Drought Monitor Update, Severe Weather Chances and Leslie Brushes Bermuda
Thursday, September 6th, 2012
Thanks to Peri Pierson for the picture below from Lake Havasu City, AZ as lightning flashed over the London Bridge. An influx in moisture across the Southwest will have more showers and thunderstorm popping up across parts of the region again today and tomorrow.
Monsoonal Moisture Continues
Monsoon season typically runs through the end of September when the hot weather starts to fade in the central and southern part of the country. That is good news as many folks are still in need of much needed precipitation. NOAA’s HPC 5 day precipitation forecast suggests a few spots picking up close to 1″ or more through early next week.
U.S. Drought Monitor Update
The U.S. Drought Monitor released their weekly update today and it’s nice to see ‘some’ improvement across the central part of the country since the remnant moisture of Hurricane Isaac meandered through the region. The image below shows the difference over 1 week after Isaac moisture pushed through.
“South: Hurricane Isaac made landfall and pushed inland to the north/northwest as a very slow-moving subtropical storm system. With the slow-moving nature and direction of movement associated with Isaac, many areas in Louisiana, Arkansas and the Midwest recorded precipitation that approached 10+ inches in places. Many areas in Arkansas and Louisiana saw a 2 class improvement in their U.S. Drought Monitor status this week in response to the rains. Most all the short-term indicators were improved and the area was labeled with an “L” for the lingering long-term issues. The full impact of this event will take time to analyze and consider.
Midwest: With the remnants of Isaac moving slowly through the region, many areas of Missouri, Illinois, and Indiana recorded rainfall in the 2-6 inch range. Some areas received more and some less, so the improvements made in these areas were based upon the totals (and in Illinois, totals over the last several weeks). Many areas of Missouri and Illinois did see a 2-category improvement this week and widespread areas of 1-category improvements were evident in Indiana and Ohio. The improvements were based upon how well soil moisture levels responded throughout the area that received the most rain and also the favorable response of the river and streamflows, which were running at near record lows. The response to the storm is interesting in that for some areas, a very tight gradient of precipitation has been observed which led to rapid changes in drought status over a short distance.
The region did see some degradation this week as portions of northwest Iowa did go into D4 status and D3 was extended into Minnesota out of Iowa. Areas of central Minnesota that were very wet a few months ago have dried out, and D0 was introduced around the Twin Cities this week. Most of central and northern Wisconsin saw full category degradation this week as the last several months have been dry and hot in this area.”
7 Day Radar Estimated Rainfall
The 7 day radar estimated rainfall from Isaac suggests pockets of 10″ to 20″ throughout the Lower Mississippi Valley. Remnant moisture from Isaac slowly pushed north into the middle part of the country with lesser rainfall amounts, but still enough to dent the drought a bit!
Drought Improvement? Looking Ahead…
“Looking Ahead: Over the next five days (September 4-9) the Plains and Midwest states are forecasted to have temperatures below normal, which may extend into the southeastern United States. Temperatures look to be 3-6 degrees Fahrenheit above normal in the Pacific Northwest and into the Great Basin. A fairly active weather pattern looks to bring a widespread chance of rain over the central Plains through the Midwest and up into New England. The greatest precipitation amounts are expected over the area from Kansas and Oklahoma to western Kentucky, where more than 1.50 inches of rain has been projected.
The CPC 6-10 day forecast (September 10-14) has temperatures below normal over the Southeast and west coast as well as for much of western Alaska. Temperatures can be expected to be above normal for much of the central and northern Plains, the Great Basin and Rocky Mountains. Much of the country should expect below-normal precipitation, with the desert southwest and portions of Florida being the only areas showing above-normal chances of precipitation.”
The image below is from NOAA’s HPC, which shows the 5 day rainfall forecast across the nation. Heavier rainfall is expected once again Friday/Saturday as a secondary cool front slides out of Canada. Severe weather chances may also pop back up again tomorrow along and east of the Mississippi River Valley.
Severe Weather Chances
The secondary cool front mentioned above will be responsible for a couple rounds of severe weather for the rest of the work week. Today’s severe weather chances will include hail and high winds along with heavy rain.
Severe Weather Chance Friday
The same cool front will continue chugging east on Friday. This may be a slightly more significant day for heavier rain potential across parts of the Ohio and Tennessee Valleys along with more hail and damaging wind chances.
The tropics continue their ways as we roll through the most active month of hurricane season (June 1st through November 30th). We currently have 2 named storms in the Atlantic, Leslie and Michael, which are both hurricanes!
Hurricane Michael became the first category 3 storm of the season with sustained winds of 115mph as of early Thursday. Good news… Michael is not a threat to the U.S.!
Hurricane Leslie (by size) is a much larger storm, but was only a category 1 storm with sustained winds of 75mph as of early Thursday. Unfortunately, it looks like Leslie with make a close encounter with Bermuda, perhaps even as a category 2 storm with stronger winds, heavy rain and significant waves/storm surge/beach erosion.
Leslie Forecast Track
The latest forecast has Leslie passing east of Bermuda by late weekend.
Isaac Turns into Nadine?
This was in Paul Douglas’ blog from earlier today, but it explains the current situation…
Hurricane Naming Conventions: When Is It OK To Recycle A Name? Here’s some additional guidance and perspective from The National Hurricane Center (NHC), via FB: “There have been quite a few inquiries about whether the name “Isaac” would be given to the area of disturbed weather currently located along the northern coast of the Gulf of Mexico, if it were to develop into a tropical cyclone. The short answer is no, it would get a new name. Our analysis of the satellite, surface, and lower-tropospheric radiosonde data suggested that the disturbance we’re currently following originated within Isaac’s broad circulation, but that it had its own surface pressure minimum distinct from Isaac’s. This was perhaps most apparent late in the day on Monday, when the residual surface center of Isaac was located over western Kentucky while a second weak low was located over northern Mississippi and Alabama. Isaac’s circulation continued to weaken after that and became difficult to track, while the new disturbance moved slowly toward the Gulf coast. So what basically happened here is that a little piece of Isaac broke away and moved south. OK, now everybody get your lawyer and grammar hats on. The National Weather Service rule that applies here reads: “if the remnant of a tropical cyclone redevelops into a tropical cyclone, it is assigned its original number or name”. Notice the rule says “the” remnant, and not “a” remnant. This means that the storm’s primary remnant (and not just any old part of it) has to re-develop in order for the name to be retained. Since the primary remnant of Isaac was still in Kentucky when the new low formed and broke away, the rule dictates that the new low is not entitled to the name Isaac. This rule actually makes a lot of sense. If a storm died and each of two parts re-developed, we couldn’t give the same name to both parts. Only the primary remnant would retain the name, while a lesser remnant or part would get a new name.”
This is interesting… the GFS model shows its solution of the three storm systems listed above. It’s kind of fun to watch the animation… take a look!
Thanks for checking in on this Thursday, have a great rest of your weekend and weekend ahead!
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