[Res] Convection and gyres

I have decided that, from now on, I will prefix [Res] to posts in which I will talk about things closely related to what I study. I will still try to make them as simple as possible though!

Just wanted to make a quick update on interesting things I've seen on the latest active MJO, which is now creeping close to the Maritime continent, as seen in the latest water vapori image from NRL. First of all, check out all those deep colors there!  Also, take a look at TS 5  a little north going to an inevitable landfall.

But what has really been  getting my attention lately has been all the apparent rotation that the model analyses keeps showing. Below is a plot of non-divergent winds and vorticity contours (Note that for this plot, negative values in the southern hemisphere is cyclonic).  There are four clear cyclonic gyres in the Indian Ocean right now (one of them being TS 5).

If we overlay them with satellite IR (once again from NRL), we can observe that some of them roughly correspond to cloud activity. It is worthwhile to notice that they seem to pop up more and more to the east as the MJO propagates, and grow as they move westward, although I do not have enough info to back it up solidly. This is why the MJO is considered a complex, made out of cloud superclusters and propagating waves inside the packet.  In the figure below I also added a red arrow indicating the westerly winds associated with this complex. They seem to have maintained the same strength through the last couple of days.

Mosaics of the World

On this entry I just want to post some global images. I find them very interesting since they show how different weather can be at different areas of the world at any given time. I will keep this entry simple and free of some of the technicalities and jargon of our field.

The first one is a global mosaic image of water vapor obtained from the University of Washington's dataset.  In this image we can appreciate how different patterns dominate different latitudes. Near the equator we see a long band of patchy cloudiness. This is what we know as the Intertropical Convergence Zone (ITCZ), and we usually associate it with ascending motion and convergence of the trade winds. In previous centuries, sailors despised this area because of its tendency to be either calm (weak winds), or because of the terrible storminess associated with the ITCZ.  Clouds in this region can be very high (more than 15 km high) and very intense!

The other area that is quite apparent is in the midlatitudes. Here we see a little waviness and some big looking storms, known as extratropical cyclones. This area is dominated by the troughs and ridges that make the everyday weather of areas like the United States and Europe. These guys are usually embedded in a west to east motion that we like to call the westerlies.

Even these features just look like everyday weather patterns that just move around, making some places sunny and other rainy, they also constitute important pieces of our planet's general circulation, and are key to the poleward transport of energy, cooling the tropics and warming the poles.


In this infrarred (IR) image, obtained from the CLAUS database, we can observe the same features. Here, bright white colors denote cold temperatures. Notice how tropical clouds can be very white, evidencing how high these clouds can be. The image is more grey-ish closer to the poles because it is much colder there than in the tropics and hence the satellite captures less outgoing radiation. A lot of satellite sensors obtain their data this way and we call them passive sensors.

This last image, recently taken from CIMMS MIMIC-TPW shows some of the aforementioned features. The big line packed with precipitable water near the equator is the ITCZ, the circle is the currently active tropical storm 5, and the black rectangle is the active phase of the MJO, which I have mentioned in previous posts. There are also some interesting river-like features at higher latitudes, which is often related to moistures being carried by frontal systems and troughs. 

More on TC's and the MJO

Thought I'd post an intermediate blog before putting another one (pt 3 of my tropics series) talking more about tropical cyclones and the MJO.

So we've had a nice fall season for MJO activity in the Indian Ocean, with a third one since September currently active over the Indian Ocean area (as can be seen in the reconstructed outgoing longwave radiation anomalies below) . There are differing forecasts on how this event will keep evolving, but it looks like the event will continue to be strong during the following week.

Velocity potentials shows what MJO phase we are currently in, showing the active phase centered over the convective region. It also gives a better perspective of the magnitude of these disturbances.

The latest loop from CIMMS MIMIC- Total Precipitable Water Vapor (TWP), shows very nicely the two gyres associated with the MJO, the area of westerly winds as well as the circulation of what now is tropical storm five (according to JTWC)! We can see as the moisture seems to migrate to the east, while the westerly winds almost appear to be fluxing drier air in. We can also observe TS 5 moving northwest as well as what appears to be the development of a new gyre close to the equator and 80 degrees of longitude.

This rotating feature (seen below), is almost looking similar to the other MJO gyres that were present previously, and is associated with a fairly large area of cloudiness.  It will be interesting to see how this new circulation feature affects the dynamics prevailing over the area at this moment, which has been largely affected by TS 5 during the last couple of days. 

Cyclogenesis in an active MJO

As we go deeper into what looks like a very promising active MJO to study in the coming years. There appears to be some areas over the Indian Ocean that appear that are grabbing our attention for possible tropical storm formation. Lets look at the latest IR image from Meteosat 7 (taken from NRL)

Sattelite imagery showing latest activity over the Indian Ocean. Red circles depict areas of potential TC development, blue circle is the approximate region of the northern Rossby gyre and the red arrow roughly depicts the region is westerly wind bursts. The green square is showing the area of the active MJO.

