# Presentation: 213186

## Storm Track Monitoring and Research at the Climate Prediction Center (CPC)

**Storm Track Monitoring and Research at the Climate Prediction Center (CPC)**

**J. Gottschalck, W. Higgins, and V. Kousky**

**1. MONITORING**

**Storms are tracked using a method originally developed at the Climate Diagnostics Center (CDC) (Serreze, 1995, Atmos.-Ocean; Serreze *****et al*****, 1997, J. Climate). The algorithm locates sea level pressure minima using a threshold of 1 mb as criteria for storm identification and storms are tracked by analyzing the position of systems between time steps and applying a maximum distance threshold between candidate pairings (800 km). The maximum distance moved north, south, or west for a particular storm between time steps is restricted. Currently, Global Data Assimilation System (GDAS) six-hourly, 2.5****o ****x 2.5o data are used for monitoring purposes. The sea level pressure fields are converted to an equal area projection before tracking is conducted.**

_**Figure 1**_**: Example storm tracks for the period from February 14 – March 15, 2005 using the algorithm described above. **

_**http://www.cpc.ncep.noaa.gov/products/precip/CWlink/stormtracks/strack.shtml**_

_**Figure 2**_**: Example storm tracks web page product for the ten day period from April 21 – April 30, 2005. Storm tracks and total ten day precipitation (mm) (top), mean ten day 925 mb anomalous wind vectors and magnitude (m/s, shaded) (middle) and mean ten day significant wave heights (m) from NCEP EMC (bottom). The 500 mb mean height and anomalies for the same period (bottom right) illustrating the strong blocking pattern across Alaska that played a major role in the evolution of the storm tracks shown. **

_**Figure 3**_**: Latitude-time plots of storm days per pentad [the number of closed circulations (6-hr data) divided by 4 in a 10 x 10 degree region] for selected cross sections in the northern hemisphere. A three pentad running mean is applied to the data.**

**Split flow in the eastern Rockies/western Plains from late February to mid-March. Alberta clippers and southern Plains cyclones**

**Southern California storminess  in early to mid February**

**Active and shifting storm track in the Pacific Ocean during the period**

_**Measure of Storm Days**__** **_

_**Figure 4**_**: Example storm tracks web page product of the week 1 operational GFS forecast for May 15, 2005. Figures show the same variables as that described in Figure 2. Storm tracks from the GFS ensemble mean forecast data are also available on the web page. **

**Heavy precipitation, high winds, and strong wave action in the Pacific Ocean with an expected strong Pacific storm track during a weekly forecast period. **

**Storms affected by blocking pattern**

**Storms beginning to undercut Alaska ridge**

**Strong anomalous meridional flow along the west coast of Alaska  **
**Enhancement into the central California coast**

**Elevated wave action in the central Pacific**

***a. Algorithm***

***b. CPC Web Page Products ***

**2. RESEARCH**

**Alaska storminess has received increasing attention as communities along the Alaskan coasts have documented severe social and economic impacts. The multi-disciplinary Pacific Region Integrated Data Enterprise (PRIDE) wind/wave coastal workshop in Anchorage, Alaska in August 2005 recommended research to better characterize possible trends/changes in storm frequency/intensity in the Alaska domain. Attributes of an initial choice of storminess index are presented here (Zhang *****et al*****, 2004, J. Climate). An index of storminess is important as it allows not only a consistent and easily interpretable measure of storm activity but also allows other disciplines (geology, ecology, *****etc*****.) to relate their findings with variations in storm frequency and intensity.  **

***a. Background and Cyclone Activity Index (CAI)***

-    	 	**	****  *****i***** = *****N,6hr***
**	****	****CAI =  sigma   [ *****SLP***** (*****x*****, *****y*****, *****t*****)****  ****–  *****SLP*****clim**** (*****x*****, *****y*****, *****month*****)]**
**	****    ****	****	****     *****i***** = 1**
*	**	**N* = Number of six-hourly cyclone centers
*	**	**SLP* = Sea level pressure of six-hourly cyclone center
*	**	**SLP*clim = Monthly climatological sea level pressure

_**Figure 7**_**: The histograms of seasonal CAI for the twelve regions depicted in Figure 6a show considerable variation in the distribution of seasonal CAI.**

_**Figure 5**_**: (a,b) Storm tracks and CAI for September, October, and November 2004, (c) CAI seasonal climatology, (d) map of specific areas for the time series shown in (e), (f), and (g) which show the monthly climatological CAI for the twelve regions.**

_**Figure 8**_**: Normalized time series of monthly CAI for AREA 2 and AREA 6 as outlined in Figure 6a for the period 1950-2004. Running means of three months, thirteen months, six years, and eleven years have been applied for top, top-center, bottom-center, and bottom respectively. **

**Realtime verification of GFS/CFS storm tracks on web page**
**Alaska storm track theme page (wave heights, sea ice, extreme events)**
**Identify/develop and evaluate other measures of storminess**
**Identify extremes in storminess in the Alaska region and document precursors **
**Relation of interannual variability and leading modes of climate variability **

**(a)**

**(f)**

**(e)**

**(b)**

**(c)**

**(d)**

**(g)**

**3. ONGOING WORK**

**21APR2005 - 30APR2005**

**21APR2005 - 30APR2005**

**21APR2005 - 30APR2005**

**21APR2005 - 30APR2005**