Hurricane warnings for Baja; 94L forming spiral bands

By: Dr. Jeff Masters , 3:36 PM GMT on August 31, 2009

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Hurricane warnings are in effect for the southern tip of Mexico's Baja Peninsula, where powerful Hurricane Jimena is expected to make landfall Tuesday night or Wednesday morning. The hurricane is in an environment with low wind shear, 5 - 10 knots, and warm Sea Surface Temperatures (SSTs), 30°C. Shear is expected to remain low, and SSTs will decline to 28°C with a corresponding decrease in total oceanic heat content between now and landfall, and these conditions should mean that Jimena will be a Category 3 or 4 hurricane at landfall. Outer rain-bands of the hurricane will be appearing on Los Cabos radar soon, though the Mexican Weather Service web site has been hard to reach today. The computer models are split, with one camp calling for a landfall in southern Baja, and the other camp calling for landfall farther north near central Baja. The official NHC forecast splits the difference between these two solutions, and landfall could occur anywhere along a long stretch of the Baja coast. At this point, the UKMET model's solution taking Jimena westward out to sea is being discounted, since it is an outlier.

After Jimena makes initial landfall on Baja, it will cross over the Gulf of California and make landfall on Mainland Mexico. Depending upon how up along the coast this second landfall occurs, Arizona may receive moisture from Jimena late this week that will be capable of causing flooding rains.


Figure 1. Image of Hurricane Jimena taken by NASA'a MODIS instrument at 2020 UTC Sunday, 8/30/09.

Invest 94L
The well-organized tropical wave (94L) near 14.5N, 52W, about 500 miles east of the central Lesser Antilles Islands, continues to be a threat to develop into a tropical depression. Visible satellite imagery and this morning's QuikSCAT pass do not show a surface circulation yet, though 94L does have a large envelope of moisture and some modest heavy thunderstorm activity. QuikSCAT noted winds up to 30 mph. Water vapor satellite loops show that 94L has moistened the region surrounding it considerably, and dry air from the Saharan Air Layer is not a major impediment to development. Wind shear is a low 5 - 10 knots, and the ocean temperature are a moderately warm 28°C. Visible satellite loops over the past two hours show low-level spiral bands developing on 94L's northeast side, and I give a 70% chance the Hurricane Hunters will find a tropical depression or tropical storm on Tuesday when they investigate 94L.


Figure 2. Morning satellite image of 94L, showing low-level spiral bands developing on the northeast side.

The center of 94L probably passed over Buoy 41040, located at 14.5N, 53W over the past hour. Winds blew northeasterly early this morning, then went calm, then shifted to southerly late this morning. The winds were less than 10 knots during the center passage, so the circulation of 94L is not yet well-defined. The pressure fell significantly as 94L moved over the buoy (seen only after one removes the wiggles due to daily atmospheric tide effect present in the tropics). 94L will appear on Martinique radar on Tuesday.

The forecast for 94L
Shear will remain low, 5 -10 knots, over the next 5 days, SSTs will be warm, in the 28 - 29°C range, and dry air should have only a minor inhibiting effect, so I can't see anything that will prevent 94L from developing into a tropical depression over the next 1 - 2 days. The HWRF model develops 94L into a hurricane 4 days from now, as does the SHIPS intensity model, but other models, such as the GFDL, ECMWF, and GFS, do not develop 94L at all.

Model solutions for the track of 94L are divergent. Water vapor satellite loops show two upper-level lows to the north and northwest of 94L that are pulling the storm to the west-northwest, and 94L's motion is expected to range between the west-northwest and northwest over the next three days. By Tuesday, 94L will slow down from its current 15 mph forward speed to about 10 mph. Most of the models predict that the steering influence of the upper-level lows will pull 94L far enough north that the storm will miss the Lesser Antilles, with a closest approach occurring Wednesday and Thursday. However, the ECMWF and HWRF models have 94L passing within 200 miles of the islands, and the northern Lesser Antilles may experience tropical storm conditions on Thursday.

At the longer ranges, the fate of 94L is highly uncertain. The Canadian model turns 94L to the north near Bermuda, then out to sea, while the NOGAPS model foresees a threat to the U.S. East Coast early next week. Both of these solutions are believable. The Hurricane Hunters are scheduled to make their first flight into 94L on Tuesday afternoon at 2pm EDT.

