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Norbert re-strengthens; Odile dumping heavy rains; Atlantic getting more active

By: Dr. Jeff Masters, 2:13 PM GMT on October 10, 2008

An area of disturbed weather (97L) has developed midway between Africa and the Lesser Antilles Islands. Wind shear is a moderate 10-15 knots over the disturbance, and waters are warm, about 29° C. Satellite loops show a large area of heavy thunderstorms that are beginning to look organized, with a little bit of upper-level outflow to the north. This morning's QuikSCAT pass mostly missed 97L, but did show an elongated, poorly organized surface circulation developing, and 20 mph winds.

Figure 1. Current satellite image of 97L.

The forecast for 97L
Wind shear is expected to remain in the moderate 10-20 knot range the next three days, and waters will remain warm, 28-29°C. This should allow 97L to come close to tropical depression status 2-3 days from now. The GFDL, HWRF, and UKMET models develop 97L into a tropical storm by Monday. NHC is giving 97L a medium (20-50% chance) of developing into a tropical depression by Sunday. The storm is expected to track to the northwest over the open Atlantic, and shouldn't affect any land areas. By Wednesday, most of the models are predicting that an extratropical storm will form just north of Puerto Rico, and this storm will probably end up pulling 97L northwards into the Atlantic hurricane graveyard.

Elsewhere in the Atlantic
Most of the models continue to forecast the possible development of a tropical depression in the south central Caribbean, off the coast of Nicaragua, as early as Tuesday next week. A very moist atmosphere with low wind shear is predicted for the southern Caribbean next week, and I put the odds of a tropical storm forming there at 30%. The potential motion of such a storm is difficult to predict at this time.

Figure 2. Hurricane Norbert at 20:55 GMT October 8, 2008. At the time, Norbert was a Category 4 hurricane with 135 mph winds. Image credit: NASA Earth Observatory.

Hurricane Norbert weakens, then re-strengthens
Hurricane Norbert stalled out yesterday afternoon for several hours, which allowed the storm's churning winds to upwell large amounts of cold water, weakening the storm. Norbert has since resumed its track towards Mexico's Baja Peninsula, and is over warmer waters. Norbert also underwent an eyewall replacement cycle yesterday, which also served to weaken it. In an eyewall replacement cycle, the eyewall collapses, and gets replaced by a new eyewall that was concentric (at a greater diameter) with the old eyewall. These cycles typically take 1-2 days to complete, and the hurricane will remain relatively weak while it struggles to adjust to the new eyewall. The most recent microwave imagery suggests that this process is complete, as there is no trace of the old inner eyewall now. Infrared satellite loops show that the cloud tops of the eyewall clouds have cooled in recent hours, indicating that they are more vigorous and extend higher into the atmosphere. There is excellent upper-level outflow in all quadrants, and wind shear is moderate, near 10-15 knots. Satellite estimates of Norbert's strength indicate the storm has probably intensified into at least a Category 2 hurricane this morning. A Hurricane Hunter mission into Norbert is scheduled for this afternoon, and we will see if this intensification has actually taken place. Yesterday, the Hurricane Hunters found that a layer of stable air near the surface was preventing Norbert's strongest winds at high levels from mixing down to the surface. It still may be the case that Norbert has only Category 1 strength winds at the surface.

The computer models continue to be tightly clustered around a landfall in southwestern Baja near San Carlos, 150 miles north of the southern tip of Baja, on Saturday afternoon. The waters along Norbert's path are unusually warm for this time of year, about 1-3° C above average (Figure 3), and will increase in temperature to 29°C as Norbert approaches Baja. However, these warm waters do not extend very deep, and the total oceanic heat content is low. Once Norbert crosses Baja and enters the Gulf of California, total heat content increases, but Norbert will not be over these warm waters long enough to take advantage of them. Wind shear is expected to increase to a high 20-25 knots tonight. Given these factors, landfall Saturday afternoon as a Category 2 hurricane with 100-105 mph winds, as predicted by the GFDL and HWRF models, is a good forecast. The SHIPS models is weaker, putting Norbert at Category 1 strength with 85 mph winds. It is only 10-20% likely that Norbert would be a major Category 3 hurricane at landfall. Tropical storm force winds should extend outwards about 130 miles at landfall, so the southern tip of Baja (San Lucas) will probably see sustained winds of 30-35 mph, should Norbert hit near San Carlos, as predicted. One can look at the forecast radius of tropical storm force winds by clicking on the wundermap for Norbert, then selecting "wind radius" in the check boxes at the bottom of the page.

