Santa Ana winds ease; tropical wave nearing Puerto Rico could develop

By: Dr. Jeff Masters , 2:24 PM GMT on October 24, 2007

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A surface low pressure area has developed near 17.5N, 60.5W, about 150 miles east-northeast of the northernmost Lesser Antilles Islands. This morning's QuickSCAT pass showed an elongated circulation that is not well organized. Top winds were about 25 mph to the northeast of the circulation center. Winds in the northern Lesser Antilles Islands were less than 10 mph this morning, but pressures have been falling for the past two days. Satellite loops show little heavy thunderstorm activity--less than yesterday. However, this activity appears to be increasing just north of the circulation center this morning.

Wind shear has dropped to 10-20 knots in the region, and some slow development of this system is possible as it moves to the west at about 5 mph. This westward motion is forecast to bring the low over Puerto Rico Thursday night and Friday morning, then to a point between Haiti and Jamaica on Saturday. All of these islands can expect heavy rains during passage of this system. Both the ECMWF and NOGAPS models develop the disturbance into a tropical depression on Saturday near the southern coast of Haiti. The GFS models does not, because of high wind shear. All of the models forecast falling pressures and low wind shear over the Western Caribbean late this week and early next week, and it would not be a surprise to see a tropical depression form in the region. Today is the 2nd anniversary of Wilma's strike on South Florida, so powerful hurricanes are still a concern at this point in the season. Wunderblogger Mike Theiss has posted a blog today recounting his experiences in the eye of Wilma.

Heavy thunderstorm activity has increased in the central Caribbean south of Haiti this morning. There is some rotation evident at mid levels of the atmosphere in satellite loops, but QuikSCAT showed no evidence of a surface circulation in this morning's pass. This disturbance will need to be watched for development. Activity in the western Caribbean between the Yucatan Peninsula and Cuba is associated with a cold front.

California's fires
Surface maps show a high pressure system centered over Nevada and Utah. This high is weakening and moving eastward away from California. The clockwise flow of air around this high is still driving northeasterly Santa Ana winds over Southern California, but these winds are much weaker than yesterday. By Thursday, the Santa Ana winds will be gone, to be replaced by a weak flow of moist air off the ocean. The new weather pattern will bring increased humidity, cooler temperatures, and lighter winds, which should allow firefighters to gain the upper hand. The long range forecast shows light winds for Southern California for most of the coming week, but no rain, and not as much onshore ocean winds as firefighters would like to see.


Figure 1. Visible satellite images from Monday and Tuesday with satellite-derived particulate air pollution levels overlaid. Image credit: NASA and EPA.

Air quality
Air quality due to particulate matter continues to be awful in Southern California (Figure 1). Exceedances of the Federal air quality standards by more than a factor of two have occurred the past four days in both Los Angeles and San Diego. The air pollution problem is expected to linger for several days after the fires are out. The onshore winds that are expected to form will recirculate smoke that is over the ocean back over land. As seen in a vertical cross section of the smoke taken by NASA's Calipso satellite Monday (Figure 2), smoke from the fires has stayed confined to the lowest 1 km (1,000 meters) of the atmosphere over the ocean regions southwest of San Diego. The cold waters of the California Current creates stable air above it that resists moving upwards, keeping the pollution trapped near the surface. However, some of the smoke is expected to rotate clockwise along the California coast, moving back over the U.S. over the northern half of California Thursday and Friday. Trajectory forecasts indicate that this smoke will be lifted as it circulates back over the U.S, thanks to the lifting motion associated with the low pressure system approaching the Pacific Northwest. The smoke should color sunsets over much of Northern California and northern Nevada over the next few days, but should not cause significant pollution problems at the surface, since most of the smoke will be aloft.


Figure 2. Altitude of smoke as measured by NASA's Calipso satellite at 3:07 am PDT Monday Oct 22. Calipso uses a LIDAR (LIght Detection And Ranging) to detect particles suspended in the atmosphere. Lidar is like radar, except that it uses a visible light beam instead of a radar-wavelength beam. Image credit: NASA.

The University of Wisconsin's CIMSS group has another excellent blog on yesterday's fires, complete with satellite animations and detailed analysis.

