Development threat increasing for Bay of Campeche as active pattern continues

Invest area 93L moving in to the Bay of Campeche

Invest area 93L moving in to the Bay of Campeche

It may take a few days, but it looks like we will get another tropical cyclone developing in the apparently fertile Bay of Campeche. The NHC says that invest area 93L should move in to the eastern portion of the region today and slowly develop – as long as it can remain over water.

Upper level winds look favorable and the water underneath is very warm. It looks like all the ingredients are in place for 93L to become our next tropical storm.

The forecast models are interesting to watch as they may be having an issue with 93L and the overall larger low pressure envelope or gyre that exists across the region, even extending in to the southeast Pacific. As such, it is difficult to determine when we may see something develop and this is somewhat important in terms of its future track and intensity.

Right now, it looks like we’ll have a low take shape over the next day or two with a track off to the north-northwest towards Mexico, well south of Texas.

However, the persistent onshore flow across the western Gulf of Mexico could lead to minor coastal flooding and an increase in showers and thunderstorms across the region. Heavy rain will be a serious issue for portions of eastern Mexico due to the slow motion of this system.

Elsewhere, Gabrielle is a tropical depression but has managed to develop limited deep convection again around its circulation center. It won’t be too much longer before Gabrielle is picked up by a trough and swept on across Nova Scotia as a post-tropical/extra-tropical system with rain and some wind but little more.

Out in the eastern Atlantic, Humberto remains a hurricane and is likely to be around for at least another week as it mills about the open Atlantic. This will help to drive up the seasonal ACE index which has been lagging quite a bit in recent weeks. There is still no indication that Humberto will impact land areas.

Beyond the short-range, the pattern looks to remain very active with the western Atlantic Basin, including the Caribbean Sea and Gulf of Mexico, being primed for development. Global models indicate numerous systems developing over the next 10 to 15 days and this is consistent with the time of year we are in coupled with the very warm water that remains intact across most of the western Atlantic and surrounding areas. There is nothing to pinpoint just yet in the long range but indications suggest that the Gulf and/or Caribbean will foster development again before the month is out. We’ll see what happens, just something to keep in mind as we progress through September.

I will have another blog post here this evening concerning 93L in the Bay of Campeche.

M. Sudduth 8:15 am ET Sept 12

 

Debby going to be a forecast challenge

The latest computer model guidance regarding tropical storm Debby has not helped to paint a clearer picture of where the storm, forecast to be a hurricane, will eventually make landfall. In fact, this could be one of the more complicated storms to deal with in quite some time.

Currently, Debby is experiencing some shear which means the upper level winds are blowing across the top of the storm from a certain direction rather than fanning out in all directions. The shear is keeping the storm from being able to align itself vertically and the deepest convection is displaced well away from the center of circulation. This shear is forecast to relax but as mentioned in the latest NHC discussion, it is not a guarantee, so Debby may have some intensity issues over the next few days. It is important to note that intensity forecasting is where the least amount of skill lies and significant changes up or down are possible. The latest forecast maintains the notion that Debby will become a hurricane as it turns west across the warm Gulf of Mexico.

The track forecast is turning out to be quite difficult. What was once a fairly straight forward forecast that Debby would turn west under a developing ridge of high pressure has turned in to a potential huge change coming up. The NHC mentions the ECMWF model which has shown Debby moving west and even south of west towards Texas for the last several days now has the storm making landfall in Louisiana in about three days. As I mentioned, this is a big change from previous runs and we’ll have to see what happens with each subsequent run. In other words, is this the beginning of a trend of just a temporary “goof” by the model and it will get back on its “west” idea soon. We’ll have to wait and see. Track forecasting is sometimes quite easy, this time, it looks to be just opposite.

HPC 3 Day Precip Forecast

HPC 3 Day Precip Forecast

Let’s talk about rain fall. Taking a look at the HPC’s precip forecast for the next three days, we can plainly see that Debby has a tremendous amount of moisture to dump along its path. The Florida peninsula through the central Gulf Coast could receive several inches of rain as Debby moves quite slowly, allowing the rain fall totals to pile up. This is not to be taken lightly. Fresh water flooding from excessive rains generated by tropical cyclones is a leading killer. Often times flooded roads are accessed by people who think that they can navigate the waters. This is a dangerous idea and I urge people to be mindful of the potential flooding impact from the rain. I would like to point out that you can use weather.gov for a wealth of information regarding your local conditions. Just type in your ZIP Code and the landing page will likely contain all sorts of locally based watch/warning info, hurricane local statements and more. This info is for your area, not a national broad brush forecast. Remember: weather.gov

I am currently in Georgia after wrapping up a project I had with CNN to launch a weather balloon and its payload to high altitude yesterday morning. The prep and launch were spectacular, I cannot wait to show you the video of that. The ascent went very well and we were able to track the payload using APRS. I will post a separate blog about this project later tomorrow, complete with some video of the launch. I’ll also talk about what went wrong and why we were not able to recover a majority of the payload after the balloon burst.

