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 FLWeatherFreak91:
That isn't a guarantee, so don't take the chance of causing people to turn the other cheek.


true, but then again is anything in a weather a guarantee?
Member Since: September 6, 2007 Posts: 0 Comments: 6704
The early models (with the exception of CLIPs) are all south of the extrapolation line (purple) ... which points toward S/N Carolina.

You can see the research mission entering from the upper left.



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404. 7544
hmm the bahamma wave is getting interesting at this hour could it form
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Quoting VAbeachhurricanes:


its never going to enter it
Why?
Evening all from Spain!

I've got a question... I've been lonking for climatological data of the most powerful hurricanes in the EPAC, and I have noticed that there haven't been any category 5. Really, is it? only 4 category 4 hurricanes since 1950, excluding JIMENA?
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Quoting sporteguy03:
with all being said though if the shear was that detrimental why not lower the chances from high to medium?

good point.. although the "high" chances equal 50% so is that really *that* high?
Member Since: August 18, 2008 Posts: 0 Comments: 474
Quoting VAbeachhurricanes:


its never going to enter it
That isn't a guarantee, so don't take the chance of causing people to turn the other cheek.
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Quoting nolacane2009:
I am very confused with this storm. Does anyone here see a chance of this storm going into the GOM?

Everything is possible at this time. It is too early to predict a sure track, however I do not really see a turn to the north anytime soon.
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Quoting hurricanehanna:

Now I am confused...I thought the anticyclone following 94L acted as a "bubble" to keep the shear at bay?


It all depends. That's the thinking behind the low shear, but one never knows how everything will pan out in the end.

NHC has obviously soured on the anti-cyclone being as much of a factor than they were before.
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Quoting Vortex95:
why is Dr. M saying low shear next 5 days and other on here saying there is high shear ahead? Just wondetring what he is seeing.


Read the ATCF statement. Shear is affecting it now but as it moves to the northwest conditions should be more favorable for development
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Showers and thunderstorms is increased in the Eastern region of Cuba by the influence of a upper level low. Kind the Cuban fans to the possible training of Erika and the outputs of the forecast models.
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Quoting FLWeatherFreak91:
If in 2 days 94l is past this shear and makes it out intact, then yes, it could come into the gulf. Don't worry just yet though.


its never going to enter it
Member Since: September 6, 2007 Posts: 0 Comments: 6704
Quoting nolacane2009:
I am very confused with this storm. Does anyone here see a chance of this storm going into the GOM?


Models are all over the place, and they don't do well on a disturbance that hasn't formed into a TD. Once a TD or a TS forms then we would have a better idea of where it's going to go.
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Quoting hurricanehanna:

this blog + good south LA food = a trip to the cardiologist


at least last year we had the aftermath of Gustav to work it off. just joking. i'll take the pounds over having to fix my house again.
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Hurricane Hunters prepare for storm season

If the 53rd WRS Airmen can reduce the evacuation area by 100 miles, the squadron's entire flying budget is covered by one hurricane. Money and lives also are saved by not evacuating people who aren't in the storm's path. Evacuating people can cause deaths, not just from the storm, according to Bill Reid, National Weather Service director. Pinpointing accurate landfall is paramount for all.

Depending upon the location of the storm, the base of operations can be at Keesler AFB, Homestead Air Reserve Base, Fla., or St. Croix. Each of the Hurricane Hunter weather missions averages about 11 hours and can cover nearly 3,500 miles.

"Having an operating center in St. Croix allows us to fly longer in the storms that are near here. It would be impractical to fly the mission from our home base at Keesler," said Lt. Col. Roger Gardner, aircraft commander for these training missions.

While the aircrew flew a series of weather training scenarios, each of the aircrew echoed the same sentiment, "You can't learn to fly in a hurricane until you do."

"These training missions prepare us as we go over checklists so that the actions are second nature when we are flying in a real-world mission," Lt. Col. Mark Stevens, navigator, said.
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Quoting nolacane2009:
I am very confused with this storm. Does anyone here see a chance of this storm going into the GOM?
If in 2 days 94l is past this shear and makes it out intact, then yes, it could come into the gulf. Don't worry just yet though.
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Quoting Vortex95:
why is Dr. M saying low shear next 5 days and other on here saying there is high shear ahead? Just wondetring what he is seeing.
go with the expert not the bloggers who think they are experts
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Quoting TreasureCoastFl:
That's what I'm thinkig, but I what do I know? lol



the shear ahead of it is being caused by the anticyclone over it....
Member Since: September 6, 2007 Posts: 0 Comments: 6704
Quoting IKE:
Hurricane forecasting is such an inexact job. I am sooo glad I don't do this for a living and I do something that is more or less, black and white.

This would drive me c-r-a-z-y.


how terrible would it be if people could file suit against forecasters?
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with all being said though if the shear was that detrimental why not lower the chances from high to medium?
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I am very confused with this storm. Does anyone here see a chance of this storm going into the GOM?
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Quoting truecajun:


I'm glad i'm not the only one.

this blog + good south LA food = a trip to the cardiologist
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Quoting WINDSMURF:

Hey Drak, do you think that they will update directly to a TS or do you think that they will play it safe and only do TD for now?


TD if it organizes further
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Member Since: September 6, 2007 Posts: 0 Comments: 6704
381. IKE
Hurricane forecasting is such an inexact job. I am sooo glad I don't do this for a living and I do something that is more or less, black and white.

This would drive me c-r-a-z-y.
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are they going in or just heading in that direction for tomorrow.
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Quoting truecajun:


I'm glad i'm not the only one.


And I have no fingernails left...
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Quoting hurricane23:
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.
That's what I'm thinkig, but I what do I know? lol
Member Since: August 18, 2008 Posts: 0 Comments: 474
Quoting Drakoen:
Close up on the center:


Hey Drak, do you think that they will update directly to a TS or do you think that they will play it safe and only do TD for now?
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Quoting IKE:


Maybe you should write up a blog?


Nah iam alright...Iam just analyzing the same data that is availiable to most.
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Quoting Vortex95:


Non tasked???


Looks like they are flying to St. Croix, preposition for tomorrows recon on 94L.
Member Since: September 23, 2005 Posts: 15 Comments: 11341
The un-tasked mission should reflect their concern.
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Quoting hurricanehanna:

Nope- I've gained 5.


I'm glad i'm not the only one.
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so i take it you guys are saying dr masters is wrong with his forecast of 5-10 mph of shear. i'll go with his forecast for now as the expert
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Seems to have spun Out and elongated again from Last Nights Symmetry and is still a Large Circulation,broad still as mentioned, trying to find its groove.


South shear noted as well.

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Quoting hurricanehanna:

Now I am confused...I thought the anticyclone following 94L acted as a "bubble" to keep the shear at bay?
To an extent.
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Quoting truecajun:
am i the only one who gains at least two pounds every hurricane season from sitting on my tush while blogging on here?

Nope- I've gained 5.
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If 94L does get sheared apart then im really going to second guess the whole ULL interacting with the anticyclone thing.
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Quoting IKE:


Maybe you should write up a blog?


LOL
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Quoting 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.

Now I am confused...I thought the anticyclone following 94L acted as a "bubble" to keep the shear at bay?
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am i the only one who gains at least two pounds every hurricane season from sitting on my tush while blogging on here?
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Sorry Folks...I Will Delete
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361. IKE
Quoting hurricane23:


Hmmm. Guess i was right.


Maybe you should write up a blog?
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If 94L had a well-defined center it would be a TD already
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no closed low = no td
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Quoting 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.


Hmmm. Guess i was right.
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Interesting update....guess looks can be deceiving.
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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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