ (which is a low pressure trough) northwards. During warm AMOs, warmer than normal SSTs result in lower than normal pressures again, attracting the ITCZ northwards.
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Quoting TampaSpin:
Alex seems to be struggling to move because the big high to it East the Bermuda High wants it to go North....while the High to its North wants it to go west.....it is sorta sandwiched in between the to highs!
Is there a hole in the top of that sandwich?
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Is it possible for Alex to go to "break thru " the ridge or whatecer alot of you said was guiding Alex and go north or are we SURE that Alex is going to make landfall in Mexico or south texas? Just wondering if Alex does become a cat 2-3 overnite could this happen?
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543. jpsb
Quoting reedzone:


Thank you.
Quoting reedzone:


Thank you.
No thank you and the other experts here that really keep the interested public informed. I hate to think what in hurricane alley would be like without folks like you telling us joe sixpacks what is really going on. So thank you.
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Really guys? There is a strengthening cyclone just 24 hours from landfall with lives at stake, you're all holding a pissing match about the stake of the blog, and immaturity, and such? Take to the emails and quit whining about it here. There are many of us reading who don't give a toss about your personal disagreements.
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541. Skyepony (Mod)
centex~ Oh.. why didn't the next scheduled flight leave early? They may a little but you just can't rip up the POD. I feel your frustration..only like 4 more hrs. That's a nap.
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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.