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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Interesting update....guess looks can be deceiving.
Member Since: September 5, 2007 Posts: 0 Comments: 3488
94L's center is still broad
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354. IKE
CONDITIONS ARE MARGINALLY
FAVORABLE FOR THIS SYSTEM TO BECOME A TROPICAL DEPRESSION DURING
THE NEXT DAY OR SO AS IT MOVES WEST-NORTHWESTWARD AT AROUND 15 MPH.


"Marginally favorable".....translated....shear.
Member Since: June 9, 2005 Posts: 23 Comments: 37860
94L RGB

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Not even a TD yet as of 2pm TWO
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Thats more like it...You can see the shear zone this thing is heading into right ahead of it.In the order of 25-30kts.
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Quoting Grothar:


We who live in the "F" state hope so too! As well as our friends in the whole caribbean and point east and west

After the year the USA has had with the economy, the LAST thing we need is a Cat 3 or 4 hurricane adding insult to injury! I would encourage everyone in the Carribean and up and down the Atlantic Seaboard to keep their eyes on 94L! Even during an El Nino cycle, there will be at least 2 or 3 Cat 3 or bigger storms! As much as we love to see hurricanes grow, none of us wants to see the loss of life and/or property anywhere!
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Quoting TreasureCoastFl:

I'm still confused about the sheer ahead of it. if the sheer is there, as some believe, and stronger than Dr Masters posted wouldn't it tear it apart?
time will tell...
it has an anticyclone over it so sheer will be low
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ABNT20 KNHC 311755
TWOAT
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
200 PM EDT MON AUG 31 2009

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

SHOWERS AND THUNDERSTORMS ASSOCIATED WITH A BROAD AREA OF LOW
PRESSURE LOCATED ABOUT 500 MILES EAST OF THE LESSER ANTILLES
CONTINUE TO SHOW SIGNS OF ORGANIZATION...HOWEVER THERE IS NO
WELL-DEFINED SURFACE CIRCULATION CENTER. CONDITIONS ARE MARGINALLY
FAVORABLE FOR THIS SYSTEM TO BECOME A TROPICAL DEPRESSION DURING
THE NEXT DAY OR SO AS IT MOVES WEST-NORTHWESTWARD AT AROUND 15 MPH.
THERE IS A HIGH CHANCE...GREATER THAN 50 PERCENT...OF TROPICAL
CYCLONE FORMATION IN THIS AREA DURING THE NEXT 48 HOURS. INTERESTS
IN THE LESSER ANTILLES SHOULD MONITOR THE PROGRESS OF THIS SYSTEM.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.

$$
FORECASTER PASCH
Member Since: August 11, 2008 Posts: 0 Comments: 2315
Quoting DaytonaBeachWatcher:

Only 2 reasons i can think of to have a floater somewhere. 1. there is something there worth watching. 2. the floater was there before watching something that is gone now and no need to move it until there is something to move it to.


Good point, could be a hangover floater from Danny, goodness knows he sat around in that area for long enough!
Member Since: Posts: Comments:
345. IKE
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
200 PM EDT MON AUG 31 2009

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

SHOWERS AND THUNDERSTORMS ASSOCIATED WITH A BROAD AREA OF LOW
PRESSURE LOCATED ABOUT 500 MILES EAST OF THE LESSER ANTILLES
CONTINUE TO SHOW SIGNS OF ORGANIZATION...HOWEVER THERE IS NO
WELL-DEFINED SURFACE CIRCULATION CENTER. CONDITIONS ARE MARGINALLY
FAVORABLE FOR THIS SYSTEM TO BECOME A TROPICAL DEPRESSION DURING
THE NEXT DAY OR SO AS IT MOVES WEST-NORTHWESTWARD AT AROUND 15 MPH.
THERE IS A HIGH CHANCE...GREATER THAN 50 PERCENT...OF TROPICAL
CYCLONE FORMATION IN THIS AREA DURING THE NEXT 48 HOURS. INTERESTS
IN THE LESSER ANTILLES SHOULD MONITOR THE PROGRESS OF THIS SYSTEM.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.

$$
FORECASTER PASCH
Member Since: June 9, 2005 Posts: 23 Comments: 37860
This Invest looks like a tropical storm already!!! just name it already... it makes the situation so much easier on all of us, it looks to have a llc already, or almost there
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Non-tasked recon mission over the Bahamas now.

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Member Since: June 9, 2007 Posts: 4 Comments: 15952
thank you 456. very well done.
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Quoting InTheCone:


Thanks, that's what I thought, but it does seem odd to have a floater on it.

Only 2 reasons i can think of to have a floater somewhere. 1. there is something there worth watching. 2. the floater was there before watching something that is gone now and no need to move it until there is something to move it to.
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Quoting Chicklit:
Where's Skyepony? He's really good at posting HH reports.


