Dr. Jeff Masters' WunderBlog

Tropical Storm Erika likely soon; a weaker Jimena powers towards Baja

Posted by: Dr. Jeff Masters, 7:48 PM GMT on September 01, 2009

Hurricane Jimena has weakened to a low-end Category 4 hurricane with 135 mph winds, thanks to the collapse of its inner eyewall. The hurricane is undergoing a process common in intense hurricanes called an Eyewall Replacement Cycle (ERC), where the eye shrinks to a size too small to be stable, resulting in the disintegration of the eyewall, and the formation of a new eyewall from one of the outer spiral bands. Once the new eyewall becomes stable tonight, Jimena has an opportunity to re-strengthen.

The latest set of 12Z model runs show little change in Jimena's track. The hurricane is still expected to make landfall Wednesday along Mexico's Baja Peninsula. If the hurricane makes landfall over the southern portion of Baja, it would likely be at major hurricane strength. However, SSTs cool quickly to 23°C at the middle of the Baja Peninsula, and Jimena would likely weaken to a Category 2 or 1 hurricane if it makes a strike towards the middle of Baja. The computer models are split on what might happen once Jimena makes landfall on Baja, with one camp predicting a northeast turn bringing the storm over Mainland Mexico and eventually into Arizona, and the other camp stalling Jimena out over or just west of Baja. Regardless, the main threat from Jimena will be flooding and mudslides due to heavy rains.

Baja's hurricane history
The most powerful hurricane on record to hit the west coast of Baja occurred last year, when Hurricane Norbert made landfall on the central Baja coast with sustained winds of 105 mph (Category 2) . Norbert's central pressure of 956 mb at landfall made it the 3rd strongest hurricane to hit the Pacific coast of Mexico since record keeping began in 1949. Norbert killed eight, knocked out power to 20,000 homes, and damaged or destroyed 40% of the homes on the islands of Margarita and Magdalena. Norbert crossed the Baja Peninsula and made landfall on Mainland Mexico as a Category 1 hurricane with 85 mph winds.

Only two major hurricanes have made landfall on Baja since record keeping began in 1949. Both hurricanes hit the east (Gulf of California) side of Baja. The first was Hurricane Olivia of 1967. Olivia made landfall on October 13, 1967 as a Category 3 hurricane with 125 mph winds. Due to its small size and the unpopulated region of coast it hit, damage was minimal. The second major hurricane was Hurricane Kiko, which made landfall on August 27, 1989, as a Category 3 hurricane with winds of 115 mph (minimal Category 3). Kiko was a small hurricane and hit a relatively unpopulated area, resulting in no loss of life and only scattered reports of damage.

Figure 1. A plot of all the major hurricanes to pass within 200 miles of Mexico's Baja Peninsula since 1949. Image credit: NOAA Coastal Services Center.

Invest 94L almost Tropical Storm Erika
The Air Force Hurricane Hunters are investigating tropical wave 94L, about 200 miles east of the Lesser Antilles Islands. So far this afternoon, they have found a broad circulation with top winds of 45 - 50 mph in heavy thunderstorms on the east side. The circulation may be too broad for 94L to be considered a tropical storm, but visible satellite imagery shows that the circulation is getting better defined, and 94L's heavy thunderstorms are moving closer to the center of circulation. Recent satellite wind shear analyses by NOAA/Colorado State University and the University of Wisconsin show that wind shear is a moderate 10 - 20 knots over 94L, and this shear is keeping any thunderstorms from developing on the system's west side.

The forecast for 94L
The latest of 12Z model runs are more in tune with the idea that 94L will become a tropical storm, with the latest ECMWF run now on board. The storm will be steered west-northwest to northwest over the next three days thanks to the presence to two upper-level lows to the northwest of the storm. Since most of 94L's heavy thunderstorms and high winds are on the east side, the northern Lesser Antilles and Puerto Rico will probably be spared tropical storm force winds from this system. The best guess track for 94L, assuming it does intensify into a tropical storm in the next 24 hours, is on a northwest path between the Bahamas and Bermuda. If 94L stays weak, a more southerly path, along the northern edge of the Bahama Islands, is more likely.

Figure 2. Infrared satellite image taken at 12pm EDT, Tuesday Sep 1, 2009. Five major African tropical waves are apparent. Image credit: Navy Research Lab, Monterey.

Elsewhere in the tropics
It's September, the most active month for hurricane activity in the Northern Hemisphere. There's every indication that the 2009 Atlantic hurricane season will have an active first half of September, since SSTs are 0.5 - 1.0°C above average, wind shear is near average, and the African monsoon is sending a long parade of African waves spinning off the coast of Africa. An IR satellite image from noon today shows this activity well (Figure 2). We can see a line-up of five African waves stretching from the Lesser Antilles to eastern Africa. The GFS model develops the waves numbered "2" and "3" into tropical depressions next week, and the waves labeled "1" and "4" also have a chance to develop into tropical depressions, as well. The wave labeled "1" is mentioned on NHC's Tropical Weather Outlook as having a low (less than 30%) chance of developing into a tropical depression by Thursday. This wave is under a moderate 10 - 15 knots of wind shear, and is over sufficiently warm waters (27 - 28°C) that some development may occur this week. The wave is far enough north that it will be hampered by dry air from the Sahara Desert.

