KATC StormTeam 3 Weather BLOG

While hurricane season officially ends November 30th, climatology dictates that by mid-October the threat of big, block-buster hurricanes in the Gulf of Mexico decreases dramatically.

Any tropical activity that may threaten the Gulf of Mexico in October usually has limited opportunity for development and movement (toward the Northern Gulf) as upper level westerly winds and associated increased wind shear become more dominant players in the region.

This doesn’t mean our hurricane season is over in Acadiana quite yet, but recent weather patterns look to continue over the next few weeks making it appear rather promising that we’ll escape without a major hurricane threat this year.

In the past, Acadiana has experienced major hurricane threats in the first week of October such as Lili (2002) and Hilda (1964) and we have dealt with other tropical systems through the end of the month including Hurricane Juan in 1985 which looped in the Gulf during the last few days of October into early November.

There have been other major hurricanes in the Gulf of Mexico in October, most recently Wilma in late October 2005, but most, like Wilma, moved from the Caribbean northeastward toward Florida and the Bahamas.

Typically tropical development in October is confined to the Caribbean and far Eastern Atlantic.

Atlantic systems that do emanate off of the African Coast normally stay Atlantic systems due to more active westerlies that steer systems away from the U.S.

Typically, storms that develop in and near the Caribbean in October usually remain Caribbean and perhaps South Florida threats.

Per the latest long range model data, there may be a window of opportunity for a significant tropical system to develop in the Western Caribbean during the second week of October, but upper level winds, per climatology, should any system smartly to the northeast…we’ll see.

Rob

Although the tropics have quieted down considerably as compared with the last two of weeks, the peak of hurricane season continues into mid-October.

Some of Louisiana’s (and Acadiana’s) bigger storms have come in the last week of September and in the first week of October including hurricanes Hilda in 1964, Lili in 2002 and Rita in 2005. So it is too early to breathe a sigh of relief when regarding the tropics.

Other than a rather disorganized Tropical Storm Maria just north of the Central Caribbean, there are just a few tropical waves worthy of our attention at this time.

Small disorganized disturbances were indicated Tuesday east of the Caribbean and emerging off of the African Coast. Both of these systems have some potential for development but at this time computer models are not suggesting significant organization.

Climatology, longer range models and Madden-JulianOscillation Forecasts all indicate that there will be some development in the Central tropical Atlantic over the next two weeks while the Caribbean will likely become active during the last week of September.

Interestingly enough, although it has been a busy tropical season with 14 named storms so far this season, only two have become hurricanes, Irene and Katia. Both of these storms attained major hurricane status during their lifetimes over water with only Irene striking much of the East Coast as a much lesser storm.

Based on earlier season forecasts of up to 4-5 major hurricanes in the Atlantic Basin it would not be unreasonable to believe that at least one or more major storms could be in the mix over the next three-four weeks with at least the Caribbean, and south of the major Caribbean islands possibly becoming the tropical hot spots later this month into early October.

Any storms that do develop in the Caribbean can be a threat to the Gulf of Mexico but persistent high pressure ridging in the Northwestern Gulf and increased frequency of frontal troughs will likely be players in steering currents over the next several weeks.

With impending tropical weather threatening Acadiana this weekend I wanted remind everyone to stay apprised of the weather conditions very closely as there will likely be big changes ahead.  Part of that obviously (or hopefully) is watching KATC TV and following us on katc.com.

In addition our weather page, you can find pertinent links to very important web-sites on our Hurricane Center Page.  Our hurricane Center includes a tracking map and links to the local National Weather Service, the National Hurricane Center and Emergency Preparedness information.  These links are all essential to have on hand during a storm.

During the last two plus years I have found Facebook and Twitter as excellent tools for not only disseminating information but gathering it.  They both have strong and weak points, but Facebook in particular I think is important to have on hand, and on your smart-phone, for a hurricane or any emergency situation where traditional lines of communication may be compromised.