San Francisco Climate Challenge
Today is the last day for San Francisco residents to sign up for the San Francisco Climate Challenge, an innovative contest designed to encourage residents to reduce energy usage. The content offers prizes up to $5000 for those residents able to reduce their energy consumption the most over the coming month. For more information, see the new Weather Underground climate page at http://www.wunderground.com/climate/.

Ricky Rood has posted a blog this morning on the ongoing Georgia/Southeast U.S. drought.

Jeff Masters

()
Erie (anvilhead)
Yet the fire was still miles away....
Erie

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633. NEwxguy
2:29 PM GMT on October 25, 2007
morning BAJA
Member Since: September 6, 2007 Posts: 875 Comments: 15639
632. BajaALemt
2:06 PM GMT on October 25, 2007
Morning folks :)
Member Since: September 25, 2007 Posts: 53 Comments: 8533
631. V26R
2:06 PM GMT on October 25, 2007
Buddies down on Antigua said that last night was the most calm and humid night there so far
Very strange no breezes, maybe the calm before the storm?
Member Since: July 20, 2006 Posts: 0 Comments: 1762
630. catastropheadjuster
2:06 PM GMT on October 25, 2007
NEW BLOG
Member Since: August 24, 2006 Posts: 21 Comments: 3657
629. V26R
2:03 PM GMT on October 25, 2007
Going to be an interesting series
Hope the wind isn't blowing too hard when they get to Denver!
Member Since: July 20, 2006 Posts: 0 Comments: 1762
628. IKE
2:01 PM GMT on October 25, 2007
Convection is firing over 90L.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
627. CaribBoy
1:59 PM GMT on October 25, 2007
Current weather here in St Barths in the Northern Leewards (18N63W)

Barometric pressure : 1007mb;
Cloudy sky with CB clouds to the north and east;
Light westerly winds with some gusts at time.
Member Since: October 6, 2007 Posts: 0 Comments: 5988
626. Ivansvrivr
1:58 PM GMT on October 25, 2007
V26R
Cat is still in her (indoor) tree snoozing. I'll let you know when she wakes up.
625. IKE
1:58 PM GMT on October 25, 2007
NEwxguy 8:56 AM CDT on October 25, 2007
617. V26R 1:53 PM GMT on October 25, 2007
As long as everything stays well south of us
NEWX
BTW Congrats on last nites Victory

Thanx,it was pretty ugly,should be a different story tonight.


Yeah...the SOX win this one by 5 runs vs. the 12 they won by last night.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
624. NEwxguy
1:58 PM GMT on October 25, 2007
619. IKE 1:56 PM GMT on October 25, 2007
V26R 8:53 AM CDT on October 25, 2007
As long as everything stays well south of us
NEWX
BTW Congrats on last nites Victory
The Red Sox are too good. A sweep is possible.

Its only the second game,but I think its a must game for the rockies tonight.
Member Since: September 6, 2007 Posts: 875 Comments: 15639
623. Floodman
1:58 PM GMT on October 25, 2007
618. IKE 8:55 AM CDT on October 25, 2007
Not sure I believe the BAM models of 90L going over DR/Haiti....that would tear it apart though.

SHIPS only goes up to 48 knots in 96 hours on 90L.



Given the steering, a miss of Hispaniola to the south would be more believable
Member Since: August 2, 2006 Posts: 10 Comments: 9922
622. quackquack
1:57 PM GMT on October 25, 2007
I thought we were done for the year.What are the feeling of 90 becomeing anything?
621. NEwxguy
1:56 PM GMT on October 25, 2007
617. V26R 1:53 PM GMT on October 25, 2007
As long as everything stays well south of us
NEWX
BTW Congrats on last nites Victory

Thanx,it was pretty ugly,should be a different story tonight.
Member Since: September 6, 2007 Posts: 875 Comments: 15639
620. Ivansvrivr
1:56 PM GMT on October 25, 2007
I agree with storm's analysis. Topography of Belize/Honduras also supports cyclonic winds during daytime. Winds head for shore during daytime. Belize faces east, Honduras north. almost perfect 90% turn. Thats half a closed low by itself. big part of why that area supports early and late season development. BBL!
619. IKE
1:56 PM GMT on October 25, 2007
V26R 8:53 AM CDT on October 25, 2007
As long as everything stays well south of us
NEWX
BTW Congrats on last nites Victory
The Red Sox are too good. A sweep is possible.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
618. IKE
1:55 PM GMT on October 25, 2007
Not sure I believe the BAM models of 90L going over DR/Haiti....that would tear it apart though.