Once I return home from GA later today, I’ll begin preparing equipment for a trip to the Gulf Coast to provide on-scene coverage and info as Debby passes by or perhaps makes a direct impact on the region. I’ll lay out my plans tomorrow as a lot will hinge on what the forecast track is and how strong Debby gets. Meanwhile, everyone along the Gulf Coast should keep close tabs on the latest forecast info from the NHC and your local NWS. I’ll have another post here tonight with frequent updates on Twitter.

Big time rains for the southern states

HPC 5-Day QPF

HPC 5-Day QPF

Get ready for some rain! If you live in eastern Texas, Arkansas and indeed a good deal of the Deep South, you’re in for some wet weather over the next five days. Take a look at the HPC QPF map. It shows the forecast precip over the next five days and a lot of it! The culprit? A potent upper level storm system now situated over southern Arizona and moving in to New Mexico. It will tap the warmer-than-normal Gulf of Mexico moisture supply and really ignite as we continue to move through the week.

While rainy, nasty weather is usually not a welcome event, in this case, I think people will be pleased to see it because of the drought relief it will bring.

U.S. Drought Monitor Map- Sept. 13, 2011

U.S. Drought Monitor Map- Sept. 13, 2011

The last few years have been exceptionally dry for the southern Plains and especially Texas. Looking at the U.S. Drought Monitor maps we can see that at the peak of last year’s hurricane season (Sept. 13 map), nearly the entire state of Texas was experiencing exceptional drought conditions. I have little doubt that this was the reason why TS Don literally dried up as it made landfall in south Texas in July. In fact, the air mass over the western Gulf remained very dry for a bulk of the hurricane season. When TS Lee formed in early September, it too entrained the bone-dry air over the region and actually transformed in to a sub-tropical storm, losing its purely tropical characteristics. I call this phenomenon the Texas Air Layer, similar to the Saharan Air Layer which can dominate the tropical Atlantic with dry, stable air.

Now let’s fast forward to the current winter pattern. We have seen quite an increase in rain fall over a significant portion of Texas and surrounding states due to a favorable storm track and possibly a warmer than normal Gulf of Mexico which supplies more moisture for storm systems. It has also been warmer than normal for the region as it has been for much of the Southeast. This is partly due to a positive NAO or North Atlantic Oscillation which has kept the deep east coast troughs which usher in Arctic Air at bay. Instead of prolonged periods of cold, dry air, the Arctic attacks are brief and the result has been a warmer, wetter winter for much of the southern tier states.

U.S. Drought Monitor Map- Jan. 17, 2012

U.S. Drought Monitor Map- Jan. 17, 2012

You can see the resulting improvements on the latest Drought Monitor map labeled January 17. A remarkable change to say the least and more rain is coming which will further knock down the dry conditions for Texas and elsewhere.

My theory is that if this pattern continues, perhaps the air mass over the southern U.S. and adjacent Gulf Waters won’t be as dry this hurricane season. If this is the case, maybe, just maybe it would open up the western Gulf, Texas included, to more tropical cyclone activity. It makes sense to some extent: if the abnormally dry air mass is gone, due in part to a wetter land mass underneath, then it stands to reason that approaching tropical cyclones won’t dry out nearly as much as we saw in 2011. I think we can all agree that watching Don erode away to nothing as it made landfall was one of most incredible demises to a tropical storm that we’ve ever witnessed. It provided next to no rain fall for the region that it impacted and was all but gone in less than 24 hours after landfall.

We’ll see how this all plays out for the upcoming hurricane season. It may have no bearing at all but I think that drought begets drought and thus more dry air; a kind of feedback mechanism. We know that tropical cyclones are incredibly sensitive to dry air and what we saw over the western Gulf last season was enough to keep the region well protected. I’ll keep tabs on the Drought Index and post a follow up report in the early part of June. For now, enjoy the abundance of rain fall but be mindful of the hazards that excessive rains can bring. It’s all good until somebody gets hurt and we don’t want that.