Crossing rugged Baja will probably knock Norbert down a full Category, by about 20-25 mph. The storm will still pack a solid punch when it makes it second landfall on mainland Mexico north of Los Mochis. Rainfall amounts in mainland Mexico will be 4-8 inches, and 6-10 inches over Baja. Norbert's remains should bring 1-2 inches of rain to portions of western Texas and southeastern New Mexico.

Figure 3. Departure of Sea Surface Temperature (SST) from average for October 6, 2008. Note the region being traversed by Norbert is 1-3 °C above average. Image credit: NOAA.

Odile dumping heavy rains on Mexico
Mexico has another storm to be concerned with, Tropical Storm Odile. Satellite estimates indicate Odile has dumped up to six inches of rain on the coast just east of Acapulco. Additional heavy rains of up to eight inches should affect the coast as Odile tracks along the coast, just offshore. Mexican radar and infrared satellite loops show that the heaviest rain is now offshore. However, heavy rain will likely move back onshore later today. Odile is under about 15 knots of wind shear, and this shear is forecast to remain in the 15-20 knot range the next 3-5 days. This should allow the storm to gradually intensify into a Categroy 1 hurricane.

Thursday update on Hurricane Ike relief efforts
Yesterday's update from Paul Timmons (Presslord) on the Hurricane Ike relief effort started by wunderground members Patrap, Presslord, and Stormjunkie:

While the devastating aftermath of hurricane Ike seems no longer to capture the interest of mainstream media, we all know that the needs continue. Chief Dickie Uzzle of the Bridge City, TX, fire department has informed us that only 14 homes in that community (population: 8700) did not sustain ruinous water damage. Many families continue to live in tents in front of their homes, with ALL of their personal belongings piled in the yard awaiting removal.

Laura Cremans, Manager of the Churches of Christ distribution center in Bridge City tells us " Only one truck of supplies has come here since Ike made landfall. We are desperate here."

This is the list of specific needs that we are currently attaining and working to attain for the rural populations and the disabilities community along the Texas Gulf Coast. We have worked closely with several local relief efforts as well as municipalities to identify these needs.

Men's & Women's Clothing (we already have a commitment for a substantial number of men's and women's pants)

Air Mattresses
Blankets/Sleeping bags
Insect repellent
All baby items
Formula (We have a commitment from Meade-Johnson to provide some of this)
Rash cream

Our strategy is to focus on attaining as many of these items as possible through donations from manufacturers and distributors. In the last three and a half days, we have made several dozen contacts to this end and are beginning to get positive results; but we need your help.

If you have any contacts or influence which might facilitate us procuring the items listed above please contact us at presslord@aol.com or admin@stormjunkie.com. All your thoughts and ideas are good. The more input we have, the more impact we can have.This will help us successfully implement our strategy of expending donated funds primarily on transportation and logistics of moving donated goods. In this way, we can most effectively steward the donated funds in the most cost effective manner.

Moving forward...

Moving through October we are committed to adjusting our fund raising effort to leverage the grassroots enthusiasm and generosity generated by our Hurricane Ike relief work.  A more proactive approach will enhance our future effectiveness. We are asking you to consider committing to a monthly pledge amount.  The amount you pledge is less important then the consistency.  A dependable monthly donor base will allow us to strategically plan and prepare for the future and help us successfully execute those plans over the long term. 

Please give thoughtful, prayerful consideration to committing to a monthly pledge amount beginning November 1 and email your intentions to presslord@aol.com.

There is much work yet to be done in helping the victims of Ike. And there will certainly be other victims of other storms we can all serve. By continuing to work together as we have the last 3 1/2 weeks, we can have a profound positive impact on thousands of unserved, underserved, and forgotten people...

Also, please remember: we should all forward this information far and
wide...and frequently..


Contributions to this highly worthy portlight.org charity fund are fully tax-deductible, and will go to provide relief supplies for those smaller communities typically bypassed by the traditional relief efforts. More details can be found at StormJunkie's blog.

Jeff Masters

The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.