Elsewhere in the Atlantic
The remains of an old cold front are bringing cloudiness and showers to the northern Gulf of Mexico and waters offshore North and South Carolina. The GFS and NAM models indicate an area of low pressure may develop along this old front near the Florida Panhandle or off the coast of North Carolina by Thursday. However, such a low may be extratropical and not tropical.

My next post will be between 3 - 5pm this afternoon.

Jeff Masters

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Quoting Patrap:
94L has only 1 CoC..as shown here.
Anything showing other Ive failed to note,anywhere,..southerly transient winds can be found in Meso vortices circulating around the Mean center,but none of note as far as Ive seen.

94L wind Field from 1200 UTC


thanks for that image. very useful!
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if you live in the central to northern islands you should be preparing for a storm.Most systems that are at or below 15n past 50w and moving west to WNW have some impact on the islands
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Quoting Dr. Masters... re: 94L this morning
".... this mornings Quikscat pass do not have a surface circulation as yet".
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Quoting BrockBerlin:


I will give you that a GOM scenario while unlikely, is a little more plausible today then say 2 days ago, but I would still say east coaster or out to sea are considerably more likely.


ok, well like I said. I am no expert....I guess time will tell.
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Quoting EarthMuffin:


I think I follow hurricanes because every few years, an extratropical storm will make its way up from the Gulf and affect us here in NE Ohio. This happened last September...we had 40+ MPH sustained winds with gusts to 80MPH. Ohio gets everyone's leftovers.

*Back to lurking*


Thats how it starts for many of us its a passion that we have always had its in our blood so to speak and if you here then i think its in yours too thats why you gain knowledge on here to where one day you can contribute on here and who knows maybe make it a career
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Comne on NHC....94L is already a storm!
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Quoting louisianaboy444:


I think that Herbert box or whatever its called is a bunch of bull...its basically like a climatology model and how often are those correct

i was being facetious. The herbert box was an observation made that many storms that pass through the box tend to strike S. Florida.
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With the GFS coming on board, KIND OF, the GFDL should start to pick up on it as well.
Quoting gator23:

and closer to the box of doom


I think that Herbert box or whatever its called is a bunch of bull...its basically like a climatology model and how often are those correct
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Quoting louisianaboy444:
Hi folks...I'm technically new here, though I've lurked on and off for a couple years. I lack any formal training in the field of meteorology, so I tend to silently observe, rather than interject my uneducated opinions. I live in Ohio, after all, we arent exactly known for hurricanes...

Anyway, now you've been acquainted with yet another one of the lurkers. I'll try to keep my mouth shut unless I'm absolutely certain I have an answer.


No join in the conversation thats how you learn don't be afraid to ask questions i'm current a Meteorology major at ULM about 2 years ahead of my classes when it comes to knowledge thanks to this blog...welcome aboard


I think I follow hurricanes because every few years, an extratropical storm will make its way up from the Gulf and affect us here in NE Ohio. This happened last September...we had 40+ MPH sustained winds with gusts to 80MPH. Ohio gets everyone's leftovers.

*Back to lurking*
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Seems the 12Z GFS loses the 850 mb vortex after 132 hours north of Haiti.


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The interesting thing is our local Met(Channel 6 Orlando)is saying that the sheer is high and it will cause it to have trouble forming. He also said he just had an update and the models are trending more west. Weird, I guess somebody should tell this guy to look again!
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Quoting WxLogic:
Well... based on the 12Z GFS run and NAM that there's more bias towards the ECMWF solution of more ridging on the W ATL / US E coast... so giving a little break to the unusual trough train.

Will remain to be seen if this trend continues... but one thing seems quite possible and is that 94L will definitely be a lot closer to the northern portion of the Leeward Islands than Bill and even closer to the northern parts of the Greater Antilles.

and closer to the box of doom
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so, from what i am reading above it seems that this will be an east coaster or out to sea....Is it me? I just don't feel it will do that. Maybe I am wrong, I mean - I am not a weather expert.
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90. IKE
Quoting gator23:


well doctor masters does anyway


I hear ya.




Quoting bystander:
Link

Is what they are saying in this article true? Seems to contradict Dr. M.


Yeah it does, but this contradicts that linked article....San Juan morning discussion...

