Archive for the ‘Satellite images’ Category

Central American Death Toll Up to 39!

NOAA IMAGE

NOAA IMAGE

LEFT CLICK IMAGE TO ENLARGE.

The entire post beyond this sentence is taken verbatim from this morning’s weblog by Dr. Jeff Masters’ at http://www.wunderground.com/tropical/.

“One of this hurricane season’s biggest disasters continues to unfold in Central America, where the death toll now stands at 39 from ten days of heavy rains triggered by last week’s Tropical Depression Sixteen and this week’s tropical disturbance 91L. At least 10,000 homes have been destroyed and 250,000 people made homeless by the floods. Hardest hit is Honduras, where 23 are dead and 8 missing in flash floods and landslides. Approximately 60% of the nation’s roads have been damaged, and the flooding is the worst since Hurricane Mitch of 1998 killed 10,000 people there. The past week’s flooding has also killed four in Guatemala, seven in Costa Rica, four in Nicaragua, and four in El Salvador. In Belize, damage is at least $15 million from the floods, and some areas are seeing flooding worse than was experienced during Hurricanes Mitch and Keith. Satellite estimates suggest that up to a foot of rain has fallen over some parts of Central America in the past week. The heavy damage to crops across the region will likely cause severe food shortages in coming months, and substantial international aid will be required.

Rains over the hardest hit areas of Central America have eased in the past day, with only 1-2 inches of rain reported. However, visible satellite loops show that heavy thunderstorm activity continues over the Western Caribbean, and has moved into northeast Honduras and Nicaragua this morning. While there is currently little chance that a tropical cyclone will form in the Western Caribbean over the next five days, persistent low pressure and sporadic heavy rains will continue to affect the region. A strong cold front is expected to push southward into the area next Tuesday or Wednesday, and the tail end of this cold front could serve as the nucleus for a new tropical disturbance that will generate another round of very heavy rains for Honduras and Belize late next week.

Elsewhere in the Tropics, no computer models are forecasting tropical storm development anywhere in the Atlantic over the next seven days.”

NORBERT IS MOVING TOWARD THE NORTHEAST, 10-12-08

LEFT CLICK IMAGE TO ENLARGE

LEFT CLICK IMAGE TO ENLARGE

LEFT CLICK IMAGE TO ENLARGE

LEFT CLICK IMAGE TO ENLARGE

IMAGES ARE TIME SENSITIVE!

Norbert has reached the mainland of Mexico after recently ripping though the Baja peninsula.  It’s strength is likely to diminish quickly but it will maintain tropical storm intensity for quite some distance into Mexico and could easily effect weather in west Texas and New Mexico early this week.  Notice that the storm is now elongated (oval, rather than circular).  The elongation is along the axis of wind shear which is depicted in the second image which was completed about two hours earlier than the first image.  So, the two images are not a perfect match-up but they are close.  It looks as though the storm is likely to continue traveling 40 to 45 degrees east of due north along the direction of winds aloft.

The Coriolis Effect In the Real World – A Tutorial (Part 2) – Cyclones & Anticyclones

Left Click To Enlarge Image

I suggest that, though there may be some repetition, please read Part 1 first.  To go to it quickly, either scroll down or click on this link:

https://cloudman23.wordpress.com/2008/10/02/the-coriolis-effect-in-the-real-world-a-tutorial-part-1/

The set of weather maps, provided by NOAA, shows the remains of Ike after it began to head toward the northeast. At this latitude there is a tendency for weather systems in the middle latitudes to travel generally from west to east.  Notice the cold fronts which indicate that Ike had changed from tropical to extratropical.  The cold fronts represent the leading edge of cooler air being thrown out of the anticyclone (high with rotation) centered over the Eastern Dakotas. That air is coming “down” from some component of the north whereas the air on the “warm” side of the cold fronts is coming up from some component of the south and is being thrown out of the anticyclone centered off Florida.  So, we have a cyclone (low with rotation), Ike, between two anticyclones.

