Carlotta inland over Mexico and weakening though heavy rain threat continues; Gulf of Mexico next place to watch

Hurricane Carlotta made landfall last night along the southern Mexican coastline with winds to near 90 mph, according to the National Hurricane Center. The circulation is now weakening rapidly over the rugged terrain of Mexico but the threat of heavy rains will continue for the next few days. Remember that tropical cyclones release a tremendous amount of heat through rain fall and it takes time for the moisture envelope to totally spin down and dissipate. The mountains of Mexico will also serve as a focusing mechanism to wring out even more moisture and should help to hasten the process. Interests in the region should continue to be aware of the rain threat, especially along the higher elevations where mud slides and flash flooding could occur with little to no warning.

There is another area of interest in the east Pacific but it is farther away from the coast and will likely move in to cooler water before it can develop much.

Now we will turn our attention to the southern and western Gulf of Mexico over the next few days. The pattern is such that there is at leas some potential for a tropical depression to form later next week. Water temps are plenty warm and the current wet phase of the MJO, coupled with the remnants of Carlotta, could trigger a low pressure area to form in the Bay of Campeche. I do not see any indication in the global computer models that anything too strong will come of this but the region will certainly bear watching as we begin the week ahead.


Carlotta nearly a hurricane as it moves slowly just off the Mexican coastline; Atlantic remains quiet

TS Carlotta in the east Pacific

TS Carlotta in the east Pacific

Tropical storm Carlotta is not in any hurry.The fairly slow moving storm continues to edge closer to becoming a hurricane and should do so later today. The NHC forecasts Carlotta to peak at 90 mph – a solid category one hurricane.

For now, the deep convection or thunderstorm activity remains mostly off shore, keeping the wind and precip with it. This could change later today as the forecast track takes the system closer and closer to the coast but without making landfall. This scenario would likely keep the core of the strongest winds off shore but heavy rains and winds to tropical storm force are a good bet for portions of the southern region of Pacific Mexico.

The big concern that I have is the fact that Carlotta is not forecast to move very much after the weekend. Its close proximity to the coast would likely mean a heavy rain event for the region. Interests in the area should be prepared for the possibility of several inches of rain over the next few days which could easily result in flash flooding and mudslides.

Atlantic Basin Quiet

The Atlantic Basin remains nice and quiet with no organized areas of convection noted on satellite imagery. I do not see any evidence that this pattern will change anytime soon although the western Gulf of Mexico could be the place to watch in about a week. Both the GFS and ECMWF models indicate the lowering of pressures across that region as a Monsoon Trough remains in place from the east Pacific, extending eastward in to the western Caribbean and Gulf of Mexico. This focusing mechanism for convection often leads to development though it usually takes several days, similar to what we see in the west Pacific with large areas of low pressure spread out over a wide area. For now, the weekend ahead looks fantastic with no trouble spots at all in the Atlantic, Caribbean or Gulf.

94-E in the southeast Pacific looks likely to develop in to a tropical storm

East Pacific Invest Area 94-E

East Pacific Invest Area 94-E

The only area of concern today continues to be invest area 94-E located in the southeast Pacific, just off the coast of Central America. As you can see in the satellite picture (courtesy of the University of Wisconsin’s CIMSS site), the low pressure area is gradually becoming better organized. The red “I” indicates the initial position of the center of the low. There is some banding of the cloud cover and deep tropical convection is maintaining itself. A majority of the reliable computer models indicate that 94-E will move WNW to NW and approach the southeast coast of Mexico in a few days. As far as intensity goes, the SHIPS model indicates category one hurricane strength, assuming that the center does not interact with land. Other intensity models are more conservative, keeping the system a moderate tropical storm at its peak.

The main impact looks to be heavy rain fall for portions of Central America and eventually southeast Mexico. The disturbance is slow moving, so it has time to dump a lot of rain along its path. Interests in the region should be aware of this hazard.

In the Atlantic Basin, things are nice and quiet. It is possible that we may see a window of opportunity for tropical cyclone formation in about a week but the only evidence of that right now is the fact that the MJO phase would be more favorable. This alone does not lead to development- there are plenty of other factors that ultimately drive the genesis of tropical storms and hurricanes. We’ll see what happens as we move towards the latter half of the month. So far, I do not see any consistency in the long range model guidance to suggest development in any location. I’ll post more about 94-E tomorrow morning.

MJO pulse starting to show up as development potential increases in southeast Pacific

MJO Chart

MJO Chart

Right on cue, the MJO or Madden-Julian Oscillation, is moving out of the west Pacific and in to the eastern portions of the Pacific. The yellow shading in the graphic indicates the forecast for the MJO from the GFS model over the next several days. The enhanced upward motion associated with the MJO is likely to give birth to a tropical cyclone off the coast of Central America in the southeast Pacific.

The NHC is currently highlighting an area of showers and thunderstorms not too far off of Costa Rica. It has a very pronounced curl to it which indicates to me that development is likely. Water temps are plenty warm and upper level winds will probably just improve over the next few days.

A look at computer models suggests that the system will move rather close to the Pacific coast as it steadily develops. Interests in the region from Costa Rica northwestward to the coast of Mexico should be paying close attention to this feature. At the very least, heavy rain and squally weather will likely impact the immediate coast along the Pacific side of Central America over the next few days. I’ll post more info on this developing system daily with additional updates on our Twitter and Facebook pages as well.

Will predicted MJO pulse bring chance for first development of the season?

GFS MJO Forecast

GFS MJO Forecast

Even though we had tropical storms Alberto and Beryl already, they were both outside of the hurricane season. Since then, things have been nice and quiet. There are, however, indications that this may change. Let’s take a look at why.

There is an atmospheric phenomenon called the MJO or Madden-Jullian Oscillation that can sometimes lead to increased tropical cyclone formation when it is in its favorable mode. Think of it as a period of fertility in the tropics. A time when rising motion in the atmosphere is more prevalent, allowing deep tropical convection to form. This is what we call the “wet phase” of the MJO pulse and it typically adds a lot more showers and thunderstorms to the tropical regions of the globe where it circulates through.

On the other hand, the “dry phase” is easy to spot due to the sinking motion of the atmosphere, suppressing tropical convection. While development can take place during an MJO dry phase, it’s a lot more common to have development during the wet phase.

There are several computer models, the global models, that predict the MJO pulse and we can track that on various sites. The graphic I have linked to for this blog shows the operational GFS and its ensemble mean- the average of the various other runs of the GFS with slightly different variables. This model, along with others such as the reliable ECMWF, point to an increase in the wet phase of the MJO for the eastern Pacific and eventually the Atlantic Basin. When the MJO is within regions 8 and 1, we should begin to look for an increase in tropical convection. So, going by the graphic, we will need to pay closer attention to the tropics after about the mid part of the month as the wet phase moves through.

You’ll notice first, as it moves through the western Pacific, that we’ll see a typhoon or two develop followed by likely development in the southeast Pacific off the coast of Mexico and Central America. After that time, it is possible that a window of opportunity will open for the western Caribbean. It’s just another piece of the puzzle or a clue that we can use to know when the tropics are perhaps a little more ready for development than at other times. I’ll keep up with it and post more here as we get closer to the predicted date of the favorable MJO pulse.