".PREV DISCUSSION... /ISSUED 430 AM AST MON AUG 31 2009/

SYNOPSIS...TUTT LOW NORTH OF PR WILL DRIFT TO THE WEST SOUTHWEST
AND SETTLE OVR HISPANIOLA BY TONIGHT. UPPER LVL RIDGE OVR THE TROP
ATLC WILL BUILD WWD INTO THE ERN CARIBBEAN TUE THROUGH WED AND
MAINTAIN A SUBSIDENT PATTERN ACROSS THE REGION. MEANWHILE...BROAD
AREA OF LOW PRES ALONG 50W THIS MORNING WILL TRACK SLOWLY TO THE
WNW OVER THE NEXT SVRL DAYS AND MOVE ACROSS THE REGIONAL WATERS
THU NIGHT.

DISCUSSION...MODELS SHOW TUTT LOW DRIFTING TO WEST SOUTHWEST WITH
SUBSIDENCE INCREASING TOWARD THE END OF THE DAY. HAVE TRENDED
POPS DOWNWARD FOR TODAY BUT STILL ANTICIPATING ISOLD/SCT STRONG
CONVECTION OVR WRN PR THIS AFTERNOON. SUBSIDENCE/DRYING INCREASES
ON TUE AND HOLDS THROUGH WED AS MID-UPPER LVL RIDGING BUILDS FROM
THE EAST FURTHER LIMITING PRECIP CHANCES. SFC WINDS TURN MORE TO
THE NORTHEAST SO HAVE LIMIT POPS TO THE SOUTHWEST CORNER OF PR."
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Link
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Well... based on the 12Z GFS run and NAM that there's more bias towards the ECMWF solution of more ridging on the W ATL / US E coast... so giving a little break to the unusual trough train.

Will remain to be seen if this trend continues... but one thing seems quite possible and is that 94L will definitely be a lot closer to the northern portion of the Leeward Islands than Bill and even closer to the northern parts of the Greater Antilles.
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Quoting CaribBoy:


Is based on these surface observations... is the center further south and west than previouslt thought?

That big blob of convection is more of a MLC imo, the possible LLC is around 13.3N/56W, looks at visible floater loop.
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Quoting BrockBerlin:


ULM= University of Louisiana at Monroe?


Yes sir...i am also a member of the national AMS
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Quoting TheCaneWhisperer:


I am actually in the low shear camp. No need for explanation here, I fully understand. I also understand that things can change instantly and there is never a 100% or 0% probability.


Yep. Never know how things will end up materializing until it happens.
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Quoting JRRP:

to me looks like 14.9n 54w


...that would not be good for people down the road
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Quoting P451:


Maybe this will help: 5 day loop.




Have a good afternoon, everyone.


That's a good visualization.
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Quoting IKE:


Easy to answer....their wrong!


I think that with the initial motion being wnw-nw and the fact that the shear is expected to move more west with the storm, and the anti-cyclone, that all of these work together, to show lower shear than the maps are showing right now. just a guess
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78. JRRP
Quoting StSimonsIslandGAGuy:
Looks like 94L is at 15.0N 52.1W

to me looks like 14.9n 54w
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Quoting EarthMuffin:
Hi folks...I'm technically new here, though I've lurked on and off for a couple years. I lack any formal training in the field of meteorology, so I tend to silently observe, rather than interject my uneducated opinions. I live in Ohio, after all, we arent exactly known for hurricanes...

Anyway, now you've been acquainted with yet another one of the lurkers. I'll try to keep my mouth shut unless I'm absolutely certain I have an answer.


Welcome! All opinions are valued as this is a place to learn. Feel free to speak up and be wrong sometimes, even the pro's are from time to time. The only thing certain in the tropics is uncertainty.
Hi folks...I'm technically new here, though I've lurked on and off for a couple years. I lack any formal training in the field of meteorology, so I tend to silently observe, rather than interject my uneducated opinions. I live in Ohio, after all, we arent exactly known for hurricanes...

Anyway, now you've been acquainted with yet another one of the lurkers. I'll try to keep my mouth shut unless I'm absolutely certain I have an answer.


No join in the conversation thats how you learn don't be afraid to ask questions i'm current a Meteorology major at ULM about 2 years ahead of my classes when it comes to knowledge thanks to this blog...welcome aboard
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I am beginning to think that 94L has a greater chance of ending in t GOMEX which means I might not go aout to sea as scheduled. There is chat about that possibility over here at the shipyard already, the navy and the USCG are keeping a close eye at 94L as well. I Might eat the crow (fried please) but I am starting to think that this will end up in the GOMEX there is too much chatter at work.
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Quoting P451:
I want to repost a couple of things because I think it's of value to anyone who doesn't see the older blog.