California fire webcams
As I discussed in this morning's post, you can use our wundermap for Los Angeles with the fire layer turned on to see where the fire and smoke are located, and track the temperatures and winds during today's air pollution event. We also have two webcams with views of the fire: Altadena and Tujunga.

Jeff Masters

Backing Down (Fotoguy77)

Part of the massive Station Fire backs down toward Sunland, Ca in this shot taken around 1am. The fire has burned through over 122,000 acres and killed two.

getting out (Fotoguy77)

This fire Chief from El Dorado County in Northern California is chased out of Aliso Canyon by a wall of flames. This was in the Acton area just off the 14 Freeway.

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3801. lordhuracan01 2:45 PM GMT on September 02, 2009
I HOPE NOT HAPPEN THIS Member Since: August 11, 2009 Posts: 0 Comments: 225

3802. jpsb 2:50 PM GMT on September 02, 2009
Quoting truecajun: i don't think this front is going to hold past friday. they never hold that long this early in "fall" I'm not saying it's going to enter GOM, but I don't think the front will last much longer. I'm surprised it's held this long! But even after the front lifts the trof will still be around protecting the GoM. If you are on the GoM, the thing to watch is that HUGE trof on the east coast. When that goes away then CV storms have a chance of reaching the GoM. Now if I were gulfcasting, lol, I say that since Erika is not stacked, (circulation wise that is, lol) she remains unorganized and she might just slide under the upper level steering currents (trof as it lifts and moves east) and continues slowly west, maybe even a little south of west. Then she organizes and makes it into the GoM after the front has lifted. the above is not likely as Erika is bond to become better organized and the trof is exceptionally strong. Any movement north makes interaction with that trof more certain. Any interaction with Island mountains will likely rip a weak T.S. like Erika apart. So if Erika stays weak and continues west the islands will get her. If the gets strong and goes more north the trof will get her. Shes got one hard road ahead of her if she wants to get into the nice warm gulf waters. Member Since: June 30, 2009 Posts: 0 Comments: 578

3803. lordhuracan01 2:55 PM GMT on September 02, 2009
.ERIKA APPROACHING THE LEEWARD ISLANDS... 11:00 AM AST Wed Sep 2 Location: 16.5°N 60.4°W Max sustained: 40 mph Moving: W at 10 mph Min pressure: 1008 mb Member Since: August 11, 2009 Posts: 0 Comments: 225

3804. lordhuracan01 3:02 PM GMT on September 02, 2009
000 WTNT31 KNHC 021447 TCPAT1 BULLETIN TROPICAL STORM ERIKA ADVISORY NUMBER 4 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL062009 1100 AM AST WED SEP 02 2009 ...ERIKA APPROACHING THE LEEWARD ISLANDS... AT 11 AM AST...1500 UTC...THE GOVERNMENT OF FRANCE HAS ISSUED A TROPICAL STORM WARNING FOR GUADELOUPE. A TROPICAL STORM WARNING IS NOW IN EFFECT FOR GUADELOUPE...ST. MARTIN AND ST. BARTHELEMY. A TROPICAL STORM WARNING REMAINS IN EFFECT FOR ANTIGUA...BARBUDA... MONTSERRAT...ST. KITTS...NEVIS...ANGUILLA...ST. MAARTEN...SABA...AND ST. EUSTATIUS. A TROPICAL STORM WARNING MEANS THAT TROPICAL STORM CONDITIONS ARE EXPECTED SOMEWHERE WITHIN THE WARNING AREA WITHIN 24 HOURS. INTERESTS ELSEWHERE IN THE LEEWARD ISLANDS...THE U.S. AND BRITISH VIRGIN ISLANDS...AND PUERTO RICO SHOULD MONITOR THE PROGRESS OF ERIKA. TROPICAL STORM WATCHES OR WARNINGS COULD BE REQUIRED FOR A PORTION OF THESE AREAS LATER TODAY. FOR STORM INFORMATION SPECIFIC TO YOUR AREA IN THE UNITED STATES...INCLUDING POSSIBLE INLAND WATCHES AND WARNINGS...PLEASE MONITOR PRODUCTS ISSUED BY YOUR LOCAL NATIONAL WEATHER SERVICE FORECAST OFFICE. FOR STORM INFORMATION SPECIFIC TO YOUR AREA OUTSIDE OF THE UNITED STATES...PLEASE MONITOR PRODUCTS ISSUED BY YOUR NATIONAL METEOROLOGICAL SERVICE. AT 1100 AM AST...1500 UTC...THE CENTER OF TROPICAL STORM ERIKA WAS ESTIMATED TO BE NEAR LATITUDE 16.5 NORTH...LONGITUDE 60.4 WEST OR ABOUT 100 MILES...165 KM...EAST-SOUTHEAST OF THE LEEWARD ISLANDS. ERIKA IS MOVING TOWARD THE WEST NEAR 10 MPH...17 KM/HR. A WEST- NORTHWESTWARD MOTION IS EXPECTED TO BEGIN LATER TODAY. ON THE FORECAST TRACK...ERIKA WILL BE MOVING THROUGH THE LEEWARD ISLANDS TONIGHT AND TOMORROW. MAXIMUM SUSTAINED WINDS HAVE DECREASED TO NEAR 40 MPH... 65 KM/HR...WITH HIGHER GUSTS. LITTLE CHANGE IN STRENGTH IS FORECAST TODAY WITH SOME SLIGHT RESTRENGTHENING POSSIBLE TOMORROW. TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP TO 105 MILES...165 KM MAINLY TO THE EAST OF THE CENTER. THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 1008 MB...29.77 INCHES. ERIKA IS EXPECTED TO PRODUCE TOTAL RAINFALL ACCUMULATIONS OF 2 TO 4 INCHES OVER MUCH OF THE LESSER ANTILLES DURING THE NEXT COUPLE OF DAYS...WITH ISOLATED MAXIMUM AMOUNTS OF 6 INCHES POSSIBLE. OVER PUERTO RICO...3 TO 5 INCHES OF RAIN ARE POSSIBLE DURING THE NEXT FEW DAYS...WITH ISOLATED MAXIMUM AMOUNTS OF 8 INCHES. ...SUMMARY OF 1100 AM AST INFORMATION... LOCATION...16.5N 60.4W MAXIMUM SUSTAINED WINDS...40 MPH PRESENT MOVEMENT...WEST OR 275 DEGREES AT 10 MPH MINIMUM CENTRAL PRESSURE...1008 MB AN INTERMEDIATE ADVISORY WILL BE ISSUED BY THE NATIONAL HURRICANE CENTER AT 200 PM AST FOLLOWED BY THE NEXT COMPLETE ADVISORY AT 500 PM AST. $$ FORECASTER BLAKE/FRANKLIN Member Since: August 11, 2009 Posts: 0 Comments: 225

