Archive for the ‘Extratropical cyclone’ Tag

Ida Is Weakening As Predicted – 11-9-09

The visible satellite image below is from 10:15 AM Eastern Time.  Wind shear has increased over Ida and it has moved off the warm Loop Current.  Dry air has been drawn in and has significantly disrupted the storms symmetry.  Water temperatures under her are barely enough to support a hurricane.  My source expects 50 to 60 mph winds when she makes landfall.  My advice is to consult the Weather Channel on television and/or your favorite on-line sources.

Currently, 19 ft. waves are being formed by the storm’s winds.  After watching a satellite loop showing the storms movement, I placed a blue dot as my approximation of the center.

Ida11-9-09-1015aEST

Some of the information on this site is published close to “real-time”  particularly as it applies to tropical weather.  But it is important to remember that the only “official” source of information is the National Hurricane Center. Decisions concerning life or death, property, and such should not be made based solely on the information found on this site or any other sites that are recommended here. unless they are official. Listen to your local authorities when conditions are life-threatening or there is possible loss of property.


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IDA FORECAST – 11-8-09

Some of the information on this site is published close to “real-time”  particularly as it applies to tropical weather.  But it is important to remember that the only “official” source of information is the National Hurricane Center. Decisions concerning life or death, property, and such should not be made based solely on the information found on this site or any other sites that are recommended here. unless they are official. Listen to your local authorities when conditions are life-threatening or there is possible loss of property.


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THE ENTIRE FIRST PARAGRAPH THAT FOLLOWS  IS A DIRECT QUOTE FROM DR. JEFF MASTERS (PICTURED BELOW) THAT WAS CUT AND PASTED FROM HIS WEATHER UNDERGROUND SITE; DR. MASTERS IS MY MOST RELIABLE AND DEPENDABLE SOURCE WHEN IT COMES TO TROPICAL WEATHER; HE IS A DEDICATED ‘WINNER:”  ONE REASON WHY I DEPEND SO HEAVILY UPON HIS WORK IS THAT HE IS NOT OPERATING UNDER THE CONSTRAINTS OF NATIONAL WEATHER SERVICE FORECASTER BUT HE BENEFITS FROM THEIR INTERPRETATIONS AS WELL AS FROM OTHER NATIONAL WEATHER SERVICE RESOURCES.  HE IS DEDICATED, “UP FRONT,” AND RESPONSIBLE.

bio_jeffm
Dr. Jeff Masters

The forecast for Ida


Posted: 10:21 AM EST on November 08, 2009


“The high wind shear of 20 – 25 knots currently affecting Ida is forecast to persist at that level until Monday night. Some slow intensification is still possible while Ida remains over the exceptionally warm water of the Loop Current in the Gulf of Mexico, through tonight (Figure 2). Late tonight, Ida will be crossing over waters of 26°C, which is barely enough to support a hurricane. With shear still expected to be at 20 -25 knots, I expect weakening to begin early Monday morning and accelerate on Monday afternoon. At that time, Ida will encounter 40 knots of wind shear associated with a cold front over the Gulf of Mexico, and begin transitioning to an extratropical storm. Exactly how strong Ida will be when it reaches the coast early Tuesday morning–and indeed if Ida even does reach the coast–is a forecast with high uncertainty. The computer models have a tough time forecasting the evolution of a tropical cyclone into an extratropical cyclone, and the models are all over the place on what will happen. Most of the models foresee a landfall near 1 am EST Tuesday between Mississippi and Pensacola, Florida, then a path northeastward over the Southeast U.S. However, Ida could come to halt before reaching the coast and turn west towards Tampa (the UKMET model’s forecast), or turn south back over the Gulf of Mexico (the NOGAPS model’s forecast). In any case, storm surge and heavy rain appear to be the main hazards from Ida. The GFDL model (Figure 3) is forecasting rain amounts of 4 – 8 inches for a large swath of the Gulf Coast, and there is a risk of tornadoes if the warm air from the core of Ida pushes ashore.”  END QUOTE

From my point of view, (this is Cloudman23 writing) everyone on the Gulf Coast  from Mississippi to Key West should have a “heads up” mindset while Ida is out there.  As Dr. Masters said, the computer models have a difficult time when the tropical to extratropical metamorphoses takes place.  Furthermore, the chance of tornadoes (mentioned by Dr. Masters) in association with warm, moist air from Ida and its inherent instability in such situations, this storm should not be taken lightly.