SHIPS only goes up to 48 knots in 96 hours on 90L.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
617. V26R
1:53 PM GMT on October 25, 2007
As long as everything stays well south of us
NEWX
BTW Congrats on last nites Victory
Member Since: July 20, 2006 Posts: 0 Comments: 1762
616. NEwxguy
1:52 PM GMT on October 25, 2007
morning,v26,coffed and donuts mix well with invests this morning,looks interesting the coming week.
Member Since: September 6, 2007 Posts: 875 Comments: 15639
615. V26R
1:52 PM GMT on October 25, 2007
Figures MLC
Thats two days in a row
Member Since: July 20, 2006 Posts: 0 Comments: 1762
614. moonlightcowboy
1:51 PM GMT on October 25, 2007


...a miss apparently.
Member Since: July 9, 2006 Posts: 184 Comments: 29595
613. V26R
1:50 PM GMT on October 25, 2007
Ivan what is Ivans Cat saying about 90L this morning???
Member Since: July 20, 2006 Posts: 0 Comments: 1762
612. V26R
1:48 PM GMT on October 25, 2007
Anyone know if QUICKSAT hit 90L this morning?
Member Since: July 20, 2006 Posts: 0 Comments: 1762
611. Ivansvrivr
1:48 PM GMT on October 25, 2007
"Wilma of 2007?"

Ike ssts arent warm enough for a wilma. More like an Irene though.
Wilma also formed farther west, had lots of time to strengthen due to slow erratic movement in Carrib. Irene formed along a stalled cold front under SW shear. Moved NE fast enough that relative shear was nullified. Strengthened over everglades.
610. moonlightcowboy
1:47 PM GMT on October 25, 2007
NRAamy, the fires are dreadful and hope that all of you get some relief there soon! Stay safe.
Member Since: July 9, 2006 Posts: 184 Comments: 29595
609. flaboyinga
1:47 PM GMT on October 25, 2007
Baroness, I was hooked on pecan sandies until my bride pointed out the cholesteral numbers and put the "spoken word" on me.
608. cattlebaroness
1:44 PM GMT on October 25, 2007
Morning all. Flaboy, I love those cookies! Flood what in the heck do you do for a living that takes you to all of those exotic places. Remember I was born and raised in FW.

So we have another invest? Ohh my.
607. flaboyinga
1:43 PM GMT on October 25, 2007
605. NEwxguy 9:41 AM EDT on October 25, 2007 Hide this comment.
So we're back to the donuts this morning.



Nah, that was on the previous page.
606. V26R
1:43 PM GMT on October 25, 2007
Hey NEWX What type of morning would it be without them???
Member Since: July 20, 2006 Posts: 0 Comments: 1762
605. NEwxguy
1:41 PM GMT on October 25, 2007
So we're back to the donuts this morning.
Member Since: September 6, 2007 Posts: 875 Comments: 15639
604. flaboyinga
1:40 PM GMT on October 25, 2007
601. Orcasystems 9:36 AM EDT on October 25, 2007 Hide this comment.
600. flaboyinga 1:34 PM GMT on October 25, 2007
Orca, I found another link to the Navy. Yhis is probably better than the other one.
******************************

Thank you :)


Click on models on the left side and there's some interesting stuff there.
603. cantoriesnumber1fan
1:40 PM GMT on October 25, 2007
Looks to me on the last few satellite loops the shear is relaxing a bit
602. CaribBoy
1:37 PM GMT on October 25, 2007
Good Morning all

Here is a closer view of 90L

Member Since: October 6, 2007 Posts: 0 Comments: 5988
601. Orcasystems
1:36 PM GMT on October 25, 2007
600. flaboyinga 1:34 PM GMT on October 25, 2007
Orca, I found another link to the Navy. Yhis is probably better than the other one.
******************************

Thank you :)
Member Since: October 1, 2007 Posts: 81 Comments: 26511
600. flaboyinga
1:34 PM GMT on October 25, 2007
Orca, I found another link to the Navy. Yhis is probably better than the other one.