===

14.600 N 56.201 W (1436'0" N 5612'2" W) - 41001 Link






===




Buoy 41040 Link - Wind just shifted from NE to S.

14.477 N 53.008 W (1428'38" N 530'28" W)









=====

Alright, speculate away what this means in term of a COC.



based on these surface observations... is the center further south and west than previouslt thought?
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the most believable of all the forecast models [NOGAPS] predicts
a possible EAST COAST US landfall unless homeland security
intervenes with alittle trough enhancement action. [laughs]

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Quoting P451:


Maybe this will help: 5 day loop.


5 day loop of wind shear tendencies

link
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Quoting Seastep:


That 30 knots IS the anticyclone. Done mentioning it. If the L moves out from under that, then yes, shear looks like it would be a problem.

Look at the "thin" lines and arrows.

Link



Thanks for breaking it down for me; I see it now.... :)
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Link

Is what they are saying in this article true? Seems to contradict Dr. M.
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The Anticyclone above will shield the shear away and give this storm good outflow i agree with the Doc i don't see any inhibiting factors except if it were to take a sudden turn southward and go over the islands and mountains but that is not likely tohappen based on current steer maps...The ridging shown by many models 7 days from now makes me have a bad feeling about this storm hopefully a weakness can sneak in there.....
Hows everyone today?
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Hi folks...I'm technically new here, though I've lurked on and off for a couple years. I lack any formal training in the field of meteorology, so I tend to silently observe, rather than interject my uneducated opinions. I live in Ohio, after all, we arent exactly known for hurricanes...

Anyway, now you've been acquainted with yet another one of the lurkers. I'll try to keep my mouth shut unless I'm absolutely certain I have an answer.
Member Since: Posts: Comments:
Quoting IKE:


What I see is an invest that has a high-pressure system near to where the COC is at. Yesterday I wondered too about the excessive shear that is west and north of 94L. Others on here(yesterday), were saying the high and 94L would move in tandem.

Now Dr. Masters and Accuweather both say the same...that shear will remain low for the next several days. I'll take them at their words. They have a lot more knowledge then I do concerning the tropics.


well doctor masters does anyway
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Quoting BrockBerlin:
Yeah Sea in that graphic it looks to be directly overhead, but the question is will they move in tandem, and Dr.Masters seems to believe they will, and I defer to his knowledge, in that matter.


If you go here and change the "field" drop down to "800-200 shear," you can step through the shear forecast. Hit the + and not "forward." I for one can't follow the shear forecast when it's animated. Way too much on the screen.

I use GFS.

You can see the anti-cyclone (clockwise wind pattern) and how it is forecast to follow along with 94L as you step through. Also can visualize how the strong shear (yellows-reds) follows out in front.
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94L has only 1 CoC..as shown here.
Anything showing other Ive failed to note,anywhere,..southerly transient winds can be found in Meso vortices circulating around the Mean center,but none of note as far as Ive seen.

94L wind Field from 1200 UTC
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Quoting hurricanehanna:
I would think if it slows down to 10mph, and putting it possibly near the Northern Lesser Antilles around Thursday, it could be the weekend before we get a good handle on which way it will go.


I agree with this...
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Quoting weathermanwannabe:


Thanks; so basically, if I read the chart correctly, that 30-40 knot sheer area will "step aisde" as the system moves onward...If that it indeed the case, then we should expect a TD/Storm by tommorow and, then, the models can get a better handle on the future track.


Yes as long as the anticyclone is there it acts as a buffer to the shear.
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Quoting mikatnight:


I wonder if part of the reason is distance on these maps is deceiving, and is the shear moving along with the wave?


Hmmm. Your on the right track. 94L is moving in tandem with its surrounding environment. The "shear" is currently aiding outflow for the disturbance. Look at a large view satellite loop and you will see this better. Happy Hunting!
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Quoting Seastep:


That 30 knots IS the anticyclone. Done mentioning it. If the L moves out from under that, then yes, shear looks like it would be a problem.

Look at the "thin" lines and arrows.

Link



I am actually in the low shear camp. No need for explanation here, I fully understand. I also understand that things can change instantly and there is never a 100% or 0% probability.

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About JeffMasters

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.