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 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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Quoting tramp96:


OK
Would I be correct in assuming that a trough would push the hurricane and ridging would trap it?


yes they are attracted to lows and ridges/highs block them.
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Quoting jrobarch:
Can someone tell me why storm systems in the Atlantic recurve to the N and then NE, whereas in the Eastern Pacific they don't seem to? Is it the same effect as the west coast of Africa?


coriolis effect
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recon getting ready to make a pass.

http://www.nhc.noaa.gov/text/URPN15-USAF.shtml?
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301. IKE
Quoting bingcrosby:
Hearing on Accuweather that Invest 94L is going to be sheared to death by Thursday. Any truth?


No...
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting Patrap:
Atlantic Basin 363 Days ago, 2 Sept 2008



AWESOME pic Patrap!
Member Since: August 28, 2006 Posts: 6 Comments: 2899
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.
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Quoting tramp96:


OK
Would I be correct in assuming that a trough would push the hurricane and ridging would trap it?


Troughs tend to attract the system (usually northward) while ridges tend to deflect the system (usually westward)
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Can someone tell me why storm systems in the Atlantic recurve to the N and then NE, whereas in the Eastern Pacific they don't seem to? Is it the same effect as the west coast of Africa?
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Station 41040
NDBC
Location: 14.477N 53.008W
Conditions as of:
Mon, 31 Aug 2009 16:50:00 UTC
Winds: SSW (200°) at 7.8 kt gusting to 9.7 kt
Significant Wave Height: 8.9 ft
Dominant Wave Period: 8 sec
Atmospheric Pressure: 29.80 in and falling
Air Temperature: 80.6 F
Dew Point: 80.4 F
Water Temperature: 82.9 F
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Quoting Chicklit:

Awesome blog.


could you link me to it. i'm just back from lunch.
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Tropical Storm conditions at most affect the Northern Leewward islands as the system passes within 150 miles to the north.

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ECMWF has been having a tendency to over-do the shear this year.
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Quoting NARCHER:
recon shpuld be near jimena please post recon reports
Where's Skyepony? He's really good at posting HH reports.
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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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WEATHER RECONNAISSANCE FLIGHTS
CARCAH, NATIONAL HURRICANE CENTER, MIAMI, FL.
0900 AM EDT MON 31 AUGUST 2009
SUBJECT: TROPICAL CYCLONE PLAN OF THE DAY (TCPOD)
VALID 01/1100Z TO 02/1100Z SEPTEMBER 2009
TCPOD NUMBER.....09-095

I. ATLANTIC REQUIREMENTS
1. SUSPECT AREA (APPROACHING THE LESSER ANTILLES)
FLIGHT ONE - TEAL 75
A. 01/1800Z
B. AFXXX 01BBA INVEST
C. 01/1600Z
D. 17.5N 56.5W
E. 01/1730Z TO 01/2200Z
F. SFC TO 10,000 FT

FLIGHT TWO - TEAL 76
A. 02/0600Z, 1200Z
B. AFXXX 0206A CYCLONE
C. 02/0400Z
D. 18.0N 58.0W
E. 02/0530Z TO 02/1200Z
F. SFC TO 10,000 FT

2. OUTLOOK FOR SUCCEEDING DAY: CONTINUE 6-HRLY FIXES
IF SYSTEM DEVELOPS AND IS A THREAT.
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1) I am perplexed that 94L isn't a TD yet....

2) I believe the area above the Bahamas bears watching....

Just my wannabe opinion.
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Quoting Weather456:
Good Afternoon all

September Outlook; Jimena; 94L


Awesome blog.
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Quoting bingcrosby:


Yikes! Just in time for Sunday football too.
thats a lil too close to me then. i was expexting maybe martin county or st lucie but thats really close to me in volusia.
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Hearing on Accuweather that Invest 94L is going to be sheared to death by Thursday. Any truth?
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Quoting hurricane23:


Iam not exactly sure were masters finds 5-10kts on shear during the next to 5 days.Per the 00z ECMWF southwesterly shear should begin to impact 94L soon.This thing should struggle for a while in my view.


