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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Recon passing over Turks and Caicos due north of Haiti is seeing very light *northeasterly* winds at 400 mb ... in the 5 knot range. If it is dropping into St. Croix, as seems likely, we will get a peek at lower levels as it approaches the island (400 mb approx 28000 ft)

- WTO
Member Since: July 15, 2005 Posts: 3 Comments: 1259
Thank you!

For any reason, in the historical data of Wunderground archive I have only found 4 category 4 hurricanes in the EPAC since 1950... Of course, in August.
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Quoting Patrap:
12 Z Dynamic Models (More sophisticated models)



When were those models ran?
Member Since: August 18, 2008 Posts: 0 Comments: 467
Quoting HadesGodWyvern:
National Hurricane Center
Special Immediate Advisory
SEVERE TROPICAL CYCLONE JIMENA (EP132009)
18:00 PM UTC August 31 2009
===============================

SUMMARY OF 1100 AM PDT INFORMATION...
LOCATION...18.1N 108.9W
MAXIMUM SUSTAINED WINDS...150 MPH
PRESENT MOVEMENT...NORTHWEST AT 8 MPH
MINIMUM CENTRAL PRESSURE...936 MB

-----
130 knots 936 hPa.. 5 knots from achieving Category 5 on the Simpson-Saffir scale (scary)


wow!
Member Since: August 18, 2008 Posts: 0 Comments: 467
Quoting Drakoen:


TD if it organizes further
Quoting Drakoen:
If 94L had a well-defined center it would be a TD already


There is a circulation now but what do we look for to see when there is a well defined circulation?
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12 Z Dynamic Models (More sophisticated models)

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Quoting nrtiwlnvragn:


Looks like they are flying to St. Croix, preposition for tomorrows recon on 94L.


They Are?! I live there! I am going to see if I can see their aircraft.
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Quoting Cazatormentas:
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?


There have been Cat 5s in the Pac, but there is often much less in number than the Atl. (Of course, the Pac has only really had effort put into research and observations in recent times, studies into the Atl seem to go back much further due to the increased likelihood of them hitting something.)

Wiki, so usual caveats of misinformation apply, but it's something for a quick search:

Link

And that's also incorrect on the Cat 4 statement; a few EPac years especially around the early 1990s had 4 Cat 4s in one season, let alone in five decades.
Member Since: August 23, 2008 Posts: 7 Comments: 5300
If 94L developes and goes west once the high builds in, how can it not go in the GOM?????? I have lived in Mobile AL for 30 years, and usually the steering patterns for this time of year put storms in the GOM when they have a pattern like 94L.
Correct me if I'm mistaken but isn't the sheer vs. invest 94L battle outcome dependent on the anti-cyclone currently over invest 94L?
Member Since: August 28, 2006 Posts: 6 Comments: 2895
I was mainly Refering to when it was not in the GOM.
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Quoting Patrap:
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.


Props to the HH's (pun intended).
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936...yowza
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Sorry about the 18 Z

I wanted the 12 Z Statistical/Simple Models (CLIPER,BAMs,LBAR,other Statistical Models) from 31 August

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Quoting SykKid:
94L is going to get torn apart.


No it won't.
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Jimena's eye is looking quite incredible on these last few frames
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i asked this last year and was answered. but I was 8 days over my due date, so I don't remember the answer.

what was the hurricane - i think it was in 2002 - that was supposed to make landfall near new iberia, LA (near where andrew made one of his landfalls) then disappeared in the middle of the night? i think it was a she.
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Quoting Patrap:
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.



Looks like that south shear is what someone noted earlier what looked like moisture that would act to help 94's development. Reckon it's just the opposite...
Member Since: October 18, 2005 Posts: 4 Comments: 3052
Quoting VAbeachhurricanes:


wilma wasnt a EPAC storm

oops.my mistake.
Member Since: August 18, 2008 Posts: 0 Comments: 467
SSD still says just N of W.

31/1745 UTC 15.5N 53.6W T1.5/1.5 94L
31/1145 UTC 15.2N 51.5W T1.5/1.5 94L
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Quoting Cazatormentas:
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?


There have been over 10 category 5 hurricanes in the EPAC.

Do a USA Google search of category 5 hurricanes in Eastern Pacific and it will bring up some data
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Quoting nolacane2009:
I guess the reason I worry alittle bit more then what I should is because when Katrina was out there. Out forcasters in New Orleas basically said that this storm will not affect us. That is when I started to come here. Then you wake up one morning and find Katrina to be a Cat 5 storm in the middle of the GOM. Lost all respect for them now and come here for updates.

There are a few folks on this blog that really know their stuff, I'm not one of those, I blog here as a way to stay informed and learn something at the same time
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432. HadesGodWyvern (Mod)
National Hurricane Center
Special Immediate Advisory
SEVERE TROPICAL CYCLONE JIMENA (EP132009)
18:00 PM UTC August 31 2009
===============================

SUMMARY OF 1100 AM PDT INFORMATION...
LOCATION...18.1N 108.9W
MAXIMUM SUSTAINED WINDS...150 MPH
PRESENT MOVEMENT...NORTHWEST AT 8 MPH
MINIMUM CENTRAL PRESSURE...936 MB

-----
130 knots 936 hPa.. 5 knots from achieving Category 5 on the Simpson-Saffir scale (scary)
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Quoting Stormchaser2007:


Yesterdays 18z.


yup
Member Since: October 28, 2006 Posts: 57 Comments: 29714
430. amd
Hurricane hunters find Jimena even stronger:

Max winds = 150 mph
Minimum pressure = 936 mb
Member Since: August 29, 2005 Posts: 0 Comments: 1024
Quoting sporteguy03:

greater than 50% chance not just 50%. if the shear was that bad as some here think 94L will face why would the NHC keep it above 50%?