The two red-orange circles denote the areas where significan tropical cyclone development is expected. Both features show deepening low pressures, increasing vorticity (rotation) and curving bands. The first features, denoted as Invest 98B, has the highest probability of development as of the latest Joint Typhoon Warning Center (JTWC) advisory. This area has also been looked at by the P3 aircraft obtaining data for DYNAMO.

The second area (pictured below), recently denominated as Invest 96S has a medium chance of development as of this writing.

Contours of height and vorticity with overlaid winds and nondivergent winds are depicting the Invests very well. The significance of this event is that these cyclones are forming while an active MJO is in place. Now this is in no way rare, active MJO phases are notorious for providing favorable environments for TC formation. The reason is because of the convective activity and deep moisture provided by it. Additionally, the Rossby gyres, which are usually at the western edge of the active phase, provide some cyclonic rotation,  favorable for development.

To add to this, convergence in the lower- mid levels is impressively high near both invest areas. Both systems are also fairly close to the equator, being at about 6 degrees of latitude. Also notice the significant divergence near the northern disturbance.

Irrotational winds and moisture convergence from the latest GFS run (12ET) 

 Overal we continue to observe an equatorial region dominated by the active MJO, and satellite imagery depicts it very well, with a somewhat skewed swallowtail feature very apparent in IR imagery.  It will be very interesting, and exciting to see how these systems continue to develop, as well as the MJO itself.

Behemoths of the tropical atmosphere and ocean system

So first of all I want to wish everyone a happy thanksgiving and hope that they are have a great weekend. This is one of my favorite holidays, not just because of the turkey!

So I just wanted to give an update on what my plots are showing while my peca pie bakes. It's the first time I make a pecan pie, so I hope it doesn't explode or something!

Also I want to point out that most of the things I write in this blog, particularly on the MJO status,  can be found on my UW-Atmospheric Sciences website (http://www.atmos.washington.edu/~angelf88) , so feel free to take a look at them. I also archive some of these plots. If you want to contact me or something, even if it's to send some hate (I hope not), you can so here!

So first of all, are you familiar with some of the most powerful phenomena of the atmosphere and ocean system. Can you recognize them if I put a picture of them below? Some of them might be at play right now! They range in spatial and temporal scales, from a few hundred kilometers and several days (like a hurricane), to global scale and lasting more than a year (like ENSO).

Hurricane Felix (2007). Tropical cyclones are some of the most impressive phenomenon on Earth. There are stories of them all the way back to the beginning of the last millenium, and them some. They are some of the most studied phenomenon on  Earth, and yet we still struggle to understand them, particularly the way they intensify.

Active MJO, January 2006. MJO's were discovered a little bit more than 40 years ago.  Even though an even lasts 30-90 days and convection is confined in the tropics, their circulation affects the whole globe, providing great challenges for forecasts. The MJO is one of the major challenges in our field at this moment.

The 1997 El Niño. One of the strongest ever recorded. ENSO is probably one of the most important oscillations in the coupled atmosphere and ocean. Its effects are massive and worldwide. Its presence can mean the difference between wet and dry, cold or hot, and so much more!

So the whole point of this short writing is to observe the different scales in which different phenomena can affect weather. This is why tudying this field can be so challenging, and why we still have such a long way to go on forecast improvement and better understanding on how the air we breathe ticks. I will make another blog post talking more about this topic in the future.

Latest GFS runs on the MJO


The latest model runs of the MJO keep showing fairly strong activity over the Indian Ocean, we can see it propagate eastward slowly, and as of yesterday or so you can see some strong activity right over the Maldive islands (about 73 degrees west, 0.2 degrees south or so) where  DYNAMO is happening.  The whole active phase looks very classi, a behemoth of clouds covering a good deal of the ocean. (thanks to Luke Madaus for giving the MJO this wonderful term)



A feature I've been meaning to mention is the tilting with height of moisture convergence over the region, which is likely an indicator of convective and stratiform clouds in the area. The major one in the back has had that shape for a couple of days now, and seems to be in the back end of most cloud activity, according to the model run.

A LOOP of the cross section below shows the feature just suddenly popping up from a lower level convergence feature that was moving eastward and becoming this large, coherent, area that we see below. Also the model indicates strong upward motion preceding it, and downward motion right below the tilt, as pointed in the figure below..

A map of moisture convergence at two levels shows a very well defined feature, with the 500 hPa showing signs of a classic "swallowtail" feature prominent in MJO events.  Notice how inmense convergence is near 80 degrees with the arrows showing a center almost at the equator!. Loops of these images can be found here (on the loop link on the page).