SHIPS forecast for shear to be favorable for development
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Quoting Bordonaro:

The way the 2009 Atlantic Hurricane Season has been going we just have to wait and see! Personally, I doubt it will get past a Cat 2!


We who live in the "F" state hope so too! As well as our friends in the whole caribbean and point east and west
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278. 7544
Quoting leftovers:
any developed system moving into the bahamaian islands has alot of potential. cat 4 sure


na na na blogers say too much shear
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Quoting StSimonsIslandGAGuy:
Savannahstorm I was thinking the same thing. But then I looked back at Floyd in 1999, forecast to move directly over St Simons as a 120 kt CAt 4. The same thing happened with Frances in 2004, forecast to move directly over St. Simons as a 115 kt Cat4. Every 5 years or so the models bring a Cat 4 to Georgia :) And we have to wait for the forecast track to change. And it always does. Till all we're left with is some lovely surf :)


Yep, Hugo was making a beeline for Savannah when he decided to make a right-hand turn the last day. The models always trend north and right when systems move this way. If the models ever bring something to the Daytona to St. Augustine area, that's when Georgia residents need to worry.
Member Since: September 22, 2005 Posts: 18 Comments: 2343
recon getting ready to make a pass.

http://www.nhc.noaa.gov/text/URPN15-USAF.shtml?
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Quoting Drakoen:
94L is moving to the Northwest.


Iam not exactly sure were masters finds 5-10kts on shear during the next to 5 days.Per the 00z ECMWF southwesterly shear should begin to impact 94L soon.This thing should struggle for a while in my view.
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recon shpuld be near jimena please post recon reports
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Quoting palmasdelrio:


what a great graphic. where did you find it?

Haven't learned how to link yet but here is the site. I think Weather456 or mikatnight directed me there.

http://www.coaps.fsu.edu/~maue/weather/
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Quoting SavannahStorm:
I can't believe what the NOGAPS is showing.

Georgia Hurricane Shield- Activate!


Yikes! Just in time for Sunday football too.
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Pressures dropping again. Elongated low looks to be tightening up this afternoon. NHC will probably look for maintained convection through DMIN before upgrading to TD.
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Quoting ALCoastGambler:
Good afternoon Patrap, Ike. Looking forward to the cooler temps for the upcoming mornings? I'll take the cool but leave the humid, wet, windy stuff away.LOL


Itsa gonna be a nice week here with N winds and below avg Temps..
always good thing in Early Sept.


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Quoting Chavalito:
I think 94L wont't affect in Puerto Rico. The model consensus sustain that. So we are blessed once more.
the models don;t have a closed low to work with so we really don't know where its going yet
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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.

The way the 2009 Atlantic Hurricane Season has been going we just have to wait and see! Personally, I doubt it will get past a Cat 2!
Member Since: August 25, 2009 Posts: 20 Comments: 6785
thanks for the links guys
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Good afternoon Patrap, Ike. Looking forward to the cooler temps for the upcoming mornings? I'll take the cool but leave the humid, wet, windy stuff away.LOL
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Don't put too much stock into the HWRF intensity. It tends to exaggerate.
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261. IKE
Quoting palmbaywhoo:
ike do you mind posting the nogaps link please?



Link
Member Since: June 9, 2005 Posts: 23 Comments: 37858
I can't believe what the NOGAPS is showing.

Georgia Hurricane Shield- Activate!
Member Since: September 22, 2005 Posts: 18 Comments: 2343
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.


what a great graphic. where did you find it?
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Atlantic Basin 363 Days ago, 2 Sept 2008

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256. JLPR
Quoting palmasdelrio:

How is it that most of the models have 94L passing well to the north of the Leewards and PR, while the surface map you show here predicts it passing to the south of PR??


no one knows where it will go
we have to wait for a defined LLC to form
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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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