Ida’s Current Model Forecasts – 11-7-09

The total amount of thermal energy at the surface in the Western Caribbean is high and wind shear aloft is relative low so it is anticipated that Ida will intensify before striking the Yucatan Peninsula.  The Yucatan does not have the type of topography that we associate with significant weakening of a storm due to friction.  But, read what Dr. Jeff Masters says this morning about the fate of Ida after she enters the Gulf of Mexico:

“Once Ida crosses into the Gulf of Mexico on Sunday night, the storm will encounter much cooler SSTs and a strong trough of low pressure that will dump cold air into the storm and bring 40 knots of wind shear. This will cause Ida to lose its tropical characteristics and become a powerful extratropical storm with 45 – 55 mph winds. It is highly unlikely that Ida will hit the U.S. as a tropical storm, but it could still bring tropical storm-force winds of 45 mph to the coast next week as an extratropical storm.”

As for me, I have been favoring the Geophysical Fluid Dynamics Laboratory Model (GFDL) for the path that Ida will take; currently,  if I had to depend upon only one of the many models, that would be the one – in most instances anyway.  I have no real science to back that up – only my perception based upon experience.  Call it a “gut level” good feeling about the model’s past performance if you will.  Therefore I expect Ida to eventually curve rightward as the GFDL shows in the plot below.  By the time it does I expect it will have lost its tropical characteristics though the winds will still be strong.  In other words, it will become extratropical.  TO GET INSTRUCTIONS ON OBTAINING THE GFDL ANIMATION CLICK ON THE FOLLOWING LINK: http://cloudman23.wordpress.com/2008/08/30/gfdl-model-a-great-source-for-an-animation/http://cloudman23.wordpress.com/2008/08/30/gfdl-model-a-great-source-for-an-animation/

The prefix, extra, means “outside of” or “beyond.”  Extratropical cyclones are sometimes called cold core lows whereas tropical cyclones are warm core lows.  When a tropical cyclone draws in cold air (as usually happens when a front interferes with the storm) it becomes extratropical.  The majority of the world’s extratropical cyclones develop in the middle latitudes (30 degrees to 60 degrees latitude) and for that reason are often referred to as middle latitude cyclones.

Graphic courtesy of Jonathan Vigh of the Department of Atmospheric Science at Colorado State University

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Gulf Coast Residents – Ida Is Worth Watching

Ida developed quickly – in fact at a record pace (see Jeff Master’s Weather Blog at http://www.wunderground.com/blog/JeffMasters/comment.html?entrynum=1372).

Though relatively high wind shear could prevent Ida from becoming a significant threat to the U.S. mainland it is a storm that is worth watching, partly because warm Gulf waters could nurture it.

Here is a recent forecast plot from the National Hurricane Center (left click to enlarge image):

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Jimena and Erika

During the next few months I will be on line only intermittently.  For quick indicators about tropical weather systems I recommend the Weather Channel if you have cable and also the Masters’ Blog at http://www.wunderground.com/tropical/

The Masters’ Blog link is usually at the upper part of the page on the right hand side.

Please remember if you are in tropical weather territory – it doesn’t always happen to the “other guy.”  And, though landfall events have not been abundant this season, 1992 was also an El Nino season with a slow start and only one hurricane made landfall upon the U.S. coast that year.  ANDREW!  My point?  “All it takes is one!”  I beg you to be prepared – even if you are far from the coast because the effects of a tropical weather system can be devastating many miles from where it makes landfall.

Here are the current potential pathway advisories on Jimena and Erika.

Left click the image in order to enlarge. In some

instances a second left click will enlarge even further.

ANA, BILL, AND CLAUDETTE!

To have this current explosion of activity in the Gulf and Atlantic after so many quiet weeks is a real attention-getter.  Most recently, a tropical system off the Florida panhandle has developed into a tropical storm.  In the meantime Ana and Bill out in the Atlantic are both commanding attention.

Tropical systems are not all bad, particularly when the wind velocities are not too high and this is because they can provide much needed precipitation.  Let’s hope that these three systems prove to be more of an advantage than anything else.  So many people are reminded of Andrew in 1992, another year in which El Nino was a  factor.  Andrew was the only hurricane to make landfall in the U.S.A. that season but he was a whopper and there are many people yet today who will testify that it changed their lives – myself included.