Facebook is easy to use and it’s a great way to stay in contact with loved ones and friends…and say what you will about social media, I believe at the very least, it is a great tool in an emergency situation.

During any emergency KATC will be broadcasting live and streaming on the web on katc.com, but you can also follow us on twitter too.  The “tweets” from the Weather Lab meteorologists can be followed right on our weather page so you don’t even have to mess with setting that up if you don’t want to.

On Facebook, I would highly recommend following KATC’s page for the latest news, Dave Baker, Natalie Noah and me (Rob) for the latest weather updates.  If you click on the aforementioned links make sure you “like” the page to get our information streaming to your home page.

Good luck with the storm this weekend and for the rest of hurricane season.  Rob

One of the more important tools I have found in recent years on forecasting tropical activity beyond the normal 1-10 day computer model forecasts is the use of the Madden-Julian Oscillation (MJO) analysis.

Without getting too technical, the MJO describes large-scale waves of weather, or atmospheric perturbations that travel across the entire planet from west to east across the tropical latitudes.  These very large waves of weather, that move roughly at 10-15mph, are characterized by large regions of either enhanced or suppressed tropical rainfall patterns.

The frequency of the large scale planetary waves, can influence an area from anywhere between 30-60 days, but also help us to determine shorter scale weather phenomenon, including areas of enhance tropical storm/hurricane activity, monsoonal rainfall patterns and short-term droughts.

The MJO can also dictate on whether an El Nino or La Nina will develop and will influence each pattern’s severity.

But the true benefit to understanding the MJO and its affect on us in Louisiana is during tropical season. 

The Climate Prediction Center provides weekly analysis of the MJO and while very technical, and challenging my meteorological background, the forecast products including the Global Tropical Hazards Assessment Discussion (GTHAD) yield very important information to us as forecasters.

The GTHAD is is a two week global forecast that depicts areas of concern including above or below normal rainfall and areas of tropical development.  I found this forecast product over the last few years to give me extra ammunition when forecasting longer range tropical predictions.

Now mind you we cannot tell you specifically how strong tropical storms or hurricanes will be, nor where will they strike this far out, but we can say with this product we can forecast where activity is expected to develop with greater certainty over a two week time frame.

Today’s note: If you examine the the most recent GTHAD, the Atlantic Basin looks quite busy, as it usually gets this time of year.

Like death and taxes it’s nearly always a certainty that tropical activity in the Atlantic Basin ramps up dramatically as mid-August approaches. 

This year should be no different.  Nearly every year the busiest part of the season and the strongest storms develop and threaten the Gulf from the last week of August through the first week of October.

On average you can count on some sort of tropical storm or hurricane watch or warning to be posted along the Louisiana Coastline for portions of at least two of the weeks during the month of September.

The consensus forecasts for the season continue to call for anywhere from 12-18 named tropical storms in the Atlantic Basin, 6-10 becoming hurricanes and 3-6 of those hurricanes will likely become major category 3 storms or stronger at some point in their life-cycles.

The Gulf of Mexico has been rather quiet over the last two years after the twin storms of Gustav and Ike wreaked havoc on Louisiana in 2008.  The statistics alone therefore indicate that we will be busier in the Gulf.  With at least one to two major storms threatening some portion of the Gulf Coast. 

How busy will it be and where will the storms make landfall?  We can’t tell you that at this point, but the time is here to have a hurricane plan in place and have your supplies ready to go before the storms threaten.

Over the last couple of weeks in July, tropical  waves have been coming off of the African Coast with regularity, with some spin and not much African dust.  So at this point the forecast for a busy season are very likely to verify.

Whether it’s a busy hurricane season or not, it only takes one strike close to home to make it a bad season. This has been the mantra of the National Hurricane Center and all emergency preparedness officials.

Still weary from the oil spill last year, recent river flooding and long-term drought issues, Acadiana now embarks upon another anticipated busy hurricane season.