The only alterations I have made to the first map are 1) cropping of the original, 2) labeling of the fronts 3) placement of the red L and the two blue H’s, and 4) darkening of two of the isobar values making it easier for you to read.

Isobars are imaginary lines, of course, and plot equal pressure.  For example, every point on the 1020 isobar was believed to have had a pressure of 1020 millibars at the time of observation. In many ways isobars are analogous to contour lines on topographic maps.  In fact, the two “highs” on a topographic map would be hills and the “low” would be a trough-shaped valley between the hills.  Sticking with that analogy, surface runoff water would tend to flow down the hillsides along a stream gradient (or gravity gradient) toward the lower valleys.  In the simplest of topographic and geological settings the water would flow down the hills in a radial pattern, just as air would flow out of the highs were it not for the Coriolis effect.  Though water flowing down hillsides in stream channels does not respond to the Coriolis effect, air flowing on the scale depicted here does by deflecting to the right of the pressure gradient direction.  So, in the second version of the weather map I have drawn blue lines of which two are comparatively long, showing the direction that the air would flow if the earth did not rotate on it’s axis.  But, remember, rotation of the globe causes the Coriolis deflection to the right in the northern hemisphere and to the left in the southern hemisphere.

It’s important to note that the deflection is with reference to the object or fluid in motion.  For example, if someone driving directly toward you turns right, he/she will have turned to your left.  Though that person’s turn would be to your left, it is still a right turn.  So, in northern Texas the green line shows that the air is moving to the right of the pressure gradient direction (light blue) – even though that green arrow points toward the left side of the map.  Just put yourself in the position of the air in motion and you should not have difficulties with this.

This, then, shows why air in the northern hemisphere moves clockwise around anticyclones and counterclockwise around cyclones.

Near the end of my first tutorial on the Coriolis effect I revealed that the following question had come up often during my teaching career: “If the Coriolis effect is an important influence in large scale weather systems, and since hurricanes are synoptic scale (a type of macroscale) system, why do hurricane winds turn left in the northern hemisphere and right in the southern hemisphere?”

The “obvious” left turning of air within hurricanes causes confusion among many people who are trying to understand air circulation – particularly if they are starting from scratch without knowledge of the Coriolis effect or the pressure gradient force and how the two engage in a tug of war.  I understand the confusion because seeing the shape of hurricane rain bands on radar and arcuate cloud band alignment clearly shows how the air turns left as it gets closer and closer to the hurricane’s eye wall.

Not too many years ago I heard a person who should know better, during a television weather report, explain to the viewing audience that hurricanes were so powerful that they did not respond to the Coriolis effect – referring to the “left turns” that she was showing on the satellite loop that was being projected.  I don’t know whether or not in some previous weather report she had mentioned the Coriolis effect but it seemed to me that might have been the case.  In her honest attempt to educate some of her audience, she gave them information which was entirely incorrect – perhaps because of misinformation given her or maybe some general assumptions she had made.  You see, it is the Coriolis effect that forces the counterclockwise rotation in the first place!

In this last illustration (below) you are looking at a satellite image of hurricane Fran (1996).  I have drawn blue pressure gradient lines and red air flow lines which clearly show the rightward deflection (in spite of the fact that the air does turn left as it approaches the eye wall.  Notice, however, that no matter where pressure gradient lines are placed along the air flow lines, the deflection of the “real wind” is always to the right of the pressure gradient line.

Once again, as in Part 1, I have not truly explained the Coriolis effect; I have merely described it and illustrated it.  I have not explored the nitty-gritty.  I have implied that it is only an apparent force.  You might want to explore other attempts to describe the Coriolis effect – perhaps via an Internet search.

Finally, in the interest of accuracy, I must admit that I have simplified to the point of leaving out some important forces that play a roll in determining the actual direction that air moves (from high toward low) in its quest to reach pressure equilibrium.  Among those are friction, centripetal force, and centrifugal force.  The conservation of angular momentum is an important consideration and accounts for the increase in wind velocity as the air gets closer to the storm’s center.