Winds and convective bursts over the Indian

As the current MJO continues to evolve over the Indian Ocean, thought I would write an update before I leave for Thanksgiving (and lots of you too!).  The latest GFS run (12 ET) continues to show an upward trend in moisture convergence over the region (40-100 degrees longitude , 15-15 degrees latitude) all the way up to the middle levels (about 500 hPa). The figures below show moisture convergence for the last 10 GFS runs (ending at 12 ET today).  Convergence has increased about 36% over the last 3 days and ascending motion continues to dominate a good portion of the Indian Ocean according to the model run.

Convergence over the area at 850 hPa

Convergence over the area at 500 hPa

Moisture convergence averaged near the equator

The 500 hPa map below shows strong convergence near the equator. Irrotational winds look fairly strong for the region. This is likely one of the strongest winds/convergence I have seen since I started making these maps (they are being archived here if you are curious). It's a change in regime from the last couple of days, where the areas of maximun convergence were about 6-8 degrees south and north of the equator (the double ITCZ)

500 hPa map of moisture convergence with irrotational wind vectors

 At 200 hPa the picture is dominated by what looks like a wind "explosion" in the irrotational field, centered at about 65 degrees longitude. We can see on the map below it that the field extends close to the Maritime Continent. The explosion, as well as the rotating Rossby-like gyres are good with what a classical MJO looks like.

One interesting observation I want to mention from saving these model runs is how the wind field has changes in the last couple of days. By filtering the winds onto only the non-divergent winds. Doing that we can observe gyres which are not always apparent in the wind field. If we go back to November 15th, we observe a couple of gyres here and there, but they are fairly weak. Winds near the equator are not strong, ranging from 5-10 knots, with only a few barbs showing stronger winds.


Then during the 18th, we observe a larger gyre north of the equator, and a smaller one south (barely visible). The northern gyre actually dissipates the next day and gets replaced by another further east. What is really noticeable is that westerlies have started to pick up in that small region near the equator, with areas of 20-25 knots.

On the 21st, you can see those non-divergent winds are still going, with some areas now up to 30 knots. Organization has increased by this day. At this point, the northern gyre is still not apparen in the GFS winds, but retrievable via wind decomposition. In fact it is not until near the 22nd that this northern gyre can be seen without any filtering

This last picture is the latest one at the time of this writing. Here the MJO is very evident, with convection flares everywhere. The winds have maintained themselves strong at near 30 knots. What is even more interesting is that the area of westerly winds has increased, covering more to the north and to the south of the equator. The centers of vorticity have also migrated away from the equator and seem to be larger than previous days.

 Well that's all I have to say for now. I hope everybody has a great Thanksgiving weekend

Ángel

The tropics, my home, pt 2: A gallery of clouds

First off. I want to give a big thank you to all the people that have sent pictures of clouds in this effort. All of you have been properly given credit. A special shout out to my friends, and colleagues in the meteorology program at the University of Puerto Rico - Mayagüez, who sent enough pictures to make ten blogs!

VIIRS image showing Puerto Rico partly covered by clouds!

On the last chapter of this series I left off saying that I love weather in the tropics, but didn't quite explain why.  In this entry I will talk about something little kids seem to enjoy a lot... Well, in reality, many of us are still fan of. I am talking about clouds.

If you are ever going to do an outreach event for kids, make sure you include two things:
1. Can crushing (or anything that might make loud noises).
2. Pictures of pretty clouds.

In fact, let me be honest. If I went to a presentation that had pictures of clouds and cans suddenly being crushed, I would be very amused, and I'm 23. So it might work for most age groups (though for some reason you need a bigger can the older you get). When I was an undergraduate, our AMS chapter crushed a metal barrel, it was the best part of the whole Weather Festival! But that could be another story, today I am concentrating on the clouds.

Some developing cumulus clouds on a clear day, right after the passage of hurricane Irene. Photo courtesy of Janice Maldonado (UPRM)

Clouds are a very important part of our culture. I think this is probably true for most places in the tropics. It is not only because of hurricanes and the monsoon, but of rain in general. There are even stories based on clouds and precipitation. Watching these clouds, and hearing these stories were an important part of my life as a kid!

A. The Folklore


In many latin american cultures we say that when it rains with sunlight the witches are getting married.  There are many variations though, some mention the daughter of the devil instead. I have traced this myth all the way back to Italy and Spain, but have not found its origin as of yet.