The forecasts from the experts this year predict anywhere from 12-18 named storms, 6-10 hurricanes and up to 3-6 major storms (cat 3 or higher) in the Atlantic Basin this year. The 40 year normal is 11, 6 and 2 respectively.

The last two hurricane seasons, especially last year, were considered busy in the Atlantic Basin. But the U.S. coast did not see a direct hurricane strike in 2009 & 2010.  The Northern Gulf of Mexico was very quiet over the last two years as well.  Odds are that won’t happen again this year.

Interestingly enough, the last two busy years in the Gulf saw back-back Louisiana strikes in the form of Rita & Katrina in 2005 and Gustav & Ike in 2008. In fact, Louisiana has averaged a major storm threatening the coastline once every three years dating back to Lili in 2002.  This year would make it three years since the last major threats.

These statistics don’t necessarily dictate that Acadiana will see a major storm. But the long-term odds do favor at least one tropical storm (near 95%) per season to strike near the area and about a one in three year hurricane threat to Acadiana.

In fact, Drs. Gray and Kltozbach do predict nearly a 47% chance of a major hurricane strike this season along the Gulf Coast from Brownsville to the western Florida Panhandle, which given any storm landfall has an impact, direct or indirectly upon Acadiana.

The question then becomes whether we all prepare for the potential threat or threats to come? 

How will this hurricane season go for Acadiana?

No one can tell us that, the science is no where near able to forecast where landfalls will be. Statistics favor the mostly likely time for major storm threats are generally from the last week of August to the first week of October.

Statistics also favor 1-2 storms possible in the Atlantic Basin in June and again in July, but by September tracking two or more storms on average per week will be likely in the Atlantic Basin given this year’s forecasts.

Respected Colorado State hurricane forecasters Drs. Klotzbach and Gray continue to call for an active hurricane season with 16 named storms, 9 hurricanes and 5 major storms (averages over the last 40 years are 11, 6 and 2 respectively).  

 “We continue to foresee well above-average activity for the 2011 Atlantic hurricane season. Our seasonal forecast has been reduced slightly from early December, since there is a little uncertainty about ENSO and the maintenance of anomalously warm tropical Atlantic SST conditions. We continue to anticipate an above-average probability of United States and Caribbean major hurricane landfall.”

Key factors this year include La Nino slowly fading to a neutral condition through the heart of hurricane season which should be an enhancing factor with less upper tropical shear(with the absence of any El Nino). 

Much above normal Atlantic sea surface temperatures continue, although some cooling has been noticed over the last few months, but will serve as an enhancing factor.

While forecasting total net tropical cyclone activity in the Atlantic has been rather accurate and useful to meteorologists, the bottom line is whether how many of these storms will strike the U.S. and more importantly for us, the northern Gulf Coast. 

Seasonal forecasting of landfalls remains mostly a statistical low skill forecast, but as Dr. Gray is famous for saying, “sooner or later the statistics will right themselves”…meaning continued active season forecast will eventually translate major landfalls a la 2004, 2005 and 2008.

After two very quiet years in the Gulf of Mexico, statistics do favor much more activity threatening the Gulf this year with the hurricane forecast team indicating a 47% chance of a major storm striking from the Florida Panhandle to Brownsville (the 100 year normal is 30% for the same area).  Since 1995 odds of Gulf Coast strikes have been 40% or greater with 2009 & 2010 odds roughly equal to this year’s forecast.

While not statistically significant, Louisiana has been struck by major or near major storms with significant storm surges every three years since 2002; Lili (2002), Katrina & Rita (2005) and Gustav & Ike (2008)…hopefully this year we can break that trend!

Drs. Klotzbach and Gray at Colorado State issued there 2011 Hurricane Season Forecast today indicating that the above normal Atlantic Basin hurricane activity will continue for 2011.  Their report cites that above normal Atlantic sea surface temperatures will likely continue on its multi-decadal high while the absence of El Nino will allow for better than average tropical numbers.