Skyepony is a Lady and I made that mistake for a year doing the same.

Shes a Great blogger and Astro Photographer..too.

Check out her wunderblog for recon and Other reports.

And she knows her Met,Tropically as well.

Check out her Shuttle Pic from the other night.

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Quoting Seastep:


What kind of winds are they finding?


I haven't looked through all of the obs, on that pass SFMR had 114 kt.
Member Since: September 23, 2005 Posts: 15 Comments: 11512
Quoting stormsurge39:
We should all listen to the ones that know what there talking about 456, StormW, kman Tampa spin, just a few ex. Until 94L has a closed low and is at least a TD, these models are crap!!!
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Quoting hurricane23:


No reason at all...ULL just spinning there.


Thanks, that's what I thought, but it does seem odd to have a floater on it.
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Looking at the 94L rainbow image (mistake) it looked like the ball of convection was centered on the COC but after looking at several visible satellite presentations I see what CCHS weatherman said earlier about the COC being on the west side of the convection. On the last couple frames it looked like it might have taken a slight northerly jog but what looks to actually be happening is the convection on the left side and right side is trying to wrap around the COC and in doing so altering the shape of the ball of convection making it look like northerly movement. The COC actually looks to be moving due west or maybe slightly south of west. Any thoughts on this? I'd like to get some feedback.
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330. LBAR
Quoting stormpetrol:
Will it go directly to Erika at 2 pm?


I think so. I am curious as to why this isn't an official depression yet, but we're naming extra-tropical systems...like Danny. Whatevs. Just beware if you're in the Bahamas. Leave Freeport alone, Erica! :(
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Quoting nrtiwlnvragn:
Recon just found the center of Jimena.


17:37:30Z 18.117N 108.917W 696.5 mb
(~ 20.57 inHg) 2,589 meters
(~ 8,494 feet) 935.7 mb
(~ 27.63 inHg)


What kind of winds are they finding?
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Quoting InTheCone:
RAMSDIS also has a floater over the area near the Bahamas. Wonder why?


No reason at all...ULL just spinning there.
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Recon just found the center of Jimena.


17:37:30Z 18.117N 108.917W 696.5 mb
(~ 20.57 inHg) 2,589 meters
(~ 8,494 feet) 935.7 mb
(~ 27.63 inHg)
Member Since: September 23, 2005 Posts: 15 Comments: 11512
RAMSDIS also has a floater over the area near the Bahamas. Wonder why?
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Sorry to ask something that was probably already asked - is HH still going out to 94L tomorrow?
Member Since: September 5, 2007 Posts: 0 Comments: 3488
Quoting fire635:


12z GFDL = obviously wrong There is NO way this system is going Poof anytime soon. I think the GFDL will initialize on it when it finally develops its LLC

I'm still confused about the sheer ahead of it. if the sheer is there, as some believe, and stronger than Dr Masters posted wouldn't it tear it apart?
time will tell...
Member Since: August 18, 2008 Posts: 0 Comments: 474
Quoting stormpetrol:
Will it go directly to Erika at 2 pm?


I don't believe so.......
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How long is the high pressure supposed to last once 94L gets N of the Islands?
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Quoting btwntx08:

throw thatcmodel in the trash for now i dont expect that imo


Depends which model you like...There is clearly 30kts of shear just ahead of this system which its gonna run right into.
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RAMSDIS center fix:

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Quoting truecajun:


could you link me to it. i'm just back from lunch.


LINK

I added a September track maps of storms occuring in the month between 1886 and 2006.
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Quoting Grothar:


This is the 126 hour HWRF forecast. Looks scary, but most agree it may be a little over-done. Most agree, at this time, a CAT 4 may be unlikely. Just showing a graphic, not endorsing it. Got to be careful on the blog.


When you look at that graphic you need to realize that is not surface winds. In that case it is 900 mb. For that model cycle at 126 hours, the surface wind is 99 kt, not the 128 kt shown on the graphic. Still 99 kt is a strong hurricane.
Member Since: September 23, 2005 Posts: 15 Comments: 11512
Regardless of where 94L may end up, and in what form, all interests in the Bahamas and Florida/Gulf/SE need to keep an eye on it towards the end of the week before you make elaborate plans/reservations on the Coast for Labor Day Weekend....Yuck.
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Quoting hurricane23:
12z GFDL=Poof


12z GFDL = obviously wrong There is NO way this system is going Poof anytime soon. I think the GFDL will initialize on it when it finally develops its LLC
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RAMSDIS just started a floater on 94L
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Will it go directly to Erika at 2 pm?
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Close up on the center:

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12z GFDL=Poof
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Quoting Drakoen:
As the system moves to the northwest conditions are forecast to become more favorable for development. Right now it is getting shear. 94L has the classic shear tropical cyclone appearance.


This may be why the HWRF keeps the system weak and then at the end of the run blows it up.
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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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