Just like the last couple weeks in June, July is off to a quiet start. While there are a few tropical waves in the Atlantic, none look too impressive on satellite nor are any expected to develop.
Typically, for the first third of July, tropical development occurs in the eastern Gulf or western Atlantic, sometimes along washed out frontal boundaries. Other areas of formation include the eastern Caribbean into the central Atlantic. Nonetheless, this time frame is not historically conducive to a lot of tropical geneses – there have only been 34 named storms that have formed between July 1 and 10th, dating back to 1851. And in fact, the entire month of July only accounts for about 8% of all tropical named storms in the Atlantic.
While the eastern Caribbean/central Atlantic may be historically an area to watch for tropical development this time of the year, it looks less favorable so far this year. One of the primary reasons is the below average temperature anomalies for the waters in that area. Sea surface temperatures are running up to 2° below average in this part of the world. On the flip side, SST’s are running up to 2° above average in the Gulf of Mexico and western Atlantic near the Gulf Stream. Therefore, this would be the most likely spot for any tropical formation over the coming days/weeks.
In addition to the cooler sea surface temperatures in the Caribbean, upper level winds remain extremely hostile to tropical development. Wind shear looks to remain unfavorable through at least the next week across the entire basin. Also, a surplus of dry Saharan air continues to advect into the Caribbean.
The biggest reason for the aforementioned hostile conditions pertains to the ongoing, and strengthening El Niño. As the waters warm across the Central and Eastern Pacific, this causes favorable conditions for strengthening tropical cyclones. A look at the sea surface temperature anomalies across the entire basin show some areas up to 3°+ above average for this time of the year. This is a good indicator of an ongoing El Niño, and one that is strengthening as well. In fact, the Climate Prediction Center is forecasting a moderate to strong El Niño to linger through the summer (and likely into the fall and winter as well) which will help to keep these conditions going. Therefore, it comes as no surprise that the Northwest and East Pacific hurricane seasons are off to near-record and record starts (respectively).
The El Niño is also likely the culprit for a rare phenomenon in the Central Pacific – twin hemisphere cyclones. Tropical Cyclones Chan-hom and Raquel are at the same longitude but on opposite sides of the equator, something extremely rare for July considering it’s the winter months in the southern hemisphere. In fact, there have been only 3 tropical cyclones in the Pacific east of Australia in the month of July (since 1970), none of which have been as far north at Raquel.