Link
598. flaboyinga
1:31 PM GMT on October 25, 2007
596. V26R 9:28 AM EDT on October 25, 2007 Hide this comment.
Morning All
Whos got the donuts???


I got my danish wedding cookies. (no cholesterol) I could stick a few in an envelope. lol
597. NRAamy
1:30 PM GMT on October 25, 2007
Correction: The Irvine, Calif. fires are only 30% contained....fires are spreading into the Cleveland National Forest....

Calgon, take me away....
Member Since: January 24, 2007 Posts: 317 Comments: 31946
596. V26R
1:28 PM GMT on October 25, 2007
Morning All
Whos got the donuts???
Member Since: July 20, 2006 Posts: 0 Comments: 1762
595. flaboyinga
1:26 PM GMT on October 25, 2007
Orca, try this.

Link
594. flaboyinga
1:23 PM GMT on October 25, 2007
590. StormW 9:18 AM EDT on October 25, 2007 Hide this comment.
583. flaboyinga 9:07 AM EDT on October 25, 2007
Storm, I've been watching a circulation that recently came off of central america that is now almost due south of the western tip of Cuber. Do you think there's any chance that will develope? I have only looked at it on the WV loops.



At this time, I don't feel it will...unless it pulls a track like Lenny did a few years ago, it should stay under some fairly decent shear. I'm gonna watch it though as crazy as this season's been.

It doesn't look like much right now, but the shear is down and the water is still warm and there seems to be plenty of moisture available to it. Kinda makes me wonder what it'll do.
593. moonlightcowboy
1:23 PM GMT on October 25, 2007
Good morning, StormW, all.

Yeah, shear still rules. The ull to its ne is also pulling convection away from the low. I doubt development is really possible. If at all, would probably take place further west as the wave tracks into the wCarib.
Member Since: July 9, 2006 Posts: 184 Comments: 29595
592. cantoriesnumber1fan
1:22 PM GMT on October 25, 2007
Which of the 3 BAMM models has most credibility?
591. Orcasystems
1:18 PM GMT on October 25, 2007
jphurricane2006

Where would I find a link for the Navy site?
Member Since: October 1, 2007 Posts: 81 Comments: 26511
589. flaboyinga
1:16 PM GMT on October 25, 2007
If anyone missed the photos Patrap and others posted of the Canadian Company's air tankers the link is below. They are something to see. If the wind and other flying conditions will cooperate, Calif. is gonna get some rain on their fires.



Link
588. beell
1:15 PM GMT on October 25, 2007
Good Morning Worldville. Houstonians are missing Summer already.

Gotta like that area at 18N 84W.
Member Since: September 11, 2007 Posts: 141 Comments: 16265
587. NRAamy
1:11 PM GMT on October 25, 2007
Morning Amy!

You doin' OK?


I need a new nose....too much smoke...

Member Since: January 24, 2007 Posts: 317 Comments: 31946
586. Floodman
1:10 PM GMT on October 25, 2007
Looks as though the CV feature from yesterday has lost a good deal of it's convection; there does appear to be another wave just off the African coast:



EUMETSAT
Member Since: August 2, 2006 Posts: 10 Comments: 9922
585. sanflee76
1:09 PM GMT on October 25, 2007
jp, where is 90L and what is the preliminary track?
584. NRAamy
1:08 PM GMT on October 25, 2007
Per local ABC news:

Irvine, Calif. fires are now only 40% contained....$70,000 reward offered for info leading to the arrest of the arsonist....
Member Since: January 24, 2007 Posts: 317 Comments: 31946
583. flaboyinga
1:07 PM GMT on October 25, 2007
Storm, I've been watching a circulation that recently came off of central america that is now almost due south of the western tip of Cuber. Do you think there's any chance that will develope? I have only looked at it on the WV loops.

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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.

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