I am likely to be inactive on this site for the next few days for two reasons.  My laptop is behaving badly and either needs some serious attention (like a new hard drive) or I need to bite the bullet and get another machine.  Also – I will be traveling.  For those of you who know me – don’t be alarmed.  The traveling has nothing to do with the current tropical weather activity.

In the meantime if you want to stay on top of things weatherwise I recommend the Weather Channel if you have cable and also the Masters’ Blog at http://www.wunderground.com/tropical/

The Masters’ Blog link is usually at the upper part of the page on the right hand side.

Peace be with you!

tat

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NANA, TROPICAL DEPRESSION 15, INVEST 90L, AND INVEST 99L.

FOR EASIER VIEWING, ENLARGE THE IMAGE WITH A LEFT CLICK.

There is “action” in the Atlantic basin today in-so-much as multiple systems are concerned.  The Gulf of Mexico and the Caribbean are considered to be a part of the Atlantic Basin.  The most immediate concerns reside in Puerto Rico, I should think, due to tropical depression 15 nearby.  If it moves northeastward, as predicted, the island will no doubt get precipitation that it doesn’t need considering the pelting it has already taken this season.

Storms do not get named until they “graduate” from tropical depressions to tropical storms.  But, there is a tropical depression out there today with a name, Nana.  She is “named” because she had reached tropical storm status earlier in her history and she retains that name even though she has now deintensified as was predicted.

That is not uncommon but there has been a very interesting occurrence with Nana.  Wind shear earlier on broke her into two distinct parts.  The northern segment (Nana) is not likely to survive but the southern segment, Invest 90L, stands a chance of intensifying.  Both Invest 90L and Invest 99L are tropical disturbances (also called tropical waves).  If you didn’t already know you might have guess that numbers are assigned to tropical disturbances and when under “investigation” they are labeled with the abbreviation, “invest.”

So, there are four systems out there being watched.

Classification of Synoptic-Scale Lows of Tropical Origin:

1. Tropical disturbance (tropical wave) – An area of organized convection, originating in the tropics and occasionally the subtropics, that maintains its identity for 24 hours or more. It is often the first developmental stage of any subsequent tropical depression, tropical storm, or hurricane.

2. Tropical depression – A tropical cyclone in which the maximum sustained surface winds are 38 miles per hour (33 knots) or less. Characteristically having one or more closed isobars, it may form slowly from a tropical disturbance or an easterly wave which has continued to organize.  NOTE FROM CLOUDMAN23 – By convention, it has been the practice of the National Hurricane Center to associate the beginning of “rotation” with the transition from disturbance to depression.  In fact, in some definitions rotation is an important element.  Generally, this causes no problem because once one or more closed isobars are needed to plot the pressure, rotation has almost always begun.

3. Tropical storm – A tropical cyclone in which the maximum sustained surface winds are from 39 miles per hour (34 knots) to 73 miles per hour (63 knots). At this point, the system is given a name to identify and track it.

4. Hurricane (or another name depending upon geographical location – e.g. typhoon) – The name for a tropical cyclone with sustained winds of 74 miles per hour (65 knots) or greater in the North Atlantic Ocean, Caribbean Sea, Gulf of Mexico, and in the eastern North Pacific Ocean. This same tropical cyclone is known as a typhoon in the western Pacific and a cyclone in the Indian Ocean.

(definitions source is the Weather Channel Glossary found at http://www.weather.com/glossary/a.html

During my long college teaching career I was asked from time to time why such a list was not labeled “Classification of Synoptic-Scale Cyclones of Tropical Origin” instead of Synoptic-Scale Lows. The reasoning is straight-forward.  The first member of the quartet, the tropical disturbance, is not cyclonic.  In order to be cyclonic there must be rotation.  Therefore, though all cyclones are lows, not all lows are cyclones.

CARIBBEAN SYSTEM HAS MEDIUM POTENTIAL FOR FURTHER DEVELOPMENT.

TWO LEFT CLICKS WILL ENLARGE IMAGES A GREAT DEAL

According to the National Hurricane Center, the tropical wave in the Caribbean has a medium potential for tropical cyclone development.  For those of you who don’t understand that here is a brief explanation.