3805. CaneHunter031472 3:16 PM GMT on September 02, 2009
Quoting jpsb: I'm surprised it's held this long! But even after the front lifts the trof will still be around protecting the GoM. If you are on the GoM, the thing to watch is that HUGE trof on the east coast. When that goes away then CV storms have a chance of reaching the GoM. Now if I were gulfcasting, lol, I say that since Erika is not stacked, (circulation wise that is, lol) she remains unorganized and she might just slide under the upper level steering currents (trof as it lifts and moves east) and continues slowly west, maybe even a little south of west. Then she organizes and makes it into the GoM after the front has lifted. the above is not likely as Erika is bond to become better organized and the trof is exceptionally strong. Any movement north makes interaction with that trof more certain. Any interaction with Island mountains will likely rip a weak T.S. like Erika apart. So if Erika stays weak and continues west the islands will get her. If the gets strong and goes more north the trof will get her. Shes got one hard road ahead of her if she wants to get into the nice warm gulf waters. I totally agree, not to mention first that we are experiencing an early Fall in the GOMEX and the whole US maybe for that matter so this fall like pattern should be able to persist. Second Erika is already struggling as it is and I expect for it to take the weaker storm route, but I also dare to say that it will be ripped appart by Puerto Rico and Hispaniola if it hits them and then its remnats should be either absorbed by the trof or redevelop which would then help it interact with the trof and take it NNW. I would be much more concerned about the waves leaving Africa unless of course you live in Puerto RIco which my family including parents and siblings still do. Member Since: August 1, 2007 Posts: 0 Comments: 895

3806. kmanhurricaneman 3:22 PM GMT on September 02, 2009
looking at RGB loop it does not appear that the coc is where nhc says it is, coc seems to be displaced from convection area.my best guess is that coc is at 16.2 and 61.5 Member Since: August 14, 2008 Posts: 0 Comments: 1002

3807. kmanhurricaneman 3:23 PM GMT on September 02, 2009
and by the way moving wsw!! Member Since: August 14, 2008 Posts: 0 Comments: 1002

3808. Brillig 6:43 PM GMT on September 02, 2009
Looks like a well-defined COC this time, so I'm changing the path line back to a solid line. 16°35'59.21"N 60°51'57.79"W Member Since: June 23, 2006 Posts: 20 Comments: 398

3809. Brillig 6:43 PM GMT on September 02, 2009
Quoting kmanhurricaneman: and by the way moving wsw!! I make it WNW, roughly. Member Since: June 23, 2006 Posts: 20 Comments: 398

3810. hurrizone 7:32 PM GMT on September 02, 2009
Erika is a unpredectible storm. NHC have a headache from this and is almost impossible to forecast already.Hope not to reorganize again quickly but nobody knows. Member Since: July 15, 2008 Posts: 0 Comments: 27

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