Warmth and humidity return this week, “best” rain chances west until late week.



A Summertime preview is in store this week as highs climb into the high 70s and low 80s.  Humidity will be back in force as well.  The west will see periodic clouds and shower/storm chances all week, peaking late week, while the east sees more sun and better rain chances hold off until late week or next weekend.

Drought Update:

Little rainfall brought little change to the map, but dryness is gaining hold again in the western district with most of the week’s rain falling west and south over parts of TX/OK and W KS which are in really bad shape. They should see some significant improvement in next week’s update.  Three days in and KC is already a half an inch below average in rainfall.  May and June are the year’s wettest months when 5.23″ of rain falls on average each month.  2015 deficits are nearing 3″. By contrast, St. Louis is only 0.55″ behind for 2015.


This week’s rainfall potential holds some real hope for the western district, and a real chance for a bust. As you can see there is a very sharp dividing line between very little rain east and several inches west.  Remember, these are generalized totals and even within the “forecast” rain bands there will be lucky locations which get lots of rain and those who just by chance, miss the significant showers.  The threat would be a westward shift in the expected rain, which would give the central Plains the heaviest totals and keep those totals..just..out of reach for the west.  The west needs about 1.25″ of rain per week this time of year just to keep up with average.

Here’s the rainfall outlook graphic:



Severe Weather:

There will be a non-zero risk for severe storms this week, but pinpointing one day over another is virtually impossible this week, there is no “overall” strong signal for severe weather. That being said, the central and southern Plains will have the greatest risk, with a few days with a marginal risk into the west.  It will all depend upon where the storm clusters form, where they track and how much cloudiness they leave behind. Later in the week as a larger system comes out of the SW U.S, there may be a potential for more widespread strong storms, but that may not happen until next weekend.  Overall, we’re in for a week with few 100% sunny days out west (more partly cloudy to cloudy at times) and periodic chances for showers and storms, while there will be more sun in the east and rain chances really stay away until late week.  One thing for certain: You’ll feel the humidity return as highs climb into the 70s and low 80s and lows remain 60 or higher over the entire district.

Week in Review:

As expected, a very quiet week across the district with a few showers across the western district on Saturday morning.  Here are the rainfall charts for the seven-day period ending today for both districts:

2015-05-03-7DAY_PRECIP 2015-05-03-7DAY_PRECIP_KEAX

Looking back at April:

2015-04-30-0853-APRTEMP_ANMLY ‘

April was a mild month for most of the country, the heat out west faded a bit and the cold in New England did as well. The cold was mainly centered near the still-cold Great Lakes, northern New England and the Rio Grande Valley, with isolated pockets elsewhere. Florida and the Gulf Coast was the warmest.

Rainfall in the west was heaviest south and east of KC and much lighter N and W.


The eastern district fared better, as has been the case for a while now, with the heaviest totals following the tracks of some of the stronger April thunderstorm clusters.


In terms of the percentage of average rainfall, a majority, but not all, of the western district finished on the dry side (again), with a few surplus spots located to the SE of KC.  The east finished with above average rains except a small corridor from the MS river through northern Randolph County, then jogging into Washington County, IL.


Global Tropics:

Two tropical cyclones were observed this week, what is likely to be the final southern Hemisphere system, and the next in what will likely be a v

ery active season for the western north Pacific.

Severe Tropical Cyclone Quang (24S/21U):

Quang developed in the typical late season development area of the Southern Indian Ocean, just south of the Indonesian Islands of Java and Bali around 11-12 degrees south. Quang developed explosively from a tropical low to a tropical cyclone (equivalent to a tropical storm) in one day, then further to an Australian Category 4 severe tropical cyclone on April 30 with wind speeds of 115 knots or 132 mph, which would also be a category 4 (hurricane) on the U.S. scale.  Quang weakened rapidly thereafter due to strong upper level wind shear and progressively colder waters, crossing the Western Australian Coast as a tropical cyclone (tropical storm) before weakening inland May 1.

Here are a series of images showing Quang’s development, peak and demise (click to zoom in to each image):

20150428_0832_mtsat-2_x_vis2km_98SINVEST_25kts-1005mb-138S-1116E_100pc 20150430_0014_mtsat-2_x_vis1km_24SQUANG_115kts-937mb-171S-1092E_100pc 20150502_0032_mtsat-2_x_vis1km_24SQUANG_25kts-1004mb-233S-1164E_100pc

From the Australian Bureau of Meteorology, Here’s the system’s track to landfall (times are local in western Australia) :


The system’s quick demise was due to rapidly approaching winter in the southern Hemisphere (remember it’s their equivalent of our early November) now.  Water temperatures are cooling, the jet stream is shifting north and large, high pressure systems are now crossing Australia, feeding cooler and drier air into the continent.  The monsoon trough, the dividing line between warm moist air flowing from the equatorial regions and cooler drier southeasterly flow is headed north toward the Equator.  Take a look at these two charts (click to make the more readable and remember that “Late Summer” in Australia is “Late Winter” here in the U.S. and “Winter” there is “Summer” here.  In the peak cyclone season,  the equatorial trough moves southward toward and over North Australia.  Converging winds act on tropical lows or disturbances within the trough, and these can spin up into tropical cyclones.  As we move into this time of year and beyond, this trough retreats to and eventually north of the Equator into the North Indian and Northwest Pacific Oceans. Meanwhile polar low pressure systems and anticyclones (high pressure systems) begin to track further north through Australia.  That brings cool winds to southern parts of the country and dry easterly flow in the center and the north, which joins with the southeasterly trade winds blowing across to the Equator and the trough located to its north.  There really is no convergence and much of central and northern (tropical) Australia is in a dry season.

Australia-Summer Australia-Winter


That’s most likely why Quang will be the southern Hemisphere’s last storm.  Storms can form near the Equator and primarily west of 90E in the Southern Indian Ocean for a few more weeks, but they become increasingly rare, and if they form are weak and short lived.

Tropical Depression 06W:

The sixth tropical cyclone of the NW Pacific season formed Saturday and will likely become TS Noul. Another disturbance further east may also develop this week.



We’ll have more on these systems on next week’s update.


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