In order for a system to be cyclonic there must be a rotation of the wind around a low pressure center.  Presently there is no indication of a closed rotation in this otherwise impressive system.  A tropical wave (also called a tropical disturbance) becomes a tropical depression if rotation begins.  Ordinarily the rotation itself signals a maturing (growth) of the system.  Once rotation begins, the conservation of angular momentum kicks in such that as the wind spirals closer and closer to the center its velocity increases.  Tropical depressions can intensify into tropical storms (39-73 mph) and the latter can intensify into hurricanes (74 or more mph).  Here is the formal statement from the Hurricane Center:

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TROPICAL WEATHER OUTLOOK

NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL

800 PM EDT SAT SEP 20 2008

FOR THE NORTH ATLANTIC…CARIBBEAN SEA AND THE GULF OF MEXICO…

1. A TROPICAL WAVE…ACCOMPANIED BY A SURFACE LOW PRESSURE SYSTEM OVER THE NORTHEASTERN CARIBBEAN SEA…IS PRODUCING WIDESPREAD CLOUDINESS AND SHOWERS OVER THE LESSER ANTILLES…AND ADJACENT CARIBBEAN AND ATLANTIC WATERS.  THIS SYSTEM IS SHOWING SIGNS OF ORGANIZATION…AND UPPER-LEVEL WINDS ARE EXPECTED TO BECOME A LITTLE MORE FAVORABLE

FOR DEVELOPMENT OVER THE NEXT COUPLE OF DAYS.  A TROPICAL

DEPRESSION COULD FORM DURING THIS TIME AS THE SYSTEM MOVES SLOWLY NORTHWESTWARD.  AN AIR FORCE RESERVE UNIT RECONNAISSANCE AIRCRAFT IS SCHEDULED TO INVESTIGATE THE SYSTEM ON SUNDAY…IF NECESSARY.  REGARDLESS OF DEVELOPMENT…LOCALLY HEAVY RAINFALL AND STRONG GUSTY WINDS WILL AFFECT MUCH OF THE LESSER ANTILLES…THE VIRGIN ISLANDS AND PUERTO RICO THROUGH SUNDAY.

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On the infrared satellite image above from the U.S. Naval Research Lab, I have marked two islands that don’t need any more precipitation for a while due to recent tropical systems having dumped heavy (and deadly) loads upon them.  Flooding and mudslides are likely if this disturbance moves as expected, over the islands.  For the same reasons, Cuba also stands a risk of increased problems.

Please visit the rest of this web-log at http://cloudman23.wordpress.com/.  If you are interested in weather, there are some tutorials scattered about and more will be added in time.

Hurricane Ike – Where Is He Going? No One Knows!

Though Hanna is a concern these days, it appears that Ike is going to be much more powerful.  Perhaps in 5 days we will know what he’s going to do but right now there are significant differences of “opinion” among the models and, I presume, among the forecasters.  One “take” is that Ike will veer at some point and stay in the Atlantic, maybe posing a substantial threat on the East Coast all the way from Florida up.  The other “take” is that he could slip into the Gulf of Mexico, at which time the West Coast of Florida and other Gulf Coast states could get a big one.

This afternoon Ike’s winds have been sustained around 140 mph – a Cat 4.  This hurricane is a classic Cape Verde type and not one to be casually regarded.  I urge you to read Dr. Jeff Masters’ assessment of Ike in his posting this morning.  If it no longer appears you can find it archived at the site.

http://www.wunderground.com/tropical/

There are some widespread misconceptions about the relationship between the wind’s velocity and the force it is able to exert.

Hanna Expected To Become A Hurricane

The forecast chart below was derived from WeatherUnderground and represents the 2 pm EDT forecast plot.  Currently tropical storm Hanna is expected to become a hurricane if it moves, as expected, over the warm waters of the Bahamas (fed by the warmth of the Florida Current and the Antilles Current).  The current between the Florida Peninsula and the Bahama platform is ofter referred to as the Gulf Stream but most physical oceanographers consider it to be the Florida Current.  It is implied that the Gulf Stream begins where the Florida Current merges with the Antilles Current.  Here is a link to Surface Currents In the Atlantic Ocean:

http://oceancurrents.rsmas.miami.edu/atlantic/florida.html

From the menu box near the top you can individually check out the Loop (mentioned in the previous posting), the Florida Current, the Antilles Current, and the Gulf Stream.

One of the most common misconceptions in physical oceanography is that the current off the eastern coast of Florida is the Gulf Stream.  If you are interested in common misconceptions in science that I have encountered through the years, here is a link to that topic (websites by Davis):

http://librarytech.org/learningzone/science1.html

If this does not come up, click on the link at the right margin of this web-log on the Common Misconceptions In Science notation.

PLEASE LEFT CLICK TO MAKE IMAGE LARGER