The forecast calls for 17 named tropical storms, 9 hurricanes and 5 major hurricanes…the average over the last 40 years is 11, 6 and 2 respectively.  These numbers are similar to the amount of activity in the Atlantic Basin for this past year where 19 storms, 12 hurricanes and 5 major storms formed. 

2010 was considered a very busy year, but the seasonal variations in weather patterns across the U.S. kept most storms either Atlantic systems or storms that were driven well to the south into Central America and Mexico.

The apparent wild-card going into next year is whether La Nina, that developed in 2010, will continue into 2011.  La Nina is cooler than normal waters that pool in the equatorial Pacific.  Typically during La Nina years there is less shear exhibited over the Caribbean and portions of the Atlantic that allows for more storms and more intense hurricanes.

The Colorado state team is not sure whether La Nina will continue into the hurricane season and their forecast is based on neutral La Nina conditions.  But if La Nina persists into the tropical season then their forecast numbers will likely increase.  On April 6 Drs. Kltozbach and Gray will update the 2011 season forecast based on the latest La Nina and other atmospheric trends.

As forecasted by Drs. Klotzbach & Gray and NOAA, the 2010 Hurricane Season was a very busy one with 19 named storms, 12 hurricanes including 5 major storms.  Fortunately for the U.S. most of the storm tracks were either Atlantic storms or systems that skirted well to the south of the Gulf Coast across the Caribbean and into Central America and Mexico.

While the amount of annual activity and hurricane potentials can be estimated quite well, forecasting where the storms are going to track remains as variable as our day to day weather patterns. 

This year was a very hot summer across much of the U.S. particularly over the nation’s mid-section and south.  In fact, June-August collectively were the hottest on record in Acadiana dating back through 1893.  This was due to a large high pressure pattern that led to a very hot and dry summer for Louisiana and Acadiana.  The strength of this ridge induced slight (or just enough) low pressure troughing along the East U.S. coast thereby steering most storms away from the U.S.  This semi-permanent ridge also shunted most activity away from the Gulf of Mexico keeping low latitude systems well to the south.

This past year had many similarities as compared to the very busy season of 1995 when none of the big storms struck the U.S.  In fact, no hurricanes made landfall along the entire U.S. coastline this year marking the first time in recorded history that as many as twelve hurricanes occurred in the Atlantic basin without a U.S. landfall.

Our luck has continued from 2009 with only three tropical storms making landfall in the U.S. over the last two years equalling the last “quiet” period during the 1990-1991 hurricane seasons.  It has been even better for the Florida Peninsula and East Coast as for the first time since reliable records have been kept dating back to 1878 that no hurricanes have made landfall in the last 5 years.

So while the forecasts were quite ominous for this past hurricane season, the amount of U.S. damage was minimal…this was due mostly to seasonal atmospheric variability outside of the tropics.  Unfortunately there will likely be more busy seasons ahead and our luck may run out and the statistics will “right” themselves…for now we can breathe easy until next year.

The preliminary blush on next year should be quite busy again with La Nina developing in the equatorial Pacific…this is usually a hurricane intensity and frequency enhancer in the Atlantic Basin.  Colorado State’s forecast for 2011 will be issued on December 8th…stay tuned.

Hurricane Hunters investigating a disturbance in the Northwest Caribbean near Honduras this afternoon found robust tropical storm force winds and thus the National Hurricane Center upgraded this system to Tropical Storm Paula.  The 16th named storm of the 2010 season.

Paula was sporting 60mph sustained winds Monday afternoon as it raked the northern coast of Honduras.  Paula is forecast to become a hurricane Tuesday and will likely bring very heavy, flooding rains to Honduras, Belize and the Yucatan Peninsula this week as the system is expected to meander in the Northwestern Caribbean through the end of this week.

Ultimately this system will get caught up in the westerlies and move northeastward or eastward affecting Cuba this weekend.  Residents of South Florida may also have to keep an eye on this meandering system later this week.

Paula will not be a threat to Louisiana as strong upper level westerlies will keep the state and Acadaiana high and dry through the weekend.