I guess if you were under this cloud, and it rained you'd need to be on the lookout of a wicked wedding. Foto taken at Gan . Courtesy of Hannah C. Barnes (UW Atmospheric Sciences)

How about here? Do you think a witch might be getting married over the ocean? Actually, it looks a little bit like the background of this page! Foto courtesy of Dennis A. Negrón (UPRM Computer Engineering/Meteorology)

Another popular saying is that if you got soaked during the first downpour of May, it is said that you will become more attractive. An alternative version of this is that you will have good luck for the rest of the year. I used to believe this when I was a kid, so I would be eager to get wet when that first shower happened. Many kids in my elementary school did it too! I always wondered why my parents never got wet themselves, didn't they want to have good luck or get prettier?

Better hurry up and get over there or else you will miss out on all the potential good luck and beauty ! Photo by Dennis A. Negrón.

The last one I will mention (I'm sure there are more)  is that if it rains the day you get married, then your matrimony will be miserable. In PR this meant that you have to get married during Christmas because otherwise you will surely have a terrible marriage, especially during summer and fall!

Let's all hope nobody got married this day because surely something terrible had to happen to their matrimony. Photo from Anthony Ortiz (UPRM Physical Sciences/Meteorology)

B. Stormy Clouds


One of the best memories I had as a kid were those stormy afternoons when it just poured and poured. Sometimes it would just be raining in my neighborhood, so if you got on your car and drove for a minute, you'd get away from the rain.  But could those small clouds pack a punch! There would be lightning, roaring downpours. It was crazy! When that happened my mom would shout "uuuuuurraaaah" and put on music and start clapping for some unknown reason.

You better run home when you see the sky getting like this, it might get nasty soon!  Photo courtesy of Irmarís Rivera-Llanova (UPRM Physics/Meteorology)

 Later in college, when that happened, I would just skip class. No way was I going to get wet! What a terrible example I am setting, although most of the time I would get to the right place early enough (before noon), and avoid getting wet altogether. Trust me, there was no umbrella that could save you. In fact there was this one time the umbrella got blown away from my hands, what a sad moment that was!

Many interesting features in this picture here. It almost looks like it was taken from one of those severe weather documentaries. Photo courtesy of Anthony Ortiz 

Sometimes you get some pretty nasty rain, and after an hour or so you think it's almost over. Well think again, you may have another cumulus popping up and bringing down more water. Such cases were pretty common in Mayagüez, the city where I went to college.  The picture below shows how those days might look like.

I think one of my favorite things about this picture is how well defined the cauliflower form of the cloud is. That actually means this cloud is mostly liquid, unlike the wispier one in the background, which can be comprised more of ice. Photo from Dennis A. Negrón

We can't leave this topic without mentioning some of people's favorite events. This first picture shows some of the remnants of tropical storm Bonnie (2010) as the hurricane hunters flew to investigate it.  An interesting fact is that a lot of people think that PR gets hurricanes all the time. This is actually not quite true, we only get these storms every couple of years, and there are times in which decades pass without any major landfalls. For example, by the time hurricane Hugo (1989) passed by eastern PR,  there was already a large fraction of the population that had never lived through a major landfall event. The interesting thing about Hugo was that it devastated the eastern part of the island, while the western part barely felt anything at all (and our island is roughly 100 miles wide).

A look out the window shows a beautiful blue sky and some puffy clouds right were a tropical cyclone used to be.  If you  come from a hurricane-prone area, the probability of you liking hurricanes is very high. That's just how it is :). Picture courtesy of Rosimar Ríos-Berríos (UPRM Physics/Meteorology).

Other types of events include water spouts. The picture below shows a big one in Mayagüez (Sept 14, 2005). They're not as common as say, lightning,  but we do see them every once in a while.

C. After it rains

It has always puzzled me how we can have the most terrible weather, and then when it's all done, we get beautiful sunsets. Such is the case of the following pictures. All in all, it is just another day. I bet most people don't take the time the think about the many things they see in just one day, and even less sit down  and appreciate that today's sky is never going to repeat again, and tomorrow's is going to be just as unique! Sounds cliché and lame, but it's true!

Nothing beats a sunset right after a stormy afternoon. Here we see combination of withering clouds with combinations of orange yellow and blue.  Picture from Yésica I. Nieves (Clinical psychology, U. Carlos Albizu) 

Sometimes we can see bright colors in clouds themselves from reflection and scattering of light.  No better moment to see this than during a good sunset!

D. Too Much for a single blog entry

There is so much to talk about in this topic, and so many pictures to describe, that I cannot just take a single blog to talk about it all. In fact my series of the tropics is not even done yet! So I will close this chapter with some more nice pictures and will see you in the next entry of "The tropics, my home" !

The sun shines through these clouds. Can you guess how high up those clouds are? Picture courtesy of  Irmarís Rivera-Llanova.

The sun's shining right behing this big guy here. Gives it a majestic feeling doesn't it!  Picture courtesy of Rosimar Ríos-Berríos