Left Click To Enlarge Image
Left Click To Enlarge Image

FLORIDA MAY HAVE A TROPICAL VISITOR LATER THIS WEEK

Left click on image to enlarge.

Left click on image to enlarge.

From late September on through the remainder of the official hurricane season, systems that can develop into named storms begin to pop up in the Caribbean and Gulf of Mexico.  One such development may be occurring now.

An interesting area in the vicinity of the Yucatan is being watched by the National Hurricane Center.  I have marked the approximate center which is hard to pinpoint since there is no apparent closed surface circulation at this time.  I may have my blue dot positioned a bit too far to the east.  It’s easier to do when using loops rather than stills like this image.  If you want to try that, here is a good page to get some nice loops:

http://www.ssd.noaa.gov/PS/TROP/trop-atl.html

I have looked at some of the models on this one and there are indications that it could eventually move toward Florida and provide significant rainfall.  It is my opinion that interests along the West Coast of Florida should pay attention to this.  Right now the wind shear over the storm is about 20 mph.  There is some chance that it could slowly strengthen as it moves toward the northeast later this week.  Probably around the middle of the week it will be influencing some part of Florida.

Tonie A. Toney

12:50 PM EDT 9-28-08

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!

THE FUJIWHARA EFFECT MAY OCCUR SOON – HEADS UP.

Though if it does occur it won’t be as stark as this Pacific Ocean weather event, but it should still be quite interesting.  If you are interested please read the previous post.  If this is the only one you see, scroll to the top of the page and click “Blog” or go to https://cloudman23.wordpress.com/

Tonie A. Toney (Cloudman23)

Tropical Wave AL 93 Might Dance Within a Few Days!

A second left click should enlarge image further.
A second left click should enlarge image further.

There is a possibility that the very interesting Fujiwhara effect might occur within the next few days.  In the image above I have placed a red dot upon the tropical disturbance that is tormenting Puerto Rico and Eastern Hispaniola and a light blue dot upon an extratropical low that is off the Eastern Seaboard and probably kicking up some big waves.  If the tropical system shoots north as the models are predicting, the two could interact in the Fujiwhara effect.  Here is a well-written link about that phenomenon.

http://weather.about.com/od/hurricaneformation/a/Fujiwhara.htm

The extratropical system might even back up a bit in response to a rotation around a common axis with the tropical system.  Go to this link now if you would like to see a rendition of what might happen:  (There are four helpful buttons – reverse, stop. forward, and single step).

http://www.atmos.washington.edu/~ovens/loops/wxloop.cgi?eta_pcpn_slp_thkn+///6

SPECIAL NOTE:  THE LINK IMMEDIATELY ABOVE IS VERY TIME SENSITIVE.  IT MAY NOT SHOW WHAT I’VE DISCUSSED IN THIS BLOG UNLESS YOU VIEW IT ON THE DAY THIS WAS POSTED.   AFTERWARDS THE FORECAST MIGHT CHANGE.  IF THE FUJIWHARA EFFECT ACTUALLY COMES TO FRUITION WE WILL BE ABLE TO SEE IT VIA LOOPS THAT ACCELERATE TIME.

Of course, I did not come up with this notion on my own.  My tip came from the WeatherUnderground blog posted by Dr. Jeff Masters at 10:43 AM EDT today (September 23, 2008).  He also mentioned it yesterday.

Natural processes can be lethal and cause heartbreak but they can also be breathtakingly beautiful.  If the Fujiwhara effect happens to occur, perhaps we will have the opportunity to watch two spiraling systems dance together for a while, just as spiraling galaxies can do as they get close to each other.  Let’s hope the prediction is “right on” and that we can focus upon an event that is NOT creating havoc as did Ike.  Enjoy!

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 https://cloudman23.wordpress.com/.  If you are interested in weather, there are some tutorials scattered about and more will be added in time.