Remember those “cool” MDR SSTs?

June sea surface temperature anomalies showing a much colder than average tropical Atlantic.

June sea surface temperature anomalies showing a much colder than average tropical Atlantic.

Take a look at this graphic from back on June 4 – just when the Atlantic hurricane season began. There was an awful lot of blue coloring across the deep tropics; the so-called MDR or Main Development Region. As such, seasonal forecasts began to be revised downward. It looked like a below average season was at hand and there as constant talk about how cool, compared to average, the MDR was. This would lead to higher pressures over the tropical Atlantic, less energy for tropical waves to tap in to, etc. etc. It seemed as though we might have a very slow hurricane season – unless things changed.

August 27 sea surface temperature anomalies showing a marked increase in positive anomalies across the MDR.

August 27 sea surface temperature anomalies showing a marked increase in positive anomalies across the MDR.

Now, let’s take a look at that same graphic from August 27, just a few days ago. Quite a difference isn’t it? The MDR has warmed significantly since June and is now running just slightly above the long term average. Why is this important? For one, we are no longer looking at cool to cold anomalies or departures from normal in the area where hurricanes like to form. That is no longer an inhibiting factor as we head in to September. The other reason this is important is that tropical waves or other seedlings don’t know that the SSTs were cooler earlier this summer. These strong impulses of energy that emerge from the west coast of Africa need warm, moist air to work with and that is derived from warm ocean temps – which we now have. It does not matter what the SST pattern was like in June or July. All of that talk about how cold the water was compared to last year or other years is moot now; just when we are entering the peak period of the Atlantic season.

And look what is happening, right on cue. A tropical depression is likely to form just off the coast of west Africa and will go on to become the season’s next hurricane – right in the middle of the MDR where SST values were quite a bit cooler just a couple of months ago. Just goes to show how things can and do change. It also signals that we are likely to be in an active period for development over the coming weeks, lasting in to early October most likely. That’s 5-6 weeks of favorable conditions. A lot can happen during that time period so don’t let your guard down – the 2018 Atlantic hurricane season is making a comeback and may be full of more surprises just yet.

M. Sudduth

8:45 AM ET August 30

For invest area 90L, think rain not wind or surge issues

NHC 5-day tropical weather outlook map showing invest area 90L and the probable area for future development. The main issue will be heavy rain which we will need to monitor closely.

NHC 5-day tropical weather outlook map showing invest area 90L and the probable area for future development.

The Atlantic hurricane season does not officially begin until June 1 but once again, we have a pre-season system to keep watch of. This seems to be the norm more often than not as of recent years. I suppose Mother Nature is simply not interested in man-made schedules.

As of this morning with the 8am ET special outlook message, the National Hurricane Center says that the system remains broad and loosely organized with plenty of dry air and strong upper level winds around to keep it from developing much anytime soon. There is perhaps a chance that it will become a little better organized once it moves in to the Gulf of Mexico over the next few days where water temps are only marginally favorable for development. This fact, coupled with strong upper level winds, should keep 90L from becoming much better organized once it reaches the Gulf later this week and in to the long holiday weekend ahead.

5 day precipitation forecast from the Weather Prediction Center showing a large area of potentially heavy rain for portions of Florida and the Southeast U.S. It is important to keep up with local information from the NWS and local media as this event unfolds since localized heavy rain chances will be impossible to predict more than a few hours out.

5 day precipitation forecast from the Weather Prediction Center showing a large area of potentially heavy rain for portions of Florida and the Southeast U.S. It is important to keep up with local information from the NWS and local media as this event unfolds since localized heavy rain chances will be impossible to predict more than a few hours out.

The main issue with this feature, as is usually the case with early season development, will be rain and perhaps a lot of it. A large area of high moisture content in the lower levels of the atmosphere will lead to plenty of rain for portions of western Cuba, the Cayman Islands and even Florida over the next several days as the low moves slowly northward and in to the Gulf of Mexico. Some areas could receive several inches of rain which could lead to localized flooding issues, especially within areas that have seen a lot of rain in recent days.