True enough.
Member Since: August 18, 2008 Posts: 0 Comments: 467
The local meteorologist (New Orleans) said that the 94L will interact with the low to its NW and move up along the East Coast...path of least resistance as it were.



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Those are old models Pat.
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Quoting stormsurge39:
Why?
Just another uneducated guess with no data to back up statement.
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Quoting Cazatormentas:
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?


There have been 8 since 2000 alone.
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Quoting Patrap:
18 Z Statistical/Simple Models (CLIPER,BAMs,LBAR,other Statistical Models)




Yesterdays 18z.
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423. edmac
I have a feeling that 94l will most likely become our next hurricane, and Im afraid its heading for a landfall. I dont think the shear will do much to it, other than slow developement, which will just increase the chances of it going to the GOM.
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Quoting nolacane2009:
I guess the reason I worry alittle bit more then what I should is because when Katrina was out there. Out forcasters in New Orleas basically said that this storm will not affect us. That is when I started to come here. Then you wake up one morning and find Katrina to be a Cat 5 storm in the middle of the GOM. Lost all respect for them now and come here for updates.


Dont know what world you Live in but Bob Breck,and All the Locals were on the trend west from the time it shifted.

Best refrain from that BS ,..as there is beaucoup archived transcripts and Video out there,..I suggest you reference them.
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Quoting nrtiwlnvragn:


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.


Thanks, makes me feel better.
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Conditions at 41040 as of
(1:50 pm EDT)
1750 GMT on 08/31/2009:

Wind Direction (WDIR): S ( 190 deg true )
Wind Speed (WSPD): 17.5 kts Wind Gust (GST): 21.4 kts Wave Height (WVHT): 7.5 ft
Dominant Wave Period (DPD): 10 sec
Average Period (APD): 6.3 sec
Atmospheric Pressure (PRES): 29.79 in
Pressure Tendency (PTDY): -0.04 in ( Falling )
Air Temperature (ATMP): 80.1 °F
Water Temperature (WTMP): 82.8 °F
Dew Point (DEWP): 80.1 °F
Heat Index (HEAT): 87.4 °F

No evidence of a closed low yet but wind speeds steadily increasing from this morning...
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Quoting Patrap:
18 Z Statistical/Simple Models (CLIPER,BAMs,LBAR,other Statistical Models)




Where did you get those models info...? They are updated or what???
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Quoting TreasureCoastFl:
Wilma was a 5, or so I thought?


wilma wasnt a EPAC storm
Member Since: September 6, 2007 Posts: 0 Comments: 5695
Quoting TreasureCoastFl:

good point.. although the "high" chances equal 50% so is that really *that* high?

greater than 50% chance not just 50%. if the shear was that bad as some here think 94L will face why would the NHC keep it above 50%?
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UK Met Office


NEW TROPICAL STORM FORECAST TO DEVELOP AFTER 12 HOURS
FORECAST POSITION AT T+ 12 : 16.0N 55.1W

VERIFYING TIME POSITION STRENGTH TENDENCY
-------------- -------- -------- --------
00UTC 01.09.2009 16.0N 55.1W WEAK
12UTC 01.09.2009 16.2N 58.2W WEAK LITTLE CHANGE
00UTC 02.09.2009 17.0N 60.3W WEAK LITTLE CHANGE
12UTC 02.09.2009 17.5N 62.3W WEAK LITTLE CHANGE
00UTC 03.09.2009 17.5N 64.3W WEAK LITTLE CHANGE
12UTC 03.09.2009 18.0N 66.3W WEAK LITTLE CHANGE
00UTC 04.09.2009 19.0N 67.9W WEAK LITTLE CHANGE
12UTC 04.09.2009 20.0N 69.2W WEAK LITTLE CHANGE
00UTC 05.09.2009 20.5N 71.3W WEAK LITTLE CHANGE
12UTC 05.09.2009 BELOW TROPICAL STORM STRENGTH

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Quoting TreasureCoastFl:
Wilma was a 5, or so I thought?


a bunch were fives, just not at landfall - i think??
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Quoting stormsurge39:
Why?


the shear out in front of the system is being caused by the anticyclone over 94L, its been "right" in front of 94L the whole time. The shear will move west just as 94L is.
Member Since: September 6, 2007 Posts: 0 Comments: 5695
What is absolutely true is that 94L won't affect Puerto Rico. Each time I see the visible loops I get convinced that this storm is gaining latitude instead of longitude. Let's see. We have to consider that with high shear it will be impossible for 94L to strenghten. Let's see.
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18 Z Statistical/Simple Models (CLIPER,BAMs,LBAR,other Statistical Models)


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#392

very interesting. i never thought about the cost benefit retio. pretty neat.
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I guess the reason I worry alittle bit more then what I should is because when Katrina was out there. Out forcasters in New Orleas basically said that this storm will not affect us. That is when I started to come here. Then you wake up one morning and find Katrina to be a Cat 5 storm in the middle of the GOM. Lost all respect for them now and come here for updates.
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Quoting Cazatormentas:
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?
Wilma was a 5, or so I thought?
Member Since: August 18, 2008 Posts: 0 Comments: 467
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: 5695

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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.