11-8-09 Ida 3pEST

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: https://cloudman23.wordpress.com/2008/08/30/gfdl-model-a-great-source-for-an-animation/https://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

11-7-09Ida

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STORM OFF THE CAROLINAS IS NOT OF TROPICAL ORIGIN

Two independent left clicks should enlarge this image.
Two independent left clicks should enlarge this image.

The storm that is at the North Carolina-South Carolina border may look like a hurricane but it is not. The National Weather Service is calling it a non-tropical cyclone. A more common term for such cyclones is “extratropical cyclone.” “Extra” means “outside of.” This refers to their developing outside of the tropics. Hurricanes are tropical cyclones. Even though in the northern hemisphere they both rotate counterclockwise around a central region of low pressure, tropical cyclones have warm cores and are often referred to as “warm core lows.” Relatively cold air occupies part of most extratropical cyclones and this is most certainly the case with this one. The doublet image of the system that I have prepared which you see (above) shows a visible satellite view of the storm earlier today and compares it with a surface analysis.  The two do not represent exactly the same time but it’s close; 44 minutes separate them. So, it’s a near match.

For those of you who know your frontal symbols, notice that there are three different types of fronts, all three representing boundaries between relatively warm air and relatively cool air. An occluded front arcs out from the center of the storm and there is a warm front whose axis runs ENE-WSW, and a stationary front curving down to the south.

In spite of the fact that it is extratropical and therefore un-named, it has many of the characteristics of a tropical storm.  People located in the storm’s vicinity should be alert to the potential hazards. Also, there is a strong chance that it will interact with tropical storm Kyle in the interesting Fujiwhara effect.  If you are interested in that phenomenon, see the following link and also view the post that followed it (at the next higher post location on the page).  To do that you will need to scroll to the top of the page and click on the “blog” tab.  That will access you to all entries.

Tropical Wave AL 93 Might Dance Within a Few Days!

HURRICANE IKE CIRCULATION – LESSON 1

LEFT CLICK THESE IMAGES TO MAKE THEM LARGER.  YOU CAN ACHIEVE A NICE HIGH RESOLUTION VIEW OF THE IMAGE OF IKE ABOVE WITH A SECOND LEFT CLICK.

Inflow consists of the harder-edged clouds with sharp contrast – Outflow consists of the more diffuse cirrus and cirrostratus of the upper layer.

PLEASE REMEMBER THAT THOUGH THIS IS A TUTORIAL, THE LOCATIONS OF STORMS AS SHOWN ON THE GRAPHICS ARE TIME-SENSITIVE.  TO AVOID MISUNDERSTANDINGS, CONSULT THE DATE AND TIME OF THE POSTING.

With this post you can either simply enjoy the high resolution image of Ike and leave it at that point or explore deeper into the dynamics of storms such as this.

I have provided a large image (above) of Ike completed earlier today followed by smaller images contrasting the circulation below with the circulation above.  Thirdly, you will find below an image of what might seem like a very odd looking hurricane compared to what you have been looking at this season.  To see it, you must ask for more detail when the invitation appears at the end of the next paragraph.

Because of only a small amount of sheer and other factors, Ike is a well-formed system.  And – if you can get past its destructive character you might marvel at its beauty.  I speak of it as though it were a living thing.  In many respects, it is a separate entity with a life of its own.  We even talk about the life cycle of such a storm.  We personify it with a name, in this case a male name.  Its winds spiral because of the Coriolis effect and the whole storm’s path responds to the Coriolis effect – sometimes that is evident, sometimes it is not.  If you find yourself confused about the Coriolis effect, please be patient because I intend to post an item soon, with an explanation of certain aspects of hurricanes which might seem to be contradictions when they are not at all.  Believe me, misunderstandings about the Coriolis effect does cause considerable confusion. If you are interested in more detail about the movement and the energy within this storm, please read on