In terms of other impacts, I really do not see much of an opportunity for 90L to strengthen beyond maybe a weak tropical storm wind-wise. We may see some stronger winds eventually that could lead to onshore flow and minor coastal flooding along the Gulf Coast this weekend but the bigger issue, I believe, is going to be the rain. It is impossible to pinpoint who will receive the most rain and when it will occur. For now, we need to just monitor the progress of this rather sprawling area of low pressure and pay attention to local NWS products concerning future flood issues, etc.

I will post a detailed video discussion concerning 90L later this afternoon which will include the latest morning model data. Elsewhere, things are nice and quiet and this includes the eastern Pacific as well.

M. Sudduth 9:15 AM ET May 22

Small window for small system to develop in extreme southern Gulf of Mexico

Invest area 90L slowly trying to organize in the extreme southern Gulf of Mexico

Invest area 90L slowly trying to organize in the extreme southern Gulf of Mexico

The only area of interest in the Atlantic Basin is 90L, situated way down deep in the southern Gulf of Mexico.

It is a small weather feature but has a chance, perhaps due in part to its small size, that it could become a tropical depression later today. Upper level winds are not especially favorable but it appears that some deeper convection is developing near the center. Water temps are quite warm and so it won’t take much for it to acquire enough organization to perhaps become the first tropical depression of the 2014 season.

The main issue has been and will continue to be rain. Fortunately, with the area being quite small, the impact to land will be limited. Nevertheless, heavy rain over portions of Central America will be something to contend with as this system festers in the Bay of Campeche.

Most computer guidance suggests that it will eventually move inland over southern Mexico, probably well south of Tampico. Even if it is able to attain tropical depression, or even become a tropical storm, it will not have much time to strengthen before upper level winds become too hostile and land interaction becomes a factor. Again, the main impact will be heavy rain and this can cause loss of life and damage due to mudslides and flash flooding.

Elsewhere, the Atlantic and east Pacific are nice and quiet as we enter the first full weekend of the hurricane season.

I will have an update here early this evening once more data becomes available on 90L – including the chance that recon will fly in to investigate.

M. Sudduth 10:11 AM ET June 6

Invest 90L in southern Gulf not much of a concern

Invest 90L in the southern Gulf of Mexico

Invest 90L in the southern Gulf of Mexico

A weak surface trough of low pressure has draped itself across the southern Gulf of Mexico. Water temps are plenty warm and there is even some growing deep ocean heat content but the limiting factor by far is upper level winds.

Water temps can be 90 degrees and it won’t matter if upper level winds are blowing too strong across a developing system. This is true for tropical waves and other areas of disturbed weather that are “trying” to develop over tropical waters.

The ideal upper pattern is one that allows the clouds to rise, we call this convection, and then be thrown out in a clock-wise direction in an even fashion. It helps to have so-called outflow channels too which aid in further evacuation of the rising air.

Strong upper level winds blowing across 90L will keep it from developing over the coming days

Strong upper level winds blowing across 90L will keep it from developing over the coming days

In the case of 90L, the upper level winds are cutting across the cloud mass which acts like blowing out a candle. The convection cannot thrive and persist and thus the heat engine never really has a chance to get going.

In any case, the NHC is monitoring and so will our team. Mike Watkins will have some interesting model plots at his site and I will post them here from time to time as we track this feature over the next few days.

The bottom line is that nothing leads me to believe this will develop in to anything substantial, at least not wind-wise. Heavy rain is always an issue with tropical weather systems and this will be no different. Fortunately, it is not a large, sprawling area so its impact will be limited in coverage.

The east Pacific is quiet now since TS Boris made landfall early this morning in extreme southeast Mexico. Some of that energy will spread across from the Pacific and in to the southern Gulf of Mexico but again, upper level winds should preclude any significant development.

I’ll have another post this evening regarding a new feature we are unveiling in our app, Hurricane Impact.

M. Sudduth 11:06 AM ET June 4